linux-kernel - Re: [PATCH RT v2] x86/mce: Defer mce wakeups to threads for PREEMPT

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20130426082407.GB20927@linutronix.de>
Date:	Fri, 26 Apr 2013 10:24:07 +0200
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	RT <linux-rt-users@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Clark Williams <clark@...hat.com>,
	John Kacur <jkacur@...hat.com>,
	Tony Luck <tony.luck@...el.com>,
	Borislav Petkov <bp@...en8.de>,
	Mauro Carvalho Chehab <mchehab@...hat.com>,
	Ingo Molnar <mingo@...nel.org>,
	"H. Peter Anvin" <hpa@...ux.intel.com>
Subject: Re: [PATCH RT v2] x86/mce: Defer mce wakeups to threads for
 PREEMPT_RT

* 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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/