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Date: Mon, 16 Nov 2009 14:33:39 +0900 From: Jupyung Lee <jupyung@...il.com> To: LKML <linux-kernel@...r.kernel.org> Cc: Thomas Gleixner <tglx@...utronix.de>, Jupyung Lee <jupyung@...il.com> Subject: [PATCH -rt 1/1] sched_rt: change spinlock primitive in post_schedule_rt() In the function post_schedule_rt() of the current preempt-rt kernel, push_rt_task() is surrounded by atomic_spin_lock_irq(&rq->lock) and atomic_spin_unlock_irq(&rq->lock), which means that the function is called with the runqueue lock held and the interrupt disabled. A problem is that after finishing post_schedule_rt(), interrupt is always re-enabled regardless of the previous condition. In practice, the function post_schedule_rt() is called by finish_task_switch() with the interrupt disabled. Thus, the interrupt should not be re-enabled at the moment. The problem can simply be resolved by replacing atomic_spin_lock_irq() and atomic_spin_unlock_irq() with atomic_spin_lock_irqsave() and atomic_spin_unlock_irqrestore(). As a sidenote, the other way to resolve the problem might be to modify codes in accordance with commit 3f029d3c6d62068d59301d90c18dbde8ee402107, titled "sched: Enhance the pre/post scheduling logic", in the vanilla tree. Signed-off-by: Jupyung Lee <jupyung@...il.com> --- kernel/sched_rt.c | 5 +++-- 1 files changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c index 274c976..bd16998 100644 --- a/kernel/sched_rt.c +++ b/kernel/sched_rt.c @@ -1536,9 +1536,10 @@ static void post_schedule_rt(struct rq *rq) * This is only called if needs_post_schedule_rt() indicates that * we need to push tasks away */ - atomic_spin_lock_irq(&rq->lock); + unsigned long flags; + atomic_spin_lock_irqsave(&rq->lock, flags); push_rt_tasks(rq); - atomic_spin_unlock_irq(&rq->lock); + atomic_spin_unlock_irqrestore(&rq->lock, flags); } /* -- 1.6.5.GIT -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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