![Paul E. McKenney](/assets/img/avatar_default.png)
Commit b1420f1c
(Make rcu_barrier() less disruptive) rearranged the
code in rcu_do_batch(), moving the ->qlen manipulation to follow
the requeueing of the callbacks. Unfortunately, this rearrangement
clobbered the value of the "count" local variable before the value
of rdp->qlen was adjusted, resulting in the value of rdp->qlen being
inaccurate. This commit therefore introduces an index variable "i",
avoiding the inadvertent multiplexing.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2682 lines
84 KiB
C
2682 lines
84 KiB
C
/*
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* Read-Copy Update mechanism for mutual exclusion
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* Copyright IBM Corporation, 2008
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*
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* Authors: Dipankar Sarma <dipankar@in.ibm.com>
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* Manfred Spraul <manfred@colorfullife.com>
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* Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical version
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*
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* Based on the original work by Paul McKenney <paulmck@us.ibm.com>
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* and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
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*
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* For detailed explanation of Read-Copy Update mechanism see -
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* Documentation/RCU
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*/
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/spinlock.h>
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#include <linux/smp.h>
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#include <linux/rcupdate.h>
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#include <linux/interrupt.h>
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#include <linux/sched.h>
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#include <linux/nmi.h>
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#include <linux/atomic.h>
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#include <linux/bitops.h>
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#include <linux/export.h>
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#include <linux/completion.h>
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#include <linux/moduleparam.h>
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#include <linux/percpu.h>
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#include <linux/notifier.h>
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#include <linux/cpu.h>
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#include <linux/mutex.h>
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#include <linux/time.h>
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#include <linux/kernel_stat.h>
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#include <linux/wait.h>
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#include <linux/kthread.h>
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#include <linux/prefetch.h>
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#include <linux/delay.h>
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#include <linux/stop_machine.h>
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#include "rcutree.h"
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#include <trace/events/rcu.h>
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#include "rcu.h"
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/* Data structures. */
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static struct lock_class_key rcu_node_class[NUM_RCU_LVLS];
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#define RCU_STATE_INITIALIZER(structname) { \
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.level = { &structname##_state.node[0] }, \
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.levelcnt = { \
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NUM_RCU_LVL_0, /* root of hierarchy. */ \
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NUM_RCU_LVL_1, \
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NUM_RCU_LVL_2, \
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NUM_RCU_LVL_3, \
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NUM_RCU_LVL_4, /* == MAX_RCU_LVLS */ \
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}, \
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.fqs_state = RCU_GP_IDLE, \
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.gpnum = -300, \
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.completed = -300, \
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.onofflock = __RAW_SPIN_LOCK_UNLOCKED(&structname##_state.onofflock), \
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.orphan_nxttail = &structname##_state.orphan_nxtlist, \
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.orphan_donetail = &structname##_state.orphan_donelist, \
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.fqslock = __RAW_SPIN_LOCK_UNLOCKED(&structname##_state.fqslock), \
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.n_force_qs = 0, \
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.n_force_qs_ngp = 0, \
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.name = #structname, \
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}
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struct rcu_state rcu_sched_state = RCU_STATE_INITIALIZER(rcu_sched);
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DEFINE_PER_CPU(struct rcu_data, rcu_sched_data);
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struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh);
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DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);
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static struct rcu_state *rcu_state;
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/*
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* The rcu_scheduler_active variable transitions from zero to one just
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* before the first task is spawned. So when this variable is zero, RCU
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* can assume that there is but one task, allowing RCU to (for example)
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* optimized synchronize_sched() to a simple barrier(). When this variable
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* is one, RCU must actually do all the hard work required to detect real
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* grace periods. This variable is also used to suppress boot-time false
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* positives from lockdep-RCU error checking.
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*/
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int rcu_scheduler_active __read_mostly;
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EXPORT_SYMBOL_GPL(rcu_scheduler_active);
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/*
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* The rcu_scheduler_fully_active variable transitions from zero to one
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* during the early_initcall() processing, which is after the scheduler
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* is capable of creating new tasks. So RCU processing (for example,
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* creating tasks for RCU priority boosting) must be delayed until after
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* rcu_scheduler_fully_active transitions from zero to one. We also
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* currently delay invocation of any RCU callbacks until after this point.
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*
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* It might later prove better for people registering RCU callbacks during
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* early boot to take responsibility for these callbacks, but one step at
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* a time.
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*/
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static int rcu_scheduler_fully_active __read_mostly;
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#ifdef CONFIG_RCU_BOOST
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/*
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* Control variables for per-CPU and per-rcu_node kthreads. These
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* handle all flavors of RCU.
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*/
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static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task);
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DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
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DEFINE_PER_CPU(int, rcu_cpu_kthread_cpu);
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DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
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DEFINE_PER_CPU(char, rcu_cpu_has_work);
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#endif /* #ifdef CONFIG_RCU_BOOST */
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static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
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static void invoke_rcu_core(void);
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static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp);
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/*
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* Track the rcutorture test sequence number and the update version
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* number within a given test. The rcutorture_testseq is incremented
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* on every rcutorture module load and unload, so has an odd value
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* when a test is running. The rcutorture_vernum is set to zero
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* when rcutorture starts and is incremented on each rcutorture update.
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* These variables enable correlating rcutorture output with the
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* RCU tracing information.
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*/
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unsigned long rcutorture_testseq;
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unsigned long rcutorture_vernum;
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/* State information for rcu_barrier() and friends. */
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static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL};
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static atomic_t rcu_barrier_cpu_count;
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static DEFINE_MUTEX(rcu_barrier_mutex);
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static struct completion rcu_barrier_completion;
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/*
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* Return true if an RCU grace period is in progress. The ACCESS_ONCE()s
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* permit this function to be invoked without holding the root rcu_node
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* structure's ->lock, but of course results can be subject to change.
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*/
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static int rcu_gp_in_progress(struct rcu_state *rsp)
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{
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return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum);
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}
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/*
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* Note a quiescent state. Because we do not need to know
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* how many quiescent states passed, just if there was at least
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* one since the start of the grace period, this just sets a flag.
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* The caller must have disabled preemption.
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*/
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void rcu_sched_qs(int cpu)
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{
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struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu);
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rdp->passed_quiesce_gpnum = rdp->gpnum;
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barrier();
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if (rdp->passed_quiesce == 0)
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trace_rcu_grace_period("rcu_sched", rdp->gpnum, "cpuqs");
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rdp->passed_quiesce = 1;
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}
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void rcu_bh_qs(int cpu)
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{
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struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
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rdp->passed_quiesce_gpnum = rdp->gpnum;
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barrier();
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if (rdp->passed_quiesce == 0)
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trace_rcu_grace_period("rcu_bh", rdp->gpnum, "cpuqs");
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rdp->passed_quiesce = 1;
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}
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/*
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* Note a context switch. This is a quiescent state for RCU-sched,
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* and requires special handling for preemptible RCU.
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* The caller must have disabled preemption.
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*/
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void rcu_note_context_switch(int cpu)
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{
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trace_rcu_utilization("Start context switch");
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rcu_sched_qs(cpu);
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trace_rcu_utilization("End context switch");
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}
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EXPORT_SYMBOL_GPL(rcu_note_context_switch);
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DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
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.dynticks_nesting = DYNTICK_TASK_EXIT_IDLE,
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.dynticks = ATOMIC_INIT(1),
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};
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static int blimit = 10; /* Maximum callbacks per rcu_do_batch. */
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static int qhimark = 10000; /* If this many pending, ignore blimit. */
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static int qlowmark = 100; /* Once only this many pending, use blimit. */
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module_param(blimit, int, 0);
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module_param(qhimark, int, 0);
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module_param(qlowmark, int, 0);
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int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */
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int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT;
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module_param(rcu_cpu_stall_suppress, int, 0644);
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module_param(rcu_cpu_stall_timeout, int, 0644);
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static void force_quiescent_state(struct rcu_state *rsp, int relaxed);
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static int rcu_pending(int cpu);
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/*
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* Return the number of RCU-sched batches processed thus far for debug & stats.
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*/
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long rcu_batches_completed_sched(void)
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{
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return rcu_sched_state.completed;
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}
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EXPORT_SYMBOL_GPL(rcu_batches_completed_sched);
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/*
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* Return the number of RCU BH batches processed thus far for debug & stats.
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*/
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long rcu_batches_completed_bh(void)
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{
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return rcu_bh_state.completed;
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}
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EXPORT_SYMBOL_GPL(rcu_batches_completed_bh);
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/*
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* Force a quiescent state for RCU BH.
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*/
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void rcu_bh_force_quiescent_state(void)
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{
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force_quiescent_state(&rcu_bh_state, 0);
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}
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EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state);
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/*
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* Record the number of times rcutorture tests have been initiated and
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* terminated. This information allows the debugfs tracing stats to be
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* correlated to the rcutorture messages, even when the rcutorture module
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* is being repeatedly loaded and unloaded. In other words, we cannot
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* store this state in rcutorture itself.
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*/
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void rcutorture_record_test_transition(void)
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{
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rcutorture_testseq++;
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rcutorture_vernum = 0;
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}
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EXPORT_SYMBOL_GPL(rcutorture_record_test_transition);
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/*
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* Record the number of writer passes through the current rcutorture test.
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* This is also used to correlate debugfs tracing stats with the rcutorture
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* messages.
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*/
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void rcutorture_record_progress(unsigned long vernum)
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{
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rcutorture_vernum++;
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}
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EXPORT_SYMBOL_GPL(rcutorture_record_progress);
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/*
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* Force a quiescent state for RCU-sched.
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*/
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void rcu_sched_force_quiescent_state(void)
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{
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force_quiescent_state(&rcu_sched_state, 0);
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}
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EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state);
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/*
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* Does the CPU have callbacks ready to be invoked?
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*/
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static int
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cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp)
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{
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return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL];
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}
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/*
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* Does the current CPU require a yet-as-unscheduled grace period?
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*/
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static int
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cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp)
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{
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return *rdp->nxttail[RCU_DONE_TAIL] && !rcu_gp_in_progress(rsp);
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}
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/*
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* Return the root node of the specified rcu_state structure.
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*/
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static struct rcu_node *rcu_get_root(struct rcu_state *rsp)
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{
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return &rsp->node[0];
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}
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/*
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* If the specified CPU is offline, tell the caller that it is in
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* a quiescent state. Otherwise, whack it with a reschedule IPI.
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* Grace periods can end up waiting on an offline CPU when that
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* CPU is in the process of coming online -- it will be added to the
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* rcu_node bitmasks before it actually makes it online. The same thing
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* can happen while a CPU is in the process of coming online. Because this
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* race is quite rare, we check for it after detecting that the grace
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* period has been delayed rather than checking each and every CPU
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* each and every time we start a new grace period.
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*/
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static int rcu_implicit_offline_qs(struct rcu_data *rdp)
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{
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/*
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* If the CPU is offline for more than a jiffy, it is in a quiescent
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* state. We can trust its state not to change because interrupts
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* are disabled. The reason for the jiffy's worth of slack is to
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* handle CPUs initializing on the way up and finding their way
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* to the idle loop on the way down.
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*/
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if (cpu_is_offline(rdp->cpu) &&
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ULONG_CMP_LT(rdp->rsp->gp_start + 2, jiffies)) {
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trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, "ofl");
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rdp->offline_fqs++;
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return 1;
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}
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return 0;
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}
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/*
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* rcu_idle_enter_common - inform RCU that current CPU is moving towards idle
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*
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* If the new value of the ->dynticks_nesting counter now is zero,
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* we really have entered idle, and must do the appropriate accounting.
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* The caller must have disabled interrupts.
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*/
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static void rcu_idle_enter_common(struct rcu_dynticks *rdtp, long long oldval)
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{
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trace_rcu_dyntick("Start", oldval, 0);
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if (!is_idle_task(current)) {
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struct task_struct *idle = idle_task(smp_processor_id());
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trace_rcu_dyntick("Error on entry: not idle task", oldval, 0);
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ftrace_dump(DUMP_ALL);
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WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
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current->pid, current->comm,
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idle->pid, idle->comm); /* must be idle task! */
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}
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rcu_prepare_for_idle(smp_processor_id());
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/* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
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smp_mb__before_atomic_inc(); /* See above. */
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atomic_inc(&rdtp->dynticks);
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smp_mb__after_atomic_inc(); /* Force ordering with next sojourn. */
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WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
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/*
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* The idle task is not permitted to enter the idle loop while
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* in an RCU read-side critical section.
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*/
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rcu_lockdep_assert(!lock_is_held(&rcu_lock_map),
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"Illegal idle entry in RCU read-side critical section.");
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rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map),
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"Illegal idle entry in RCU-bh read-side critical section.");
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rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map),
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"Illegal idle entry in RCU-sched read-side critical section.");
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}
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/**
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* rcu_idle_enter - inform RCU that current CPU is entering idle
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*
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* Enter idle mode, in other words, -leave- the mode in which RCU
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* read-side critical sections can occur. (Though RCU read-side
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* critical sections can occur in irq handlers in idle, a possibility
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* handled by irq_enter() and irq_exit().)
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*
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* We crowbar the ->dynticks_nesting field to zero to allow for
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* the possibility of usermode upcalls having messed up our count
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* of interrupt nesting level during the prior busy period.
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*/
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void rcu_idle_enter(void)
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{
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unsigned long flags;
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long long oldval;
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struct rcu_dynticks *rdtp;
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local_irq_save(flags);
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rdtp = &__get_cpu_var(rcu_dynticks);
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oldval = rdtp->dynticks_nesting;
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WARN_ON_ONCE((oldval & DYNTICK_TASK_NEST_MASK) == 0);
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if ((oldval & DYNTICK_TASK_NEST_MASK) == DYNTICK_TASK_NEST_VALUE)
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rdtp->dynticks_nesting = 0;
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else
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rdtp->dynticks_nesting -= DYNTICK_TASK_NEST_VALUE;
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rcu_idle_enter_common(rdtp, oldval);
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local_irq_restore(flags);
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}
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EXPORT_SYMBOL_GPL(rcu_idle_enter);
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/**
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* rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle
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*
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* Exit from an interrupt handler, which might possibly result in entering
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* idle mode, in other words, leaving the mode in which read-side critical
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* sections can occur.
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*
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* This code assumes that the idle loop never does anything that might
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* result in unbalanced calls to irq_enter() and irq_exit(). If your
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* architecture violates this assumption, RCU will give you what you
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* deserve, good and hard. But very infrequently and irreproducibly.
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*
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* Use things like work queues to work around this limitation.
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*
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* You have been warned.
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*/
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void rcu_irq_exit(void)
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{
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unsigned long flags;
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long long oldval;
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struct rcu_dynticks *rdtp;
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local_irq_save(flags);
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rdtp = &__get_cpu_var(rcu_dynticks);
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oldval = rdtp->dynticks_nesting;
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rdtp->dynticks_nesting--;
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WARN_ON_ONCE(rdtp->dynticks_nesting < 0);
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if (rdtp->dynticks_nesting)
|
|
trace_rcu_dyntick("--=", oldval, rdtp->dynticks_nesting);
|
|
else
|
|
rcu_idle_enter_common(rdtp, oldval);
|
|
local_irq_restore(flags);
|
|
}
|
|
|
|
/*
|
|
* rcu_idle_exit_common - inform RCU that current CPU is moving away from idle
|
|
*
|
|
* If the new value of the ->dynticks_nesting counter was previously zero,
|
|
* we really have exited idle, and must do the appropriate accounting.
|
|
* The caller must have disabled interrupts.
|
|
*/
|
|
static void rcu_idle_exit_common(struct rcu_dynticks *rdtp, long long oldval)
|
|
{
|
|
smp_mb__before_atomic_inc(); /* Force ordering w/previous sojourn. */
|
|
atomic_inc(&rdtp->dynticks);
|
|
/* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
|
|
smp_mb__after_atomic_inc(); /* See above. */
|
|
WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
|
|
rcu_cleanup_after_idle(smp_processor_id());
|
|
trace_rcu_dyntick("End", oldval, rdtp->dynticks_nesting);
|
|
if (!is_idle_task(current)) {
|
|
struct task_struct *idle = idle_task(smp_processor_id());
|
|
|
|
trace_rcu_dyntick("Error on exit: not idle task",
|
|
oldval, rdtp->dynticks_nesting);
|
|
ftrace_dump(DUMP_ALL);
|
|
WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
|
|
current->pid, current->comm,
|
|
idle->pid, idle->comm); /* must be idle task! */
|
|
}
|
|
}
|
|
|
|
/**
|
|
* rcu_idle_exit - inform RCU that current CPU is leaving idle
|
|
*
|
|
* Exit idle mode, in other words, -enter- the mode in which RCU
|
|
* read-side critical sections can occur.
|
|
*
|
|
* We crowbar the ->dynticks_nesting field to DYNTICK_TASK_NEST to
|
|
* allow for the possibility of usermode upcalls messing up our count
|
|
* of interrupt nesting level during the busy period that is just
|
|
* now starting.
|
|
*/
|
|
void rcu_idle_exit(void)
|
|
{
|
|
unsigned long flags;
|
|
struct rcu_dynticks *rdtp;
|
|
long long oldval;
|
|
|
|
local_irq_save(flags);
|
|
rdtp = &__get_cpu_var(rcu_dynticks);
|
|
oldval = rdtp->dynticks_nesting;
|
|
WARN_ON_ONCE(oldval < 0);
|
|
if (oldval & DYNTICK_TASK_NEST_MASK)
|
|
rdtp->dynticks_nesting += DYNTICK_TASK_NEST_VALUE;
|
|
else
|
|
rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
|
|
rcu_idle_exit_common(rdtp, oldval);
|
|
local_irq_restore(flags);
|
|
}
|
|
EXPORT_SYMBOL_GPL(rcu_idle_exit);
|
|
|
|
/**
|
|
* rcu_irq_enter - inform RCU that current CPU is entering irq away from idle
|
|
*
|
|
* Enter an interrupt handler, which might possibly result in exiting
|
|
* idle mode, in other words, entering the mode in which read-side critical
|
|
* sections can occur.
|
|
*
|
|
* Note that the Linux kernel is fully capable of entering an interrupt
|
|
* handler that it never exits, for example when doing upcalls to
|
|
* user mode! This code assumes that the idle loop never does upcalls to
|
|
* user mode. If your architecture does do upcalls from the idle loop (or
|
|
* does anything else that results in unbalanced calls to the irq_enter()
|
|
* and irq_exit() functions), RCU will give you what you deserve, good
|
|
* and hard. But very infrequently and irreproducibly.
|
|
*
|
|
* Use things like work queues to work around this limitation.
|
|
*
|
|
* You have been warned.
|
|
*/
|
|
void rcu_irq_enter(void)
|
|
{
|
|
unsigned long flags;
|
|
struct rcu_dynticks *rdtp;
|
|
long long oldval;
|
|
|
|
local_irq_save(flags);
|
|
rdtp = &__get_cpu_var(rcu_dynticks);
|
|
oldval = rdtp->dynticks_nesting;
|
|
rdtp->dynticks_nesting++;
|
|
WARN_ON_ONCE(rdtp->dynticks_nesting == 0);
|
|
if (oldval)
|
|
trace_rcu_dyntick("++=", oldval, rdtp->dynticks_nesting);
|
|
else
|
|
rcu_idle_exit_common(rdtp, oldval);
|
|
local_irq_restore(flags);
|
|
}
|
|
|
|
/**
|
|
* rcu_nmi_enter - inform RCU of entry to NMI context
|
|
*
|
|
* If the CPU was idle with dynamic ticks active, and there is no
|
|
* irq handler running, this updates rdtp->dynticks_nmi to let the
|
|
* RCU grace-period handling know that the CPU is active.
|
|
*/
|
|
void rcu_nmi_enter(void)
|
|
{
|
|
struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
|
|
|
|
if (rdtp->dynticks_nmi_nesting == 0 &&
|
|
(atomic_read(&rdtp->dynticks) & 0x1))
|
|
return;
|
|
rdtp->dynticks_nmi_nesting++;
|
|
smp_mb__before_atomic_inc(); /* Force delay from prior write. */
|
|
atomic_inc(&rdtp->dynticks);
|
|
/* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
|
|
smp_mb__after_atomic_inc(); /* See above. */
|
|
WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
|
|
}
|
|
|
|
/**
|
|
* rcu_nmi_exit - inform RCU of exit from NMI context
|
|
*
|
|
* If the CPU was idle with dynamic ticks active, and there is no
|
|
* irq handler running, this updates rdtp->dynticks_nmi to let the
|
|
* RCU grace-period handling know that the CPU is no longer active.
|
|
*/
|
|
void rcu_nmi_exit(void)
|
|
{
|
|
struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
|
|
|
|
if (rdtp->dynticks_nmi_nesting == 0 ||
|
|
--rdtp->dynticks_nmi_nesting != 0)
|
|
return;
|
|
/* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
|
|
smp_mb__before_atomic_inc(); /* See above. */
|
|
atomic_inc(&rdtp->dynticks);
|
|
smp_mb__after_atomic_inc(); /* Force delay to next write. */
|
|
WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
|
|
}
|
|
|
|
#ifdef CONFIG_PROVE_RCU
|
|
|
|
/**
|
|
* rcu_is_cpu_idle - see if RCU thinks that the current CPU is idle
|
|
*
|
|
* If the current CPU is in its idle loop and is neither in an interrupt
|
|
* or NMI handler, return true.
|
|
*/
|
|
int rcu_is_cpu_idle(void)
|
|
{
|
|
int ret;
|
|
|
|
preempt_disable();
|
|
ret = (atomic_read(&__get_cpu_var(rcu_dynticks).dynticks) & 0x1) == 0;
|
|
preempt_enable();
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(rcu_is_cpu_idle);
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
|
|
/*
|
|
* Is the current CPU online? Disable preemption to avoid false positives
|
|
* that could otherwise happen due to the current CPU number being sampled,
|
|
* this task being preempted, its old CPU being taken offline, resuming
|
|
* on some other CPU, then determining that its old CPU is now offline.
|
|
* It is OK to use RCU on an offline processor during initial boot, hence
|
|
* the check for rcu_scheduler_fully_active. Note also that it is OK
|
|
* for a CPU coming online to use RCU for one jiffy prior to marking itself
|
|
* online in the cpu_online_mask. Similarly, it is OK for a CPU going
|
|
* offline to continue to use RCU for one jiffy after marking itself
|
|
* offline in the cpu_online_mask. This leniency is necessary given the
|
|
* non-atomic nature of the online and offline processing, for example,
|
|
* the fact that a CPU enters the scheduler after completing the CPU_DYING
|
|
* notifiers.
|
|
*
|
|
* This is also why RCU internally marks CPUs online during the
|
|
* CPU_UP_PREPARE phase and offline during the CPU_DEAD phase.
|
|
*
|
|
* Disable checking if in an NMI handler because we cannot safely report
|
|
* errors from NMI handlers anyway.
|
|
*/
|
|
bool rcu_lockdep_current_cpu_online(void)
|
|
{
|
|
struct rcu_data *rdp;
|
|
struct rcu_node *rnp;
|
|
bool ret;
|
|
|
|
if (in_nmi())
|
|
return 1;
|
|
preempt_disable();
|
|
rdp = &__get_cpu_var(rcu_sched_data);
|
|
rnp = rdp->mynode;
|
|
ret = (rdp->grpmask & rnp->qsmaskinit) ||
|
|
!rcu_scheduler_fully_active;
|
|
preempt_enable();
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online);
|
|
|
|
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
|
|
|
|
#endif /* #ifdef CONFIG_PROVE_RCU */
|
|
|
|
/**
|
|
* rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle
|
|
*
|
|
* If the current CPU is idle or running at a first-level (not nested)
|
|
* interrupt from idle, return true. The caller must have at least
|
|
* disabled preemption.
|
|
*/
|
|
int rcu_is_cpu_rrupt_from_idle(void)
|
|
{
|
|
return __get_cpu_var(rcu_dynticks).dynticks_nesting <= 1;
|
|
}
|
|
|
|
/*
|
|
* Snapshot the specified CPU's dynticks counter so that we can later
|
|
* credit them with an implicit quiescent state. Return 1 if this CPU
|
|
* is in dynticks idle mode, which is an extended quiescent state.
|
|
*/
|
|
static int dyntick_save_progress_counter(struct rcu_data *rdp)
|
|
{
|
|
rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks);
|
|
return (rdp->dynticks_snap & 0x1) == 0;
|
|
}
|
|
|
|
/*
|
|
* Return true if the specified CPU has passed through a quiescent
|
|
* state by virtue of being in or having passed through an dynticks
|
|
* idle state since the last call to dyntick_save_progress_counter()
|
|
* for this same CPU.
|
|
*/
|
|
static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
|
|
{
|
|
unsigned int curr;
|
|
unsigned int snap;
|
|
|
|
curr = (unsigned int)atomic_add_return(0, &rdp->dynticks->dynticks);
|
|
snap = (unsigned int)rdp->dynticks_snap;
|
|
|
|
/*
|
|
* If the CPU passed through or entered a dynticks idle phase with
|
|
* no active irq/NMI handlers, then we can safely pretend that the CPU
|
|
* already acknowledged the request to pass through a quiescent
|
|
* state. Either way, that CPU cannot possibly be in an RCU
|
|
* read-side critical section that started before the beginning
|
|
* of the current RCU grace period.
|
|
*/
|
|
if ((curr & 0x1) == 0 || UINT_CMP_GE(curr, snap + 2)) {
|
|
trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, "dti");
|
|
rdp->dynticks_fqs++;
|
|
return 1;
|
|
}
|
|
|
|
/* Go check for the CPU being offline. */
|
|
return rcu_implicit_offline_qs(rdp);
|
|
}
|
|
|
|
static int jiffies_till_stall_check(void)
|
|
{
|
|
int till_stall_check = ACCESS_ONCE(rcu_cpu_stall_timeout);
|
|
|
|
/*
|
|
* Limit check must be consistent with the Kconfig limits
|
|
* for CONFIG_RCU_CPU_STALL_TIMEOUT.
|
|
*/
|
|
if (till_stall_check < 3) {
|
|
ACCESS_ONCE(rcu_cpu_stall_timeout) = 3;
|
|
till_stall_check = 3;
|
|
} else if (till_stall_check > 300) {
|
|
ACCESS_ONCE(rcu_cpu_stall_timeout) = 300;
|
|
till_stall_check = 300;
|
|
}
|
|
return till_stall_check * HZ + RCU_STALL_DELAY_DELTA;
|
|
}
|
|
|
|
static void record_gp_stall_check_time(struct rcu_state *rsp)
|
|
{
|
|
rsp->gp_start = jiffies;
|
|
rsp->jiffies_stall = jiffies + jiffies_till_stall_check();
|
|
}
|
|
|
|
static void print_other_cpu_stall(struct rcu_state *rsp)
|
|
{
|
|
int cpu;
|
|
long delta;
|
|
unsigned long flags;
|
|
int ndetected;
|
|
struct rcu_node *rnp = rcu_get_root(rsp);
|
|
|
|
/* Only let one CPU complain about others per time interval. */
|
|
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
delta = jiffies - rsp->jiffies_stall;
|
|
if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) {
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
return;
|
|
}
|
|
rsp->jiffies_stall = jiffies + 3 * jiffies_till_stall_check() + 3;
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
|
|
/*
|
|
* OK, time to rat on our buddy...
|
|
* See Documentation/RCU/stallwarn.txt for info on how to debug
|
|
* RCU CPU stall warnings.
|
|
*/
|
|
printk(KERN_ERR "INFO: %s detected stalls on CPUs/tasks:",
|
|
rsp->name);
|
|
print_cpu_stall_info_begin();
|
|
rcu_for_each_leaf_node(rsp, rnp) {
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
ndetected += rcu_print_task_stall(rnp);
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
if (rnp->qsmask == 0)
|
|
continue;
|
|
for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++)
|
|
if (rnp->qsmask & (1UL << cpu)) {
|
|
print_cpu_stall_info(rsp, rnp->grplo + cpu);
|
|
ndetected++;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Now rat on any tasks that got kicked up to the root rcu_node
|
|
* due to CPU offlining.
|
|
*/
|
|
rnp = rcu_get_root(rsp);
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
ndetected = rcu_print_task_stall(rnp);
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
|
|
print_cpu_stall_info_end();
|
|
printk(KERN_CONT "(detected by %d, t=%ld jiffies)\n",
|
|
smp_processor_id(), (long)(jiffies - rsp->gp_start));
|
|
if (ndetected == 0)
|
|
printk(KERN_ERR "INFO: Stall ended before state dump start\n");
|
|
else if (!trigger_all_cpu_backtrace())
|
|
dump_stack();
|
|
|
|
/* If so configured, complain about tasks blocking the grace period. */
|
|
|
|
rcu_print_detail_task_stall(rsp);
|
|
|
|
force_quiescent_state(rsp, 0); /* Kick them all. */
|
|
}
|
|
|
|
static void print_cpu_stall(struct rcu_state *rsp)
|
|
{
|
|
unsigned long flags;
|
|
struct rcu_node *rnp = rcu_get_root(rsp);
|
|
|
|
/*
|
|
* OK, time to rat on ourselves...
|
|
* See Documentation/RCU/stallwarn.txt for info on how to debug
|
|
* RCU CPU stall warnings.
|
|
*/
|
|
printk(KERN_ERR "INFO: %s self-detected stall on CPU", rsp->name);
|
|
print_cpu_stall_info_begin();
|
|
print_cpu_stall_info(rsp, smp_processor_id());
|
|
print_cpu_stall_info_end();
|
|
printk(KERN_CONT " (t=%lu jiffies)\n", jiffies - rsp->gp_start);
|
|
if (!trigger_all_cpu_backtrace())
|
|
dump_stack();
|
|
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall))
|
|
rsp->jiffies_stall = jiffies +
|
|
3 * jiffies_till_stall_check() + 3;
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
|
|
set_need_resched(); /* kick ourselves to get things going. */
|
|
}
|
|
|
|
static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
|
|
{
|
|
unsigned long j;
|
|
unsigned long js;
|
|
struct rcu_node *rnp;
|
|
|
|
if (rcu_cpu_stall_suppress)
|
|
return;
|
|
j = ACCESS_ONCE(jiffies);
|
|
js = ACCESS_ONCE(rsp->jiffies_stall);
|
|
rnp = rdp->mynode;
|
|
if ((ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && ULONG_CMP_GE(j, js)) {
|
|
|
|
/* We haven't checked in, so go dump stack. */
|
|
print_cpu_stall(rsp);
|
|
|
|
} else if (rcu_gp_in_progress(rsp) &&
|
|
ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) {
|
|
|
|
/* They had a few time units to dump stack, so complain. */
|
|
print_other_cpu_stall(rsp);
|
|
}
|
|
}
|
|
|
|
static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr)
|
|
{
|
|
rcu_cpu_stall_suppress = 1;
|
|
return NOTIFY_DONE;
|
|
}
|
|
|
|
/**
|
|
* rcu_cpu_stall_reset - prevent further stall warnings in current grace period
|
|
*
|
|
* Set the stall-warning timeout way off into the future, thus preventing
|
|
* any RCU CPU stall-warning messages from appearing in the current set of
|
|
* RCU grace periods.
|
|
*
|
|
* The caller must disable hard irqs.
|
|
*/
|
|
void rcu_cpu_stall_reset(void)
|
|
{
|
|
rcu_sched_state.jiffies_stall = jiffies + ULONG_MAX / 2;
|
|
rcu_bh_state.jiffies_stall = jiffies + ULONG_MAX / 2;
|
|
rcu_preempt_stall_reset();
|
|
}
|
|
|
|
static struct notifier_block rcu_panic_block = {
|
|
.notifier_call = rcu_panic,
|
|
};
|
|
|
|
static void __init check_cpu_stall_init(void)
|
|
{
|
|
atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block);
|
|
}
|
|
|
|
/*
|
|
* Update CPU-local rcu_data state to record the newly noticed grace period.
|
|
* This is used both when we started the grace period and when we notice
|
|
* that someone else started the grace period. The caller must hold the
|
|
* ->lock of the leaf rcu_node structure corresponding to the current CPU,
|
|
* and must have irqs disabled.
|
|
*/
|
|
static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
|
|
{
|
|
if (rdp->gpnum != rnp->gpnum) {
|
|
/*
|
|
* If the current grace period is waiting for this CPU,
|
|
* set up to detect a quiescent state, otherwise don't
|
|
* go looking for one.
|
|
*/
|
|
rdp->gpnum = rnp->gpnum;
|
|
trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpustart");
|
|
if (rnp->qsmask & rdp->grpmask) {
|
|
rdp->qs_pending = 1;
|
|
rdp->passed_quiesce = 0;
|
|
} else
|
|
rdp->qs_pending = 0;
|
|
zero_cpu_stall_ticks(rdp);
|
|
}
|
|
}
|
|
|
|
static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp)
|
|
{
|
|
unsigned long flags;
|
|
struct rcu_node *rnp;
|
|
|
|
local_irq_save(flags);
|
|
rnp = rdp->mynode;
|
|
if (rdp->gpnum == ACCESS_ONCE(rnp->gpnum) || /* outside lock. */
|
|
!raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */
|
|
local_irq_restore(flags);
|
|
return;
|
|
}
|
|
__note_new_gpnum(rsp, rnp, rdp);
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
}
|
|
|
|
/*
|
|
* Did someone else start a new RCU grace period start since we last
|
|
* checked? Update local state appropriately if so. Must be called
|
|
* on the CPU corresponding to rdp.
|
|
*/
|
|
static int
|
|
check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp)
|
|
{
|
|
unsigned long flags;
|
|
int ret = 0;
|
|
|
|
local_irq_save(flags);
|
|
if (rdp->gpnum != rsp->gpnum) {
|
|
note_new_gpnum(rsp, rdp);
|
|
ret = 1;
|
|
}
|
|
local_irq_restore(flags);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Advance this CPU's callbacks, but only if the current grace period
|
|
* has ended. This may be called only from the CPU to whom the rdp
|
|
* belongs. In addition, the corresponding leaf rcu_node structure's
|
|
* ->lock must be held by the caller, with irqs disabled.
|
|
*/
|
|
static void
|
|
__rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
|
|
{
|
|
/* Did another grace period end? */
|
|
if (rdp->completed != rnp->completed) {
|
|
|
|
/* Advance callbacks. No harm if list empty. */
|
|
rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL];
|
|
rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL];
|
|
rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
|
|
|
|
/* Remember that we saw this grace-period completion. */
|
|
rdp->completed = rnp->completed;
|
|
trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuend");
|
|
|
|
/*
|
|
* If we were in an extended quiescent state, we may have
|
|
* missed some grace periods that others CPUs handled on
|
|
* our behalf. Catch up with this state to avoid noting
|
|
* spurious new grace periods. If another grace period
|
|
* has started, then rnp->gpnum will have advanced, so
|
|
* we will detect this later on.
|
|
*/
|
|
if (ULONG_CMP_LT(rdp->gpnum, rdp->completed))
|
|
rdp->gpnum = rdp->completed;
|
|
|
|
/*
|
|
* If RCU does not need a quiescent state from this CPU,
|
|
* then make sure that this CPU doesn't go looking for one.
|
|
*/
|
|
if ((rnp->qsmask & rdp->grpmask) == 0)
|
|
rdp->qs_pending = 0;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Advance this CPU's callbacks, but only if the current grace period
|
|
* has ended. This may be called only from the CPU to whom the rdp
|
|
* belongs.
|
|
*/
|
|
static void
|
|
rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp)
|
|
{
|
|
unsigned long flags;
|
|
struct rcu_node *rnp;
|
|
|
|
local_irq_save(flags);
|
|
rnp = rdp->mynode;
|
|
if (rdp->completed == ACCESS_ONCE(rnp->completed) || /* outside lock. */
|
|
!raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */
|
|
local_irq_restore(flags);
|
|
return;
|
|
}
|
|
__rcu_process_gp_end(rsp, rnp, rdp);
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
}
|
|
|
|
/*
|
|
* Do per-CPU grace-period initialization for running CPU. The caller
|
|
* must hold the lock of the leaf rcu_node structure corresponding to
|
|
* this CPU.
|
|
*/
|
|
static void
|
|
rcu_start_gp_per_cpu(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
|
|
{
|
|
/* Prior grace period ended, so advance callbacks for current CPU. */
|
|
__rcu_process_gp_end(rsp, rnp, rdp);
|
|
|
|
/*
|
|
* Because this CPU just now started the new grace period, we know
|
|
* that all of its callbacks will be covered by this upcoming grace
|
|
* period, even the ones that were registered arbitrarily recently.
|
|
* Therefore, advance all outstanding callbacks to RCU_WAIT_TAIL.
|
|
*
|
|
* Other CPUs cannot be sure exactly when the grace period started.
|
|
* Therefore, their recently registered callbacks must pass through
|
|
* an additional RCU_NEXT_READY stage, so that they will be handled
|
|
* by the next RCU grace period.
|
|
*/
|
|
rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
|
|
rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
|
|
|
|
/* Set state so that this CPU will detect the next quiescent state. */
|
|
__note_new_gpnum(rsp, rnp, rdp);
|
|
}
|
|
|
|
/*
|
|
* Start a new RCU grace period if warranted, re-initializing the hierarchy
|
|
* in preparation for detecting the next grace period. The caller must hold
|
|
* the root node's ->lock, which is released before return. Hard irqs must
|
|
* be disabled.
|
|
*
|
|
* Note that it is legal for a dying CPU (which is marked as offline) to
|
|
* invoke this function. This can happen when the dying CPU reports its
|
|
* quiescent state.
|
|
*/
|
|
static void
|
|
rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
|
|
__releases(rcu_get_root(rsp)->lock)
|
|
{
|
|
struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
|
|
struct rcu_node *rnp = rcu_get_root(rsp);
|
|
|
|
if (!rcu_scheduler_fully_active ||
|
|
!cpu_needs_another_gp(rsp, rdp)) {
|
|
/*
|
|
* Either the scheduler hasn't yet spawned the first
|
|
* non-idle task or this CPU does not need another
|
|
* grace period. Either way, don't start a new grace
|
|
* period.
|
|
*/
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
return;
|
|
}
|
|
|
|
if (rsp->fqs_active) {
|
|
/*
|
|
* This CPU needs a grace period, but force_quiescent_state()
|
|
* is running. Tell it to start one on this CPU's behalf.
|
|
*/
|
|
rsp->fqs_need_gp = 1;
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
return;
|
|
}
|
|
|
|
/* Advance to a new grace period and initialize state. */
|
|
rsp->gpnum++;
|
|
trace_rcu_grace_period(rsp->name, rsp->gpnum, "start");
|
|
WARN_ON_ONCE(rsp->fqs_state == RCU_GP_INIT);
|
|
rsp->fqs_state = RCU_GP_INIT; /* Hold off force_quiescent_state. */
|
|
rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
|
|
record_gp_stall_check_time(rsp);
|
|
raw_spin_unlock(&rnp->lock); /* leave irqs disabled. */
|
|
|
|
/* Exclude any concurrent CPU-hotplug operations. */
|
|
raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */
|
|
|
|
/*
|
|
* Set the quiescent-state-needed bits in all the rcu_node
|
|
* structures for all currently online CPUs in breadth-first
|
|
* order, starting from the root rcu_node structure. This
|
|
* operation relies on the layout of the hierarchy within the
|
|
* rsp->node[] array. Note that other CPUs will access only
|
|
* the leaves of the hierarchy, which still indicate that no
|
|
* grace period is in progress, at least until the corresponding
|
|
* leaf node has been initialized. In addition, we have excluded
|
|
* CPU-hotplug operations.
|
|
*
|
|
* Note that the grace period cannot complete until we finish
|
|
* the initialization process, as there will be at least one
|
|
* qsmask bit set in the root node until that time, namely the
|
|
* one corresponding to this CPU, due to the fact that we have
|
|
* irqs disabled.
|
|
*/
|
|
rcu_for_each_node_breadth_first(rsp, rnp) {
|
|
raw_spin_lock(&rnp->lock); /* irqs already disabled. */
|
|
rcu_preempt_check_blocked_tasks(rnp);
|
|
rnp->qsmask = rnp->qsmaskinit;
|
|
rnp->gpnum = rsp->gpnum;
|
|
rnp->completed = rsp->completed;
|
|
if (rnp == rdp->mynode)
|
|
rcu_start_gp_per_cpu(rsp, rnp, rdp);
|
|
rcu_preempt_boost_start_gp(rnp);
|
|
trace_rcu_grace_period_init(rsp->name, rnp->gpnum,
|
|
rnp->level, rnp->grplo,
|
|
rnp->grphi, rnp->qsmask);
|
|
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
|
|
}
|
|
|
|
rnp = rcu_get_root(rsp);
|
|
raw_spin_lock(&rnp->lock); /* irqs already disabled. */
|
|
rsp->fqs_state = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */
|
|
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
|
|
raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
|
|
}
|
|
|
|
/*
|
|
* Report a full set of quiescent states to the specified rcu_state
|
|
* data structure. This involves cleaning up after the prior grace
|
|
* period and letting rcu_start_gp() start up the next grace period
|
|
* if one is needed. Note that the caller must hold rnp->lock, as
|
|
* required by rcu_start_gp(), which will release it.
|
|
*/
|
|
static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags)
|
|
__releases(rcu_get_root(rsp)->lock)
|
|
{
|
|
unsigned long gp_duration;
|
|
struct rcu_node *rnp = rcu_get_root(rsp);
|
|
struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
|
|
|
|
WARN_ON_ONCE(!rcu_gp_in_progress(rsp));
|
|
|
|
/*
|
|
* Ensure that all grace-period and pre-grace-period activity
|
|
* is seen before the assignment to rsp->completed.
|
|
*/
|
|
smp_mb(); /* See above block comment. */
|
|
gp_duration = jiffies - rsp->gp_start;
|
|
if (gp_duration > rsp->gp_max)
|
|
rsp->gp_max = gp_duration;
|
|
|
|
/*
|
|
* We know the grace period is complete, but to everyone else
|
|
* it appears to still be ongoing. But it is also the case
|
|
* that to everyone else it looks like there is nothing that
|
|
* they can do to advance the grace period. It is therefore
|
|
* safe for us to drop the lock in order to mark the grace
|
|
* period as completed in all of the rcu_node structures.
|
|
*
|
|
* But if this CPU needs another grace period, it will take
|
|
* care of this while initializing the next grace period.
|
|
* We use RCU_WAIT_TAIL instead of the usual RCU_DONE_TAIL
|
|
* because the callbacks have not yet been advanced: Those
|
|
* callbacks are waiting on the grace period that just now
|
|
* completed.
|
|
*/
|
|
if (*rdp->nxttail[RCU_WAIT_TAIL] == NULL) {
|
|
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
|
|
|
|
/*
|
|
* Propagate new ->completed value to rcu_node structures
|
|
* so that other CPUs don't have to wait until the start
|
|
* of the next grace period to process their callbacks.
|
|
*/
|
|
rcu_for_each_node_breadth_first(rsp, rnp) {
|
|
raw_spin_lock(&rnp->lock); /* irqs already disabled. */
|
|
rnp->completed = rsp->gpnum;
|
|
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
|
|
}
|
|
rnp = rcu_get_root(rsp);
|
|
raw_spin_lock(&rnp->lock); /* irqs already disabled. */
|
|
}
|
|
|
|
rsp->completed = rsp->gpnum; /* Declare the grace period complete. */
|
|
trace_rcu_grace_period(rsp->name, rsp->completed, "end");
|
|
rsp->fqs_state = RCU_GP_IDLE;
|
|
rcu_start_gp(rsp, flags); /* releases root node's rnp->lock. */
|
|
}
|
|
|
|
/*
|
|
* Similar to rcu_report_qs_rdp(), for which it is a helper function.
|
|
* Allows quiescent states for a group of CPUs to be reported at one go
|
|
* to the specified rcu_node structure, though all the CPUs in the group
|
|
* must be represented by the same rcu_node structure (which need not be
|
|
* a leaf rcu_node structure, though it often will be). That structure's
|
|
* lock must be held upon entry, and it is released before return.
|
|
*/
|
|
static void
|
|
rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp,
|
|
struct rcu_node *rnp, unsigned long flags)
|
|
__releases(rnp->lock)
|
|
{
|
|
struct rcu_node *rnp_c;
|
|
|
|
/* Walk up the rcu_node hierarchy. */
|
|
for (;;) {
|
|
if (!(rnp->qsmask & mask)) {
|
|
|
|
/* Our bit has already been cleared, so done. */
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
return;
|
|
}
|
|
rnp->qsmask &= ~mask;
|
|
trace_rcu_quiescent_state_report(rsp->name, rnp->gpnum,
|
|
mask, rnp->qsmask, rnp->level,
|
|
rnp->grplo, rnp->grphi,
|
|
!!rnp->gp_tasks);
|
|
if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) {
|
|
|
|
/* Other bits still set at this level, so done. */
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
return;
|
|
}
|
|
mask = rnp->grpmask;
|
|
if (rnp->parent == NULL) {
|
|
|
|
/* No more levels. Exit loop holding root lock. */
|
|
|
|
break;
|
|
}
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
rnp_c = rnp;
|
|
rnp = rnp->parent;
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
WARN_ON_ONCE(rnp_c->qsmask);
|
|
}
|
|
|
|
/*
|
|
* Get here if we are the last CPU to pass through a quiescent
|
|
* state for this grace period. Invoke rcu_report_qs_rsp()
|
|
* to clean up and start the next grace period if one is needed.
|
|
*/
|
|
rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */
|
|
}
|
|
|
|
/*
|
|
* Record a quiescent state for the specified CPU to that CPU's rcu_data
|
|
* structure. This must be either called from the specified CPU, or
|
|
* called when the specified CPU is known to be offline (and when it is
|
|
* also known that no other CPU is concurrently trying to help the offline
|
|
* CPU). The lastcomp argument is used to make sure we are still in the
|
|
* grace period of interest. We don't want to end the current grace period
|
|
* based on quiescent states detected in an earlier grace period!
|
|
*/
|
|
static void
|
|
rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastgp)
|
|
{
|
|
unsigned long flags;
|
|
unsigned long mask;
|
|
struct rcu_node *rnp;
|
|
|
|
rnp = rdp->mynode;
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
if (lastgp != rnp->gpnum || rnp->completed == rnp->gpnum) {
|
|
|
|
/*
|
|
* The grace period in which this quiescent state was
|
|
* recorded has ended, so don't report it upwards.
|
|
* We will instead need a new quiescent state that lies
|
|
* within the current grace period.
|
|
*/
|
|
rdp->passed_quiesce = 0; /* need qs for new gp. */
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
return;
|
|
}
|
|
mask = rdp->grpmask;
|
|
if ((rnp->qsmask & mask) == 0) {
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
} else {
|
|
rdp->qs_pending = 0;
|
|
|
|
/*
|
|
* This GP can't end until cpu checks in, so all of our
|
|
* callbacks can be processed during the next GP.
|
|
*/
|
|
rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
|
|
|
|
rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Check to see if there is a new grace period of which this CPU
|
|
* is not yet aware, and if so, set up local rcu_data state for it.
|
|
* Otherwise, see if this CPU has just passed through its first
|
|
* quiescent state for this grace period, and record that fact if so.
|
|
*/
|
|
static void
|
|
rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp)
|
|
{
|
|
/* If there is now a new grace period, record and return. */
|
|
if (check_for_new_grace_period(rsp, rdp))
|
|
return;
|
|
|
|
/*
|
|
* Does this CPU still need to do its part for current grace period?
|
|
* If no, return and let the other CPUs do their part as well.
|
|
*/
|
|
if (!rdp->qs_pending)
|
|
return;
|
|
|
|
/*
|
|
* Was there a quiescent state since the beginning of the grace
|
|
* period? If no, then exit and wait for the next call.
|
|
*/
|
|
if (!rdp->passed_quiesce)
|
|
return;
|
|
|
|
/*
|
|
* Tell RCU we are done (but rcu_report_qs_rdp() will be the
|
|
* judge of that).
|
|
*/
|
|
rcu_report_qs_rdp(rdp->cpu, rsp, rdp, rdp->passed_quiesce_gpnum);
|
|
}
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
|
|
/*
|
|
* Send the specified CPU's RCU callbacks to the orphanage. The
|
|
* specified CPU must be offline, and the caller must hold the
|
|
* ->onofflock.
|
|
*/
|
|
static void
|
|
rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp,
|
|
struct rcu_node *rnp, struct rcu_data *rdp)
|
|
{
|
|
int i;
|
|
|
|
/*
|
|
* Orphan the callbacks. First adjust the counts. This is safe
|
|
* because ->onofflock excludes _rcu_barrier()'s adoption of
|
|
* the callbacks, thus no memory barrier is required.
|
|
*/
|
|
if (rdp->nxtlist != NULL) {
|
|
rsp->qlen_lazy += rdp->qlen_lazy;
|
|
rsp->qlen += rdp->qlen;
|
|
rdp->n_cbs_orphaned += rdp->qlen;
|
|
rdp->qlen_lazy = 0;
|
|
rdp->qlen = 0;
|
|
}
|
|
|
|
/*
|
|
* Next, move those callbacks still needing a grace period to
|
|
* the orphanage, where some other CPU will pick them up.
|
|
* Some of the callbacks might have gone partway through a grace
|
|
* period, but that is too bad. They get to start over because we
|
|
* cannot assume that grace periods are synchronized across CPUs.
|
|
* We don't bother updating the ->nxttail[] array yet, instead
|
|
* we just reset the whole thing later on.
|
|
*/
|
|
if (*rdp->nxttail[RCU_DONE_TAIL] != NULL) {
|
|
*rsp->orphan_nxttail = *rdp->nxttail[RCU_DONE_TAIL];
|
|
rsp->orphan_nxttail = rdp->nxttail[RCU_NEXT_TAIL];
|
|
*rdp->nxttail[RCU_DONE_TAIL] = NULL;
|
|
}
|
|
|
|
/*
|
|
* Then move the ready-to-invoke callbacks to the orphanage,
|
|
* where some other CPU will pick them up. These will not be
|
|
* required to pass though another grace period: They are done.
|
|
*/
|
|
if (rdp->nxtlist != NULL) {
|
|
*rsp->orphan_donetail = rdp->nxtlist;
|
|
rsp->orphan_donetail = rdp->nxttail[RCU_DONE_TAIL];
|
|
}
|
|
|
|
/* Finally, initialize the rcu_data structure's list to empty. */
|
|
rdp->nxtlist = NULL;
|
|
for (i = 0; i < RCU_NEXT_SIZE; i++)
|
|
rdp->nxttail[i] = &rdp->nxtlist;
|
|
}
|
|
|
|
/*
|
|
* Adopt the RCU callbacks from the specified rcu_state structure's
|
|
* orphanage. The caller must hold the ->onofflock.
|
|
*/
|
|
static void rcu_adopt_orphan_cbs(struct rcu_state *rsp)
|
|
{
|
|
int i;
|
|
struct rcu_data *rdp = __this_cpu_ptr(rsp->rda);
|
|
|
|
/*
|
|
* If there is an rcu_barrier() operation in progress, then
|
|
* only the task doing that operation is permitted to adopt
|
|
* callbacks. To do otherwise breaks rcu_barrier() and friends
|
|
* by causing them to fail to wait for the callbacks in the
|
|
* orphanage.
|
|
*/
|
|
if (rsp->rcu_barrier_in_progress &&
|
|
rsp->rcu_barrier_in_progress != current)
|
|
return;
|
|
|
|
/* Do the accounting first. */
|
|
rdp->qlen_lazy += rsp->qlen_lazy;
|
|
rdp->qlen += rsp->qlen;
|
|
rdp->n_cbs_adopted += rsp->qlen;
|
|
if (rsp->qlen_lazy != rsp->qlen)
|
|
rcu_idle_count_callbacks_posted();
|
|
rsp->qlen_lazy = 0;
|
|
rsp->qlen = 0;
|
|
|
|
/*
|
|
* We do not need a memory barrier here because the only way we
|
|
* can get here if there is an rcu_barrier() in flight is if
|
|
* we are the task doing the rcu_barrier().
|
|
*/
|
|
|
|
/* First adopt the ready-to-invoke callbacks. */
|
|
if (rsp->orphan_donelist != NULL) {
|
|
*rsp->orphan_donetail = *rdp->nxttail[RCU_DONE_TAIL];
|
|
*rdp->nxttail[RCU_DONE_TAIL] = rsp->orphan_donelist;
|
|
for (i = RCU_NEXT_SIZE - 1; i >= RCU_DONE_TAIL; i--)
|
|
if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL])
|
|
rdp->nxttail[i] = rsp->orphan_donetail;
|
|
rsp->orphan_donelist = NULL;
|
|
rsp->orphan_donetail = &rsp->orphan_donelist;
|
|
}
|
|
|
|
/* And then adopt the callbacks that still need a grace period. */
|
|
if (rsp->orphan_nxtlist != NULL) {
|
|
*rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxtlist;
|
|
rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxttail;
|
|
rsp->orphan_nxtlist = NULL;
|
|
rsp->orphan_nxttail = &rsp->orphan_nxtlist;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Trace the fact that this CPU is going offline.
|
|
*/
|
|
static void rcu_cleanup_dying_cpu(struct rcu_state *rsp)
|
|
{
|
|
RCU_TRACE(unsigned long mask);
|
|
RCU_TRACE(struct rcu_data *rdp = this_cpu_ptr(rsp->rda));
|
|
RCU_TRACE(struct rcu_node *rnp = rdp->mynode);
|
|
|
|
RCU_TRACE(mask = rdp->grpmask);
|
|
trace_rcu_grace_period(rsp->name,
|
|
rnp->gpnum + 1 - !!(rnp->qsmask & mask),
|
|
"cpuofl");
|
|
}
|
|
|
|
/*
|
|
* The CPU has been completely removed, and some other CPU is reporting
|
|
* this fact from process context. Do the remainder of the cleanup,
|
|
* including orphaning the outgoing CPU's RCU callbacks, and also
|
|
* adopting them, if there is no _rcu_barrier() instance running.
|
|
* There can only be one CPU hotplug operation at a time, so no other
|
|
* CPU can be attempting to update rcu_cpu_kthread_task.
|
|
*/
|
|
static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
|
|
{
|
|
unsigned long flags;
|
|
unsigned long mask;
|
|
int need_report = 0;
|
|
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
|
|
struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */
|
|
|
|
/* Adjust any no-longer-needed kthreads. */
|
|
rcu_stop_cpu_kthread(cpu);
|
|
rcu_node_kthread_setaffinity(rnp, -1);
|
|
|
|
/* Remove the dead CPU from the bitmasks in the rcu_node hierarchy. */
|
|
|
|
/* Exclude any attempts to start a new grace period. */
|
|
raw_spin_lock_irqsave(&rsp->onofflock, flags);
|
|
|
|
/* Orphan the dead CPU's callbacks, and adopt them if appropriate. */
|
|
rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp);
|
|
rcu_adopt_orphan_cbs(rsp);
|
|
|
|
/* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */
|
|
mask = rdp->grpmask; /* rnp->grplo is constant. */
|
|
do {
|
|
raw_spin_lock(&rnp->lock); /* irqs already disabled. */
|
|
rnp->qsmaskinit &= ~mask;
|
|
if (rnp->qsmaskinit != 0) {
|
|
if (rnp != rdp->mynode)
|
|
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
|
|
break;
|
|
}
|
|
if (rnp == rdp->mynode)
|
|
need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp);
|
|
else
|
|
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
|
|
mask = rnp->grpmask;
|
|
rnp = rnp->parent;
|
|
} while (rnp != NULL);
|
|
|
|
/*
|
|
* We still hold the leaf rcu_node structure lock here, and
|
|
* irqs are still disabled. The reason for this subterfuge is
|
|
* because invoking rcu_report_unblock_qs_rnp() with ->onofflock
|
|
* held leads to deadlock.
|
|
*/
|
|
raw_spin_unlock(&rsp->onofflock); /* irqs remain disabled. */
|
|
rnp = rdp->mynode;
|
|
if (need_report & RCU_OFL_TASKS_NORM_GP)
|
|
rcu_report_unblock_qs_rnp(rnp, flags);
|
|
else
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
if (need_report & RCU_OFL_TASKS_EXP_GP)
|
|
rcu_report_exp_rnp(rsp, rnp, true);
|
|
}
|
|
|
|
#else /* #ifdef CONFIG_HOTPLUG_CPU */
|
|
|
|
static void rcu_adopt_orphan_cbs(struct rcu_state *rsp)
|
|
{
|
|
}
|
|
|
|
static void rcu_cleanup_dying_cpu(struct rcu_state *rsp)
|
|
{
|
|
}
|
|
|
|
static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
|
|
{
|
|
}
|
|
|
|
#endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
|
|
|
|
/*
|
|
* Invoke any RCU callbacks that have made it to the end of their grace
|
|
* period. Thottle as specified by rdp->blimit.
|
|
*/
|
|
static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
|
|
{
|
|
unsigned long flags;
|
|
struct rcu_head *next, *list, **tail;
|
|
int bl, count, count_lazy, i;
|
|
|
|
/* If no callbacks are ready, just return.*/
|
|
if (!cpu_has_callbacks_ready_to_invoke(rdp)) {
|
|
trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, 0);
|
|
trace_rcu_batch_end(rsp->name, 0, !!ACCESS_ONCE(rdp->nxtlist),
|
|
need_resched(), is_idle_task(current),
|
|
rcu_is_callbacks_kthread());
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Extract the list of ready callbacks, disabling to prevent
|
|
* races with call_rcu() from interrupt handlers.
|
|
*/
|
|
local_irq_save(flags);
|
|
WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
|
|
bl = rdp->blimit;
|
|
trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, bl);
|
|
list = rdp->nxtlist;
|
|
rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL];
|
|
*rdp->nxttail[RCU_DONE_TAIL] = NULL;
|
|
tail = rdp->nxttail[RCU_DONE_TAIL];
|
|
for (i = RCU_NEXT_SIZE - 1; i >= 0; i--)
|
|
if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL])
|
|
rdp->nxttail[i] = &rdp->nxtlist;
|
|
local_irq_restore(flags);
|
|
|
|
/* Invoke callbacks. */
|
|
count = count_lazy = 0;
|
|
while (list) {
|
|
next = list->next;
|
|
prefetch(next);
|
|
debug_rcu_head_unqueue(list);
|
|
if (__rcu_reclaim(rsp->name, list))
|
|
count_lazy++;
|
|
list = next;
|
|
/* Stop only if limit reached and CPU has something to do. */
|
|
if (++count >= bl &&
|
|
(need_resched() ||
|
|
(!is_idle_task(current) && !rcu_is_callbacks_kthread())))
|
|
break;
|
|
}
|
|
|
|
local_irq_save(flags);
|
|
trace_rcu_batch_end(rsp->name, count, !!list, need_resched(),
|
|
is_idle_task(current),
|
|
rcu_is_callbacks_kthread());
|
|
|
|
/* Update count, and requeue any remaining callbacks. */
|
|
if (list != NULL) {
|
|
*tail = rdp->nxtlist;
|
|
rdp->nxtlist = list;
|
|
for (i = 0; i < RCU_NEXT_SIZE; i++)
|
|
if (&rdp->nxtlist == rdp->nxttail[i])
|
|
rdp->nxttail[i] = tail;
|
|
else
|
|
break;
|
|
}
|
|
smp_mb(); /* List handling before counting for rcu_barrier(). */
|
|
rdp->qlen_lazy -= count_lazy;
|
|
rdp->qlen -= count;
|
|
rdp->n_cbs_invoked += count;
|
|
|
|
/* Reinstate batch limit if we have worked down the excess. */
|
|
if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark)
|
|
rdp->blimit = blimit;
|
|
|
|
/* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */
|
|
if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) {
|
|
rdp->qlen_last_fqs_check = 0;
|
|
rdp->n_force_qs_snap = rsp->n_force_qs;
|
|
} else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark)
|
|
rdp->qlen_last_fqs_check = rdp->qlen;
|
|
|
|
local_irq_restore(flags);
|
|
|
|
/* Re-invoke RCU core processing if there are callbacks remaining. */
|
|
if (cpu_has_callbacks_ready_to_invoke(rdp))
|
|
invoke_rcu_core();
|
|
}
|
|
|
|
/*
|
|
* Check to see if this CPU is in a non-context-switch quiescent state
|
|
* (user mode or idle loop for rcu, non-softirq execution for rcu_bh).
|
|
* Also schedule RCU core processing.
|
|
*
|
|
* This function must be called from hardirq context. It is normally
|
|
* invoked from the scheduling-clock interrupt. If rcu_pending returns
|
|
* false, there is no point in invoking rcu_check_callbacks().
|
|
*/
|
|
void rcu_check_callbacks(int cpu, int user)
|
|
{
|
|
trace_rcu_utilization("Start scheduler-tick");
|
|
increment_cpu_stall_ticks();
|
|
if (user || rcu_is_cpu_rrupt_from_idle()) {
|
|
|
|
/*
|
|
* Get here if this CPU took its interrupt from user
|
|
* mode or from the idle loop, and if this is not a
|
|
* nested interrupt. In this case, the CPU is in
|
|
* a quiescent state, so note it.
|
|
*
|
|
* No memory barrier is required here because both
|
|
* rcu_sched_qs() and rcu_bh_qs() reference only CPU-local
|
|
* variables that other CPUs neither access nor modify,
|
|
* at least not while the corresponding CPU is online.
|
|
*/
|
|
|
|
rcu_sched_qs(cpu);
|
|
rcu_bh_qs(cpu);
|
|
|
|
} else if (!in_softirq()) {
|
|
|
|
/*
|
|
* Get here if this CPU did not take its interrupt from
|
|
* softirq, in other words, if it is not interrupting
|
|
* a rcu_bh read-side critical section. This is an _bh
|
|
* critical section, so note it.
|
|
*/
|
|
|
|
rcu_bh_qs(cpu);
|
|
}
|
|
rcu_preempt_check_callbacks(cpu);
|
|
if (rcu_pending(cpu))
|
|
invoke_rcu_core();
|
|
trace_rcu_utilization("End scheduler-tick");
|
|
}
|
|
|
|
/*
|
|
* Scan the leaf rcu_node structures, processing dyntick state for any that
|
|
* have not yet encountered a quiescent state, using the function specified.
|
|
* Also initiate boosting for any threads blocked on the root rcu_node.
|
|
*
|
|
* The caller must have suppressed start of new grace periods.
|
|
*/
|
|
static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *))
|
|
{
|
|
unsigned long bit;
|
|
int cpu;
|
|
unsigned long flags;
|
|
unsigned long mask;
|
|
struct rcu_node *rnp;
|
|
|
|
rcu_for_each_leaf_node(rsp, rnp) {
|
|
mask = 0;
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
if (!rcu_gp_in_progress(rsp)) {
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
return;
|
|
}
|
|
if (rnp->qsmask == 0) {
|
|
rcu_initiate_boost(rnp, flags); /* releases rnp->lock */
|
|
continue;
|
|
}
|
|
cpu = rnp->grplo;
|
|
bit = 1;
|
|
for (; cpu <= rnp->grphi; cpu++, bit <<= 1) {
|
|
if ((rnp->qsmask & bit) != 0 &&
|
|
f(per_cpu_ptr(rsp->rda, cpu)))
|
|
mask |= bit;
|
|
}
|
|
if (mask != 0) {
|
|
|
|
/* rcu_report_qs_rnp() releases rnp->lock. */
|
|
rcu_report_qs_rnp(mask, rsp, rnp, flags);
|
|
continue;
|
|
}
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
}
|
|
rnp = rcu_get_root(rsp);
|
|
if (rnp->qsmask == 0) {
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Force quiescent states on reluctant CPUs, and also detect which
|
|
* CPUs are in dyntick-idle mode.
|
|
*/
|
|
static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
|
|
{
|
|
unsigned long flags;
|
|
struct rcu_node *rnp = rcu_get_root(rsp);
|
|
|
|
trace_rcu_utilization("Start fqs");
|
|
if (!rcu_gp_in_progress(rsp)) {
|
|
trace_rcu_utilization("End fqs");
|
|
return; /* No grace period in progress, nothing to force. */
|
|
}
|
|
if (!raw_spin_trylock_irqsave(&rsp->fqslock, flags)) {
|
|
rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */
|
|
trace_rcu_utilization("End fqs");
|
|
return; /* Someone else is already on the job. */
|
|
}
|
|
if (relaxed && ULONG_CMP_GE(rsp->jiffies_force_qs, jiffies))
|
|
goto unlock_fqs_ret; /* no emergency and done recently. */
|
|
rsp->n_force_qs++;
|
|
raw_spin_lock(&rnp->lock); /* irqs already disabled */
|
|
rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
|
|
if(!rcu_gp_in_progress(rsp)) {
|
|
rsp->n_force_qs_ngp++;
|
|
raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
|
|
goto unlock_fqs_ret; /* no GP in progress, time updated. */
|
|
}
|
|
rsp->fqs_active = 1;
|
|
switch (rsp->fqs_state) {
|
|
case RCU_GP_IDLE:
|
|
case RCU_GP_INIT:
|
|
|
|
break; /* grace period idle or initializing, ignore. */
|
|
|
|
case RCU_SAVE_DYNTICK:
|
|
if (RCU_SIGNAL_INIT != RCU_SAVE_DYNTICK)
|
|
break; /* So gcc recognizes the dead code. */
|
|
|
|
raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
|
|
|
|
/* Record dyntick-idle state. */
|
|
force_qs_rnp(rsp, dyntick_save_progress_counter);
|
|
raw_spin_lock(&rnp->lock); /* irqs already disabled */
|
|
if (rcu_gp_in_progress(rsp))
|
|
rsp->fqs_state = RCU_FORCE_QS;
|
|
break;
|
|
|
|
case RCU_FORCE_QS:
|
|
|
|
/* Check dyntick-idle state, send IPI to laggarts. */
|
|
raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
|
|
force_qs_rnp(rsp, rcu_implicit_dynticks_qs);
|
|
|
|
/* Leave state in case more forcing is required. */
|
|
|
|
raw_spin_lock(&rnp->lock); /* irqs already disabled */
|
|
break;
|
|
}
|
|
rsp->fqs_active = 0;
|
|
if (rsp->fqs_need_gp) {
|
|
raw_spin_unlock(&rsp->fqslock); /* irqs remain disabled */
|
|
rsp->fqs_need_gp = 0;
|
|
rcu_start_gp(rsp, flags); /* releases rnp->lock */
|
|
trace_rcu_utilization("End fqs");
|
|
return;
|
|
}
|
|
raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
|
|
unlock_fqs_ret:
|
|
raw_spin_unlock_irqrestore(&rsp->fqslock, flags);
|
|
trace_rcu_utilization("End fqs");
|
|
}
|
|
|
|
/*
|
|
* This does the RCU core processing work for the specified rcu_state
|
|
* and rcu_data structures. This may be called only from the CPU to
|
|
* whom the rdp belongs.
|
|
*/
|
|
static void
|
|
__rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
|
|
{
|
|
unsigned long flags;
|
|
|
|
WARN_ON_ONCE(rdp->beenonline == 0);
|
|
|
|
/*
|
|
* If an RCU GP has gone long enough, go check for dyntick
|
|
* idle CPUs and, if needed, send resched IPIs.
|
|
*/
|
|
if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies))
|
|
force_quiescent_state(rsp, 1);
|
|
|
|
/*
|
|
* Advance callbacks in response to end of earlier grace
|
|
* period that some other CPU ended.
|
|
*/
|
|
rcu_process_gp_end(rsp, rdp);
|
|
|
|
/* Update RCU state based on any recent quiescent states. */
|
|
rcu_check_quiescent_state(rsp, rdp);
|
|
|
|
/* Does this CPU require a not-yet-started grace period? */
|
|
if (cpu_needs_another_gp(rsp, rdp)) {
|
|
raw_spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags);
|
|
rcu_start_gp(rsp, flags); /* releases above lock */
|
|
}
|
|
|
|
/* If there are callbacks ready, invoke them. */
|
|
if (cpu_has_callbacks_ready_to_invoke(rdp))
|
|
invoke_rcu_callbacks(rsp, rdp);
|
|
}
|
|
|
|
/*
|
|
* Do RCU core processing for the current CPU.
|
|
*/
|
|
static void rcu_process_callbacks(struct softirq_action *unused)
|
|
{
|
|
trace_rcu_utilization("Start RCU core");
|
|
__rcu_process_callbacks(&rcu_sched_state,
|
|
&__get_cpu_var(rcu_sched_data));
|
|
__rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data));
|
|
rcu_preempt_process_callbacks();
|
|
trace_rcu_utilization("End RCU core");
|
|
}
|
|
|
|
/*
|
|
* Schedule RCU callback invocation. If the specified type of RCU
|
|
* does not support RCU priority boosting, just do a direct call,
|
|
* otherwise wake up the per-CPU kernel kthread. Note that because we
|
|
* are running on the current CPU with interrupts disabled, the
|
|
* rcu_cpu_kthread_task cannot disappear out from under us.
|
|
*/
|
|
static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
|
|
{
|
|
if (unlikely(!ACCESS_ONCE(rcu_scheduler_fully_active)))
|
|
return;
|
|
if (likely(!rsp->boost)) {
|
|
rcu_do_batch(rsp, rdp);
|
|
return;
|
|
}
|
|
invoke_rcu_callbacks_kthread();
|
|
}
|
|
|
|
static void invoke_rcu_core(void)
|
|
{
|
|
raise_softirq(RCU_SOFTIRQ);
|
|
}
|
|
|
|
static void
|
|
__call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
|
|
struct rcu_state *rsp, bool lazy)
|
|
{
|
|
unsigned long flags;
|
|
struct rcu_data *rdp;
|
|
|
|
WARN_ON_ONCE((unsigned long)head & 0x3); /* Misaligned rcu_head! */
|
|
debug_rcu_head_queue(head);
|
|
head->func = func;
|
|
head->next = NULL;
|
|
|
|
smp_mb(); /* Ensure RCU update seen before callback registry. */
|
|
|
|
/*
|
|
* Opportunistically note grace-period endings and beginnings.
|
|
* Note that we might see a beginning right after we see an
|
|
* end, but never vice versa, since this CPU has to pass through
|
|
* a quiescent state betweentimes.
|
|
*/
|
|
local_irq_save(flags);
|
|
rdp = this_cpu_ptr(rsp->rda);
|
|
|
|
/* Add the callback to our list. */
|
|
rdp->qlen++;
|
|
if (lazy)
|
|
rdp->qlen_lazy++;
|
|
else
|
|
rcu_idle_count_callbacks_posted();
|
|
smp_mb(); /* Count before adding callback for rcu_barrier(). */
|
|
*rdp->nxttail[RCU_NEXT_TAIL] = head;
|
|
rdp->nxttail[RCU_NEXT_TAIL] = &head->next;
|
|
|
|
if (__is_kfree_rcu_offset((unsigned long)func))
|
|
trace_rcu_kfree_callback(rsp->name, head, (unsigned long)func,
|
|
rdp->qlen_lazy, rdp->qlen);
|
|
else
|
|
trace_rcu_callback(rsp->name, head, rdp->qlen_lazy, rdp->qlen);
|
|
|
|
/* If interrupts were disabled, don't dive into RCU core. */
|
|
if (irqs_disabled_flags(flags)) {
|
|
local_irq_restore(flags);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Force the grace period if too many callbacks or too long waiting.
|
|
* Enforce hysteresis, and don't invoke force_quiescent_state()
|
|
* if some other CPU has recently done so. Also, don't bother
|
|
* invoking force_quiescent_state() if the newly enqueued callback
|
|
* is the only one waiting for a grace period to complete.
|
|
*/
|
|
if (unlikely(rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) {
|
|
|
|
/* Are we ignoring a completed grace period? */
|
|
rcu_process_gp_end(rsp, rdp);
|
|
check_for_new_grace_period(rsp, rdp);
|
|
|
|
/* Start a new grace period if one not already started. */
|
|
if (!rcu_gp_in_progress(rsp)) {
|
|
unsigned long nestflag;
|
|
struct rcu_node *rnp_root = rcu_get_root(rsp);
|
|
|
|
raw_spin_lock_irqsave(&rnp_root->lock, nestflag);
|
|
rcu_start_gp(rsp, nestflag); /* rlses rnp_root->lock */
|
|
} else {
|
|
/* Give the grace period a kick. */
|
|
rdp->blimit = LONG_MAX;
|
|
if (rsp->n_force_qs == rdp->n_force_qs_snap &&
|
|
*rdp->nxttail[RCU_DONE_TAIL] != head)
|
|
force_quiescent_state(rsp, 0);
|
|
rdp->n_force_qs_snap = rsp->n_force_qs;
|
|
rdp->qlen_last_fqs_check = rdp->qlen;
|
|
}
|
|
} else if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies))
|
|
force_quiescent_state(rsp, 1);
|
|
local_irq_restore(flags);
|
|
}
|
|
|
|
/*
|
|
* Queue an RCU-sched callback for invocation after a grace period.
|
|
*/
|
|
void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
|
|
{
|
|
__call_rcu(head, func, &rcu_sched_state, 0);
|
|
}
|
|
EXPORT_SYMBOL_GPL(call_rcu_sched);
|
|
|
|
/*
|
|
* Queue an RCU callback for invocation after a quicker grace period.
|
|
*/
|
|
void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
|
|
{
|
|
__call_rcu(head, func, &rcu_bh_state, 0);
|
|
}
|
|
EXPORT_SYMBOL_GPL(call_rcu_bh);
|
|
|
|
/*
|
|
* Because a context switch is a grace period for RCU-sched and RCU-bh,
|
|
* any blocking grace-period wait automatically implies a grace period
|
|
* if there is only one CPU online at any point time during execution
|
|
* of either synchronize_sched() or synchronize_rcu_bh(). It is OK to
|
|
* occasionally incorrectly indicate that there are multiple CPUs online
|
|
* when there was in fact only one the whole time, as this just adds
|
|
* some overhead: RCU still operates correctly.
|
|
*
|
|
* Of course, sampling num_online_cpus() with preemption enabled can
|
|
* give erroneous results if there are concurrent CPU-hotplug operations.
|
|
* For example, given a demonic sequence of preemptions in num_online_cpus()
|
|
* and CPU-hotplug operations, there could be two or more CPUs online at
|
|
* all times, but num_online_cpus() might well return one (or even zero).
|
|
*
|
|
* However, all such demonic sequences require at least one CPU-offline
|
|
* operation. Furthermore, rcu_blocking_is_gp() giving the wrong answer
|
|
* is only a problem if there is an RCU read-side critical section executing
|
|
* throughout. But RCU-sched and RCU-bh read-side critical sections
|
|
* disable either preemption or bh, which prevents a CPU from going offline.
|
|
* Therefore, the only way that rcu_blocking_is_gp() can incorrectly return
|
|
* that there is only one CPU when in fact there was more than one throughout
|
|
* is when there were no RCU readers in the system. If there are no
|
|
* RCU readers, the grace period by definition can be of zero length,
|
|
* regardless of the number of online CPUs.
|
|
*/
|
|
static inline int rcu_blocking_is_gp(void)
|
|
{
|
|
might_sleep(); /* Check for RCU read-side critical section. */
|
|
return num_online_cpus() <= 1;
|
|
}
|
|
|
|
/**
|
|
* synchronize_sched - wait until an rcu-sched grace period has elapsed.
|
|
*
|
|
* Control will return to the caller some time after a full rcu-sched
|
|
* grace period has elapsed, in other words after all currently executing
|
|
* rcu-sched read-side critical sections have completed. These read-side
|
|
* critical sections are delimited by rcu_read_lock_sched() and
|
|
* rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(),
|
|
* local_irq_disable(), and so on may be used in place of
|
|
* rcu_read_lock_sched().
|
|
*
|
|
* This means that all preempt_disable code sequences, including NMI and
|
|
* hardware-interrupt handlers, in progress on entry will have completed
|
|
* before this primitive returns. However, this does not guarantee that
|
|
* softirq handlers will have completed, since in some kernels, these
|
|
* handlers can run in process context, and can block.
|
|
*
|
|
* This primitive provides the guarantees made by the (now removed)
|
|
* synchronize_kernel() API. In contrast, synchronize_rcu() only
|
|
* guarantees that rcu_read_lock() sections will have completed.
|
|
* In "classic RCU", these two guarantees happen to be one and
|
|
* the same, but can differ in realtime RCU implementations.
|
|
*/
|
|
void synchronize_sched(void)
|
|
{
|
|
rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
|
|
!lock_is_held(&rcu_lock_map) &&
|
|
!lock_is_held(&rcu_sched_lock_map),
|
|
"Illegal synchronize_sched() in RCU-sched read-side critical section");
|
|
if (rcu_blocking_is_gp())
|
|
return;
|
|
wait_rcu_gp(call_rcu_sched);
|
|
}
|
|
EXPORT_SYMBOL_GPL(synchronize_sched);
|
|
|
|
/**
|
|
* synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed.
|
|
*
|
|
* Control will return to the caller some time after a full rcu_bh grace
|
|
* period has elapsed, in other words after all currently executing rcu_bh
|
|
* read-side critical sections have completed. RCU read-side critical
|
|
* sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(),
|
|
* and may be nested.
|
|
*/
|
|
void synchronize_rcu_bh(void)
|
|
{
|
|
rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
|
|
!lock_is_held(&rcu_lock_map) &&
|
|
!lock_is_held(&rcu_sched_lock_map),
|
|
"Illegal synchronize_rcu_bh() in RCU-bh read-side critical section");
|
|
if (rcu_blocking_is_gp())
|
|
return;
|
|
wait_rcu_gp(call_rcu_bh);
|
|
}
|
|
EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
|
|
|
|
static atomic_t sync_sched_expedited_started = ATOMIC_INIT(0);
|
|
static atomic_t sync_sched_expedited_done = ATOMIC_INIT(0);
|
|
|
|
static int synchronize_sched_expedited_cpu_stop(void *data)
|
|
{
|
|
/*
|
|
* There must be a full memory barrier on each affected CPU
|
|
* between the time that try_stop_cpus() is called and the
|
|
* time that it returns.
|
|
*
|
|
* In the current initial implementation of cpu_stop, the
|
|
* above condition is already met when the control reaches
|
|
* this point and the following smp_mb() is not strictly
|
|
* necessary. Do smp_mb() anyway for documentation and
|
|
* robustness against future implementation changes.
|
|
*/
|
|
smp_mb(); /* See above comment block. */
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* synchronize_sched_expedited - Brute-force RCU-sched grace period
|
|
*
|
|
* Wait for an RCU-sched grace period to elapse, but use a "big hammer"
|
|
* approach to force the grace period to end quickly. This consumes
|
|
* significant time on all CPUs and is unfriendly to real-time workloads,
|
|
* so is thus not recommended for any sort of common-case code. In fact,
|
|
* if you are using synchronize_sched_expedited() in a loop, please
|
|
* restructure your code to batch your updates, and then use a single
|
|
* synchronize_sched() instead.
|
|
*
|
|
* Note that it is illegal to call this function while holding any lock
|
|
* that is acquired by a CPU-hotplug notifier. And yes, it is also illegal
|
|
* to call this function from a CPU-hotplug notifier. Failing to observe
|
|
* these restriction will result in deadlock.
|
|
*
|
|
* This implementation can be thought of as an application of ticket
|
|
* locking to RCU, with sync_sched_expedited_started and
|
|
* sync_sched_expedited_done taking on the roles of the halves
|
|
* of the ticket-lock word. Each task atomically increments
|
|
* sync_sched_expedited_started upon entry, snapshotting the old value,
|
|
* then attempts to stop all the CPUs. If this succeeds, then each
|
|
* CPU will have executed a context switch, resulting in an RCU-sched
|
|
* grace period. We are then done, so we use atomic_cmpxchg() to
|
|
* update sync_sched_expedited_done to match our snapshot -- but
|
|
* only if someone else has not already advanced past our snapshot.
|
|
*
|
|
* On the other hand, if try_stop_cpus() fails, we check the value
|
|
* of sync_sched_expedited_done. If it has advanced past our
|
|
* initial snapshot, then someone else must have forced a grace period
|
|
* some time after we took our snapshot. In this case, our work is
|
|
* done for us, and we can simply return. Otherwise, we try again,
|
|
* but keep our initial snapshot for purposes of checking for someone
|
|
* doing our work for us.
|
|
*
|
|
* If we fail too many times in a row, we fall back to synchronize_sched().
|
|
*/
|
|
void synchronize_sched_expedited(void)
|
|
{
|
|
int firstsnap, s, snap, trycount = 0;
|
|
|
|
/* Note that atomic_inc_return() implies full memory barrier. */
|
|
firstsnap = snap = atomic_inc_return(&sync_sched_expedited_started);
|
|
get_online_cpus();
|
|
WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id()));
|
|
|
|
/*
|
|
* Each pass through the following loop attempts to force a
|
|
* context switch on each CPU.
|
|
*/
|
|
while (try_stop_cpus(cpu_online_mask,
|
|
synchronize_sched_expedited_cpu_stop,
|
|
NULL) == -EAGAIN) {
|
|
put_online_cpus();
|
|
|
|
/* No joy, try again later. Or just synchronize_sched(). */
|
|
if (trycount++ < 10)
|
|
udelay(trycount * num_online_cpus());
|
|
else {
|
|
synchronize_sched();
|
|
return;
|
|
}
|
|
|
|
/* Check to see if someone else did our work for us. */
|
|
s = atomic_read(&sync_sched_expedited_done);
|
|
if (UINT_CMP_GE((unsigned)s, (unsigned)firstsnap)) {
|
|
smp_mb(); /* ensure test happens before caller kfree */
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Refetching sync_sched_expedited_started allows later
|
|
* callers to piggyback on our grace period. We subtract
|
|
* 1 to get the same token that the last incrementer got.
|
|
* We retry after they started, so our grace period works
|
|
* for them, and they started after our first try, so their
|
|
* grace period works for us.
|
|
*/
|
|
get_online_cpus();
|
|
snap = atomic_read(&sync_sched_expedited_started);
|
|
smp_mb(); /* ensure read is before try_stop_cpus(). */
|
|
}
|
|
|
|
/*
|
|
* Everyone up to our most recent fetch is covered by our grace
|
|
* period. Update the counter, but only if our work is still
|
|
* relevant -- which it won't be if someone who started later
|
|
* than we did beat us to the punch.
|
|
*/
|
|
do {
|
|
s = atomic_read(&sync_sched_expedited_done);
|
|
if (UINT_CMP_GE((unsigned)s, (unsigned)snap)) {
|
|
smp_mb(); /* ensure test happens before caller kfree */
|
|
break;
|
|
}
|
|
} while (atomic_cmpxchg(&sync_sched_expedited_done, s, snap) != s);
|
|
|
|
put_online_cpus();
|
|
}
|
|
EXPORT_SYMBOL_GPL(synchronize_sched_expedited);
|
|
|
|
/*
|
|
* Check to see if there is any immediate RCU-related work to be done
|
|
* by the current CPU, for the specified type of RCU, returning 1 if so.
|
|
* The checks are in order of increasing expense: checks that can be
|
|
* carried out against CPU-local state are performed first. However,
|
|
* we must check for CPU stalls first, else we might not get a chance.
|
|
*/
|
|
static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
|
|
{
|
|
struct rcu_node *rnp = rdp->mynode;
|
|
|
|
rdp->n_rcu_pending++;
|
|
|
|
/* Check for CPU stalls, if enabled. */
|
|
check_cpu_stall(rsp, rdp);
|
|
|
|
/* Is the RCU core waiting for a quiescent state from this CPU? */
|
|
if (rcu_scheduler_fully_active &&
|
|
rdp->qs_pending && !rdp->passed_quiesce) {
|
|
|
|
/*
|
|
* If force_quiescent_state() coming soon and this CPU
|
|
* needs a quiescent state, and this is either RCU-sched
|
|
* or RCU-bh, force a local reschedule.
|
|
*/
|
|
rdp->n_rp_qs_pending++;
|
|
if (!rdp->preemptible &&
|
|
ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs) - 1,
|
|
jiffies))
|
|
set_need_resched();
|
|
} else if (rdp->qs_pending && rdp->passed_quiesce) {
|
|
rdp->n_rp_report_qs++;
|
|
return 1;
|
|
}
|
|
|
|
/* Does this CPU have callbacks ready to invoke? */
|
|
if (cpu_has_callbacks_ready_to_invoke(rdp)) {
|
|
rdp->n_rp_cb_ready++;
|
|
return 1;
|
|
}
|
|
|
|
/* Has RCU gone idle with this CPU needing another grace period? */
|
|
if (cpu_needs_another_gp(rsp, rdp)) {
|
|
rdp->n_rp_cpu_needs_gp++;
|
|
return 1;
|
|
}
|
|
|
|
/* Has another RCU grace period completed? */
|
|
if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */
|
|
rdp->n_rp_gp_completed++;
|
|
return 1;
|
|
}
|
|
|
|
/* Has a new RCU grace period started? */
|
|
if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */
|
|
rdp->n_rp_gp_started++;
|
|
return 1;
|
|
}
|
|
|
|
/* Has an RCU GP gone long enough to send resched IPIs &c? */
|
|
if (rcu_gp_in_progress(rsp) &&
|
|
ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) {
|
|
rdp->n_rp_need_fqs++;
|
|
return 1;
|
|
}
|
|
|
|
/* nothing to do */
|
|
rdp->n_rp_need_nothing++;
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Check to see if there is any immediate RCU-related work to be done
|
|
* by the current CPU, returning 1 if so. This function is part of the
|
|
* RCU implementation; it is -not- an exported member of the RCU API.
|
|
*/
|
|
static int rcu_pending(int cpu)
|
|
{
|
|
return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) ||
|
|
__rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)) ||
|
|
rcu_preempt_pending(cpu);
|
|
}
|
|
|
|
/*
|
|
* Check to see if any future RCU-related work will need to be done
|
|
* by the current CPU, even if none need be done immediately, returning
|
|
* 1 if so.
|
|
*/
|
|
static int rcu_cpu_has_callbacks(int cpu)
|
|
{
|
|
/* RCU callbacks either ready or pending? */
|
|
return per_cpu(rcu_sched_data, cpu).nxtlist ||
|
|
per_cpu(rcu_bh_data, cpu).nxtlist ||
|
|
rcu_preempt_cpu_has_callbacks(cpu);
|
|
}
|
|
|
|
/*
|
|
* RCU callback function for _rcu_barrier(). If we are last, wake
|
|
* up the task executing _rcu_barrier().
|
|
*/
|
|
static void rcu_barrier_callback(struct rcu_head *notused)
|
|
{
|
|
if (atomic_dec_and_test(&rcu_barrier_cpu_count))
|
|
complete(&rcu_barrier_completion);
|
|
}
|
|
|
|
/*
|
|
* Called with preemption disabled, and from cross-cpu IRQ context.
|
|
*/
|
|
static void rcu_barrier_func(void *type)
|
|
{
|
|
int cpu = smp_processor_id();
|
|
struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu);
|
|
void (*call_rcu_func)(struct rcu_head *head,
|
|
void (*func)(struct rcu_head *head));
|
|
|
|
atomic_inc(&rcu_barrier_cpu_count);
|
|
call_rcu_func = type;
|
|
call_rcu_func(head, rcu_barrier_callback);
|
|
}
|
|
|
|
/*
|
|
* Orchestrate the specified type of RCU barrier, waiting for all
|
|
* RCU callbacks of the specified type to complete.
|
|
*/
|
|
static void _rcu_barrier(struct rcu_state *rsp,
|
|
void (*call_rcu_func)(struct rcu_head *head,
|
|
void (*func)(struct rcu_head *head)))
|
|
{
|
|
int cpu;
|
|
unsigned long flags;
|
|
struct rcu_data *rdp;
|
|
struct rcu_head rh;
|
|
|
|
init_rcu_head_on_stack(&rh);
|
|
|
|
/* Take mutex to serialize concurrent rcu_barrier() requests. */
|
|
mutex_lock(&rcu_barrier_mutex);
|
|
|
|
smp_mb(); /* Prevent any prior operations from leaking in. */
|
|
|
|
/*
|
|
* Initialize the count to one rather than to zero in order to
|
|
* avoid a too-soon return to zero in case of a short grace period
|
|
* (or preemption of this task). Also flag this task as doing
|
|
* an rcu_barrier(). This will prevent anyone else from adopting
|
|
* orphaned callbacks, which could cause otherwise failure if a
|
|
* CPU went offline and quickly came back online. To see this,
|
|
* consider the following sequence of events:
|
|
*
|
|
* 1. We cause CPU 0 to post an rcu_barrier_callback() callback.
|
|
* 2. CPU 1 goes offline, orphaning its callbacks.
|
|
* 3. CPU 0 adopts CPU 1's orphaned callbacks.
|
|
* 4. CPU 1 comes back online.
|
|
* 5. We cause CPU 1 to post an rcu_barrier_callback() callback.
|
|
* 6. Both rcu_barrier_callback() callbacks are invoked, awakening
|
|
* us -- but before CPU 1's orphaned callbacks are invoked!!!
|
|
*/
|
|
init_completion(&rcu_barrier_completion);
|
|
atomic_set(&rcu_barrier_cpu_count, 1);
|
|
raw_spin_lock_irqsave(&rsp->onofflock, flags);
|
|
rsp->rcu_barrier_in_progress = current;
|
|
raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
|
|
|
|
/*
|
|
* Force every CPU with callbacks to register a new callback
|
|
* that will tell us when all the preceding callbacks have
|
|
* been invoked. If an offline CPU has callbacks, wait for
|
|
* it to either come back online or to finish orphaning those
|
|
* callbacks.
|
|
*/
|
|
for_each_possible_cpu(cpu) {
|
|
preempt_disable();
|
|
rdp = per_cpu_ptr(rsp->rda, cpu);
|
|
if (cpu_is_offline(cpu)) {
|
|
preempt_enable();
|
|
while (cpu_is_offline(cpu) && ACCESS_ONCE(rdp->qlen))
|
|
schedule_timeout_interruptible(1);
|
|
} else if (ACCESS_ONCE(rdp->qlen)) {
|
|
smp_call_function_single(cpu, rcu_barrier_func,
|
|
(void *)call_rcu_func, 1);
|
|
preempt_enable();
|
|
} else {
|
|
preempt_enable();
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Now that all online CPUs have rcu_barrier_callback() callbacks
|
|
* posted, we can adopt all of the orphaned callbacks and place
|
|
* an rcu_barrier_callback() callback after them. When that is done,
|
|
* we are guaranteed to have an rcu_barrier_callback() callback
|
|
* following every callback that could possibly have been
|
|
* registered before _rcu_barrier() was called.
|
|
*/
|
|
raw_spin_lock_irqsave(&rsp->onofflock, flags);
|
|
rcu_adopt_orphan_cbs(rsp);
|
|
rsp->rcu_barrier_in_progress = NULL;
|
|
raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
|
|
atomic_inc(&rcu_barrier_cpu_count);
|
|
smp_mb__after_atomic_inc(); /* Ensure atomic_inc() before callback. */
|
|
call_rcu_func(&rh, rcu_barrier_callback);
|
|
|
|
/*
|
|
* Now that we have an rcu_barrier_callback() callback on each
|
|
* CPU, and thus each counted, remove the initial count.
|
|
*/
|
|
if (atomic_dec_and_test(&rcu_barrier_cpu_count))
|
|
complete(&rcu_barrier_completion);
|
|
|
|
/* Wait for all rcu_barrier_callback() callbacks to be invoked. */
|
|
wait_for_completion(&rcu_barrier_completion);
|
|
|
|
/* Other rcu_barrier() invocations can now safely proceed. */
|
|
mutex_unlock(&rcu_barrier_mutex);
|
|
|
|
destroy_rcu_head_on_stack(&rh);
|
|
}
|
|
|
|
/**
|
|
* rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete.
|
|
*/
|
|
void rcu_barrier_bh(void)
|
|
{
|
|
_rcu_barrier(&rcu_bh_state, call_rcu_bh);
|
|
}
|
|
EXPORT_SYMBOL_GPL(rcu_barrier_bh);
|
|
|
|
/**
|
|
* rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks.
|
|
*/
|
|
void rcu_barrier_sched(void)
|
|
{
|
|
_rcu_barrier(&rcu_sched_state, call_rcu_sched);
|
|
}
|
|
EXPORT_SYMBOL_GPL(rcu_barrier_sched);
|
|
|
|
/*
|
|
* Do boot-time initialization of a CPU's per-CPU RCU data.
|
|
*/
|
|
static void __init
|
|
rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
|
|
{
|
|
unsigned long flags;
|
|
int i;
|
|
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
|
|
struct rcu_node *rnp = rcu_get_root(rsp);
|
|
|
|
/* Set up local state, ensuring consistent view of global state. */
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo);
|
|
rdp->nxtlist = NULL;
|
|
for (i = 0; i < RCU_NEXT_SIZE; i++)
|
|
rdp->nxttail[i] = &rdp->nxtlist;
|
|
rdp->qlen_lazy = 0;
|
|
rdp->qlen = 0;
|
|
rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
|
|
WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE);
|
|
WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1);
|
|
rdp->cpu = cpu;
|
|
rdp->rsp = rsp;
|
|
raw_spin_unlock_irqrestore(&rnp->lock, flags);
|
|
}
|
|
|
|
/*
|
|
* Initialize a CPU's per-CPU RCU data. Note that only one online or
|
|
* offline event can be happening at a given time. Note also that we
|
|
* can accept some slop in the rsp->completed access due to the fact
|
|
* that this CPU cannot possibly have any RCU callbacks in flight yet.
|
|
*/
|
|
static void __cpuinit
|
|
rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible)
|
|
{
|
|
unsigned long flags;
|
|
unsigned long mask;
|
|
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
|
|
struct rcu_node *rnp = rcu_get_root(rsp);
|
|
|
|
/* Set up local state, ensuring consistent view of global state. */
|
|
raw_spin_lock_irqsave(&rnp->lock, flags);
|
|
rdp->beenonline = 1; /* We have now been online. */
|
|
rdp->preemptible = preemptible;
|
|
rdp->qlen_last_fqs_check = 0;
|
|
rdp->n_force_qs_snap = rsp->n_force_qs;
|
|
rdp->blimit = blimit;
|
|
rdp->dynticks->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
|
|
atomic_set(&rdp->dynticks->dynticks,
|
|
(atomic_read(&rdp->dynticks->dynticks) & ~0x1) + 1);
|
|
rcu_prepare_for_idle_init(cpu);
|
|
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
|
|
|
|
/*
|
|
* A new grace period might start here. If so, we won't be part
|
|
* of it, but that is OK, as we are currently in a quiescent state.
|
|
*/
|
|
|
|
/* Exclude any attempts to start a new GP on large systems. */
|
|
raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */
|
|
|
|
/* Add CPU to rcu_node bitmasks. */
|
|
rnp = rdp->mynode;
|
|
mask = rdp->grpmask;
|
|
do {
|
|
/* Exclude any attempts to start a new GP on small systems. */
|
|
raw_spin_lock(&rnp->lock); /* irqs already disabled. */
|
|
rnp->qsmaskinit |= mask;
|
|
mask = rnp->grpmask;
|
|
if (rnp == rdp->mynode) {
|
|
/*
|
|
* If there is a grace period in progress, we will
|
|
* set up to wait for it next time we run the
|
|
* RCU core code.
|
|
*/
|
|
rdp->gpnum = rnp->completed;
|
|
rdp->completed = rnp->completed;
|
|
rdp->passed_quiesce = 0;
|
|
rdp->qs_pending = 0;
|
|
rdp->passed_quiesce_gpnum = rnp->gpnum - 1;
|
|
trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuonl");
|
|
}
|
|
raw_spin_unlock(&rnp->lock); /* irqs already disabled. */
|
|
rnp = rnp->parent;
|
|
} while (rnp != NULL && !(rnp->qsmaskinit & mask));
|
|
|
|
raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
|
|
}
|
|
|
|
static void __cpuinit rcu_prepare_cpu(int cpu)
|
|
{
|
|
rcu_init_percpu_data(cpu, &rcu_sched_state, 0);
|
|
rcu_init_percpu_data(cpu, &rcu_bh_state, 0);
|
|
rcu_preempt_init_percpu_data(cpu);
|
|
}
|
|
|
|
/*
|
|
* Handle CPU online/offline notification events.
|
|
*/
|
|
static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
|
|
unsigned long action, void *hcpu)
|
|
{
|
|
long cpu = (long)hcpu;
|
|
struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu);
|
|
struct rcu_node *rnp = rdp->mynode;
|
|
|
|
trace_rcu_utilization("Start CPU hotplug");
|
|
switch (action) {
|
|
case CPU_UP_PREPARE:
|
|
case CPU_UP_PREPARE_FROZEN:
|
|
rcu_prepare_cpu(cpu);
|
|
rcu_prepare_kthreads(cpu);
|
|
break;
|
|
case CPU_ONLINE:
|
|
case CPU_DOWN_FAILED:
|
|
rcu_node_kthread_setaffinity(rnp, -1);
|
|
rcu_cpu_kthread_setrt(cpu, 1);
|
|
break;
|
|
case CPU_DOWN_PREPARE:
|
|
rcu_node_kthread_setaffinity(rnp, cpu);
|
|
rcu_cpu_kthread_setrt(cpu, 0);
|
|
break;
|
|
case CPU_DYING:
|
|
case CPU_DYING_FROZEN:
|
|
/*
|
|
* The whole machine is "stopped" except this CPU, so we can
|
|
* touch any data without introducing corruption. We send the
|
|
* dying CPU's callbacks to an arbitrarily chosen online CPU.
|
|
*/
|
|
rcu_cleanup_dying_cpu(&rcu_bh_state);
|
|
rcu_cleanup_dying_cpu(&rcu_sched_state);
|
|
rcu_preempt_cleanup_dying_cpu();
|
|
rcu_cleanup_after_idle(cpu);
|
|
break;
|
|
case CPU_DEAD:
|
|
case CPU_DEAD_FROZEN:
|
|
case CPU_UP_CANCELED:
|
|
case CPU_UP_CANCELED_FROZEN:
|
|
rcu_cleanup_dead_cpu(cpu, &rcu_bh_state);
|
|
rcu_cleanup_dead_cpu(cpu, &rcu_sched_state);
|
|
rcu_preempt_cleanup_dead_cpu(cpu);
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
trace_rcu_utilization("End CPU hotplug");
|
|
return NOTIFY_OK;
|
|
}
|
|
|
|
/*
|
|
* This function is invoked towards the end of the scheduler's initialization
|
|
* process. Before this is called, the idle task might contain
|
|
* RCU read-side critical sections (during which time, this idle
|
|
* task is booting the system). After this function is called, the
|
|
* idle tasks are prohibited from containing RCU read-side critical
|
|
* sections. This function also enables RCU lockdep checking.
|
|
*/
|
|
void rcu_scheduler_starting(void)
|
|
{
|
|
WARN_ON(num_online_cpus() != 1);
|
|
WARN_ON(nr_context_switches() > 0);
|
|
rcu_scheduler_active = 1;
|
|
}
|
|
|
|
/*
|
|
* Compute the per-level fanout, either using the exact fanout specified
|
|
* or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT.
|
|
*/
|
|
#ifdef CONFIG_RCU_FANOUT_EXACT
|
|
static void __init rcu_init_levelspread(struct rcu_state *rsp)
|
|
{
|
|
int i;
|
|
|
|
for (i = NUM_RCU_LVLS - 1; i > 0; i--)
|
|
rsp->levelspread[i] = CONFIG_RCU_FANOUT;
|
|
rsp->levelspread[0] = CONFIG_RCU_FANOUT_LEAF;
|
|
}
|
|
#else /* #ifdef CONFIG_RCU_FANOUT_EXACT */
|
|
static void __init rcu_init_levelspread(struct rcu_state *rsp)
|
|
{
|
|
int ccur;
|
|
int cprv;
|
|
int i;
|
|
|
|
cprv = NR_CPUS;
|
|
for (i = NUM_RCU_LVLS - 1; i >= 0; i--) {
|
|
ccur = rsp->levelcnt[i];
|
|
rsp->levelspread[i] = (cprv + ccur - 1) / ccur;
|
|
cprv = ccur;
|
|
}
|
|
}
|
|
#endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */
|
|
|
|
/*
|
|
* Helper function for rcu_init() that initializes one rcu_state structure.
|
|
*/
|
|
static void __init rcu_init_one(struct rcu_state *rsp,
|
|
struct rcu_data __percpu *rda)
|
|
{
|
|
static char *buf[] = { "rcu_node_level_0",
|
|
"rcu_node_level_1",
|
|
"rcu_node_level_2",
|
|
"rcu_node_level_3" }; /* Match MAX_RCU_LVLS */
|
|
int cpustride = 1;
|
|
int i;
|
|
int j;
|
|
struct rcu_node *rnp;
|
|
|
|
BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */
|
|
|
|
/* Initialize the level-tracking arrays. */
|
|
|
|
for (i = 1; i < NUM_RCU_LVLS; i++)
|
|
rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1];
|
|
rcu_init_levelspread(rsp);
|
|
|
|
/* Initialize the elements themselves, starting from the leaves. */
|
|
|
|
for (i = NUM_RCU_LVLS - 1; i >= 0; i--) {
|
|
cpustride *= rsp->levelspread[i];
|
|
rnp = rsp->level[i];
|
|
for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) {
|
|
raw_spin_lock_init(&rnp->lock);
|
|
lockdep_set_class_and_name(&rnp->lock,
|
|
&rcu_node_class[i], buf[i]);
|
|
rnp->gpnum = 0;
|
|
rnp->qsmask = 0;
|
|
rnp->qsmaskinit = 0;
|
|
rnp->grplo = j * cpustride;
|
|
rnp->grphi = (j + 1) * cpustride - 1;
|
|
if (rnp->grphi >= NR_CPUS)
|
|
rnp->grphi = NR_CPUS - 1;
|
|
if (i == 0) {
|
|
rnp->grpnum = 0;
|
|
rnp->grpmask = 0;
|
|
rnp->parent = NULL;
|
|
} else {
|
|
rnp->grpnum = j % rsp->levelspread[i - 1];
|
|
rnp->grpmask = 1UL << rnp->grpnum;
|
|
rnp->parent = rsp->level[i - 1] +
|
|
j / rsp->levelspread[i - 1];
|
|
}
|
|
rnp->level = i;
|
|
INIT_LIST_HEAD(&rnp->blkd_tasks);
|
|
}
|
|
}
|
|
|
|
rsp->rda = rda;
|
|
rnp = rsp->level[NUM_RCU_LVLS - 1];
|
|
for_each_possible_cpu(i) {
|
|
while (i > rnp->grphi)
|
|
rnp++;
|
|
per_cpu_ptr(rsp->rda, i)->mynode = rnp;
|
|
rcu_boot_init_percpu_data(i, rsp);
|
|
}
|
|
}
|
|
|
|
void __init rcu_init(void)
|
|
{
|
|
int cpu;
|
|
|
|
rcu_bootup_announce();
|
|
rcu_init_one(&rcu_sched_state, &rcu_sched_data);
|
|
rcu_init_one(&rcu_bh_state, &rcu_bh_data);
|
|
__rcu_init_preempt();
|
|
open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
|
|
|
|
/*
|
|
* We don't need protection against CPU-hotplug here because
|
|
* this is called early in boot, before either interrupts
|
|
* or the scheduler are operational.
|
|
*/
|
|
cpu_notifier(rcu_cpu_notify, 0);
|
|
for_each_online_cpu(cpu)
|
|
rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
|
|
check_cpu_stall_init();
|
|
}
|
|
|
|
#include "rcutree_plugin.h"
|