linux-kernel - Re: [PATCH v2] locking/rwsem: Add reader-owned state to the owner field

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Message-ID: <20160519013753.GF21200@dastard>
Date:	Thu, 19 May 2016 11:37:53 +1000
From:	Dave Chinner <david@...morbit.com>
To:	Waiman Long <Waiman.Long@....com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Davidlohr Bueso <dave@...olabs.net>,
	Jason Low <jason.low2@...com>,
	Scott J Norton <scott.norton@....com>,
	Douglas Hatch <doug.hatch@....com>
Subject: Re: [PATCH v2] locking/rwsem: Add reader-owned state to the owner
 field

On Fri, May 06, 2016 at 08:20:24PM -0400, Waiman Long wrote:
> Currently, it is not possible to determine for sure if a reader
> owns a rwsem by looking at the content of the rwsem data structure.
> This patch adds a new state RWSEM_READER_OWNED to the owner field
> to indicate that readers currently own the lock.

Oh, yes please. This will enable us to get rid of the remaining
mrlock rwsem abstraction we've carried since the days of Irix in
XFS. The only reason the abstraction still exists is that we track
write locks for the purposes of checking for correct inode locking
contexts via ASSERT(xfs_isilocked()) calls....

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com