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sched: fix RT task-wakeup logic

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Dmitry Adamushko pointed out a logic error in task_wake_up_rt() where we
will always evaluate to "true".  You can find the thread here:

http://lkml.org/lkml/2008/4/22/296

In reality, we only want to try to push tasks away when a wake up request is
not going to preempt the current task.  So lets fix it.

Note: We introduce test_tsk_need_resched() instead of open-coding the flag
check so that the merge-conflict with -rt should help remind us that we
may need to support NEEDS_RESCHED_DELAYED in the future, too.

Signed-off-by: Gregory Haskins <ghaskins@novell.com>
CC: Dmitry Adamushko <dmitry.adamushko@gmail.com>
CC: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Gregory Haskins 2008-04-23 07:13:29 -04:00 committed by Ingo Molnar
parent 983ed7a66b
commit 8ae121ac86
2 changed files with 11 additions and 3 deletions
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7
include/linux/sched.h
View file

@ -1977,6 +1977,11 @@ static inline void clear_tsk_need_resched(struct task_struct *tsk)
clear_tsk_thread_flag(tsk,TIF_NEED_RESCHED);
}
static inline int test_tsk_need_resched(struct task_struct *tsk)
{
return unlikely(test_tsk_thread_flag(tsk,TIF_NEED_RESCHED));
}
static inline int signal_pending(struct task_struct *p)
{
return unlikely(test_tsk_thread_flag(p,TIF_SIGPENDING));
@ -1991,7 +1996,7 @@ static inline int fatal_signal_pending(struct task_struct *p)
static inline int need_resched(void)
{
return unlikely(test_thread_flag(TIF_NEED_RESCHED));
return unlikely(test_tsk_need_resched(current));
}
/*

7
kernel/sched_rt.c
View file

@ -1098,11 +1098,14 @@ static void post_schedule_rt(struct rq *rq)
}
}
/*
* If we are not running and we are not going to reschedule soon, we should
* try to push tasks away now
*/
static void task_wake_up_rt(struct rq *rq, struct task_struct *p)
{
if (!task_running(rq, p) &&
(p->prio >= rq->rt.highest_prio) &&
!test_tsk_need_resched(rq->curr) &&
rq->rt.overloaded)
push_rt_tasks(rq);
}