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sched: Drop rq->lock from sched_exec() 

Since we can now call select_task_rq() and set_task_cpu() with only
p->pi_lock held, and sched_exec() load-balancing has always been
optimistic, drop all rq->lock usage.

Oleg also noted that need_migrate_task() will always be true for
current, so don't bother calling that at all.

Reviewed-by: Frank Rowand <frank.rowand@am.sony.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20110405152729.314204889@chello.nl
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2011-04-05 17:23:53 +02:00 committed by Ingo Molnar
parent ab2515c4b9
commit 8f42ced974
1 changed files with 5 additions and 10 deletions
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15
kernel/sched.c
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@ -3465,27 +3465,22 @@ void sched_exec(void)
{
struct task_struct *p = current;
unsigned long flags;
struct rq *rq;
int dest_cpu;
rq = task_rq_lock(p, &flags);
raw_spin_lock_irqsave(&p->pi_lock, flags);
dest_cpu = p->sched_class->select_task_rq(p, SD_BALANCE_EXEC, 0);
if (dest_cpu == smp_processor_id())
goto unlock;
/*
* select_task_rq() can race against ->cpus_allowed
*/
if (cpumask_test_cpu(dest_cpu, &p->cpus_allowed) &&
likely(cpu_active(dest_cpu)) && need_migrate_task(p)) {
if (likely(cpu_active(dest_cpu))) {
struct migration_arg arg = { p, dest_cpu };
task_rq_unlock(rq, p, &flags);
stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg);
raw_spin_unlock_irqrestore(&p->pi_lock, flags);
stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg);
return;
}
unlock:
task_rq_unlock(rq, p, &flags);
raw_spin_unlock_irqrestore(&p->pi_lock, flags);
}
#endif