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rcu: add grace-period age and more kthread state to tracing

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This commit adds the age in jiffies of the current grace period along
with the duration in jiffies of the longest grace period since boot
to the rcu/rcugp debugfs file.  It also adds an additional "O" state
to kthread tracing to differentiate between the kthread waiting due to
having nothing to do on the one hand and waiting due to being on the
wrong CPU on the other hand.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney
2011-04-06 16:01:16 -07:00
committed by Paul E. McKenney
parent a9f4793d89
commit 15ba0ba860
4 changed files with 54 additions and 12 deletions
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10
kernel/rcutree.c
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@@ -92,6 +92,7 @@ EXPORT_SYMBOL_GPL(rcu_scheduler_active);
*/
static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task);
DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
DEFINE_PER_CPU(int, rcu_cpu_kthread_cpu);
static DEFINE_PER_CPU(wait_queue_head_t, rcu_cpu_wq);
DEFINE_PER_CPU(char, rcu_cpu_has_work);
static char rcu_kthreads_spawnable;
@@ -888,6 +889,8 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags)
__releases(rcu_get_root(rsp)->lock)
{
unsigned long gp_duration;
WARN_ON_ONCE(!rcu_gp_in_progress(rsp));
/*
@@ -895,6 +898,9 @@ static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags)
* 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;
rsp->completed = rsp->gpnum;
rsp->signaled = RCU_GP_IDLE;
rcu_start_gp(rsp, flags); /* releases root node's rnp->lock. */
@@ -1583,12 +1589,15 @@ static int rcu_cpu_kthread_should_stop(int cpu)
smp_processor_id() != cpu) {
if (kthread_should_stop())
return 1;
per_cpu(rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU;
per_cpu(rcu_cpu_kthread_cpu, cpu) = raw_smp_processor_id();
local_bh_enable();
schedule_timeout_uninterruptible(1);
if (!cpumask_equal(&current->cpus_allowed, cpumask_of(cpu)))
set_cpus_allowed_ptr(current, cpumask_of(cpu));
local_bh_disable();
}
per_cpu(rcu_cpu_kthread_cpu, cpu) = cpu;
return 0;
}
@@ -1656,6 +1665,7 @@ static int __cpuinit rcu_spawn_one_cpu_kthread(int cpu)
if (IS_ERR(t))
return PTR_ERR(t);
kthread_bind(t, cpu);
per_cpu(rcu_cpu_kthread_cpu, cpu) = cpu;
WARN_ON_ONCE(per_cpu(rcu_cpu_kthread_task, cpu) != NULL);
per_cpu(rcu_cpu_kthread_task, cpu) = t;
wake_up_process(t);