Re: [PATCH 2/4] perf/core: convert call_rcu(free_ctx) to kfree_rcu()

From: Peter Zijlstra
Date: Wed Nov 20 2024 - 04:12:40 EST


On Wed, Nov 20, 2024 at 06:47:14AM +0000, Ran Xiaokai wrote:
> From: Ran Xiaokai <ran.xiaokai@xxxxxxxxxx>
>
> The rcu callback free_ctx() simply calls kfree().
> It's better to directly call kfree_rcu().

Why is it better?

> Signed-off-by: Ran Xiaokai <ran.xiaokai@xxxxxxxxxx>
> ---
> kernel/events/core.c | 10 +---------
> 1 file changed, 1 insertion(+), 9 deletions(-)
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 065f9188b44a..7f4cc9c41bbe 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -1210,14 +1210,6 @@ static void free_task_ctx_data(struct pmu *pmu, void *task_ctx_data)
> kmem_cache_free(pmu->task_ctx_cache, task_ctx_data);
> }
>
> -static void free_ctx(struct rcu_head *head)
> -{
> - struct perf_event_context *ctx;
> -
> - ctx = container_of(head, struct perf_event_context, rcu_head);
> - kfree(ctx);
> -}
> -
> static void put_ctx(struct perf_event_context *ctx)
> {
> if (refcount_dec_and_test(&ctx->refcount)) {
> @@ -1225,7 +1217,7 @@ static void put_ctx(struct perf_event_context *ctx)
> put_ctx(ctx->parent_ctx);
> if (ctx->task && ctx->task != TASK_TOMBSTONE)
> put_task_struct(ctx->task);
> - call_rcu(&ctx->rcu_head, free_ctx);
> + kfree_rcu(ctx, rcu_head);
> }
> }
>
> --
> 2.17.1
>
>