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rcu: Add stall warnings to synchronize_sched_expedited() 

Although synchronize_sched_expedited() historically has no RCU CPU stall
warnings, the availability of the rcupdate.rcu_expedited boot parameter
invalidates the old assumption that synchronize_sched()'s stall warnings
would suffice.  This commit therefore adds RCU CPU stall warnings to
synchronize_sched_expedited().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2015-06-30 11:14:32 -07:00
parent 2cd6ffafec
commit cf3620a6c7
2 changed files with 55 additions and 4 deletions
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58
kernel/rcu/tree.c
View File

@ -3369,16 +3369,65 @@ static struct rcu_node *exp_funnel_lock(struct rcu_state *rsp, unsigned long s)
return rnp1;
}
/* Invoked on each online non-idle CPU for expedited quiescent state. */
static int synchronize_sched_expedited_cpu_stop(void *data)
{
struct rcu_state *rsp = data;
struct rcu_data *rdp = data;
struct rcu_state *rsp = rdp->rsp;
/* We are here: If we are last, do the wakeup. */
rdp->exp_done = true;
if (atomic_dec_and_test(&rsp->expedited_need_qs))
wake_up(&rsp->expedited_wq);
return 0;
}
static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
{
int cpu;
unsigned long jiffies_stall;
unsigned long jiffies_start;
struct rcu_data *rdp;
int ret;
jiffies_stall = rcu_jiffies_till_stall_check();
jiffies_start = jiffies;
for (;;) {
ret = wait_event_interruptible_timeout(
rsp->expedited_wq,
!atomic_read(&rsp->expedited_need_qs),
jiffies_stall);
if (ret > 0)
return;
if (ret < 0) {
/* Hit a signal, disable CPU stall warnings. */
wait_event(rsp->expedited_wq,
!atomic_read(&rsp->expedited_need_qs));
return;
}
pr_err("INFO: %s detected expedited stalls on CPUs: {",
rsp->name);
for_each_online_cpu(cpu) {
rdp = per_cpu_ptr(rsp->rda, cpu);
if (rdp->exp_done)
continue;
pr_cont(" %d", cpu);
}
pr_cont(" } %lu jiffies s: %lu\n",
jiffies - jiffies_start, rsp->expedited_sequence);
for_each_online_cpu(cpu) {
rdp = per_cpu_ptr(rsp->rda, cpu);
if (rdp->exp_done)
continue;
dump_cpu_task(cpu);
}
jiffies_stall = 3 * rcu_jiffies_till_stall_check() + 3;
}
}
/**
* synchronize_sched_expedited - Brute-force RCU-sched grace period
*
@ -3428,19 +3477,20 @@ void synchronize_sched_expedited(void)
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
rdp->exp_done = false;
/* Skip our CPU and any idle CPUs. */
if (raw_smp_processor_id() == cpu ||
!(atomic_add_return(0, &rdtp->dynticks) & 0x1))
continue;
atomic_inc(&rsp->expedited_need_qs);
stop_one_cpu_nowait(cpu, synchronize_sched_expedited_cpu_stop,
rsp, &rdp->exp_stop_work);
rdp, &rdp->exp_stop_work);
}
/* Remove extra count and, if necessary, wait for CPUs to stop. */
if (!atomic_dec_and_test(&rsp->expedited_need_qs))
wait_event(rsp->expedited_wq,
!atomic_read(&rsp->expedited_need_qs));
synchronize_sched_expedited_wait(rsp);
rcu_exp_gp_seq_end(rsp);
mutex_unlock(&rnp->exp_funnel_mutex);

1
kernel/rcu/tree.h
View File

@ -370,6 +370,7 @@ struct rcu_data {
struct rcu_head oom_head;
#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
struct mutex exp_funnel_mutex;
bool exp_done; /* Expedited QS for this CPU? */
/* 7) Callback offloading. */
#ifdef CONFIG_RCU_NOCB_CPU