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

From: Ingo Molnar <mingo@elte.hu>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: nigel@nigel.suspend2.net,
	Kexec Mailing List <kexec@lists.infradead.org>,
	linux-kernel@vger.kernel.org, "Rafael J. Wysocki" <rjw@sisk.pl>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Pavel Machek <pavel@ucw.cz>, Huang Ying <ying.huang@intel.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Vivek Goyal <vgoyal@redhat.com>
Subject: Re: [PATCH] kexec jump: fix compiling warning on xchg(&kexec_lock, 0) in kernel_kexec()
Date: Wed, 13 Aug 2008 19:59:15 +0200	[thread overview]
Message-ID: <20080813175915.GA3938@elte.hu> (raw)
In-Reply-To: <20080813102504.7ce478eb.akpm@linux-foundation.org>

* Andrew Morton <akpm@linux-foundation.org> wrote:

> > instead? Not that that's really right either, but at least it avoids 
> > the _ridiculous_ crap. The real solution is probably to use a 
> > spinlock and trylock/unlock.
> 
> Or test_and_set_bit().  That's what I've been saying too, only 
> differently ;)
> 
> But cleaning up the long-standing silly usage of xchg() is a different 
> activity from suppressing this recently-added compile warning.

actually, in this case i disagree: the warning here is a canary that 
there's something wrong about this code - i.e. gcc is _right_ about 
warning us. The warning is also totally harmless - the warning shows us 
the suckiness of the code structure - and squashing the warning doesnt 
fix that.

So im coal-mine analogies, i disagree with squashing the canary, we 
should find and fix the shaft that emits the smelly methane instead ;-)

	Ingo

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