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Date: Fri, 31 Oct 2008 10:39:24 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>,
       "jens.axboe@oracle.com" <jens.axboe@oracle.com>,
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       "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
       "Mallick, Asit K" <asit.k.mallick@intel.com>
Subject: Re: [patch] generic-ipi: fix the smp_mb() placement
Message-ID: <20081031093924.GG30317@elte.hu>
References: <20081029224229.GK30573@linux-os.sc.intel.com> <20081030185322.GE17822@elte.hu> <20081030202322.GM30573@linux-os.sc.intel.com> <490A9337.6090504@goop.org>
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* Jeremy Fitzhardinge <jeremy@goop.org> wrote:

> Suresh Siddha wrote:
>> We didn't see the lockup in our tests but Xen folks reported similar failures
>> with their smp call function code.
>>   
>
> ...really?  I don't remember anything like that, but perhaps I'm 
> forgetting something.  In Xen the IPI is sent with a hypercall, 
> which is definitely a solid enough barrier for these purposes.

i think Suresh might be referring to some of the fragilities Xen had 
with generic-ipi. But those AFAICT were due to the on-stack lifetime 
bug that Nick fixed via the kmalloc? v2.6.26-ish issue.

	Ingo