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Subject: Re: [PATCH] x86: avoid calling arch_trigger_all_cpu_backtrace() at
 the same time on SMP
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Ingo Molnar <mingo@elte.hu>
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
In-Reply-To: <20101111092301.GD18789@elte.hu>
References: <1289442042-2515-1-git-send-email-dongdong.deng@windriver.com>
	 <20101111092301.GD18789@elte.hu>
Content-Type: text/plain; charset="UTF-8"
Date: Thu, 11 Nov 2010 10:51:44 +0100
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Le jeudi 11 novembre 2010 à 10:23 +0100, Ingo Molnar a écrit :

> 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);

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