Messages in this thread Patch in this message | | | Date | Tue, 22 Jul 2008 16:17:43 -0700 | From | Greg KH <> | Subject | [patch 46/47] hrtimer: prevent migration for raising softirq |
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2.6.25-stable review patch. If anyone has any objections, please let us know.
------------------ From: Steven Rostedt <rostedt@goodmis.org>
commit ee3ece830f6db9837f7ac67008f532a8c1e755f4 upstream.
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 <srostedt@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- kernel/hrtimer.c | 8 ++++++++ 1 file changed, 8 insertions(+)
--- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -896,10 +896,18 @@ hrtimer_start(struct hrtimer *timer, kti */ 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; } --
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