linux-kernel - Re: [PATCH v2 4/4] MCS Lock: Make mcs_spinlock.h includable in other files

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Date:	Wed, 6 Nov 2013 17:08:15 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Waiman Long <waiman.long@...com>
Cc:	Tim Chen <tim.c.chen@...ux.intel.com>, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, linux-mm <linux-mm@...ck.org>,
	linux-arch@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Alex Shi <alex.shi@...aro.org>,
	Andi Kleen <andi@...stfloor.org>,
	Michel Lespinasse <walken@...gle.com>,
	Davidlohr Bueso <davidlohr.bueso@...com>,
	Matthew R Wilcox <matthew.r.wilcox@...el.com>,
	Dave Hansen <dave.hansen@...el.com>,
	Rik van Riel <riel@...hat.com>,
	Peter Hurley <peter@...leysoftware.com>,
	"Paul E.McKenney" <paulmck@...ux.vnet.ibm.com>,
	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	George Spelvin <linux@...izon.com>,
	"H. Peter Anvin" <hpa@...or.com>, Arnd Bergmann <arnd@...db.de>,
	Aswin Chandramouleeswaran <aswin@...com>,
	Scott J Norton <scott.norton@...com>,
	Will Deacon <will.deacon@....com>
Subject: Re: [PATCH v2 4/4] MCS Lock: Make mcs_spinlock.h includable in other
 files

On Wed, Nov 06, 2013 at 10:31:47AM -0500, Waiman Long wrote:
> On 11/05/2013 02:30 PM, Tim Chen wrote:
> >On Tue, 2013-11-05 at 19:57 +0100, Peter Zijlstra wrote:
> >>On Tue, Nov 05, 2013 at 09:42:39AM -0800, Tim Chen wrote:
> >>>+ * The _raw_mcs_spin_lock() function should not be called directly. Instead,
> >>>+ * users should call mcs_spin_lock().
> >>>   */
> >>>-static noinline
> >>>-void mcs_spin_lock(struct mcs_spinlock **lock, struct mcs_spinlock *node)
> >>>+static inline
> >>>+void _raw_mcs_spin_lock(struct mcs_spinlock **lock, struct mcs_spinlock *node)
> >>>  {
> >>>  	struct mcs_spinlock *prev;
> >>>
> >>So why keep it in the header at all?
> >I also made the suggestion originally of keeping both lock and unlock in
> >mcs_spinlock.c.  Wonder if Waiman decides to keep them in header
> >because in-lining the unlock function makes execution a bit faster?
> >
> >Tim
> >
> 
> I was following the example of the spinlock code where the lock function is
> not inlined, but the unlock function is. I have no objection to make them
> both as non-inlined functions, if you think that is the right move.

I don't care, what I do find odd is the existence of
_raw_mcs_spin_lock(). If you want to out-of-line it, just move the
entire thing into a .c file already.
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