linux-kernel - Re: processes hung after sys_renameat, and 'missing' processes

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Date:	Wed, 6 Jun 2012 21:42:47 -0400
From:	Dave Jones <davej@...hat.com>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Miklos Szeredi <mszeredi@...e.cz>, Jan Kara <jack@...e.cz>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: processes hung after sys_renameat, and 'missing' processes

On Thu, Jun 07, 2012 at 02:31:49AM +0100, Al Viro wrote:
 > On Thu, Jun 07, 2012 at 02:29:00AM +0100, Al Viro wrote:
 > > On Wed, Jun 06, 2012 at 09:19:15PM -0400, Dave Jones wrote:
 > > > On Wed, Jun 06, 2012 at 05:42:35PM -0700, Linus Torvalds wrote:
 > > > 
 > > >  > So Al meant you to test mutex_is_locked(dentry->d_inode->i_mutex) of
 > > >  > the parents.
 > > > 
 > > > ok, I ended up with..
 > > > 
 > > >         WARN_ON_ONCE(!mutex_is_locked(&target->d_parent->d_inode->i_mutex));
 > > > 
 > > >         if (dentry->d_parent != NULL)
 > > 			       != dentry)
 > > 
 > > ->d_parent *never* should be NULL; when dentry is disconnected from the
 > > tree (or hadn't been connected to it yet), it points to that dentry itself.
 > 
 > And you want to check i_mutex on old parent, not the file being moved
 > itself.  IOW, the second one should be
 > 
 > if (dentry->d_parent != dentry)
 > 	WARN_ON_ONCE(!mutex_is_locked(&dentry->d_parent->d_inode->i_mutex));

ok, now that you've both found one per in every line I've written tonight,
things seem to have booted without incident. I'll rerun the tests, and get
back to you if/when they start spewing anything interesting.

	Dave

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