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Message-ID: <1351025831.13456.43.camel@twins>
Subject: Re: [PATCH 1/2] percpu-rw-semaphores: use light/heavy barriers
From: Peter Zijlstra <peterz@infradead.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Ingo Molnar <mingo@elte.hu>,
        Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
        Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
        Anton Arapov <anton@redhat.com>, linux-kernel@vger.kernel.org
Date: Tue, 23 Oct 2012 22:57:11 +0200
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On Tue, 2012-10-23 at 21:23 +0200, Oleg Nesterov wrote:
> 
>         static void mb_ipi(void *arg)
>         {
>                 smp_mb(); /* unneeded ? */
>         }
> 
>         static void force_mb_on_each_cpu(void)
>         {
>                 smp_mb();
>                 smp_call_function(mb_ipi, NULL, 1);
>         } 

You know we're spending an awful lot of time and effort to get rid of
such things, right? RT and HPC people absolutely hate these random IPI
things.