Date: Thu, 11 Nov 2010 10:57:50 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Dongdong Deng <dongdong.deng@windriver.com>, dzickus@redhat.com,
        peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com,
        hpa@zytor.com, x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86: avoid calling arch_trigger_all_cpu_backtrace() at
 the same time on SMP
Message-ID: <20101111095750.GA24558@elte.hu>
References: <1289442042-2515-1-git-send-email-dongdong.deng@windriver.com>
 <20101111092301.GD18789@elte.hu>
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* Eric Dumazet <eric.dumazet@gmail.com> wrote:

> Le jeudi 11 novembre 2010 ? 10:23 +0100, Ingo Molnar a ?crit :
> 
> > Also, variables that cmpxchg or test_and_set operates on need to be long, not int.
> 
> Hmm, ok for test_and_set(), it operates on a long.
> 
> cmpxchg() is ok on an int AFAIK. If not we have to make some changes :(
> 
> btrfs_orphan_cleanup() for example does this :
> 
> 	if (cmpxchg(&root->orphan_cleanup_state, 0, ORPHAN_CLEANUP_STARTED))
> 		...
> 
> 
> Same in build_ehash_secret() (net/ipv4/af_inet.c)
> 
> 	cmpxchg(&inet_ehash_secret, 0, rnd);

You are right - cmpxchg() auto-detects the word size and thus should work on int 
too.

Thanks,

	Ingo
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