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From: Peter Zijlstra <peterz@infradead.org>
To: Eric B Munson <emunson@mgebm.net>
Cc: mingo@elte.hu, borislav.petkov@amd.com, bblum@andrew.cmu.edu,
	linux-kernel@vger.kernel.org, mhack@us.ibm.com,
	eranian@google.com
Subject: Re: [PATCH 3/3] events: Ensure that timers are updated without requiring read() call
Date: Fri, 24 Jun 2011 11:46:21 +0200	[thread overview]
Message-ID: <1308908781.27849.23.camel@twins> (raw)
In-Reply-To: <1308908656.27849.21.camel@twins>

On Fri, 2011-06-24 at 11:44 +0200, Peter Zijlstra wrote:
> > +     calc_timer_values(event,
> > +                             &event->total_time_enabled,
> > +                             &event->total_time_running);
> 
> I'm not sure writing those from NMI context is a sane thing to do, best
> is to compute the values into a local variable and use that variable
> below. 

To clarify, on 32bit architectures the NMI might come in the middle of
writing the two words of one of those, writing them again from the NMI
handler will result in overlapping writes, which might lead to some
weird end-results.


  reply	other threads:[~2011-06-24  9:47 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-06-23 20:34 [PATCH 1/3] events: Add note to update_event_times comment about holding ctx->lock Eric B Munson
2011-06-23 20:34 ` [PATCH 2/3] events: Move lockless timer calculation into helper function Eric B Munson
2011-07-01 15:20   ` [tip:perf/core] " tip-bot for Eric B Munson
2011-06-23 20:34 ` [PATCH 3/3] events: Ensure that timers are updated without requiring read() call Eric B Munson
2011-06-24  9:44   ` Peter Zijlstra
2011-06-24  9:46     ` Peter Zijlstra [this message]
2011-06-24 12:44     ` Eric B Munson
2011-06-24 12:49     ` Eric B Munson
2011-06-27  9:34       ` Peter Zijlstra
2011-07-01 15:19 ` [tip:perf/core] events: Add note to update_event_times comment about holding ctx->lock tip-bot for Eric B Munson

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