linux-kernel - Re: [1/2] 2.6.22-rc7: known regressions

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Date:	Thu, 05 Jul 2007 12:43:22 -0400
From:	David Woodhouse <dwmw2@...radead.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Michal Piotrowski <michal.k.k.piotrowski@...il.com>,
	marcel@...tmann.org, Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	reiserfs-devel@...r.kernel.org,
	"Vladimir V. Saveliev" <vs@...esys.com>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	linux-ide@...r.kernel.org, David Chinner <dgc@....com>,
	sparclinux@...r.kernel.org, David Miller <davem@...emloft.net>,
	Mikael Pettersson <mikpe@...uu.se>,
	Mark Fortescue <mark@...hpc.demon.co.uk>,
	William Lee Irwin III <wli@...omorphy.com>
Subject: Re: [1/2] 2.6.22-rc7: known regressions

On Thu, 2007-07-05 at 09:28 -0700, Linus Torvalds wrote:
> 
> On Wed, 4 Jul 2007, David Woodhouse wrote:
> > 
> > Oh, and here's another one for you. My Bluetooth mouse just stopped
> > working and hidd is deadlocked...
> 
> Looks like it is stuck on hidp_session_sem.
> 
> Nothing after 2.6.21 seems to have even touched that semaphore usage, and 
> in fact there's not a whole lot of changes to the hidp code at all (and 
> none of them look even remotely interesting). 
> 
> So I suspect it's something lower down in the bluetooth stack, or it's a 
> long-standing problem that you are somehow able to trigger more easily 
> now. Is it consistent?

It happened twice before I gave up on my 2.6.22-rc7 test kernel and went
back to something earlier. I suppose I should double-check that it
wasn't my slab changes, but I really don't think that's it.

> Can you showo the traces for the _other_ processes that are in bluetooth 
> functions? Because there should be other processes there, holding that 
> hidp_session_sem rwsem.

There was nothing, apart from a later 'hidd -l' which got stuck on the
same semaphore. I have an hcidump of it happening, at
http://david.woodhou.se/hidd-lockup-dump.txt -- it doesn't seem
particularly enlightening though. There's just a disconnection and
reconnect, as happens quite frequently with this mouse, and then we're
deadlocked. I'll build with hidp debugging.

-- 
dwmw2

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