Re: [PATCH RT v2] x86/mce: Defer mce wakeups to threads for PREEMPT_RT

Sebastian Andrzej Siewior
2013-04-26T08:24:12Z

* Steven Rostedt | 2013-04-11 14:33:34 [-0400]:

>diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
>index e8d8ad0..060e473 100644
>--- a/arch/x86/kernel/cpu/mcheck/mce.c
>+++ b/arch/x86/kernel/cpu/mcheck/mce.c
>@@ -1308,6 +1309,61 @@ static void mce_do_trigger(struct work_struct *work)
>
> static DECLARE_WORK(mce_trigger_work, mce_do_trigger);
>
>+static void __mce_notify_work(void)
>+{
>+ /* Not more than two messages every minute */
>+ static DEFINE_RATELIMIT_STATE(ratelimit, 60*HZ, 2);
>+
>+ /* wake processes polling /dev/mcelog */
>+ wake_up_interruptible(&mce_chrdev_wait);
>+
>+ /*
>+ * There is no risk of missing notifications because
>+ * work_pending is always cleared before the function is
>+ * executed.
>+ */
>+ if (mce_helper[0] && !work_pending(&mce_trigger_work))
>+ schedule_work(&mce_trigger_work);

Why is here this work_pending() check? You can't enqueue a work item
twice.

Sebastian