linux-kernel - Re: [Xen-devel] [PATCH] x86, locking: Remove ticket (spin)lock implementation

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Message-ID: <20160518193431.GQ3193@twins.programming.kicks-ass.net>
Date:	Wed, 18 May 2016 21:34:31 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:	mingo@...nel.org, kvm@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org, Waiman.Long@....com,
	dhowells@...hat.com, david.vrabel@...rix.com, pbonzini@...hat.com,
	xen-devel@...ts.xenproject.org
Subject: Re: [Xen-devel] [PATCH] x86, locking: Remove ticket (spin)lock
 implementation

On Wed, May 18, 2016 at 03:13:44PM -0400, Konrad Rzeszutek Wilk wrote:
> On Wed, May 18, 2016 at 08:43:02PM +0200, Peter Zijlstra wrote:
> > 
> > We've unconditionally used the queued spinlock for many releases now.
> 
> Like since 4.2?

Yeah, that seems to be the right number.

> I don't know of any enterprise distro that is shipping anything
> more modern than 4.1?

RHEL 7			-- v3.10
SLES 12			-- v3.12
Debian Jessie		-- v3.16
Ubuntu 16.04 LTS	-- v4.4

But waiting for the major enterprise distros (RHEL/SLES) would mean
another decade or so before people start using it. We don't usually wait
this long for anything.

> Perhaps it would be good to wait until they
> at least ship and then give them some time to see if they have found
> any issues?

My motivation was that people keep trying to send patches against the
ticket lock code... David did just today, and he's not the first.