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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2009-09-15 14:43:03 +0200
committerIngo Molnar <mingo@elte.hu>2009-09-15 16:01:05 +0200
commite9c8431185d6c406887190519f6dbdd112641686 (patch)
tree3c502201451df7bbfcd653fee940fcb40bdaaeb6 /kernel/sched.c
parent5f3edc1b1ead6d9bd45a85c551f44eff8fe76b9f (diff)
sched: Add TASK_WAKING
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>
Diffstat (limited to 'kernel/sched.c')
-rw-r--r--kernel/sched.c31
1 files changed, 15 insertions, 16 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index 32b7a81230c..fc6fda881d2 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -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;
+ /*
+ * 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);
+
cpu = p->sched_class->select_task_rq(p, SD_BALANCE_WAKE, sync);
- if (cpu != orig_cpu) {
+ 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;
- this_cpu = smp_processor_id();
- cpu = task_cpu(p);
- }
+ 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;
}