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Date: Mon, 28 Apr 2008 09:24:57 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
       Gautham R Shenoy <ego@in.ibm.com>, Paul Jackson <pj@sgi.com>,
       linux-kernel@vger.kernel.org, Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [PATCH] sched: missing locking in sched_domains code
Message-ID: <20080428072456.GA26944@elte.hu>
References: <20080427211224.GA21830@osiris.boeblingen.de.ibm.com> <20080427183926.acb66fff.akpm@linux-foundation.org> <20080428070946.GA4507@osiris.boeblingen.de.ibm.com>
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* Heiko Carstens <heiko.carstens@de.ibm.com> wrote:

>  
>  /*
> + * Protects against concurrent calls to detach_destroy_domains
> + * and arch_init_sched_domains.
> + */
> +static DEFINE_MUTEX(sched_domains_mutex);
> +
> +/*
>   * Partition sched domains as specified by the 'ndoms_new'
>   * cpumasks in the array doms_new[] of cpumasks. This compares
>   * doms_new[] to the current sched domain partitioning, doms_cur[].
> @@ -7756,7 +7762,8 @@ void partition_sched_domains(int ndoms_n
>  	int i, j;
>  
>  	lock_doms_cur();
> -
> +	mutex_lock(&sched_domains_mutex);

i might be missing something but why not make doms_cur_mutex locking 
unconditional and extend it to detach_destroy_domains() as well?

	Ingo