linux-kernel - Re: [PATCH 1/5] perf: Wrap perf_lock_task_context using __cond

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Date:	Thu, 30 Sep 2010 13:38:49 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Namhyung Kim <namhyung@...il.com>
Cc:	Paul Mackerras <paulus@...ba.org>, Ingo Molnar <mingo@...e.hu>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] perf: Wrap perf_lock_task_context using
 __cond_lock()

On Mon, 2010-09-27 at 19:39 +0900, Namhyung Kim wrote:
> perf_lock_task_context() conditionally grabs ctx->lock in case of
> returning non-NULL. Rename and wrap it using __cond_lock to make
> sparse happy.
> 
> Signed-off-by: Namhyung Kim <namhyung@...il.com>
> ---
>  kernel/perf_event.c |   10 +++++++++-
>  1 files changed, 9 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/perf_event.c b/kernel/perf_event.c
> index db5b560..c058a42 100644
> --- a/kernel/perf_event.c
> +++ b/kernel/perf_event.c
> @@ -151,7 +151,7 @@ static u64 primary_event_id(struct perf_event *event)
>   * the context could get moved to another task.
>   */
>  static struct perf_event_context *
> -perf_lock_task_context(struct task_struct *task, unsigned long *flags)
> +__perf_lock_task_context(struct task_struct *task, unsigned long *flags)
>  {
>  	struct perf_event_context *ctx;
>  
> @@ -184,6 +184,14 @@ perf_lock_task_context(struct task_struct *task, unsigned long *flags)
>  	return ctx;
>  }
>  
> +static inline struct perf_event_context *
> +perf_lock_task_context(struct task_struct *task, unsigned long *flags)
> +{
> +	struct perf_event_context *ctx;
> +	__cond_lock(&ctx->lock, ctx = __perf_lock_task_context(task, flags));
> +	return ctx;
> +}
> +
>  /*
>   * Get the context for a task and increment its pin_count so it
>   * can't get swapped to another task.  This also increments its

This is a rather ugly annotation... why can't sparse use something like
the regular __acquire() function annotation but instead all it
__cond_acquire() ?


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