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Message-ID: <20080813183156.GA20974@redhat.com>
Date: Wed, 13 Aug 2008 14:31:56 -0400
From: Vivek Goyal <vgoyal@...hat.com>
To: "Eric W. Biederman" <ebiederm@...ssion.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
Huang Ying <ying.huang@...el.com>, Pavel Machek <pavel@....cz>,
nigel@...el.suspend2.net, "Rafael J. Wysocki" <rjw@...k.pl>,
Andrew Morton <akpm@...ux-foundation.org>, mingo@...e.hu,
linux-kernel@...r.kernel.org,
Kexec Mailing List <kexec@...ts.infradead.org>
Subject: Re: [PATCH] kexec jump: fix compiling warning on xchg(&kexec_lock,
0) in kernel_kexec()
On Wed, Aug 13, 2008 at 11:12:48AM -0700, Eric W. Biederman wrote:
> Linus Torvalds <torvalds@...ux-foundation.org> writes:
>
> > On Wed, 13 Aug 2008, Huang Ying wrote:
> >>
> >> - xchg(&kexec_lock, 0);
> >> + locked = xchg(&kexec_lock, 0);
> >> + BUG_ON(!locked);
> >
> > Why do you want to do this at all?
> >
> > And why do you implement your locks with xchg() in the first place? That's
> > total and utter crap.
> >
> > Hint: we have _real_ locking primitives in the kernel.
>
> This part certainly.
>
> The way the code should work, and the way it has in the past is:
> image = xchg(&kexec_image, NULL)
> if (!image)
> return -EINVAL;
>
> Very simple and very obvious and very easy to get right, and it has
> been that way for years.
>
Hi Eric,
Are there any issues with usage of test_and_set_bit() or usage of spinlock
primitives?
Thanks
Vivek
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