Message-ID: <5269AB47.4000007@hp.com>
Date: Thu, 24 Oct 2013 19:20:39 -0400
From: Waiman Long <waiman.long@hp.com>
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To: Tim Chen <tim.c.chen@linux.intel.com>
CC: Ingo Molnar <mingo@elte.hu>, Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>, linux-kernel@vger.kernel.org,
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        Davidlohr Bueso <davidlohr.bueso@hp.com>,
        Alex Shi <alex.shi@linaro.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
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        Michel Lespinasse <walken@google.com>,
        Andi Kleen <andi@firstfloor.org>,
        Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
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        Scott J Norton <scott.norton@hp.com>,
        Davidlohr Bueso <davidlohr@hp.com>, Jason Low <jason.low2@hp.com>
Subject: Re: [PATCH v8 10/10] MCS Lock: Make mcs_spinlock.h includable in
 other files
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On 10/24/2013 04:58 PM, Tim Chen wrote:
>
> Do we want to inline the unlock?  Will that prevent proper profile
> accounting of unlock overhead?
>
> Can we keep the mcs_spin_unlock and mcs_spin_lock in the same
> kernel/mcs_spinlock.c file? That makes it easier to read and
> maintain the code.

The unlock code is fast. The lock code, however, can run for a long 
time. It will greatly increase the reported time spent in the calling 
function if it is inlined. The same is true for spinlock. The 
_raw_spin_lock() is a real function while _raw_spin_unlock() is inlined 
in most cases.

Yes, I can bring the lock function back to the mcs_spinlock.h file with 
name like _raw_mcs_spin_lock() and the mcs_spin_lock() in mcs_spinlock.c 
will include the raw function. In that way, the mcs_spin_lock() will 
still be a separate function while both the lock and unlock code will be 
together.

> Can you check if you have applied all the previous MCS patches?
> The last two for barrier corrections and optimizations seem
> to be missing.
>
> MCS Lock: optimizations and extra comments
> https://lkml.org/lkml/2013/10/2/644
> MCS Lock: Barrier corrections
> https://lkml.org/lkml/2013/10/2/650
>
> Thanks.
>
> Tim
>

Apparently, I does have all the MCS patch  in my git tree. I will 
regenerate a new one with the right diff. Thank for the review.

-Longman
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