![Lai Jiangshan](/assets/img/avatar_default.png)
Impact: reduce memory footprint add __cpuinit to rcu_init_percpu_data(), and this function's text will be discarded after boot when !CONFIG_HOTPLUG_CPU. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
1533 lines
44 KiB
C
1533 lines
44 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 <asm/atomic.h>
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#include <linux/bitops.h>
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#include <linux/module.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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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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static struct lock_class_key rcu_lock_key;
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struct lockdep_map rcu_lock_map =
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STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key);
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EXPORT_SYMBOL_GPL(rcu_lock_map);
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#endif
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/* Data structures. */
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#define RCU_STATE_INITIALIZER(name) { \
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.level = { &name.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, /* == MAX_RCU_LVLS */ \
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}, \
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.signaled = RCU_SIGNAL_INIT, \
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.gpnum = -300, \
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.completed = -300, \
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.onofflock = __SPIN_LOCK_UNLOCKED(&name.onofflock), \
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.fqslock = __SPIN_LOCK_UNLOCKED(&name.fqslock), \
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.n_force_qs = 0, \
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.n_force_qs_ngp = 0, \
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}
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struct rcu_state rcu_state = RCU_STATE_INITIALIZER(rcu_state);
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DEFINE_PER_CPU(struct rcu_data, rcu_data);
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struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state);
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DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);
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#ifdef CONFIG_NO_HZ
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DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
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.dynticks_nesting = 1,
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.dynticks = 1,
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};
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#endif /* #ifdef CONFIG_NO_HZ */
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static int blimit = 10; /* Maximum callbacks per softirq. */
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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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static void force_quiescent_state(struct rcu_state *rsp, int relaxed);
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/*
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* Return the number of RCU batches processed thus far for debug & stats.
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*/
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long rcu_batches_completed(void)
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{
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return rcu_state.completed;
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}
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EXPORT_SYMBOL_GPL(rcu_batches_completed);
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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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* 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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/* ACCESS_ONCE() because we are accessing outside of lock. */
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return *rdp->nxttail[RCU_DONE_TAIL] &&
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ACCESS_ONCE(rsp->completed) == ACCESS_ONCE(rsp->gpnum);
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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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#ifdef CONFIG_SMP
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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, it is in a quiescent state. We can
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* trust its state not to change because interrupts are disabled.
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*/
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if (cpu_is_offline(rdp->cpu)) {
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rdp->offline_fqs++;
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return 1;
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}
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/* The CPU is online, so send it a reschedule IPI. */
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if (rdp->cpu != smp_processor_id())
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smp_send_reschedule(rdp->cpu);
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else
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set_need_resched();
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rdp->resched_ipi++;
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return 0;
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}
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#endif /* #ifdef CONFIG_SMP */
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#ifdef CONFIG_NO_HZ
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static DEFINE_RATELIMIT_STATE(rcu_rs, 10 * HZ, 5);
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/**
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* rcu_enter_nohz - inform RCU that current CPU is entering nohz
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*
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* Enter nohz 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 nohz mode, a possibility
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* handled by rcu_irq_enter() and rcu_irq_exit()).
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*/
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void rcu_enter_nohz(void)
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{
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unsigned long flags;
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struct rcu_dynticks *rdtp;
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smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
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local_irq_save(flags);
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rdtp = &__get_cpu_var(rcu_dynticks);
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rdtp->dynticks++;
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rdtp->dynticks_nesting--;
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WARN_ON_RATELIMIT(rdtp->dynticks & 0x1, &rcu_rs);
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local_irq_restore(flags);
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}
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/*
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* rcu_exit_nohz - inform RCU that current CPU is leaving nohz
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*
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* Exit nohz mode, in other words, -enter- the mode in which RCU
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* read-side critical sections normally occur.
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*/
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void rcu_exit_nohz(void)
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{
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unsigned long flags;
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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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rdtp->dynticks++;
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rdtp->dynticks_nesting++;
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WARN_ON_RATELIMIT(!(rdtp->dynticks & 0x1), &rcu_rs);
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local_irq_restore(flags);
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smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
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}
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/**
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* rcu_nmi_enter - inform RCU of entry to NMI context
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*
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* If the CPU was idle with dynamic ticks active, and there is no
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* irq handler running, this updates rdtp->dynticks_nmi to let the
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* RCU grace-period handling know that the CPU is active.
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*/
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void rcu_nmi_enter(void)
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{
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struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
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if (rdtp->dynticks & 0x1)
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return;
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rdtp->dynticks_nmi++;
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WARN_ON_RATELIMIT(!(rdtp->dynticks_nmi & 0x1), &rcu_rs);
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smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
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}
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/**
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* rcu_nmi_exit - inform RCU of exit from NMI context
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*
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* If the CPU was idle with dynamic ticks active, and there is no
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* irq handler running, this updates rdtp->dynticks_nmi to let the
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* RCU grace-period handling know that the CPU is no longer active.
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*/
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void rcu_nmi_exit(void)
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{
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struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
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if (rdtp->dynticks & 0x1)
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return;
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smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
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rdtp->dynticks_nmi++;
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WARN_ON_RATELIMIT(rdtp->dynticks_nmi & 0x1, &rcu_rs);
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}
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/**
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* rcu_irq_enter - inform RCU of entry to hard irq context
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*
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* If the CPU was idle with dynamic ticks active, this updates the
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* rdtp->dynticks to let the RCU handling know that the CPU is active.
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*/
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void rcu_irq_enter(void)
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{
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struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
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if (rdtp->dynticks_nesting++)
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return;
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rdtp->dynticks++;
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WARN_ON_RATELIMIT(!(rdtp->dynticks & 0x1), &rcu_rs);
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smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
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}
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/**
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* rcu_irq_exit - inform RCU of exit from hard irq context
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*
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* If the CPU was idle with dynamic ticks active, update the rdp->dynticks
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* to put let the RCU handling be aware that the CPU is going back to idle
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* with no ticks.
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*/
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void rcu_irq_exit(void)
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{
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struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
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if (--rdtp->dynticks_nesting)
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return;
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smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
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rdtp->dynticks++;
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WARN_ON_RATELIMIT(rdtp->dynticks & 0x1, &rcu_rs);
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/* If the interrupt queued a callback, get out of dyntick mode. */
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if (__get_cpu_var(rcu_data).nxtlist ||
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__get_cpu_var(rcu_bh_data).nxtlist)
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set_need_resched();
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}
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/*
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* Record the specified "completed" value, which is later used to validate
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* dynticks counter manipulations. Specify "rsp->completed - 1" to
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* unconditionally invalidate any future dynticks manipulations (which is
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* useful at the beginning of a grace period).
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*/
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static void dyntick_record_completed(struct rcu_state *rsp, long comp)
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{
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rsp->dynticks_completed = comp;
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}
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#ifdef CONFIG_SMP
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/*
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* Recall the previously recorded value of the completion for dynticks.
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*/
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static long dyntick_recall_completed(struct rcu_state *rsp)
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{
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return rsp->dynticks_completed;
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}
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/*
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* Snapshot the specified CPU's dynticks counter so that we can later
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* credit them with an implicit quiescent state. Return 1 if this CPU
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* is already in a quiescent state courtesy of dynticks idle mode.
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*/
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static int dyntick_save_progress_counter(struct rcu_data *rdp)
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{
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int ret;
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int snap;
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int snap_nmi;
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snap = rdp->dynticks->dynticks;
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snap_nmi = rdp->dynticks->dynticks_nmi;
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smp_mb(); /* Order sampling of snap with end of grace period. */
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rdp->dynticks_snap = snap;
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rdp->dynticks_nmi_snap = snap_nmi;
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ret = ((snap & 0x1) == 0) && ((snap_nmi & 0x1) == 0);
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if (ret)
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rdp->dynticks_fqs++;
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return ret;
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}
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/*
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* Return true if the specified CPU has passed through a quiescent
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* state by virtue of being in or having passed through an dynticks
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* idle state since the last call to dyntick_save_progress_counter()
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* for this same CPU.
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*/
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static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
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{
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long curr;
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long curr_nmi;
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long snap;
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long snap_nmi;
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curr = rdp->dynticks->dynticks;
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snap = rdp->dynticks_snap;
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curr_nmi = rdp->dynticks->dynticks_nmi;
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snap_nmi = rdp->dynticks_nmi_snap;
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smp_mb(); /* force ordering with cpu entering/leaving dynticks. */
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/*
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* If the CPU passed through or entered a dynticks idle phase with
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* no active irq/NMI handlers, then we can safely pretend that the CPU
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* already acknowledged the request to pass through a quiescent
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* state. Either way, that CPU cannot possibly be in an RCU
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* read-side critical section that started before the beginning
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* of the current RCU grace period.
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*/
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if ((curr != snap || (curr & 0x1) == 0) &&
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(curr_nmi != snap_nmi || (curr_nmi & 0x1) == 0)) {
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rdp->dynticks_fqs++;
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return 1;
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}
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/* Go check for the CPU being offline. */
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return rcu_implicit_offline_qs(rdp);
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}
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#endif /* #ifdef CONFIG_SMP */
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#else /* #ifdef CONFIG_NO_HZ */
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static void dyntick_record_completed(struct rcu_state *rsp, long comp)
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{
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}
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#ifdef CONFIG_SMP
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/*
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* If there are no dynticks, then the only way that a CPU can passively
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* be in a quiescent state is to be offline. Unlike dynticks idle, which
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* is a point in time during the prior (already finished) grace period,
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* an offline CPU is always in a quiescent state, and thus can be
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* unconditionally applied. So just return the current value of completed.
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*/
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static long dyntick_recall_completed(struct rcu_state *rsp)
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{
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return rsp->completed;
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}
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static int dyntick_save_progress_counter(struct rcu_data *rdp)
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{
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return 0;
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}
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static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
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{
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return rcu_implicit_offline_qs(rdp);
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}
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#endif /* #ifdef CONFIG_SMP */
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#endif /* #else #ifdef CONFIG_NO_HZ */
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#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
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static void record_gp_stall_check_time(struct rcu_state *rsp)
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{
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rsp->gp_start = jiffies;
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rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_CHECK;
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}
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static void print_other_cpu_stall(struct rcu_state *rsp)
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{
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int cpu;
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long delta;
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unsigned long flags;
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struct rcu_node *rnp = rcu_get_root(rsp);
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struct rcu_node *rnp_cur = rsp->level[NUM_RCU_LVLS - 1];
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struct rcu_node *rnp_end = &rsp->node[NUM_RCU_NODES];
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/* Only let one CPU complain about others per time interval. */
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spin_lock_irqsave(&rnp->lock, flags);
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delta = jiffies - rsp->jiffies_stall;
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if (delta < RCU_STALL_RAT_DELAY || rsp->gpnum == rsp->completed) {
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spin_unlock_irqrestore(&rnp->lock, flags);
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return;
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}
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rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_RECHECK;
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spin_unlock_irqrestore(&rnp->lock, flags);
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/* OK, time to rat on our buddy... */
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printk(KERN_ERR "INFO: RCU detected CPU stalls:");
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for (; rnp_cur < rnp_end; rnp_cur++) {
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if (rnp_cur->qsmask == 0)
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continue;
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for (cpu = 0; cpu <= rnp_cur->grphi - rnp_cur->grplo; cpu++)
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if (rnp_cur->qsmask & (1UL << cpu))
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printk(" %d", rnp_cur->grplo + cpu);
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}
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printk(" (detected by %d, t=%ld jiffies)\n",
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smp_processor_id(), (long)(jiffies - rsp->gp_start));
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force_quiescent_state(rsp, 0); /* Kick them all. */
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}
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static void print_cpu_stall(struct rcu_state *rsp)
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{
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unsigned long flags;
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struct rcu_node *rnp = rcu_get_root(rsp);
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printk(KERN_ERR "INFO: RCU detected CPU %d stall (t=%lu jiffies)\n",
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smp_processor_id(), jiffies - rsp->gp_start);
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dump_stack();
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spin_lock_irqsave(&rnp->lock, flags);
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if ((long)(jiffies - rsp->jiffies_stall) >= 0)
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rsp->jiffies_stall =
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jiffies + RCU_SECONDS_TILL_STALL_RECHECK;
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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)
|
|
{
|
|
long delta;
|
|
struct rcu_node *rnp;
|
|
|
|
delta = jiffies - rsp->jiffies_stall;
|
|
rnp = rdp->mynode;
|
|
if ((rnp->qsmask & rdp->grpmask) && delta >= 0) {
|
|
|
|
/* We haven't checked in, so go dump stack. */
|
|
print_cpu_stall(rsp);
|
|
|
|
} else if (rsp->gpnum != rsp->completed &&
|
|
delta >= RCU_STALL_RAT_DELAY) {
|
|
|
|
/* They had two time units to dump stack, so complain. */
|
|
print_other_cpu_stall(rsp);
|
|
}
|
|
}
|
|
|
|
#else /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
|
|
|
|
static void record_gp_stall_check_time(struct rcu_state *rsp)
|
|
{
|
|
}
|
|
|
|
static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
|
|
{
|
|
}
|
|
|
|
#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp)
|
|
{
|
|
rdp->qs_pending = 1;
|
|
rdp->passed_quiesc = 0;
|
|
rdp->gpnum = rsp->gpnum;
|
|
rdp->n_rcu_pending_force_qs = rdp->n_rcu_pending +
|
|
RCU_JIFFIES_TILL_FORCE_QS;
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
}
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
static void
|
|
rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
|
|
__releases(rcu_get_root(rsp)->lock)
|
|
{
|
|
struct rcu_data *rdp = rsp->rda[smp_processor_id()];
|
|
struct rcu_node *rnp = rcu_get_root(rsp);
|
|
struct rcu_node *rnp_cur;
|
|
struct rcu_node *rnp_end;
|
|
|
|
if (!cpu_needs_another_gp(rsp, rdp)) {
|
|
spin_unlock_irqrestore(&rnp->lock, flags);
|
|
return;
|
|
}
|
|
|
|
/* Advance to a new grace period and initialize state. */
|
|
rsp->gpnum++;
|
|
rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */
|
|
rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
|
|
rdp->n_rcu_pending_force_qs = rdp->n_rcu_pending +
|
|
RCU_JIFFIES_TILL_FORCE_QS;
|
|
record_gp_stall_check_time(rsp);
|
|
dyntick_record_completed(rsp, rsp->completed - 1);
|
|
note_new_gpnum(rsp, rdp);
|
|
|
|
/*
|
|
* Because we are first, we know that all our callbacks will
|
|
* be covered by this upcoming grace period, even the ones
|
|
* that were registered arbitrarily recently.
|
|
*/
|
|
rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
|
|
rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
|
|
|
|
/* Special-case the common single-level case. */
|
|
if (NUM_RCU_NODES == 1) {
|
|
rnp->qsmask = rnp->qsmaskinit;
|
|
rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */
|
|
spin_unlock_irqrestore(&rnp->lock, flags);
|
|
return;
|
|
}
|
|
|
|
spin_unlock(&rnp->lock); /* leave irqs disabled. */
|
|
|
|
|
|
/* Exclude any concurrent CPU-hotplug operations. */
|
|
spin_lock(&rsp->onofflock); /* irqs already disabled. */
|
|
|
|
/*
|
|
* Set the quiescent-state-needed bits in all the non-leaf RCU
|
|
* nodes for all currently online CPUs. 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. In addition, we have excluded CPU-hotplug operations.
|
|
*
|
|
* We therefore do not need to hold any locks. Any required
|
|
* memory barriers will be supplied by the locks guarding the
|
|
* leaf rcu_nodes in the hierarchy.
|
|
*/
|
|
|
|
rnp_end = rsp->level[NUM_RCU_LVLS - 1];
|
|
for (rnp_cur = &rsp->node[0]; rnp_cur < rnp_end; rnp_cur++)
|
|
rnp_cur->qsmask = rnp_cur->qsmaskinit;
|
|
|
|
/*
|
|
* Now set up the leaf nodes. Here we must be careful. First,
|
|
* we need to hold the lock in order to exclude other CPUs, which
|
|
* might be contending for the leaf nodes' locks. Second, as
|
|
* soon as we initialize a given leaf node, its CPUs might run
|
|
* up the rest of the hierarchy. We must therefore acquire locks
|
|
* for each node that we touch during this stage. (But we still
|
|
* are excluding 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.
|
|
*/
|
|
rnp_end = &rsp->node[NUM_RCU_NODES];
|
|
rnp_cur = rsp->level[NUM_RCU_LVLS - 1];
|
|
for (; rnp_cur < rnp_end; rnp_cur++) {
|
|
spin_lock(&rnp_cur->lock); /* irqs already disabled. */
|
|
rnp_cur->qsmask = rnp_cur->qsmaskinit;
|
|
spin_unlock(&rnp_cur->lock); /* irqs already disabled. */
|
|
}
|
|
|
|
rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */
|
|
spin_unlock_irqrestore(&rsp->onofflock, flags);
|
|
}
|
|
|
|
/*
|
|
* 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)
|
|
{
|
|
long completed_snap;
|
|
unsigned long flags;
|
|
|
|
local_irq_save(flags);
|
|
completed_snap = ACCESS_ONCE(rsp->completed); /* outside of lock. */
|
|
|
|
/* Did another grace period end? */
|
|
if (rdp->completed != completed_snap) {
|
|
|
|
/* 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 = completed_snap;
|
|
}
|
|
local_irq_restore(flags);
|
|
}
|
|
|
|
/*
|
|
* Similar to cpu_quiet(), for which it is a helper function. Allows
|
|
* a group of CPUs to be quieted at one go, though all the CPUs in the
|
|
* group must be represented by the same leaf rcu_node structure.
|
|
* That structure's lock must be held upon entry, and it is released
|
|
* before return.
|
|
*/
|
|
static void
|
|
cpu_quiet_msk(unsigned long mask, struct rcu_state *rsp, struct rcu_node *rnp,
|
|
unsigned long flags)
|
|
__releases(rnp->lock)
|
|
{
|
|
/* Walk up the rcu_node hierarchy. */
|
|
for (;;) {
|
|
if (!(rnp->qsmask & mask)) {
|
|
|
|
/* Our bit has already been cleared, so done. */
|
|
spin_unlock_irqrestore(&rnp->lock, flags);
|
|
return;
|
|
}
|
|
rnp->qsmask &= ~mask;
|
|
if (rnp->qsmask != 0) {
|
|
|
|
/* Other bits still set at this level, so done. */
|
|
spin_unlock_irqrestore(&rnp->lock, flags);
|
|
return;
|
|
}
|
|
mask = rnp->grpmask;
|
|
if (rnp->parent == NULL) {
|
|
|
|
/* No more levels. Exit loop holding root lock. */
|
|
|
|
break;
|
|
}
|
|
spin_unlock_irqrestore(&rnp->lock, flags);
|
|
rnp = rnp->parent;
|
|
spin_lock_irqsave(&rnp->lock, flags);
|
|
}
|
|
|
|
/*
|
|
* Get here if we are the last CPU to pass through a quiescent
|
|
* state for this grace period. Clean up and let rcu_start_gp()
|
|
* start up the next grace period if one is needed. Note that
|
|
* we still hold rnp->lock, as required by rcu_start_gp(), which
|
|
* will release it.
|
|
*/
|
|
rsp->completed = rsp->gpnum;
|
|
rcu_process_gp_end(rsp, rsp->rda[smp_processor_id()]);
|
|
rcu_start_gp(rsp, flags); /* releases rnp->lock. */
|
|
}
|
|
|
|
/*
|
|
* Record a quiescent state for the specified CPU, which must either be
|
|
* the current CPU or an 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
|
|
cpu_quiet(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp)
|
|
{
|
|
unsigned long flags;
|
|
unsigned long mask;
|
|
struct rcu_node *rnp;
|
|
|
|
rnp = rdp->mynode;
|
|
spin_lock_irqsave(&rnp->lock, flags);
|
|
if (lastcomp != ACCESS_ONCE(rsp->completed)) {
|
|
|
|
/*
|
|
* Someone beat us to it for this grace period, so leave.
|
|
* The race with GP start is resolved by the fact that we
|
|
* hold the leaf rcu_node lock, so that the per-CPU bits
|
|
* cannot yet be initialized -- so we would simply find our
|
|
* CPU's bit already cleared in cpu_quiet_msk() if this race
|
|
* occurred.
|
|
*/
|
|
rdp->passed_quiesc = 0; /* try again later! */
|
|
spin_unlock_irqrestore(&rnp->lock, flags);
|
|
return;
|
|
}
|
|
mask = rdp->grpmask;
|
|
if ((rnp->qsmask & mask) == 0) {
|
|
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 = rsp->rda[smp_processor_id()];
|
|
rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
|
|
|
|
cpu_quiet_msk(mask, rsp, rnp, flags); /* releases 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_quiesc)
|
|
return;
|
|
|
|
/* Tell RCU we are done (but cpu_quiet() will be the judge of that). */
|
|
cpu_quiet(rdp->cpu, rsp, rdp, rdp->passed_quiesc_completed);
|
|
}
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
|
|
/*
|
|
* Remove the outgoing CPU from the bitmasks in the rcu_node hierarchy
|
|
* and move all callbacks from the outgoing CPU to the current one.
|
|
*/
|
|
static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
|
|
{
|
|
int i;
|
|
unsigned long flags;
|
|
long lastcomp;
|
|
unsigned long mask;
|
|
struct rcu_data *rdp = rsp->rda[cpu];
|
|
struct rcu_data *rdp_me;
|
|
struct rcu_node *rnp;
|
|
|
|
/* Exclude any attempts to start a new grace period. */
|
|
spin_lock_irqsave(&rsp->onofflock, flags);
|
|
|
|
/* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */
|
|
rnp = rdp->mynode;
|
|
mask = rdp->grpmask; /* rnp->grplo is constant. */
|
|
do {
|
|
spin_lock(&rnp->lock); /* irqs already disabled. */
|
|
rnp->qsmaskinit &= ~mask;
|
|
if (rnp->qsmaskinit != 0) {
|
|
spin_unlock(&rnp->lock); /* irqs already disabled. */
|
|
break;
|
|
}
|
|
mask = rnp->grpmask;
|
|
spin_unlock(&rnp->lock); /* irqs already disabled. */
|
|
rnp = rnp->parent;
|
|
} while (rnp != NULL);
|
|
lastcomp = rsp->completed;
|
|
|
|
spin_unlock(&rsp->onofflock); /* irqs remain disabled. */
|
|
|
|
/* Being offline is a quiescent state, so go record it. */
|
|
cpu_quiet(cpu, rsp, rdp, lastcomp);
|
|
|
|
/*
|
|
* Move callbacks from the outgoing CPU to the running CPU.
|
|
* Note that the outgoing CPU is now quiscent, so it is now
|
|
* (uncharacteristically) safe to access it rcu_data structure.
|
|
* Note also that we must carefully retain the order of the
|
|
* outgoing CPU's callbacks in order for rcu_barrier() to work
|
|
* correctly. Finally, note that we start all the callbacks
|
|
* afresh, even those that have passed through a grace period
|
|
* and are therefore ready to invoke. The theory is that hotplug
|
|
* events are rare, and that if they are frequent enough to
|
|
* indefinitely delay callbacks, you have far worse things to
|
|
* be worrying about.
|
|
*/
|
|
rdp_me = rsp->rda[smp_processor_id()];
|
|
if (rdp->nxtlist != NULL) {
|
|
*rdp_me->nxttail[RCU_NEXT_TAIL] = rdp->nxtlist;
|
|
rdp_me->nxttail[RCU_NEXT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
|
|
rdp->nxtlist = NULL;
|
|
for (i = 0; i < RCU_NEXT_SIZE; i++)
|
|
rdp->nxttail[i] = &rdp->nxtlist;
|
|
rdp_me->qlen += rdp->qlen;
|
|
rdp->qlen = 0;
|
|
}
|
|
local_irq_restore(flags);
|
|
}
|
|
|
|
/*
|
|
* Remove the specified CPU from the RCU hierarchy and move any pending
|
|
* callbacks that it might have to the current CPU. This code assumes
|
|
* that at least one CPU in the system will remain running at all times.
|
|
* Any attempt to offline -all- CPUs is likely to strand RCU callbacks.
|
|
*/
|
|
static void rcu_offline_cpu(int cpu)
|
|
{
|
|
__rcu_offline_cpu(cpu, &rcu_state);
|
|
__rcu_offline_cpu(cpu, &rcu_bh_state);
|
|
}
|
|
|
|
#else /* #ifdef CONFIG_HOTPLUG_CPU */
|
|
|
|
static void rcu_offline_cpu(int cpu)
|
|
{
|
|
}
|
|
|
|
#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_data *rdp)
|
|
{
|
|
unsigned long flags;
|
|
struct rcu_head *next, *list, **tail;
|
|
int count;
|
|
|
|
/* If no callbacks are ready, just return.*/
|
|
if (!cpu_has_callbacks_ready_to_invoke(rdp))
|
|
return;
|
|
|
|
/*
|
|
* Extract the list of ready callbacks, disabling to prevent
|
|
* races with call_rcu() from interrupt handlers.
|
|
*/
|
|
local_irq_save(flags);
|
|
list = rdp->nxtlist;
|
|
rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL];
|
|
*rdp->nxttail[RCU_DONE_TAIL] = NULL;
|
|
tail = rdp->nxttail[RCU_DONE_TAIL];
|
|
for (count = RCU_NEXT_SIZE - 1; count >= 0; count--)
|
|
if (rdp->nxttail[count] == rdp->nxttail[RCU_DONE_TAIL])
|
|
rdp->nxttail[count] = &rdp->nxtlist;
|
|
local_irq_restore(flags);
|
|
|
|
/* Invoke callbacks. */
|
|
count = 0;
|
|
while (list) {
|
|
next = list->next;
|
|
prefetch(next);
|
|
list->func(list);
|
|
list = next;
|
|
if (++count >= rdp->blimit)
|
|
break;
|
|
}
|
|
|
|
local_irq_save(flags);
|
|
|
|
/* Update count, and requeue any remaining callbacks. */
|
|
rdp->qlen -= count;
|
|
if (list != NULL) {
|
|
*tail = rdp->nxtlist;
|
|
rdp->nxtlist = list;
|
|
for (count = 0; count < RCU_NEXT_SIZE; count++)
|
|
if (&rdp->nxtlist == rdp->nxttail[count])
|
|
rdp->nxttail[count] = tail;
|
|
else
|
|
break;
|
|
}
|
|
|
|
/* Reinstate batch limit if we have worked down the excess. */
|
|
if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark)
|
|
rdp->blimit = blimit;
|
|
|
|
local_irq_restore(flags);
|
|
|
|
/* Re-raise the RCU softirq if there are callbacks remaining. */
|
|
if (cpu_has_callbacks_ready_to_invoke(rdp))
|
|
raise_softirq(RCU_SOFTIRQ);
|
|
}
|
|
|
|
/*
|
|
* 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 the RCU softirq handler.
|
|
*
|
|
* This function must be called with hardirqs disabled. 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)
|
|
{
|
|
if (user ||
|
|
(idle_cpu(cpu) && !in_softirq() &&
|
|
hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
|
|
|
|
/*
|
|
* 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 count it.
|
|
*
|
|
* No memory barrier is required here because both
|
|
* rcu_qsctr_inc() and rcu_bh_qsctr_inc() reference
|
|
* only CPU-local variables that other CPUs neither
|
|
* access nor modify, at least not while the corresponding
|
|
* CPU is online.
|
|
*/
|
|
|
|
rcu_qsctr_inc(cpu);
|
|
rcu_bh_qsctr_inc(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 count it.
|
|
*/
|
|
|
|
rcu_bh_qsctr_inc(cpu);
|
|
}
|
|
raise_softirq(RCU_SOFTIRQ);
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
|
|
/*
|
|
* Scan the leaf rcu_node structures, processing dyntick state for any that
|
|
* have not yet encountered a quiescent state, using the function specified.
|
|
* Returns 1 if the current grace period ends while scanning (possibly
|
|
* because we made it end).
|
|
*/
|
|
static int rcu_process_dyntick(struct rcu_state *rsp, long lastcomp,
|
|
int (*f)(struct rcu_data *))
|
|
{
|
|
unsigned long bit;
|
|
int cpu;
|
|
unsigned long flags;
|
|
unsigned long mask;
|
|
struct rcu_node *rnp_cur = rsp->level[NUM_RCU_LVLS - 1];
|
|
struct rcu_node *rnp_end = &rsp->node[NUM_RCU_NODES];
|
|
|
|
for (; rnp_cur < rnp_end; rnp_cur++) {
|
|
mask = 0;
|
|
spin_lock_irqsave(&rnp_cur->lock, flags);
|
|
if (rsp->completed != lastcomp) {
|
|
spin_unlock_irqrestore(&rnp_cur->lock, flags);
|
|
return 1;
|
|
}
|
|
if (rnp_cur->qsmask == 0) {
|
|
spin_unlock_irqrestore(&rnp_cur->lock, flags);
|
|
continue;
|
|
}
|
|
cpu = rnp_cur->grplo;
|
|
bit = 1;
|
|
for (; cpu <= rnp_cur->grphi; cpu++, bit <<= 1) {
|
|
if ((rnp_cur->qsmask & bit) != 0 && f(rsp->rda[cpu]))
|
|
mask |= bit;
|
|
}
|
|
if (mask != 0 && rsp->completed == lastcomp) {
|
|
|
|
/* cpu_quiet_msk() releases rnp_cur->lock. */
|
|
cpu_quiet_msk(mask, rsp, rnp_cur, flags);
|
|
continue;
|
|
}
|
|
spin_unlock_irqrestore(&rnp_cur->lock, flags);
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
long lastcomp;
|
|
struct rcu_data *rdp = rsp->rda[smp_processor_id()];
|
|
struct rcu_node *rnp = rcu_get_root(rsp);
|
|
u8 signaled;
|
|
|
|
if (ACCESS_ONCE(rsp->completed) == ACCESS_ONCE(rsp->gpnum))
|
|
return; /* No grace period in progress, nothing to force. */
|
|
if (!spin_trylock_irqsave(&rsp->fqslock, flags)) {
|
|
rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */
|
|
return; /* Someone else is already on the job. */
|
|
}
|
|
if (relaxed &&
|
|
(long)(rsp->jiffies_force_qs - jiffies) >= 0 &&
|
|
(rdp->n_rcu_pending_force_qs - rdp->n_rcu_pending) >= 0)
|
|
goto unlock_ret; /* no emergency and done recently. */
|
|
rsp->n_force_qs++;
|
|
spin_lock(&rnp->lock);
|
|
lastcomp = rsp->completed;
|
|
signaled = rsp->signaled;
|
|
rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
|
|
rdp->n_rcu_pending_force_qs = rdp->n_rcu_pending +
|
|
RCU_JIFFIES_TILL_FORCE_QS;
|
|
if (lastcomp == rsp->gpnum) {
|
|
rsp->n_force_qs_ngp++;
|
|
spin_unlock(&rnp->lock);
|
|
goto unlock_ret; /* no GP in progress, time updated. */
|
|
}
|
|
spin_unlock(&rnp->lock);
|
|
switch (signaled) {
|
|
case RCU_GP_INIT:
|
|
|
|
break; /* grace period still initializing, ignore. */
|
|
|
|
case RCU_SAVE_DYNTICK:
|
|
|
|
if (RCU_SIGNAL_INIT != RCU_SAVE_DYNTICK)
|
|
break; /* So gcc recognizes the dead code. */
|
|
|
|
/* Record dyntick-idle state. */
|
|
if (rcu_process_dyntick(rsp, lastcomp,
|
|
dyntick_save_progress_counter))
|
|
goto unlock_ret;
|
|
|
|
/* Update state, record completion counter. */
|
|
spin_lock(&rnp->lock);
|
|
if (lastcomp == rsp->completed) {
|
|
rsp->signaled = RCU_FORCE_QS;
|
|
dyntick_record_completed(rsp, lastcomp);
|
|
}
|
|
spin_unlock(&rnp->lock);
|
|
break;
|
|
|
|
case RCU_FORCE_QS:
|
|
|
|
/* Check dyntick-idle state, send IPI to laggarts. */
|
|
if (rcu_process_dyntick(rsp, dyntick_recall_completed(rsp),
|
|
rcu_implicit_dynticks_qs))
|
|
goto unlock_ret;
|
|
|
|
/* Leave state in case more forcing is required. */
|
|
|
|
break;
|
|
}
|
|
unlock_ret:
|
|
spin_unlock_irqrestore(&rsp->fqslock, flags);
|
|
}
|
|
|
|
#else /* #ifdef CONFIG_SMP */
|
|
|
|
static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
|
|
{
|
|
set_need_resched();
|
|
}
|
|
|
|
#endif /* #else #ifdef CONFIG_SMP */
|
|
|
|
/*
|
|
* This does the RCU processing work from softirq context 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;
|
|
|
|
/*
|
|
* If an RCU GP has gone long enough, go check for dyntick
|
|
* idle CPUs and, if needed, send resched IPIs.
|
|
*/
|
|
if ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0 ||
|
|
(rdp->n_rcu_pending_force_qs - rdp->n_rcu_pending) < 0)
|
|
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)) {
|
|
spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags);
|
|
rcu_start_gp(rsp, flags); /* releases above lock */
|
|
}
|
|
|
|
/* If there are callbacks ready, invoke them. */
|
|
rcu_do_batch(rdp);
|
|
}
|
|
|
|
/*
|
|
* Do softirq processing for the current CPU.
|
|
*/
|
|
static void rcu_process_callbacks(struct softirq_action *unused)
|
|
{
|
|
/*
|
|
* Memory references from any prior RCU read-side critical sections
|
|
* executed by the interrupted code must be seen before any RCU
|
|
* grace-period manipulations below.
|
|
*/
|
|
smp_mb(); /* See above block comment. */
|
|
|
|
__rcu_process_callbacks(&rcu_state, &__get_cpu_var(rcu_data));
|
|
__rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data));
|
|
|
|
/*
|
|
* Memory references from any later RCU read-side critical sections
|
|
* executed by the interrupted code must be seen after any RCU
|
|
* grace-period manipulations above.
|
|
*/
|
|
smp_mb(); /* See above block comment. */
|
|
}
|
|
|
|
static void
|
|
__call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
|
|
struct rcu_state *rsp)
|
|
{
|
|
unsigned long flags;
|
|
struct rcu_data *rdp;
|
|
|
|
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 = rsp->rda[smp_processor_id()];
|
|
rcu_process_gp_end(rsp, rdp);
|
|
check_for_new_grace_period(rsp, rdp);
|
|
|
|
/* Add the callback to our list. */
|
|
*rdp->nxttail[RCU_NEXT_TAIL] = head;
|
|
rdp->nxttail[RCU_NEXT_TAIL] = &head->next;
|
|
|
|
/* Start a new grace period if one not already started. */
|
|
if (ACCESS_ONCE(rsp->completed) == ACCESS_ONCE(rsp->gpnum)) {
|
|
unsigned long nestflag;
|
|
struct rcu_node *rnp_root = rcu_get_root(rsp);
|
|
|
|
spin_lock_irqsave(&rnp_root->lock, nestflag);
|
|
rcu_start_gp(rsp, nestflag); /* releases rnp_root->lock. */
|
|
}
|
|
|
|
/* Force the grace period if too many callbacks or too long waiting. */
|
|
if (unlikely(++rdp->qlen > qhimark)) {
|
|
rdp->blimit = LONG_MAX;
|
|
force_quiescent_state(rsp, 0);
|
|
} else if ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0 ||
|
|
(rdp->n_rcu_pending_force_qs - rdp->n_rcu_pending) < 0)
|
|
force_quiescent_state(rsp, 1);
|
|
local_irq_restore(flags);
|
|
}
|
|
|
|
/*
|
|
* Queue an RCU callback for invocation after a grace period.
|
|
*/
|
|
void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
|
|
{
|
|
__call_rcu(head, func, &rcu_state);
|
|
}
|
|
EXPORT_SYMBOL_GPL(call_rcu);
|
|
|
|
/*
|
|
* Queue an RCU 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);
|
|
}
|
|
EXPORT_SYMBOL_GPL(call_rcu_bh);
|
|
|
|
/*
|
|
* 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)
|
|
{
|
|
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 (rdp->qs_pending)
|
|
return 1;
|
|
|
|
/* Does this CPU have callbacks ready to invoke? */
|
|
if (cpu_has_callbacks_ready_to_invoke(rdp))
|
|
return 1;
|
|
|
|
/* Has RCU gone idle with this CPU needing another grace period? */
|
|
if (cpu_needs_another_gp(rsp, rdp))
|
|
return 1;
|
|
|
|
/* Has another RCU grace period completed? */
|
|
if (ACCESS_ONCE(rsp->completed) != rdp->completed) /* outside of lock */
|
|
return 1;
|
|
|
|
/* Has a new RCU grace period started? */
|
|
if (ACCESS_ONCE(rsp->gpnum) != rdp->gpnum) /* outside of lock */
|
|
return 1;
|
|
|
|
/* Has an RCU GP gone long enough to send resched IPIs &c? */
|
|
if (ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum) &&
|
|
((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0 ||
|
|
(rdp->n_rcu_pending_force_qs - rdp->n_rcu_pending) < 0))
|
|
return 1;
|
|
|
|
/* nothing to do */
|
|
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.
|
|
*/
|
|
int rcu_pending(int cpu)
|
|
{
|
|
return __rcu_pending(&rcu_state, &per_cpu(rcu_data, cpu)) ||
|
|
__rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, 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. This function is part of the RCU implementation; it is -not-
|
|
* an exported member of the RCU API.
|
|
*/
|
|
int rcu_needs_cpu(int cpu)
|
|
{
|
|
/* RCU callbacks either ready or pending? */
|
|
return per_cpu(rcu_data, cpu).nxtlist ||
|
|
per_cpu(rcu_bh_data, cpu).nxtlist;
|
|
}
|
|
|
|
/*
|
|
* Initialize a CPU's per-CPU RCU data. We take this "scorched earth"
|
|
* approach so that we don't have to worry about how long the CPU has
|
|
* been gone, or whether it ever was online previously. We do trust the
|
|
* ->mynode field, as it is constant for a given struct rcu_data and
|
|
* initialized during early boot.
|
|
*
|
|
* 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)
|
|
{
|
|
unsigned long flags;
|
|
int i;
|
|
long lastcomp;
|
|
unsigned long mask;
|
|
struct rcu_data *rdp = rsp->rda[cpu];
|
|
struct rcu_node *rnp = rcu_get_root(rsp);
|
|
|
|
/* Set up local state, ensuring consistent view of global state. */
|
|
spin_lock_irqsave(&rnp->lock, flags);
|
|
lastcomp = rsp->completed;
|
|
rdp->completed = lastcomp;
|
|
rdp->gpnum = lastcomp;
|
|
rdp->passed_quiesc = 0; /* We could be racing with new GP, */
|
|
rdp->qs_pending = 1; /* so set up to respond to current GP. */
|
|
rdp->beenonline = 1; /* We have now been online. */
|
|
rdp->passed_quiesc_completed = lastcomp - 1;
|
|
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 = 0;
|
|
rdp->blimit = blimit;
|
|
#ifdef CONFIG_NO_HZ
|
|
rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
|
|
#endif /* #ifdef CONFIG_NO_HZ */
|
|
rdp->cpu = cpu;
|
|
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. */
|
|
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. */
|
|
spin_lock(&rnp->lock); /* irqs already disabled. */
|
|
rnp->qsmaskinit |= mask;
|
|
mask = rnp->grpmask;
|
|
spin_unlock(&rnp->lock); /* irqs already disabled. */
|
|
rnp = rnp->parent;
|
|
} while (rnp != NULL && !(rnp->qsmaskinit & mask));
|
|
|
|
spin_unlock(&rsp->onofflock); /* irqs remain disabled. */
|
|
|
|
/*
|
|
* A new grace period might start here. If so, we will be part of
|
|
* it, and its gpnum will be greater than ours, so we will
|
|
* participate. It is also possible for the gpnum to have been
|
|
* incremented before this function was called, and the bitmasks
|
|
* to not be filled out until now, in which case we will also
|
|
* participate due to our gpnum being behind.
|
|
*/
|
|
|
|
/* Since it is coming online, the CPU is in a quiescent state. */
|
|
cpu_quiet(cpu, rsp, rdp, lastcomp);
|
|
local_irq_restore(flags);
|
|
}
|
|
|
|
static void __cpuinit rcu_online_cpu(int cpu)
|
|
{
|
|
rcu_init_percpu_data(cpu, &rcu_state);
|
|
rcu_init_percpu_data(cpu, &rcu_bh_state);
|
|
open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
|
|
}
|
|
|
|
/*
|
|
* Handle CPU online/offline notifcation events.
|
|
*/
|
|
static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
|
|
unsigned long action, void *hcpu)
|
|
{
|
|
long cpu = (long)hcpu;
|
|
|
|
switch (action) {
|
|
case CPU_UP_PREPARE:
|
|
case CPU_UP_PREPARE_FROZEN:
|
|
rcu_online_cpu(cpu);
|
|
break;
|
|
case CPU_DEAD:
|
|
case CPU_DEAD_FROZEN:
|
|
case CPU_UP_CANCELED:
|
|
case CPU_UP_CANCELED_FROZEN:
|
|
rcu_offline_cpu(cpu);
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
return NOTIFY_OK;
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
}
|
|
#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)
|
|
{
|
|
int cpustride = 1;
|
|
int i;
|
|
int j;
|
|
struct rcu_node *rnp;
|
|
|
|
/* 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++) {
|
|
spin_lock_init(&rnp->lock);
|
|
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;
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Helper macro for __rcu_init(). To be used nowhere else!
|
|
* Assigns leaf node pointers into each CPU's rcu_data structure.
|
|
*/
|
|
#define RCU_DATA_PTR_INIT(rsp, rcu_data) \
|
|
do { \
|
|
rnp = (rsp)->level[NUM_RCU_LVLS - 1]; \
|
|
j = 0; \
|
|
for_each_possible_cpu(i) { \
|
|
if (i > rnp[j].grphi) \
|
|
j++; \
|
|
per_cpu(rcu_data, i).mynode = &rnp[j]; \
|
|
(rsp)->rda[i] = &per_cpu(rcu_data, i); \
|
|
} \
|
|
} while (0)
|
|
|
|
static struct notifier_block __cpuinitdata rcu_nb = {
|
|
.notifier_call = rcu_cpu_notify,
|
|
};
|
|
|
|
void __init __rcu_init(void)
|
|
{
|
|
int i; /* All used by RCU_DATA_PTR_INIT(). */
|
|
int j;
|
|
struct rcu_node *rnp;
|
|
|
|
printk(KERN_WARNING "Experimental hierarchical RCU implementation.\n");
|
|
#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
|
|
printk(KERN_INFO "RCU-based detection of stalled CPUs is enabled.\n");
|
|
#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
|
|
rcu_init_one(&rcu_state);
|
|
RCU_DATA_PTR_INIT(&rcu_state, rcu_data);
|
|
rcu_init_one(&rcu_bh_state);
|
|
RCU_DATA_PTR_INIT(&rcu_bh_state, rcu_bh_data);
|
|
|
|
for_each_online_cpu(i)
|
|
rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE, (void *)(long)i);
|
|
/* Register notifier for non-boot CPUs */
|
|
register_cpu_notifier(&rcu_nb);
|
|
printk(KERN_WARNING "Experimental hierarchical RCU init done.\n");
|
|
}
|
|
|
|
module_param(blimit, int, 0);
|
|
module_param(qhimark, int, 0);
|
|
module_param(qlowmark, int, 0);
|