Le Fri, 6 Jan 2012 22:42:31 +0100,
Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxxxxxxxxx> a écrit :
> Hello,
>
> I'm running the Hauppauge USB-Live 2 device on an ARM OMAP3 platform.
> After loading the cx231xx driver and launching v4l2grab, I immediately
> get:
>
> [ 407.087158] cx231xx #0: setPowerMode::mode = 48, No Change req.
> [ 407.145477]
> [ 407.147064] ======================================================
> [ 407.153533] [ INFO: possible circular locking dependency detected ]
> [ 407.160095] 3.2.0-00007-gb928298 #18
> [ 407.163848] -------------------------------------------------------
One code path is (mmap_sem taken before, video_device lock taken
afterwards) :
-> sys_mmap_pgoff()
grabs current->mm->mmap_sem at
http://lxr.free-electrons.com/source/mm/mmap.c#L1111
-> do_mmap_pgoff()
-> mmap_region()
-> v4l2_mmap()
grabs struct video_device->lock at
http://lxr.free-electrons.com/source/drivers/media/video/v4l2-dev.c#L396
The other code path is (video_device taken first, mmap_sem taken
afterwards) :
-> v4l2_ioctl()
grabs video_device->lock at
http://lxr.free-electrons.com/source/drivers/media/video/v4l2-dev.c#L327
-> video_ioctl2()
-> video_usercopy()
-> __video_do_ioctl()
-> videobuf_qbuf()
grabs current->mm->mmap_sem at
http://lxr.free-electrons.com/source/drivers/media/video/videobuf-core.c#L537
Regards,
Thomas
--
Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com
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