linux-kernel - Re: [PATCH] kexec jump: fix compiling warning on xchg(&kexec_lock, 0) in kernel

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Message-ID: <alpine.LFD.1.10.0808130956360.3462@nehalem.linux-foundation.org>
Date:	Wed, 13 Aug 2008 09:57:33 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Huang Ying <ying.huang@...el.com>
cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Pavel Machek <pavel@....cz>, nigel@...el.suspend2.net,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Vivek Goyal <vgoyal@...hat.com>, 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, 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
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