diff options
author | Kirill Tkhai <ktkhai@parallels.com> | 2014-08-20 13:47:50 +0400 |
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committer | Ingo Molnar <mingo@kernel.org> | 2014-08-20 14:53:02 +0200 |
commit | a1e01829796aa7a993e28ffd7fee5c8d525be175 (patch) | |
tree | 9ae2970e5c0dc25972bf3d7663d997ab8808ddad /kernel/sched/core.c | |
parent | cca26e8009d1939a6a5bf0200d276fa26f03e536 (diff) | |
download | linux-a1e01829796aa7a993e28ffd7fee5c8d525be175.tar.bz2 |
sched: Remove double_rq_lock() from __migrate_task()
Avoid double_rq_lock() and use TASK_ON_RQ_MIGRATING for
__migrate_task(). The advantage is (obviously) not holding two
rq->lock's at the same time and thereby increasing parallelism.
The important point to note is that because we acquire dst->lock
immediately after releasing src->lock the potential wait time of
task_rq_lock() callers on TASK_ON_RQ_MIGRATING is not longer
than it would have been in the double rq lock scenario.
Signed-off-by: Kirill Tkhai <ktkhai@parallels.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Turner <pjt@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Kirill Tkhai <tkhai@yandex.ru>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1408528070.23412.89.camel@tkhai
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched/core.c')
-rw-r--r-- | kernel/sched/core.c | 23 |
1 files changed, 15 insertions, 8 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 71b836034912..a773c919d88d 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4679,20 +4679,20 @@ EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr); */ static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu) { - struct rq *rq_dest, *rq_src; + struct rq *rq; int ret = 0; if (unlikely(!cpu_active(dest_cpu))) return ret; - rq_src = cpu_rq(src_cpu); - rq_dest = cpu_rq(dest_cpu); + rq = cpu_rq(src_cpu); raw_spin_lock(&p->pi_lock); - double_rq_lock(rq_src, rq_dest); + raw_spin_lock(&rq->lock); /* Already moved. */ if (task_cpu(p) != src_cpu) goto done; + /* Affinity changed (again). */ if (!cpumask_test_cpu(dest_cpu, tsk_cpus_allowed(p))) goto fail; @@ -4702,15 +4702,22 @@ static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu) * placed properly. */ if (task_on_rq_queued(p)) { - dequeue_task(rq_src, p, 0); + dequeue_task(rq, p, 0); + p->on_rq = TASK_ON_RQ_MIGRATING; set_task_cpu(p, dest_cpu); - enqueue_task(rq_dest, p, 0); - check_preempt_curr(rq_dest, p, 0); + raw_spin_unlock(&rq->lock); + + rq = cpu_rq(dest_cpu); + raw_spin_lock(&rq->lock); + BUG_ON(task_rq(p) != rq); + p->on_rq = TASK_ON_RQ_QUEUED; + enqueue_task(rq, p, 0); + check_preempt_curr(rq, p, 0); } done: ret = 1; fail: - double_rq_unlock(rq_src, rq_dest); + raw_spin_unlock(&rq->lock); raw_spin_unlock(&p->pi_lock); return ret; } |