From: Peter Zijlstra <peterz@infradead.org>
To: Stephane Eranian <eranian@google.com>
Cc: eranian@gmail.com, Corey Ashford <cjashfor@linux.vnet.ibm.com>,
LKML <linux-kernel@vger.kernel.org>,
Paul Mackerras <paulus@samba.org>
Subject: Re: [BUG] perf_event: when events are grouped, the time enabled / running values are incorrect
Date: Tue, 11 May 2010 22:27:51 +0200 [thread overview]
Message-ID: <1273609671.1810.74.camel@laptop> (raw)
In-Reply-To: <AANLkTilVGy3nLymHUj-blglsL3y5ApyhUWrunxJYeQPb@mail.gmail.com>
On Tue, 2010-05-11 at 22:23 +0200, Stephane Eranian wrote:
> On Tue, May 11, 2010 at 10:11 PM, Peter Zijlstra <peterz@infradead.org> wrote:
> > On Tue, 2010-05-11 at 21:55 +0200, stephane eranian wrote:
> >> Events are also grouped in this example. Both this same issue exists
> >> also when only
> >> one event is used. I suspect an update_event_times() or
> >> update_group_times() is also
> >> missing on the sampling path in perf_overflow_handler().
> >
> > Hrmm, you're right, except fixing that is non-trivial.
> > update_event_times() wants to be called with ctx->lock held and we can't
> > do that from NMI context.
> >
> Why do you need the lock when the event is running on a CPU in NMI context?
> What action issued remotely could modify the data used by this function without
> the need for IPI?
Not sure, would at the very least have to verify that. I'll try and have
a look.
next prev parent reply other threads:[~2010-05-11 20:27 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-08 1:56 [BUG] perf_event: when events are grouped, the time enabled / running values are incorrect Corey Ashford
2010-05-08 2:24 ` Corey Ashford
2010-05-11 14:42 ` Peter Zijlstra
2010-05-11 15:43 ` [tip:perf/core] perf: Fix exit() vs event-groups tip-bot for Peter Zijlstra
2010-05-11 19:55 ` [BUG] perf_event: when events are grouped, the time enabled / running values are incorrect stephane eranian
2010-05-11 20:11 ` Peter Zijlstra
2010-05-11 20:23 ` Stephane Eranian
2010-05-11 20:27 ` Peter Zijlstra [this message]
2010-05-12 17:25 ` Corey Ashford
2010-05-12 17:50 ` Peter Zijlstra
2010-05-12 18:15 ` Corey Ashford
2010-05-12 18:42 ` Corey Ashford
2010-05-13 0:10 ` Paul Mackerras
2010-05-13 10:17 ` Paul Mackerras
2010-05-13 17:37 ` Corey Ashford
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