linux-kernel - Re: [RESEND, tip/locking/core, v5, 1/6] powerpc: atomic: Make _return atomics and *{cmp}xchg fully ordered

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Message-ID: <20151102012033.GA965@fixme-laptop.cn.ibm.com>
Date:	Mon, 2 Nov 2015 09:22:41 +0800
From:	Boqun Feng <boqun.feng@...il.com>
To:	Michael Ellerman <mpe@...erman.id.au>
Cc:	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	Waiman Long <waiman.long@...com>,
	Davidlohr Bueso <dave@...olabs.net>,
	Peter Zijlstra <peterz@...radead.org>,
	Will Deacon <will.deacon@....com>, stable@...r.kernel.org,
	Paul Mackerras <paulus@...ba.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [RESEND, tip/locking/core, v5, 1/6] powerpc: atomic: Make
 _return atomics and *{cmp}xchg fully ordered

On Fri, Oct 30, 2015 at 08:56:33AM +0800, Boqun Feng wrote:
> On Tue, Oct 27, 2015 at 11:06:52AM +0800, Boqun Feng wrote:
> > On Tue, Oct 27, 2015 at 01:33:47PM +1100, Michael Ellerman wrote:
> > > On Mon, 2015-26-10 at 10:15:36 UTC, Boqun Feng wrote:
> > > > This patch fixes two problems to make value-returning atomics and
> > > > {cmp}xchg fully ordered on PPC.
> > > 
> > > Hi Boqun,
> > > 
> > > Can you please split this into two patches. One that does the cmpxchg change
> > > and one that changes PPC_ATOMIC_ENTRY_BARRIER.
> > > 
> > 
> > OK, make sense ;-)
> > 
> > > Also given how pervasive this change is I'd like to take it via the powerpc
> > > next tree, so can you please send this patch (which will be two after you split
> > > it) as powerpc patches. And the rest can go via tip?
> > > 
> > 
> > One problem is that patch 5 will remove __xchg_u32 and __xchg_64
> > entirely, which are modified in this patch(patch 1), so there will be
> > some conflicts if two branch get merged, I think.
> > 
> > Alternative way is that all this series go to powerpc next tree as most
> > of the dependent patches are already there. I just need to remove
> > inc/dec related code and resend them when appropriate. Besides, I can
> > pull patch 2 out and send it as a tip patch because it's general code
> > and no one depends on this in this series.
> > 
> > To summerize:
> > 
> > patch 1(split to two), 3, 4(remove inc/dec implementation), 5, 6 sent as
> > powerpc patches for powerpc next, patch 2(unmodified) sent as tip patch
> > for locking/core.
> > 
> > Peter and Michael, this works for you both?
> > 
> 
> Thoughts? ;-)
> 

Peter and Michael, I will split patch 1 to two and send them as patches
for powerpc next first. The rest of this can wait util we are on the
same page of where they'd better go.

Regards,
Boqun

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