On Thu, Jul 03, 2014 at 11:36:38AM +0800, Chen LinX wrote: > From: "Chen LinX" <linx.z.c...@intel.com> > > when do cpu hotplug test and run below perf test together, pmu may access > freed perf_event > > while true; > do > perf record -a -g -f sleep 10 > rm perf.* > done > > the scenario is that when cpu offline firstly, the 'perf_cpu_notify' will > disable event on the > pmu and remove it from the context list. after cpu online, the perf app may > enable the event
But it does not, right? > that without linked in context list again. when cpu offine the second time, > the 'perf_cpu_notify' > can't disable event on the pmu as the event doesn't link to context list. the > perf app may free > this event later(the free procedure try to disable event on the pmu but as > the cpu is offline, > the 'cpu_function_call(event->cpu, __perf_remove_from_context, event)' is > failed) Failed how, below is __perf_install_in_context. > . then after > cpu online again, pmu will access freed perf_event and hit panic. > > so adding PERF_ATTACH_CONTEXT flag check before enable event to avoid this > scenario. In fact it does not. If you look at perf_event_enable() there's a code path that doesn't call __perf_event_enable(). > [ 157.670138 ] [<ffffffff8216321f>] __perf_install_in_context+0xff/0x170 And yet, __perf_install_in_context isn't mentioned at all in the above. > Change-Id: I7265d83159b9180e9be3a370ba50e067385547bd > Signed-off-by: Yanmin Zhang <yanmin.zh...@intel.com> > Signed-off-by: Chen LinX <linx.z.c...@intel.com> Wrong SoB-chain, Yanmin didn't author this patch did he, seeing how From is you. And Yanmin didn't actually send me this patch either.
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