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

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Date:	Wed, 13 Aug 2008 13:31:24 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	ebiederm@...ssion.com, ying.huang@...el.com, pavel@....cz,
	nigel@...el.suspend2.net, rjw@...k.pl, vgoyal@...hat.com,
	mingo@...e.hu, linux-kernel@...r.kernel.org,
	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, Andrew Morton wrote:
> 
> #2:

I thought you said there were things that want to sleep in the region?

If so, spinlocks will work as long as you don't have CONFIG_PREEMPT or 
lock validation (there's no way to deadlock thanks to all the lock getters 
using the "trylock" variant), but will blow up because a successful 
trylock will obviously also disable preemption and/or trigger all the lock 
detection.

So if there are potential sleepers, you'd need the mutex instead.

		Linus
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