This is a note to let you know that I've just added the patch titled
perf/x86: Fix lockdep warning in for_each_sibling_event() on SPR
to the 6.4-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-fix-lockdep-warning-in-for_each_sibling_event-on-spr.patch
and it can be found in the queue-6.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 27c68c216ee1f1b086e789a64486e6511e380b8a Mon Sep 17 00:00:00 2001
From: Namhyung Kim <namhyung@xxxxxxxxxx>
Date: Tue, 4 Jul 2023 11:15:15 -0700
Subject: perf/x86: Fix lockdep warning in for_each_sibling_event() on SPR
From: Namhyung Kim <namhyung@xxxxxxxxxx>
commit 27c68c216ee1f1b086e789a64486e6511e380b8a upstream.
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@xxxxxxxxxx>
Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20230704181516.3293665-1-namhyung@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/events/intel/core.c | 7 +++++++
1 file changed, 7 insertions(+)
--- 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 pe
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))
Patches currently in stable-queue which might be from namhyung@xxxxxxxxxx are
queue-6.4/perf-x86-fix-lockdep-warning-in-for_each_sibling_event-on-spr.patch
