redonkable
/
alistair23-linux
1
0
Fork 0
Code Releases Activity

rcu: Add CPU online/offline state to dump_blkd_tasks() 

Interactions between CPU-hotplug operations and grace-period
initialization can result in dump_blkd_tasks().  One of the first
debugging actions in this case is to search back in dmesg to work
out which of the affected rcu_node structure's CPUs are online and to
determine the last CPU-hotplug operation affecting any of those CPUs.
This can be laborious and error-prone, especially when console output
is lost.

This commit therefore causes dump_blkd_tasks() to dump the state of
the affected rcu_node structure's CPUs and the last grace period during
which the last offline and online operation affected each of these CPUs.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
hifive-unleashed-5.1
Paul E. McKenney 2018-05-08 14:18:57 -07:00
parent ff3cee3908
commit 5773894231
3 changed files with 39 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
kernel/rcu/tree.c
View File

@ -1954,7 +1954,7 @@ static bool rcu_gp_init(struct rcu_state *rsp)
rcu_gp_slow(rsp, gp_init_delay);
raw_spin_lock_irqsave_rcu_node(rnp, flags);
rdp = this_cpu_ptr(rsp->rda);
rcu_preempt_check_blocked_tasks(rnp);
rcu_preempt_check_blocked_tasks(rsp, rnp);
rnp->qsmask = rnp->qsmaskinit;
WRITE_ONCE(rnp->gp_seq, rsp->gp_seq);
if (rnp == rdp->mynode)
@ -2063,7 +2063,7 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
rcu_for_each_node_breadth_first(rsp, rnp) {
raw_spin_lock_irq_rcu_node(rnp);
if (WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)))
dump_blkd_tasks(rnp, 10);
dump_blkd_tasks(rsp, rnp, 10);
WARN_ON_ONCE(rnp->qsmask);
WRITE_ONCE(rnp->gp_seq, new_gp_seq);
rdp = this_cpu_ptr(rsp->rda);
@ -3516,6 +3516,10 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != 1);
WARN_ON_ONCE(rcu_dynticks_in_eqs(rcu_dynticks_snap(rdp->dynticks)));
rdp->rcu_ofl_gp_seq = rsp->gp_seq;
rdp->rcu_ofl_gp_flags = RCU_GP_CLEANED;
rdp->rcu_onl_gp_seq = rsp->gp_seq;
rdp->rcu_onl_gp_flags = RCU_GP_CLEANED;
rdp->cpu = cpu;
rdp->rsp = rsp;
rcu_boot_init_nocb_percpu_data(rdp);
@ -3711,6 +3715,8 @@ void rcu_cpu_starting(unsigned int cpu)
/* Allow lockless access for expedited grace periods. */
smp_store_release(&rsp->ncpus, rsp->ncpus + nbits); /* ^^^ */
rcu_gpnum_ovf(rnp, rdp); /* Offline-induced counter wrap? */
rdp->rcu_onl_gp_seq = READ_ONCE(rsp->gp_seq);
rdp->rcu_onl_gp_flags = READ_ONCE(rsp->gp_flags);
if (rnp->qsmask & mask) { /* RCU waiting on incoming CPU? */
/* Report QS -after- changing ->qsmaskinitnext! */
rcu_report_qs_rnp(mask, rsp, rnp, rnp->gp_seq, flags);
@ -3738,6 +3744,8 @@ static void rcu_cleanup_dying_idle_cpu(int cpu, struct rcu_state *rsp)
mask = rdp->grpmask;
spin_lock(&rsp->ofl_lock);
raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Enforce GP memory-order guarantee. */
rdp->rcu_ofl_gp_seq = READ_ONCE(rsp->gp_seq);
rdp->rcu_ofl_gp_flags = READ_ONCE(rsp->gp_flags);
if (rnp->qsmask & mask) { /* RCU waiting on outgoing CPU? */
/* Report quiescent state -before- changing ->qsmaskinitnext! */
rcu_report_qs_rnp(mask, rsp, rnp, rnp->gp_seq, flags);

12
kernel/rcu/tree.h
View File

@ -255,12 +255,16 @@ struct rcu_data {
/* Leader CPU takes GP-end wakeups. */
#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
/* 7) RCU CPU stall data. */
/* 7) Diagnostic data, including RCU CPU stall warnings. */
unsigned int softirq_snap; /* Snapshot of softirq activity. */
/* ->rcu_iw* fields protected by leaf rcu_node ->lock. */
struct irq_work rcu_iw; /* Check for non-irq activity. */
bool rcu_iw_pending; /* Is ->rcu_iw pending? */
unsigned long rcu_iw_gp_seq; /* ->gp_seq associated with ->rcu_iw. */
unsigned long rcu_ofl_gp_seq; /* ->gp_seq at last offline. */
short rcu_ofl_gp_flags; /* ->gp_flags at last offline. */
unsigned long rcu_onl_gp_seq; /* ->gp_seq at last online. */
short rcu_onl_gp_flags; /* ->gp_flags at last online. */
int cpu;
struct rcu_state *rsp;
@ -431,11 +435,13 @@ static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
static void rcu_print_detail_task_stall(struct rcu_state *rsp);
static int rcu_print_task_stall(struct rcu_node *rnp);
static int rcu_print_task_exp_stall(struct rcu_node *rnp);
static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
static void rcu_preempt_check_blocked_tasks(struct rcu_state *rsp,
struct rcu_node *rnp);
static void rcu_preempt_check_callbacks(void);
void call_rcu(struct rcu_head *head, rcu_callback_t func);
static void __init __rcu_init_preempt(void);
static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck);
static void dump_blkd_tasks(struct rcu_state *rsp, struct rcu_node *rnp,
int ncheck);
static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
static void invoke_rcu_callbacks_kthread(void);

25
kernel/rcu/tree_plugin.h
View File

@ -699,13 +699,14 @@ static int rcu_print_task_exp_stall(struct rcu_node *rnp)
* Also, if there are blocked tasks on the list, they automatically
* block the newly created grace period, so set up ->gp_tasks accordingly.
*/
static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp)
static void
rcu_preempt_check_blocked_tasks(struct rcu_state *rsp, struct rcu_node *rnp)
{
struct task_struct *t;
RCU_LOCKDEP_WARN(preemptible(), "rcu_preempt_check_blocked_tasks() invoked with preemption enabled!!!\n");
if (WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)))
dump_blkd_tasks(rnp, 10);
dump_blkd_tasks(rsp, rnp, 10);
if (rcu_preempt_has_tasks(rnp) &&
(rnp->qsmaskinit || rnp->wait_blkd_tasks)) {
rnp->gp_tasks = rnp->blkd_tasks.next;
@ -854,10 +855,14 @@ void exit_rcu(void)
* Dump the blocked-tasks state, but limit the list dump to the
* specified number of elements.
*/
static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck)
static void
dump_blkd_tasks(struct rcu_state *rsp, struct rcu_node *rnp, int ncheck)
{
int cpu;
int i;
struct list_head *lhp;
bool onl;
struct rcu_data *rdp;
struct rcu_node *rnp1;
raw_lockdep_assert_held_rcu_node(rnp);
@ -877,6 +882,14 @@ static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck)
break;
}
pr_cont("\n");
for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++) {
rdp = per_cpu_ptr(rsp->rda, cpu);
onl = !!(rdp->grpmask & rcu_rnp_online_cpus(rnp));
pr_info("\t%d: %c online: %ld(%d) offline: %ld(%d)\n",
cpu, ".o"[onl],
(long)rdp->rcu_onl_gp_seq, rdp->rcu_onl_gp_flags,
(long)rdp->rcu_ofl_gp_seq, rdp->rcu_ofl_gp_flags);
}
}
#else /* #ifdef CONFIG_PREEMPT_RCU */
@ -949,7 +962,8 @@ static int rcu_print_task_exp_stall(struct rcu_node *rnp)
* so there is no need to check for blocked tasks. So check only for
* bogus qsmask values.
*/
static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp)
static void
rcu_preempt_check_blocked_tasks(struct rcu_state *rsp, struct rcu_node *rnp)
{
WARN_ON_ONCE(rnp->qsmask);
}
@ -990,7 +1004,8 @@ void exit_rcu(void)
/*
* Dump the guaranteed-empty blocked-tasks state. Trust but verify.
*/
static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck)
static void
dump_blkd_tasks(struct rcu_state *rsp, struct rcu_node *rnp, int ncheck)
{
WARN_ON_ONCE(!list_empty(&rnp->blkd_tasks));
}