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Date: Fri, 03 May 2013 11:31:39 +0200
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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To: Steven Rostedt <rostedt@goodmis.org>
CC: LKML <linux-kernel@vger.kernel.org>, RT <linux-rt-users@vger.kernel.org>,
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        Mauro Carvalho Chehab <mchehab@redhat.com>,
        Ingo Molnar <mingo@kernel.org>, "H. Peter Anvin" <hpa@linux.intel.com>
Subject: Re: [PATCH RT v2] x86/mce: Defer mce wakeups to threads for PREEMPT_RT
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On 05/02/2013 04:33 PM, Steven Rostedt wrote:
>> mce_notify_irq() can use simple_waitqueue, no?
> 
> Yeah, and I went down that path.
> 
> But it also schedules work, which has the issue.

Hmm, okay.

>> 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.
> 
> Yeah, that looks like it can be an issue too. I wonder if we can use the
> same thread and use flags check what to do. Atomically set the flag for
> the function to perform, and then have the thread clear it before doing
> the function and only go to sleep when all flags are cleared.

This should work. It uses per-cpu workthreads, not sure why. Maybe to
avoid locking issues when invoked from NMI.

> 
> -- Steve

Sebastian