linux-kernel - Re: [PATCH] kernel/freezer.c : Removing extra checking.

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Message-ID: <20081211123152.GA1842@ucw.cz>
Date:	Thu, 11 Dec 2008 13:31:53 +0100
From:	Pavel Machek <pavel@...e.cz>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Rakib Mullick <rakib.mullick@...il.com>,
	Linux-kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] kernel/freezer.c : Removing extra checking.

On Sat 2008-12-06 17:52:57, Rafael J. Wysocki wrote:
> On Saturday, 6 of December 2008, Rakib Mullick wrote:
> > On 12/6/08, Rafael J. Wysocki <rjw@...k.pl> wrote:
> > > On Saturday, 6 of December 2008, Rakib Mullick wrote:
> > >  > Impact: Reduces an extra checking.
> > >  >
> > >  > Following patch removes an extra checking. We can remove it since, the
> > >  > current task is frozen. If the current task is not frozen, then it
> > >  > will return from __else__ condition of freezing(current) check. So,
> > >  > the check becames unnecessary. It also reduces 32 bytes of text space
> > >  > on my x86  (32 bit) system.
> > >
> > >
> > > What will happen with this patch applied when a task is woken up for some
> > >  reason other than thawing?
> > thawing is usually used for woken up a frozzen process. Would you
> > please tell me what are the other ways to woken up a frozzen process?
> > Am I missing anything ?
> 
> Well, in theory the process can be woken up for another reason.

...like pending signal...

> I don't have any particular examples in mind, but in this case the burden is
> yours to show that it won't happen and to say why exactly you think so in the
> changelog, because this is the very reason why the code has been written this
> way in the first place.
> 
> Thanks,
> Rafael
> 
> 
> > >  > Signed-off-by: Rakib Mullick <rakib.mullick@...il.com>
> > >  >
> > >  > --- linux-2.6-orig/kernel/freezer.c   2008-12-05 19:53:45.000000000 +0600
> > >  > +++ linux-2.6/kernel/freezer.c        2008-12-05 19:55:40.000000000 +0600
> > >  > @@ -46,8 +46,6 @@ void refrigerator(void)
> > >  >
> > >  >       for (;;) {
> > >  >               set_current_state(TASK_UNINTERRUPTIBLE);
> > >  > -             if (!frozen(current))
> > >  > -                     break;
> > >  >               schedule();
> > >  >       }
> > >  >       pr_debug("%s left refrigerator\n", current->comm);
> > >

Plus this looks like infinite loop after your change. Have you tested
it?


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