linux-kernel - Re: [patch] generic-ipi: fix the smp

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Message-ID: <20081105092052.GE21867@kernel.dk>
Date:	Wed, 5 Nov 2008 10:20:52 +0100
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Jeremy Fitzhardinge <jeremy@...p.org>,
	"paulmck@...ux.vnet.ibm.com" <paulmck@...ux.vnet.ibm.com>,
	"nickpiggin@...oo.com.au" <nickpiggin@...oo.com.au>,
	"torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Mallick, Asit K" <asit.k.mallick@...el.com>,
	venkatesh.pallipadi@...el.com
Subject: Re: [patch] generic-ipi: fix the smp_mb() placement

On Tue, Nov 04 2008, Suresh Siddha wrote:
> On Tue, Nov 04, 2008 at 02:19:56AM -0700, Ingo Molnar wrote:
> > 
> > * Jeremy Fitzhardinge <jeremy@...p.org> wrote:
> > 
> > > Ingo Molnar wrote:
> > >> ok - so that makes it a v2.6.28 item i guess.
> > >>   
> > >
> > > The case Suresh is talking about was a fix to Xen itself, rather 
> > > than on the kernel side, so it doesn't need to be a .28 issue on 
> > > Xen's account.
> > 
> > ok - but still the portion of the fix that strengthens barriers looks 
> > obvious to have and there's little downside that i can see.
> > 
> > Suresh, you might want to split the patch(es) in two: get the barrier 
> > strengthening changes into v2.6.28 (to fix the x2apic bug), while the 
> > aspects that _weaken_ barriers can wait for v2.6.29.
> > 
> > With that it would be a 100% safe change for v2.6.28-rc4.
> 
> Ok. I just posted three patches (including the x86 specific change).
> 
> [patch 1/3] generic-ipi: add smp_mb() before sending the IPI
> [patch 2/3] x86: Add smp_mb() before sending INVALIDATE_TLB_VECTOR
> [patch 3/3] generic-ipi: fix the smp_mb() usage
> 
> First two patches are safe to go into v2.6.28. Third patch can wait for v2.6.29.

I already have the combined 1+3 patch queued up...

-- 
Jens Axboe

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