linux-kernel - Re: [patch -mm] slab: use CPU_LOCK

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Message-ID: <Pine.LNX.4.64.0701101012460.21379@schroedinger.engr.sgi.com>
Date:	Wed, 10 Jan 2007 10:20:28 -0800 (PST)
From:	Christoph Lameter <clameter@....com>
To:	Heiko Carstens <heiko.carstens@...ibm.com>
cc:	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Benjamin Gilbert <bgilbert@...cmu.edu>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Gautham shenoy <ego@...ibm.com>, Andrew Morton <akpm@...l.org>,
	Pekka Enberg <penberg@...helsinki.fi>
Subject: Re: [patch -mm] slab: use CPU_LOCK_[ACQUIRE|RELEASE]

On Tue, 9 Jan 2007, Heiko Carstens wrote:

> -	case CPU_UP_PREPARE:
> +	case CPU_LOCK_ACQUIRE:
>  		mutex_lock(&cache_chain_mutex);
> +		break;

I have got a bad feeling about upcoming deadlock problems when looking at 
the mutex_lock / unlock code in cpuup_callback in slab.c. Branches 
that just obtain a lock or release a lock? I hope there is some 
control of  what happens between lock acquisition and release?

You are aware that this lock is taken for cache shrinking/destroy, tuning 
of cpu cache sizes, proc output and cache creation? Any of those run on 
the same processor should cause a deadlock.
-
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