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

[PATCH] 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 | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/perf/arm_smmuv3_pmu.c b/drivers/perf/arm_smmuv3_pmu.c
index d5fa92ba8373..09789599fccc 100644
--- a/drivers/perf/arm_smmuv3_pmu.c
+++ b/drivers/perf/arm_smmuv3_pmu.c
@@ -431,6 +431,11 @@ static int smmu_pmu_event_init(struct perf_event *event)
 			return -EINVAL;
 	}
 
+	hwc->idx = -1;
+
+	if (event->group_leader == event)
+		return 0;
+
 	for_each_sibling_event(sibling, event->group_leader) {
 		if (is_software_event(sibling))
 			continue;
@@ -442,8 +447,6 @@ 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.
-- 
2.47.0.277.g8800431eea-goog

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

[Namhyung Kim]

On Thu, Nov 07, 2024 at 09:59:20PM +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 | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/perf/arm_smmuv3_pmu.c b/drivers/perf/arm_smmuv3_pmu.c
> index d5fa92ba8373..09789599fccc 100644
> --- a/drivers/perf/arm_smmuv3_pmu.c
> +++ b/drivers/perf/arm_smmuv3_pmu.c
> @@ -431,6 +431,11 @@ static int smmu_pmu_event_init(struct perf_event *event)
>  			return -EINVAL;
>  	}
>  
> +	hwc->idx = -1;

I think you should update the event->cpu as well.

Thanks,
Namhyung

> +
> +	if (event->group_leader == event)
> +		return 0;
> +
>  	for_each_sibling_event(sibling, event->group_leader) {
>  		if (is_software_event(sibling))
>  			continue;
> @@ -442,8 +447,6 @@ 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.
> -- 
> 2.47.0.277.g8800431eea-goog
> 

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

[Chun-Tse Shao]

Thank you for your feedback, Namhyung! Please see my v2 patch:
https://lore.kernel.org/all/20241108050806.3730811-1-ctshao@google.com/

On Thu, Nov 7, 2024 at 5:23 PM Namhyung Kim <namhyung@kernel.org> wrote:
>
> On Thu, Nov 07, 2024 at 09:59:20PM +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 | 7 +++++--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/perf/arm_smmuv3_pmu.c b/drivers/perf/arm_smmuv3_pmu.c
> > index d5fa92ba8373..09789599fccc 100644
> > --- a/drivers/perf/arm_smmuv3_pmu.c
> > +++ b/drivers/perf/arm_smmuv3_pmu.c
> > @@ -431,6 +431,11 @@ static int smmu_pmu_event_init(struct perf_event *event)
> >                       return -EINVAL;
> >       }
> >
> > +     hwc->idx = -1;
>
> I think you should update the event->cpu as well.
>
> Thanks,
> Namhyung
>
> > +
> > +     if (event->group_leader == event)
> > +             return 0;
> > +
> >       for_each_sibling_event(sibling, event->group_leader) {
> >               if (is_software_event(sibling))
> >                       continue;
> > @@ -442,8 +447,6 @@ 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.
> > --
> > 2.47.0.277.g8800431eea-goog
> >