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authorNamhyung Kim <namhyung@kernel.org>2023-07-04 11:15:15 -0700
committerPeter Zijlstra <peterz@infradead.org>2023-07-10 09:52:20 +0200
commit27c68c216ee1f1b086e789a64486e6511e380b8a (patch)
tree97a8cd337fea5c01f6d8b5050cef2863be6d2e33 /arch
parent06c2afb862f9da8dc5efa4b6076a0e48c3fbaaa5 (diff)
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.c7
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))