From: Christoph Hellwig <hch@lst.de>
To: Dave Chinner <david@fromorbit.com>
Cc: peterz@infradead.org, Christoph Hellwig <hch@lst.de>, xfs@oss.sgi.com
Subject: Re: [PATCH, RFC] xfs: remove i_iolock and use i_rwsem in the VFS inode instead
Date: Fri, 9 Sep 2016 10:33:06 +0200 [thread overview]
Message-ID: <20160909083306.GA19964@lst.de> (raw)
In-Reply-To: <20160907214536.GQ30056@dastard>
On Thu, Sep 08, 2016 at 07:45:36AM +1000, Dave Chinner wrote:
> It's a semaphore, not a mutex. Semaphore locking is independent of
> task context, the lock follows the object it protects, not the task
> that took the lock. i.e. Lockdep is wrong to assume the "owner" of a
> rw_sem will not change between lock and unlock.
That's not the case - rw_semaphores had strict owner semanics for a
long time (although I wish we could get rid of that for a different
reason..).
The problem here is not that we have different tasks acquire and release
the lock - it's always the same.
The "problem" is that that we hand off work to a different task inbetween
and that task asserts that the lock is held. With the old mrlock hack
our islocked macros would return true as long as _someone_ holds the
lock, while lockdep is generally more strict and wants the current
process to hold the lock.
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next prev parent reply other threads:[~2016-09-09 8:33 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-11 17:10 [PATCH, RFC] xfs: remove i_iolock and use i_rwsem in the VFS inode instead Christoph Hellwig
2016-08-11 21:54 ` Peter Zijlstra
2016-08-18 17:37 ` Christoph Hellwig
2016-08-19 13:27 ` Peter Zijlstra
2016-08-20 6:37 ` Christoph Hellwig
2016-08-22 8:34 ` Peter Zijlstra
2016-09-05 15:12 ` Christoph Hellwig
2016-09-07 7:43 ` Peter Zijlstra
2016-09-08 6:06 ` Ingo Molnar
2016-08-11 23:43 ` Dave Chinner
2016-08-12 2:50 ` Christoph Hellwig
2016-08-12 9:58 ` Dave Chinner
2016-09-05 15:15 ` Christoph Hellwig
2016-09-07 21:45 ` Dave Chinner
2016-09-08 6:54 ` Peter Zijlstra
2016-09-09 1:06 ` Dave Chinner
2016-09-09 8:21 ` Peter Zijlstra
2016-09-09 8:34 ` Christoph Hellwig
2016-09-11 0:17 ` Dave Chinner
2016-09-13 19:42 ` Peter Zijlstra
2016-09-09 8:33 ` Christoph Hellwig [this message]
2016-09-09 8:44 ` Peter Zijlstra
2016-09-09 9:05 ` Christoph Hellwig
2016-09-09 9:51 ` Peter Zijlstra
2016-09-10 16:20 ` Christoph Hellwig
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