From: ebiederm@xmission.com (Eric W. Biederman)
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Huang Ying <ying.huang@intel.com>, Pavel Machek <pavel@ucw.cz>,
nigel@nigel.suspend2.net, "Rafael J. Wysocki" <rjw@sisk.pl>,
Andrew Morton <akpm@linux-foundation.org>,
Vivek Goyal <vgoyal@redhat.com>,
mingo@elte.hu, linux-kernel@vger.kernel.org,
Kexec Mailing List <kexec@lists.infradead.org>
Subject: Re: [PATCH] kexec jump: fix compiling warning on xchg(&kexec_lock, 0) in kernel_kexec()
Date: Wed, 13 Aug 2008 11:12:48 -0700 [thread overview]
Message-ID: <m1r68shjhb.fsf@frodo.ebiederm.org> (raw)
In-Reply-To: <alpine.LFD.1.10.0808130956360.3462@nehalem.linux-foundation.org> (Linus Torvalds's message of "Wed, 13 Aug 2008 09:57:33 -0700 (PDT)")
Linus Torvalds <torvalds@linux-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.
Eric
next prev parent reply other threads:[~2008-08-13 18:23 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-13 9:12 [PATCH] kexec jump: fix compiling warning on xchg(&kexec_lock, 0) in kernel_kexec() Huang Ying
2008-08-13 9:27 ` Andrew Morton
2008-08-13 17:01 ` Linus Torvalds
2008-08-13 17:25 ` Andrew Morton
2008-08-13 17:59 ` Ingo Molnar
2008-08-13 16:57 ` Linus Torvalds
2008-08-13 18:12 ` Eric W. Biederman [this message]
2008-08-13 18:31 ` Vivek Goyal
2008-08-13 19:44 ` Andrew Morton
2008-08-13 19:50 ` Linus Torvalds
2008-08-13 20:07 ` Andrew Morton
2008-08-13 20:13 ` Linus Torvalds
2008-08-13 20:25 ` Andrew Morton
2008-08-13 20:31 ` Linus Torvalds
2008-08-13 20:41 ` Andrew Morton
2008-08-13 21:21 ` Vivek Goyal
2008-08-13 22:17 ` Linus Torvalds
2008-08-13 20:15 ` Trond Myklebust
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