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

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

* 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