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authorSteven Rostedt <rostedt@goodmis.org>2008-07-03 14:31:26 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2008-07-03 14:36:48 -0400
commitee3ece830f6db9837f7ac67008f532a8c1e755f4 (patch)
tree86512e4fe0a03970003260671a3c28045f57f5e8 /kernel
parent6beef7eb0c16b5216814148b04838cfa963d2cb4 (diff)
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 <srostedt@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/hrtimer.c8
1 files changed, 8 insertions, 0 deletions
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)
1003 */ 1003 */
1004 raise = timer->state == HRTIMER_STATE_PENDING; 1004 raise = timer->state == HRTIMER_STATE_PENDING;
1005 1005
1006 /*
1007 * We use preempt_disable to prevent this task from migrating after
1008 * setting up the softirq and raising it. Otherwise, if me migrate
1009 * we will raise the softirq on the wrong CPU.
1010 */
1011 preempt_disable();
1012
1006 unlock_hrtimer_base(timer, &flags); 1013 unlock_hrtimer_base(timer, &flags);
1007 1014
1008 if (raise) 1015 if (raise)
1009 hrtimer_raise_softirq(); 1016 hrtimer_raise_softirq();
1017 preempt_enable();
1010 1018
1011 return ret; 1019 return ret;
1012} 1020}