linux-kernel - Re: [PATCH] Change wait_for_completion_*

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Message-Id: <20110105145725.3fa6d659.akpm@linux-foundation.org>
Date:	Wed, 5 Jan 2011 14:57:25 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	NeilBrown <neilb@...e.de>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	"J. Bruce Fields" <bfields@...ldses.org>
Subject: Re: [PATCH] Change wait_for_completion_*_timeout to return a signed
 long

On Wed, 5 Jan 2011 12:50:16 +1100
NeilBrown <neilb@...e.de> wrote:

> 
> wait_for_completion_*_timeout can return:
> 
>  0 if the wait timed out
>  -ve if the wait was interrupted
>  +ve if the completion was completed.
> 
> As they currently return an 'unsigned long', the last two cases are not
> easily distinguished which can easily result in buggy code, as is the
> case for the recently added wait_for_completion_interruptible_timeout
> call in net/sunrpc/cache.c
> 
> So change them both to return 'long'.  As MAX_SCHEDULE_TIMEOUT is
> LONG_MAX, a large +ve return value should never overflow.
> 
> ...
>
> --- a/include/linux/completion.h
> +++ b/include/linux/completion.h
> @@ -80,11 +80,11 @@ extern void wait_for_completion(struct completion *);
>  extern int wait_for_completion_interruptible(struct completion *x);
>  extern int wait_for_completion_killable(struct completion *x);
>  extern unsigned long wait_for_completion_timeout(struct completion *x,
>  						   unsigned long timeout);
> -extern unsigned long wait_for_completion_interruptible_timeout(
> -			struct completion *x, unsigned long timeout);
> -extern unsigned long wait_for_completion_killable_timeout(
> -			struct completion *x, unsigned long timeout);
> +extern long wait_for_completion_interruptible_timeout(
> +	struct completion *x, unsigned long timeout);
> +extern long wait_for_completion_killable_timeout(
> +	struct completion *x, unsigned long timeout);
>  extern bool try_wait_for_completion(struct completion *x);
>  extern bool completion_done(struct completion *x);
>  

That's a half-patch, isn't it?  wait_for_completion_interruptible()
still incorrectly returns `int' and wait_for_completion_timeout() still
returns `unsigned long'.

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