diff options
author | Peter Zijlstra <a.p.zijlstra@chello.nl> | 2011-08-11 15:03:35 +0200 |
---|---|---|
committer | Clark Williams <williams@redhat.com> | 2012-04-13 11:01:36 -0500 |
commit | f2d52cc217f08f485581412f7a7fdb34972fbba8 (patch) | |
tree | e696ff4ac72a6353126c679468a48b9a39b81929 /kernel | |
parent | f5c5f692da0b11a4963de5d9e86b239e4848c9ff (diff) |
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')
-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 7d807cfd155c..bdbf6fd42db4 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5071,7 +5071,19 @@ 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); @@ -5082,7 +5094,7 @@ void migrate_disable(void) p->sched_class->set_cpus_allowed(p, mask); p->rt.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); @@ -5110,7 +5122,11 @@ 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); @@ -5122,7 +5138,7 @@ void migrate_enable(void) p->rt.nr_cpus_allowed = cpumask_weight(mask); } - task_rq_unlock(rq, p, &flags); + raw_spin_unlock_irqrestore(&rq->lock, flags); unpin_current_cpu(); preempt_enable(); } |