linux-kernel - Re: [tip:sched/core] sched: Change wait_for_completion_*

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Date:	Wed, 12 Jan 2011 09:07:07 +1100
From:	NeilBrown <neilb@...e.de>
To:	"J. Bruce Fields" <bfields@...ldses.org>
Cc:	mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	a.p.zijlstra@...llo.nl, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, tglx@...utronix.de, mingo@...e.hu,
	stable@...nel.org, linux-tip-commits@...r.kernel.org
Subject: Re: [tip:sched/core] sched: Change wait_for_completion_*_timeout()
 to return a signed long

On Tue, 11 Jan 2011 16:44:58 -0500 "J. Bruce Fields" <bfields@...ldses.org>
wrote:

> Doesn't this belong in 2.6.37.y as well?

Yes indeed!
I should have tagged it for Cc:stable@...nel.org in the first place.  I had
been meaning to forward it to stable@...nel.org, but you beat me to it!

Thanks,
NeilBrown


> 
> --b.
> 
> On Wed, Jan 05, 2011 at 02:07:12PM +0000, tip-bot for NeilBrown wrote:
> > Commit-ID:  6bf4123760a5aece6e4829ce90b70b6ffd751d65
> > Gitweb:     http://git.kernel.org/tip/6bf4123760a5aece6e4829ce90b70b6ffd751d65
> > Author:     NeilBrown <neilb@...e.de>
> > AuthorDate: Wed, 5 Jan 2011 12:50:16 +1100
> > Committer:  Ingo Molnar <mingo@...e.hu>
> > CommitDate: Wed, 5 Jan 2011 14:15:50 +0100
> > 
> > sched: Change wait_for_completion_*_timeout() to return a signed long
> > 
> > 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.
> > 
> > Signed-off-by: NeilBrown <neilb@...e.de>
> > Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> > Cc: J.  Bruce Fields <bfields@...ldses.org>
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> > LKML-Reference: <20110105125016.64ccab0e@...abene.brown>
> > Signed-off-by: Ingo Molnar <mingo@...e.hu>
> > ---
> >  include/linux/completion.h |    8 ++++----
> >  kernel/sched.c             |    4 ++--
> >  2 files changed, 6 insertions(+), 6 deletions(-)
> > 
> > diff --git a/include/linux/completion.h b/include/linux/completion.h
> > index 36d57f7..51494e6 100644
> > --- a/include/linux/completion.h
> > +++ b/include/linux/completion.h
> > @@ -81,10 +81,10 @@ 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);
> >  
> > diff --git a/kernel/sched.c b/kernel/sched.c
> > index f2f914e..114a0de 100644
> > --- a/kernel/sched.c
> > +++ b/kernel/sched.c
> > @@ -4395,7 +4395,7 @@ EXPORT_SYMBOL(wait_for_completion_interruptible);
> >   * This waits for either a completion of a specific task to be signaled or for a
> >   * specified timeout to expire. It is interruptible. The timeout is in jiffies.
> >   */
> > -unsigned long __sched
> > +long __sched
> >  wait_for_completion_interruptible_timeout(struct completion *x,
> >  					  unsigned long timeout)
> >  {
> > @@ -4428,7 +4428,7 @@ EXPORT_SYMBOL(wait_for_completion_killable);
> >   * signaled or for a specified timeout to expire. It can be
> >   * interrupted by a kill signal. The timeout is in jiffies.
> >   */
> > -unsigned long __sched
> > +long __sched
> >  wait_for_completion_killable_timeout(struct completion *x,
> >  				     unsigned long timeout)
> >  {

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