linux-kernel - Re: [PATCH] signal: annotate siglock acquisition

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Date:	Sat, 25 Sep 2010 11:42:07 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Namhyung Kim <namhyung@...il.com>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	Roland McGrath <roland@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] signal: annotate siglock acquisition

Le samedi 25 septembre 2010 à 18:21 +0900, Namhyung Kim a écrit :
> lock_task_sighand() conditionally acquires sighand->siglock in case of
> returning non-NULL but unlock_task_sighand() releases it unconditionally.
> This leads sparse to complain about the lock context imbalance. Annotate it
> to make sparse happier.

> @@ -1403,7 +1404,9 @@ int send_sigqueue(struct sigqueue *q, struct task_struct *t, int group)
>  	BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
>  
>  	ret = -1;
> -	if (!likely(lock_task_sighand(t, &flags)))
> +	if (likely(lock_task_sighand(t, &flags)))
> +		__acquire(&t->sighand->siglock);
> +	else
>  		goto ret;
>  
>  	ret = 1; /* the signal is ignored */

making sparse happy is good, but changing a likely clause is not,
unless you meant it ;)

maybe -->

	if (!likely(lock_task_sighand(t, &flags)))
		goto ret;
	else
		__acquire(&t->sighand->siglock);



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