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| author | Peter Zijlstra <peterz@infradead.org> | 2011-05-30 13:34:51 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2011-05-31 10:01:48 +0200 |
| commit | d72bce0e67e8afc6eb959f656013cbb577426f1e (patch) | |
| tree | 9c93d4df9aa895d6f2f555e0cf50e7ae5ebaded4 /kernel/rcutree_plugin.h | |
| parent | 55922c9d1b84b89cb946c777fddccb3247e7df2c (diff) | |
| download | lwn-d72bce0e67e8afc6eb959f656013cbb577426f1e.tar.gz lwn-d72bce0e67e8afc6eb959f656013cbb577426f1e.zip | |
rcu: Cure load woes
Commit cc3ce5176d83 (rcu: Start RCU kthreads in TASK_INTERRUPTIBLE
state) fudges a sleeping task' state, resulting in the scheduler seeing
a TASK_UNINTERRUPTIBLE task going to sleep, but a TASK_INTERRUPTIBLE
task waking up. The result is unbalanced load calculation.
The problem that patch tried to address is that the RCU threads could
stay in UNINTERRUPTIBLE state for quite a while and triggering the hung
task detector due to on-demand wake-ups.
Cure the problem differently by always giving the tasks at least one
wake-up once the CPU is fully up and running, this will kick them out of
the initial UNINTERRUPTIBLE state and into the regular INTERRUPTIBLE
wait state.
[ The alternative would be teaching kthread_create() to start threads as
INTERRUPTIBLE but that needs a tad more thought. ]
Reported-by: Damien Wyart <damien.wyart@free.fr>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Paul E. McKenney <paul.mckenney@linaro.org>
Link: http://lkml.kernel.org/r/1306755291.1200.2872.camel@twins
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/rcutree_plugin.h')
| -rw-r--r-- | kernel/rcutree_plugin.h | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index a767b7dac365..c8bff3099a89 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -1295,7 +1295,6 @@ static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp, if (IS_ERR(t)) return PTR_ERR(t); raw_spin_lock_irqsave(&rnp->lock, flags); - set_task_state(t, TASK_INTERRUPTIBLE); rnp->boost_kthread_task = t; raw_spin_unlock_irqrestore(&rnp->lock, flags); sp.sched_priority = RCU_KTHREAD_PRIO; @@ -1303,6 +1302,12 @@ static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp, return 0; } +static void __cpuinit rcu_wake_one_boost_kthread(struct rcu_node *rnp) +{ + if (rnp->boost_kthread_task) + wake_up_process(rnp->boost_kthread_task); +} + #else /* #ifdef CONFIG_RCU_BOOST */ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) @@ -1326,6 +1331,10 @@ static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp, return 0; } +static void __cpuinit rcu_wake_one_boost_kthread(struct rcu_node *rnp) +{ +} + #endif /* #else #ifdef CONFIG_RCU_BOOST */ #ifndef CONFIG_SMP |