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sched: Add TASK_WAKING

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We're going to want to drop rq->lock in try_to_wake_up() for a
longer period of time, however we also want to deal with concurrent
waking of the same task, which is currently handled by holding
rq->lock.

So introduce a new TASK state, namely TASK_WAKING, which indicates
someone is already waking the task (other wakers will fail p->state
& state).

We also keep preemption disabled over the whole ttwu().

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-09-15 14:43:03 +02:00 committed by Ingo Molnar
parent 5f3edc1b1e
commit e9c8431185
2 changed files with 18 additions and 18 deletions
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1
include/linux/sched.h
View File

@ -190,6 +190,7 @@ extern unsigned long long time_sync_thresh;
/* in tsk->state again */
#define TASK_DEAD 64
#define TASK_WAKEKILL 128
#define TASK_WAKING 256
/* Convenience macros for the sake of set_task_state */
#define TASK_KILLABLE (TASK_WAKEKILL | TASK_UNINTERRUPTIBLE)

35
kernel/sched.c
View File

@ -2310,7 +2310,6 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)
{
int cpu, orig_cpu, this_cpu, success = 0;
unsigned long flags;
long old_state;
struct rq *rq;
if (!sched_feat(SYNC_WAKEUPS))
@ -2332,11 +2331,12 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)
}
#endif
this_cpu = get_cpu();
smp_wmb();
rq = task_rq_lock(p, &flags);
update_rq_clock(rq);
old_state = p->state;
if (!(old_state & state))
if (!(p->state & state))
goto out;
if (p->se.on_rq)
@ -2344,27 +2344,25 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)
cpu = task_cpu(p);
orig_cpu = cpu;
this_cpu = smp_processor_id();
#ifdef CONFIG_SMP
if (unlikely(task_running(rq, p)))
goto out_activate;
cpu = p->sched_class->select_task_rq(p, SD_BALANCE_WAKE, sync);
if (cpu != orig_cpu) {
set_task_cpu(p, cpu);
task_rq_unlock(rq, &flags);
/* might preempt at this point */
rq = task_rq_lock(p, &flags);
old_state = p->state;
if (!(old_state & state))
goto out;
if (p->se.on_rq)
goto out_running;
/*
* In order to handle concurrent wakeups and release the rq->lock
* we put the task in TASK_WAKING state.
*/
p->state = TASK_WAKING;
task_rq_unlock(rq, &flags);
this_cpu = smp_processor_id();
cpu = task_cpu(p);
}
cpu = p->sched_class->select_task_rq(p, SD_BALANCE_WAKE, sync);
if (cpu != orig_cpu)
set_task_cpu(p, cpu);
rq = task_rq_lock(p, &flags);
WARN_ON(p->state != TASK_WAKING);
cpu = task_cpu(p);
#ifdef CONFIG_SCHEDSTATS
schedstat_inc(rq, ttwu_count);
@ -2422,6 +2420,7 @@ out_running:
#endif
out:
task_rq_unlock(rq, &flags);
put_cpu();
return success;
}