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sched/rt: Clean up check_preempt_equal_prio()

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This patch checks if current can be pushed/pulled somewhere else
in advance to make logic clear, the same behavior as dl class.

- If current can't be migrated, useless to reschedule, let's hope
  task can move out.
- If task is migratable, so let's not schedule it and see if it
  can be pushed or pulled somewhere else.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Kirill Tkhai <ktkhai@parallels.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1414708776-124078-1-git-send-email-wanpeng.li@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Wanpeng Li 2014-10-31 06:39:31 +08:00 committed by Ingo Molnar
parent 75e23e49db
commit 308a623a40
1 changed files with 10 additions and 4 deletions
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14
kernel/sched/rt.c
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@ -1351,16 +1351,22 @@ select_task_rq_rt(struct task_struct *p, int cpu, int sd_flag, int flags)
static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
{
if (rq->curr->nr_cpus_allowed == 1)
/*
* Current can't be migrated, useless to reschedule,
* let's hope p can move out.
*/
if (rq->curr->nr_cpus_allowed == 1 ||
!cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
return;
/*
* p is migratable, so let's not schedule it and
* see if it is pushed or pulled somewhere else.
*/
if (p->nr_cpus_allowed != 1
&& cpupri_find(&rq->rd->cpupri, p, NULL))
return;
if (!cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
return;
/*
* There appears to be other cpus that can accept
* current and none to run 'p', so lets reschedule