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| author | Namhyung Kim <namhyung@kernel.org> | 2023-07-04 20:15:15 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2023-07-10 09:52:20 +0200 |
| commit | 27c68c216ee1f1b086e789a64486e6511e380b8a (patch) | |
| tree | 97a8cd337fea5c01f6d8b5050cef2863be6d2e33 /arch | |
| parent | Linux 6.5-rc1 (diff) | |
| download | linux-27c68c216ee1f1b086e789a64486e6511e380b8a.tar.xz linux-27c68c216ee1f1b086e789a64486e6511e380b8a.zip | |
perf/x86: Fix lockdep warning in for_each_sibling_event() on SPR
On SPR, the load latency event needs an auxiliary event in the same
group to work properly. There's a check in intel_pmu_hw_config()
for this to iterate sibling events and find a mem-loads-aux event.
The for_each_sibling_event() has a lockdep assert to make sure if it
disabled hardirq or hold leader->ctx->mutex. This works well if the
given event has a separate leader event since perf_try_init_event()
grabs the leader->ctx->mutex to protect the sibling list. But it can
cause a problem when the event itself is a leader since the event is
not initialized yet and there's no ctx for the event.
Actually I got a lockdep warning when I run the below command on SPR,
but I guess it could be a NULL pointer dereference.
$ perf record -d -e cpu/mem-loads/uP true
The code path to the warning is:
sys_perf_event_open()
perf_event_alloc()
perf_init_event()
perf_try_init_event()
x86_pmu_event_init()
hsw_hw_config()
intel_pmu_hw_config()
for_each_sibling_event()
lockdep_assert_event_ctx()
We don't need for_each_sibling_event() when it's a standalone event.
Let's return the error code directly.
Fixes: f3c0eba28704 ("perf: Add a few assertions")
Reported-by: Greg Thelen <gthelen@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20230704181516.3293665-1-namhyung@kernel.org
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/events/intel/core.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c index a149fafad813..2a284ba951b7 100644 --- a/arch/x86/events/intel/core.c +++ b/arch/x86/events/intel/core.c @@ -3993,6 +3993,13 @@ static int intel_pmu_hw_config(struct perf_event *event) struct perf_event *leader = event->group_leader; struct perf_event *sibling = NULL; + /* + * When this memload event is also the first event (no group + * exists yet), then there is no aux event before it. + */ + if (leader == event) + return -ENODATA; + if (!is_mem_loads_aux_event(leader)) { for_each_sibling_event(sibling, leader) { if (is_mem_loads_aux_event(sibling)) |