This is a note to let you know that I've just added the patch titled perf/x86: Reset destroy callback on event init failure to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: perf-x86-reset-destroy-callback-on-event-init-failur.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit de9dc4077167fa8e0b1b846ee4139a1d4149d5f1 Author: Anand K Mistry <amistry@xxxxxxxxxx> Date: Wed Sep 29 17:04:21 2021 +1000 perf/x86: Reset destroy callback on event init failure [ Upstream commit 02d029a41dc986e2d5a77ecca45803857b346829 ] perf_init_event tries multiple init callbacks and does not reset the event state between tries. When x86_pmu_event_init runs, it unconditionally sets the destroy callback to hw_perf_event_destroy. On the next init attempt after x86_pmu_event_init, in perf_try_init_event, if the pmu's capabilities includes PERF_PMU_CAP_NO_EXCLUDE, the destroy callback will be run. However, if the next init didn't set the destroy callback, hw_perf_event_destroy will be run (since the callback wasn't reset). Looking at other pmu init functions, the common pattern is to only set the destroy callback on a successful init. Resetting the callback on failure tries to replicate that pattern. This was discovered after commit f11dd0d80555 ("perf/x86/amd/ibs: Extend PERF_PMU_CAP_NO_EXCLUDE to IBS Op") when the second (and only second) run of the perf tool after a reboot results in 0 samples being generated. The extra run of hw_perf_event_destroy results in active_events having an extra decrement on each perf run. The second run has active_events == 0 and every subsequent run has active_events < 0. When active_events == 0, the NMI handler will early-out and not record any samples. Signed-off-by: Anand K Mistry <amistry@xxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Link: https://lkml.kernel.org/r/20210929170405.1.I078b98ee7727f9ae9d6df8262bad7e325e40faf0@changeid Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c index c26cca506f64..c20df6a3540c 100644 --- a/arch/x86/events/core.c +++ b/arch/x86/events/core.c @@ -2075,6 +2075,7 @@ static int x86_pmu_event_init(struct perf_event *event) if (err) { if (event->destroy) event->destroy(event); + event->destroy = NULL; } if (ACCESS_ONCE(x86_pmu.attr_rdpmc))