From 5ee326b8c3535ac93a3761fdf57a15ae48a80aef Mon Sep 17 00:00:00 2001 From: Anand K Mistry Date: Wed, 29 Sep 2021 17:04:21 +1000 Subject: 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 Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20210929170405.1.I078b98ee7727f9ae9d6df8262bad7e325e40faf0@changeid Signed-off-by: Sasha Levin --- arch/x86/kernel/cpu/perf_event.c | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/x86/kernel/cpu/perf_event.c') diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c index b983d3dc4e6c..851fbdb99767 100644 --- a/arch/x86/kernel/cpu/perf_event.c +++ b/arch/x86/kernel/cpu/perf_event.c @@ -2001,6 +2001,7 @@ 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)) -- cgit v1.2.3