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Date: Sat, 16 Oct 2010 12:12:38 +0100 From: Matt Fleming <matt@...sole-pimps.org> To: Peter Zijlstra <peterz@...radead.org> Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>, Arnaldo Carvalho de Melo <acme@...hat.com>, Frederic Weisbecker <fweisbec@...il.com> Subject: Re: [PATCH] perf: Detach group events when removing event from ctx 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() :-( -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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