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From: Andrea Righi <righi.andrea@gmail.com>
To: Johannes Weiner <hannes@saeurebad.de>
Cc: Krzysztof Helt <krzysztof.h1@wp.pl>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: lockdep splat from fbmem
Date: Thu, 23 Oct 2008 15:10:12 +0200	[thread overview]
Message-ID: <490077B4.5020909@gmail.com> (raw)
In-Reply-To: <87ljwgj8p1.fsf@saeurebad.de>

Johannes Weiner wrote:
> Hi,
> 
> fb_mmap() is called under mmap_sem and acquires fb_info->lock.
> 
> Since 3e680aae4e53ab "fb: convert lock/unlock_kernel() into local fb
> mutex", fb_ioctl() takes fb_info->lock and does copy_to/from_user()
> under it, which in turn might acquire mmap_sem.
> 
> Just noticed the trace and wanted to let you know.
> 
>         Hannes

Good catch. We could try to push down the mutex and call all the
copy_to/from_user() outside the lock. I can try look at it tonight,
if someone doesn't fix it before.

Thanks for reporting,
-Andrea

  reply	other threads:[~2008-10-23 13:10 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-10-23  3:23 lockdep splat from fbmem Johannes Weiner
2008-10-23 13:10 ` Andrea Righi [this message]
2008-10-23 13:58 ` lockdep splat from ioctl and mmap fops sharing lock Johannes Weiner
2008-10-23 15:08   ` Stefan Richter
2008-10-23 16:32     ` Johannes Weiner
2008-10-25  9:12       ` Stefan Richter
2008-10-28 22:33 ` lockdep splat from fbmem Andrea Righi

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