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author | Peter Zijlstra <a.p.zijlstra@chello.nl> | 2011-08-11 13:03:35 (GMT) |
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committer | Scott Wood <scottwood@freescale.com> | 2014-05-14 18:38:17 (GMT) |
commit | 852966311c98b98674d1c5c6fbbbbb28bd71d2cb (patch) | |
tree | e787c92a3580f23a30c815bb5b8eb90283303edb /kernel/sched | |
parent | 1b678644e09edc8163fd91fe5a3d4ac6e3aaac79 (diff) | |
download | linux-fsl-qoriq-852966311c98b98674d1c5c6fbbbbb28bd71d2cb.tar.xz |
sched: Optimize migrate_disable
Change from task_rq_lock() to raw_spin_lock(&rq->lock) to avoid a few
atomic ops. See comment on why it should be safe.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-cbz6hkl5r5mvwtx5s3tor2y6@git.kernel.org
Diffstat (limited to 'kernel/sched')
-rw-r--r-- | kernel/sched/core.c | 24 |
1 files changed, 20 insertions, 4 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 7ef7cd3..8cdf838 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4435,7 +4435,19 @@ void migrate_disable(void) preempt_enable(); return; } - rq = task_rq_lock(p, &flags); + + /* + * Since this is always current we can get away with only locking + * rq->lock, the ->cpus_allowed value can normally only be changed + * while holding both p->pi_lock and rq->lock, but seeing that this + * it current, we cannot actually be waking up, so all code that + * relies on serialization against p->pi_lock is out of scope. + * + * Taking rq->lock serializes us against things like + * set_cpus_allowed_ptr() that can still happen concurrently. + */ + rq = this_rq(); + raw_spin_lock_irqsave(&rq->lock, flags); p->migrate_disable = 1; mask = tsk_cpus_allowed(p); @@ -4446,7 +4458,7 @@ void migrate_disable(void) p->sched_class->set_cpus_allowed(p, mask); p->nr_cpus_allowed = cpumask_weight(mask); } - task_rq_unlock(rq, p, &flags); + raw_spin_unlock_irqrestore(&rq->lock, flags); preempt_enable(); } EXPORT_SYMBOL(migrate_disable); @@ -4474,7 +4486,11 @@ void migrate_enable(void) return; } - rq = task_rq_lock(p, &flags); + /* + * See comment in migrate_disable(). + */ + rq = this_rq(); + raw_spin_lock_irqsave(&rq->lock, flags); p->migrate_disable = 0; mask = tsk_cpus_allowed(p); @@ -4486,7 +4502,7 @@ void migrate_enable(void) p->nr_cpus_allowed = cpumask_weight(mask); } - task_rq_unlock(rq, p, &flags); + raw_spin_unlock_irqrestore(&rq->lock, flags); unpin_current_cpu(); preempt_enable(); } |