[PATCH v2] perf/arm-smmuv3: Fix lockdep assert in ->event_init()

[PATCH v2] perf/arm-smmuv3: Fix lockdep assert in ->event_init()

[Chun-Tse Shao]

Same as
https://lore.kernel.org/all/20240514180050.182454-1-namhyung@kernel.org/,
we should skip `for_each_sibling_event()` for group leader since it
doesn't have the ctx yet.

Fixes: f3c0eba28704 ("perf: Add a few assertions")
Reported-by: Greg Thelen <gthelen@google.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Tuan Phan <tuanphan@os.amperecomputing.com>
Signed-off-by: Chun-Tse Shao <ctshao@google.com>
---
 drivers/perf/arm_smmuv3_pmu.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/perf/arm_smmuv3_pmu.c b/drivers/perf/arm_smmuv3_pmu.c
index d5fa92ba8373..dabdb9f7bb82 100644
--- a/drivers/perf/arm_smmuv3_pmu.c
+++ b/drivers/perf/arm_smmuv3_pmu.c
@@ -431,6 +431,17 @@ static int smmu_pmu_event_init(struct perf_event *event)
 			return -EINVAL;
 	}
 
+	/*
+	 * Ensure all events are on the same cpu so all events are in the
+	 * same cpu context, to avoid races on pmu_enable etc.
+	 */
+	event->cpu = smmu_pmu->on_cpu;
+
+	hwc->idx = -1;
+
+	if (event->group_leader == event)
+		return 0;
+
 	for_each_sibling_event(sibling, event->group_leader) {
 		if (is_software_event(sibling))
 			continue;
@@ -442,14 +453,6 @@ static int smmu_pmu_event_init(struct perf_event *event)
 			return -EINVAL;
 	}
 
-	hwc->idx = -1;
-
-	/*
-	 * Ensure all events are on the same cpu so all events are in the
-	 * same cpu context, to avoid races on pmu_enable etc.
-	 */
-	event->cpu = smmu_pmu->on_cpu;
-
 	return 0;
 }
 
-- 
2.47.0.277.g8800431eea-goog

Re: [PATCH v2] perf/arm-smmuv3: Fix lockdep assert in ->event_init()

[Will Deacon]

On Fri, Nov 08, 2024 at 05:08:05AM +0000, Chun-Tse Shao wrote:
> Same as
> https://lore.kernel.org/all/20240514180050.182454-1-namhyung@kernel.org/,
> we should skip `for_each_sibling_event()` for group leader since it
> doesn't have the ctx yet.
> 
> Fixes: f3c0eba28704 ("perf: Add a few assertions")
> Reported-by: Greg Thelen <gthelen@google.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Cc: Tuan Phan <tuanphan@os.amperecomputing.com>
> Signed-off-by: Chun-Tse Shao <ctshao@google.com>
> ---
>  drivers/perf/arm_smmuv3_pmu.c | 19 +++++++++++--------
>  1 file changed, 11 insertions(+), 8 deletions(-)

Acked-by: Will Deacon <will@kernel.org>

Catalin -- please can you pick this up for -rc1?

Will

Re: [PATCH v2] perf/arm-smmuv3: Fix lockdep assert in ->event_init()

[Catalin Marinas]

On Fri, 08 Nov 2024 05:08:05 +0000, Chun-Tse Shao wrote:
> Same as
> https://lore.kernel.org/all/20240514180050.182454-1-namhyung@kernel.org/,
> we should skip `for_each_sibling_event()` for group leader since it
> doesn't have the ctx yet.
> 
> 

Applied to arm64 (for-next/fixes), thanks!

[1/1] perf/arm-smmuv3: Fix lockdep assert in ->event_init()
      https://git.kernel.org/arm64/c/02a55f274301

-- 
Catalin