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

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Message-ID: <20130426084137.GC20927@linutronix.de>
Date:	Fri, 26 Apr 2013 10:41:37 +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]:

>As wait queue locks are notorious for long hold times, we can not
>convert them to raw_spin_locks without causing issues with -rt. But
>Thomas has created a "simple-wait" structure that uses raw spin locks
>which may have been a good fit.
>
>Unfortunately, wait queues are not the only issue, as the mce_notify_irq
>also does a schedule_work(), which grabs the workqueue spin locks that
>have the exact same issue.

mce_notify_irq() can use simple_waitqueue, no?
The other issue is that mce_report_event() is scheduling a per-cpu
workqueue (mce_schedule_work) in case of a memory fault. This has the
same issue.

Sebastian
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