linux-kernel - Re: [PATCH RT] rt: add rwsem_is_contended() definition to rwsem

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Message-ID: <20150217130857.24e233ea@sluggy>
Date:	Tue, 17 Feb 2015 13:08:57 -0600
From:	Clark Williams <williams@...hat.com>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	RT <linux-rt-users@...r.kernel.org>
Subject: Re: [PATCH RT]  rt: add rwsem_is_contended() definition to
 rwsem_rt.h

On Tue, 17 Feb 2015 11:09:11 +0100
Sebastian Andrzej Siewior <bigeasy@...utronix.de> wrote:

> * Clark Williams | 2014-08-27 16:09:28 [-0500]:
> 
> >Thomas,
> >
> >The latest btrfs code uses rwsem_is_contended() in the function
> >caching_thread(). On RT systems, include/linux/rwsem.h is replaced with
> >include/linux/rwsem_rt.h which does not provide a definition for
> >rwsem_is_contended().  This commit provides a definition that should
> >work on RT (where the lock is actually an rt_mutex).
> 
> I see that I added rwsem_is_contended() in v3.14-rt1 which does:
> |static inline int rwsem_is_contended(struct rw_semaphore *sem)
> |{
> |      /* rt_mutex_has_waiters() */
> |      return !RB_EMPTY_ROOT(&sem->lock.waiters);
> |}
> 
> Do you lack this in kernel prior to v3.14?
> 
> Sebastian

Yes, that was the problem. I was back-porting to a 3.10 and was missing
the definition. Sorry for the noise.

Clark

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