linux-kernel - Re: fs/dcache.c - BUG: soft lockup - CPU#5 stuck for 22s! [systemd-udevd:1667]

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Message-ID: <20140529035233.GF18016@ZenIV.linux.org.uk>
Date:	Thu, 29 May 2014 04:52:33 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Miklos Szeredi <mszeredi@...e.cz>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: fs/dcache.c - BUG: soft lockup - CPU#5 stuck for 22s!
 [systemd-udevd:1667]

On Thu, May 29, 2014 at 04:11:49AM +0100, Al Viro wrote:
> On Wed, May 28, 2014 at 07:39:54PM +0100, Al Viro wrote:
> 
> > OK, the warnings about averting your eyes very much apply; the thing below
> > definitely needs more massage before it becomes acceptable (and no, it's
> > not a single commit; I'm not that insane), but it changes behaviour in the
> > way described above.  Could you check if the livelock persists with it?
> > No trace-generating code in there, so the logs should be compact enough...
> 
> Here's an updated patch, hopefully slightly less vomit-inducing.  Should
> give the same behaviour as the previous one...  Again, it's a cumulative
> diff - I'm still massaging the splitup here.

BTW, it still leaves the "proceed to parent" case in shrink_dentry_list();
in theory, it's also vulnerable to the same livelock.  Can be dealt pretty
much the same way; I'd rather leave that one for right after -final, though,
if the already posted variant turns out to be sufficient...
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