linux-kernel - Re: [BUG] wireless : cpu stuck for 61s

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Message-ID: <20080805122408.GA5000@hash.localnet>
Date:	Tue, 5 Aug 2008 08:24:08 -0400
From:	Bob Copeland <me@...copeland.com>
To:	Dave Young <hidave.darkstar@...il.com>
Cc:	Jiri Slaby <jirislaby@...il.com>,
	Pekka J Enberg <penberg@...helsinki.fi>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Berg <johannes@...solutions.net>,
	linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org
Subject: Re: [BUG] wireless : cpu stuck for 61s

On Tue, Aug 05, 2008 at 09:29:26AM +0800, Dave Young wrote:
> With the patch I cann't reproduce the bug with 27-rc1 now.
> 
> >  [<c02375a6>] ? debugfs_create_file+0x46/0x210
> >  [<c02375a6>] ? debugfs_create_file+0x46/0x210
> >  [<c02375a6>] debugfs_create_file+0x46/0x210
> >  [<c02377f1>] debugfs_create_dir+0x21/0x30
> >  [<f8901f6d>] ieee80211_sta_debugfs_add+0x2d/0x150 [mac80211]
> >  [<f88eba89>] sta_info_debugfs_add_work+0x89/0x130 [mac80211]
> >  [<f890a170>] ? rate_control_pid_add_sta_debugfs+0x0/0x30 [mac80211]

I wonder if there were two separate problems here.  I looked into
this with some detail yesterday and agree with Johannes that the above 
trace is on locking the parent directory's i_mutex, but I too couldn't
see any problems with sta_info_debugfs_add_work.  Other stuff could also 
modify the directory with or without rtnl_lock, but not in a way that 
to my untrained eyes would lead to deadlock.

Or is the trace just wrong?

-- 
Bob Copeland %% www.bobcopeland.com

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