From ee3ece830f6db9837f7ac67008f532a8c1e755f4 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Thu, 3 Jul 2008 14:31:26 -0400 Subject: hrtimer: prevent migration for raising softirq Due to a possible deadlock, the waking of the softirq was pushed outside of the hrtimer base locks. See commit 0c96c5979a522c3323c30a078a70120e29b5bdbc Unfortunately this allows the task to migrate after setting up the softirq and raising it. Since softirqs run a queue that is per-cpu we may raise the softirq on the wrong CPU and this will keep the queued softirq task from running. To solve this issue, this patch disables preemption around the releasing of the hrtimer lock and raising of the softirq. Signed-off-by: Steven Rostedt Signed-off-by: Linus Torvalds --- kernel/hrtimer.c | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'kernel') diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index 421be5fe5cc7..ab80515008f4 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -1003,10 +1003,18 @@ hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode) */ raise = timer->state == HRTIMER_STATE_PENDING; + /* + * We use preempt_disable to prevent this task from migrating after + * setting up the softirq and raising it. Otherwise, if me migrate + * we will raise the softirq on the wrong CPU. + */ + preempt_disable(); + unlock_hrtimer_base(timer, &flags); if (raise) hrtimer_raise_softirq(); + preempt_enable(); return ret; } -- cgit v1.2.3