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Subject: Re: [RFC][PATCH v2 5/5] mutex: Give spinners a chance to
 spin_on_owner if need_resched() triggered while queued
From: Jason Low <jason.low2@hp.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>, Paul McKenney <paulmck@linux.vnet.ibm.com>,
        Waiman Long <Waiman.Long@hp.com>,
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        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
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        Andi Kleen <andi@firstfloor.org>,
        "Chandramouleeswaran, Aswin" <aswin@hp.com>,
        "Norton, Scott J" <scott.norton@hp.com>, chegu_vinod@hp.com
Date: Mon, 03 Feb 2014 12:55:34 -0800
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On Mon, 2014-02-03 at 20:25 +0100, Peter Zijlstra wrote:
> On Mon, Feb 03, 2014 at 10:39:20AM -0800, Jason Low wrote:
> > > To avoid the xchg on every loop.
> > 
> > Ah yes, we want to use xchg() on &node->next.
> > 
> > Since the cmpxchg() is now in a loop in the unlock function, an
> > additional (*lock == node) check before the cmpxchg() would also be nice
> > to avoid spinning on cmpxchg() there too.
> 
> Right, I have the below; you can find the patches this depends upon
> here:
> 
>   http://programming.kicks-ass.net/sekrit/patches.tar.bz2
> 
> ---
> Subject: locking, mutex: Cancelable MCS lock for adaptive spinning
> From: Peter Zijlstra <peterz@infradead.org>
> Date: Wed, 29 Jan 2014 12:51:42 +0100
> 
> Since we want a task waiting for a mutex_lock() to go to sleep and
> reschedule on need_resched() we must be able to abort the
> mcs_spin_lock() around the adaptive spin.
> 
> Therefore implement a cancelable mcs lock.
> 
> XXX: anybody got a better name than m_spinlock?

So I was thinking something along the lines of
mcs_spin_lock_cancelable() as that's essentially what this function
does.