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From: Cyrill Gorcunov <gorcunov@gmail.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@elte.hu>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH -tip] x86,perf: P4 PMU -- protect sensible procedures from preemption
Date: Thu, 6 May 2010 18:48:54 +0400	[thread overview]
Message-ID: <20100506144854.GB5583@lenovo> (raw)
In-Reply-To: <1273153525.22438.39.camel@gandalf.stny.rr.com>

On Thu, May 06, 2010 at 09:45:24AM -0400, Steven Rostedt wrote:
...
> > > We want the one with the least runtime overhead. These are instrumentation
> > > routines, so we want to optimize them as much as possible.
> 
> 
> Yeah, my point was either disable preemption or keep the checks. In
> other words, if you don't disable preemption, do not use
> raw_smp_procesor_id(), because then we will not catch it if it changes
> in the future.
> 
> > ok, Ingo, dont apply this patch then for a while.
> 
> Send another patch, I'll test it again ;-)
> 
> -- Steve
> 
> 

Ingo, Steven, it seems we have potential preemtion available
in perf_event.c:validate_group:x86_pmu.schedule_events() which
is reached via syscall from userspace perf_event_open() call,
so get_cpu is still needed. But I'm a bit messed with call
graph at the moment :(

	-- Cyrill

  reply	other threads:[~2010-05-06 14:49 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-05-05 15:07 Cyrill Gorcunov
2010-05-05 16:57 ` Frederic Weisbecker
2010-05-05 17:42   ` Cyrill Gorcunov
2010-05-05 17:58     ` Frederic Weisbecker
2010-05-06  6:44     ` Ingo Molnar
2010-05-06  7:39       ` Cyrill Gorcunov
2010-05-06  7:42         ` Ingo Molnar
2010-05-06  7:45           ` Cyrill Gorcunov
2010-05-06 13:45             ` Steven Rostedt
2010-05-06 14:48               ` Cyrill Gorcunov [this message]
2010-05-06 15:26                 ` Cyrill Gorcunov
2010-05-06 18:32                   ` Steven Rostedt
2010-05-06 18:36                     ` Cyrill Gorcunov
2010-05-07 15:05 Cyrill Gorcunov
2010-05-08  8:06 ` Ingo Molnar
2010-05-08  8:09   ` Cyrill Gorcunov

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