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SubjectRe: [PATCH] perf/arm-dmc620: Fix lockdep assert in ->event_init()
On Tue, May 14, 2024 at 11:00:50AM -0700, Namhyung Kim wrote:
> for_each_sibling_event() checks leader's ctx but it doesn't have the ctx
> yet if it's the leader. Like in perf_event_validate_size(), we should
> skip checking siblings in that case.
>
> Fixes: f3c0eba287049 ("perf: Add a few assertions")
> Reported-by: Greg Thelen <gthelen@google.com>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Cc: Tuan Phan <tuanphan@os.amperecomputing.com>
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> ---
> drivers/perf/arm_dmc620_pmu.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/perf/arm_dmc620_pmu.c b/drivers/perf/arm_dmc620_pmu.c
> index 8a81be2dd5ec..88c17c1d6d49 100644
> --- a/drivers/perf/arm_dmc620_pmu.c
> +++ b/drivers/perf/arm_dmc620_pmu.c
> @@ -542,12 +542,16 @@ static int dmc620_pmu_event_init(struct perf_event *event)
> if (event->cpu < 0)
> return -EINVAL;
>
> + hwc->idx = -1;
> +
> + if (event->group_leader == event)
> + return 0;
> +
> /*
> * We can't atomically disable all HW counters so only one event allowed,
> * although software events are acceptable.
> */
> - if (event->group_leader != event &&
> - !is_software_event(event->group_leader))
> + if (!is_software_event(event->group_leader))
> return -EINVAL;
>
> for_each_sibling_event(sibling, event->group_leader) {
> @@ -556,7 +560,6 @@ static int dmc620_pmu_event_init(struct perf_event *event)
> return -EINVAL;
> }
>
> - hwc->idx = -1;
> return 0;
> }

Thanks, I'll pick this up, although Mark reckoned he'd found some other
issues over at:

https://lore.kernel.org/r/Zg0l642PgQ7T3a8Z@FVFF77S0Q05N

but didn't elaborate on what exactly he'd found :/

Will

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