From: Matt Fleming <matt@console-pimps.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Frederic Weisbecker <fweisbec@gmail.com>
Subject: Re: [PATCH] perf: Detach group events when removing event from ctx
Date: Sat, 16 Oct 2010 12:12:38 +0100 [thread overview]
Message-ID: <20101016111238.GA7806@console-pimps.org> (raw)
In-Reply-To: <1287135757.29097.1368.camel@twins>
On Fri, Oct 15, 2010 at 11:42:37AM +0200, Peter Zijlstra wrote:
> On Sun, 2010-10-03 at 20:35 +0100, Matt Fleming wrote:
> > When removing an event from a task's list of events we need to make sure
> > that we also detach all group events. If we don't, then when we later
> > call perf_group_attach() we'll hit the WARN_ON_ONCE() like so,
> >
> > [ 1200.449161] ------------[ cut here ]------------
> > [ 1200.449171] WARNING: at kernel/perf_event.c:313 add_event_to_ctx+0xe1/0x159()
> > [ 1200.449174] Hardware name: MacBook2,1
> > [ 1200.449176] Modules linked in: dm_mod sg sd_mod
> > [ 1200.449183] Pid: 7619, comm: perf Not tainted 2.6.36-rc6-tip+ #2
> > [ 1200.449186] Call Trace:
> > [ 1200.449193] [<ffffffff8103b71e>] warn_slowpath_common+0x85/0x9d
> > [ 1200.449197] [<ffffffff8103b750>] warn_slowpath_null+0x1a/0x1c
> > [ 1200.449201] [<ffffffff810a16fb>] add_event_to_ctx+0xe1/0x159
> > [ 1200.449206] [<ffffffff810a2f01>] perf_install_in_context+0x85/0x99
> > [ 1200.449210] [<ffffffff810a7811>] sys_perf_event_open+0x4da/0x633
> > [ 1200.449216] [<ffffffff81002b1b>] system_call_fastpath+0x16/0x1b
> > [ 1200.449218] ---[ end trace 9df38c30c6cacb50 ]---
>
> I think its due to the new and fancy move groups around context code
> from: b04243ef70 (perf: Complete software pmu grouping).
>
> Does the below cure it?
>
> It only detaches the group when we move it from one context to another,
> the perf_install_in_context() later on will then re-assemble the group
> on the other context.
>
> ---
> Index: linux-2.6/kernel/perf_event.c
> ===================================================================
> --- linux-2.6.orig/kernel/perf_event.c
> +++ linux-2.6/kernel/perf_event.c
> @@ -5592,6 +5592,7 @@ SYSCALL_DEFINE5(perf_event_open,
> list_for_each_entry(sibling, &group_leader->sibling_list,
> group_entry) {
> perf_event_remove_from_context(sibling);
> + perf_group_detach(sibling);
> put_ctx(gctx);
> }
> mutex_unlock(&gctx->mutex);
>
Unfortunately this still hits the WARN_ON_ONCE() :-(
next prev parent reply other threads:[~2010-10-16 11:12 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-03 19:35 Matt Fleming
2010-10-11 10:25 ` Matt Fleming
2010-10-15 9:42 ` Peter Zijlstra
2010-10-16 11:12 ` Matt Fleming [this message]
2010-10-18 19:19 ` [tip:perf/core] perf: Fix group moving tip-bot for Peter Zijlstra
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