The patch titled
hrtimer: prevent migration for raising softirq
has been added to the -mm tree. Its filename is
hrtimer-prevent-migration-for-raising-softirq.patch
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See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: hrtimer: prevent migration for raising softirq
From: Steven Rostedt <rostedt@xxxxxxxxxxx>
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@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/hrtimer.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff -puN kernel/hrtimer.c~hrtimer-prevent-migration-for-raising-softirq kernel/hrtimer.c
--- a/kernel/hrtimer.c~hrtimer-prevent-migration-for-raising-softirq
+++ a/kernel/hrtimer.c
@@ -1000,10 +1000,18 @@ 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;
}
_
Patches currently in -mm which might be from rostedt@xxxxxxxxxxx are
linux-next.patch
ftrace-disable-function-tracing-bringing-up-new-cpu.patch
hrtimer-prevent-migration-for-raising-softirq.patch
split-the-typecheck-macros-out-of-include-linux-kernelh.patch
locking-add-typecheck-on-irqsave-and-friends-for-correct-flags.patch
locking-add-typecheck-on-irqsave-and-friends-for-correct-flags-fix.patch
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