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Date: Wed, 13 Aug 2008 09:57:33 -0700 (PDT)
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Huang Ying <ying.huang@intel.com>
cc: "Eric W. Biederman" <ebiederm@xmission.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()
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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.

			Linus