Re: [PATCH] perf/lock: enable end-timestamp accounting for cgroup aggregation

[Namhyung Kim <namhyung@kernel.org>]

On Tue, Apr 21, 2026 at 12:16:56AM +0530, Suchit Karunakaran wrote:
> update_lock_stat() handles lock contentions that start but never reach a
> contention_end event (e.g., locks still held when profiling stops), but
> previously treated LOCK_AGGR_CGROUP as a no-op due to missing cgroup
> context in userspace; fix this by adding a cgroup_id field to
> struct tstamp_data, recording it at contention_begin using
> get_current_cgroup_id() when aggr_mode == LOCK_AGGR_CGROUP, and using
> ts_data->cgroup_id to build the aggregation key in update_lock_stat(),
> matching the contention_end behavior in BPF and ensuring correct
> attribution of incomplete events.
> 
> Signed-off-by: Suchit Karunakaran <suchitkarunakaran@gmail.com>
> ---
>  tools/perf/util/bpf_lock_contention.c          | 4 ++--
>  tools/perf/util/bpf_skel/lock_contention.bpf.c | 2 ++
>  tools/perf/util/bpf_skel/lock_data.h           | 1 +
>  3 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/util/bpf_lock_contention.c b/tools/perf/util/bpf_lock_contention.c
> index cbd7435579fe..1a5bd2ff8ee4 100644
> --- a/tools/perf/util/bpf_lock_contention.c
> +++ b/tools/perf/util/bpf_lock_contention.c
> @@ -463,8 +463,8 @@ static void update_lock_stat(int map_fd, int pid, u64 end_ts,
>  		stat_key.lock_addr_or_cgroup = ts_data->lock;
>  		break;
>  	case LOCK_AGGR_CGROUP:
> -		/* TODO */
> -		return;
> +		stat_key.lock_addr_or_cgroup = ts_data->cgroup_id;
> +		break;
>  	default:
>  		return;
>  	}
> diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/util/bpf_skel/lock_contention.bpf.c
> index 96e7d853b9ed..d0e2cad02fa3 100644
> --- a/tools/perf/util/bpf_skel/lock_contention.bpf.c
> +++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c
> @@ -536,6 +536,8 @@ int contention_begin(u64 *ctx)
>  	pelem->timestamp = bpf_ktime_get_ns();
>  	pelem->lock = (__u64)ctx[0];
>  	pelem->flags = (__u32)ctx[1];
> +	if (aggr_mode == LOCK_AGGR_CGROUP)
> +		pelem->cgroup_id = get_current_cgroup_id();

If we do this, we can use it in contention_end() too.

Thanks,
Namhyung

>  
>  	if (needs_callstack) {
>  		u32 i = 0;
> diff --git a/tools/perf/util/bpf_skel/lock_data.h b/tools/perf/util/bpf_skel/lock_data.h
> index 28c5e5aced7f..652e114e6b87 100644
> --- a/tools/perf/util/bpf_skel/lock_data.h
> +++ b/tools/perf/util/bpf_skel/lock_data.h
> @@ -13,6 +13,7 @@ struct owner_tracing_data {
>  struct tstamp_data {
>  	u64 timestamp;
>  	u64 lock;
> +	u64 cgroup_id;
>  	u32 flags;
>  	s32 stack_id;
>  };
> -- 
> 2.53.0
>