sched: fix RT task-wakeup logic (8ae121ac) · Commits · 戴 / test

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>

include/linux/sched.h

+6 −1

Original line number	Diff line number	Diff line
		@@ -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));
		}

		/*

kernel/sched_rt.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -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);
		}

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