Re: DVB suspend/resume regression on 3.19

[Takashi Iwai <tiwai@suse.de>]

At Fri, 13 Feb 2015 16:12:40 +0100,
Takashi Iwai wrote:
> 
> At Fri, 13 Feb 2015 12:41:25 -0200,
> Mauro Carvalho Chehab wrote:
> > 
> > Em Fri, 13 Feb 2015 15:02:42 +0100
> > Takashi Iwai <tiwai@suse.de> escreveu:
> > 
> > > At Mon, 09 Feb 2015 11:59:07 +0100,
> > > Takashi Iwai wrote:
> > > > 
> > > > Hi,
> > > > 
> > > > we've got a bug report about the suspend/resume regression of DVB
> > > > device with 3.19.  The symptom is VLC doesn't work after S3 or S4
> > > > resume.  strace shows that /dev/dvb/adaptor0/dvr returns -ENODEV.
> > > > 
> > > > The reporter confirmed that 3.18 works fine, so the regression must be
> > > > in 3.19.
> > > > 
> > > > There is a relevant kernel warning while suspending:
> > > > 
> > > >  WARNING: CPU: 1 PID: 3603 at ../kernel/module.c:1001 module_put+0xc7/0xd0()
> > > >  Workqueue: events_unbound async_run_entry_fn
> > > >   0000000000000000 ffffffff81a45779 ffffffff81664f12 0000000000000000
> > > >   ffffffff81062381 0000000000000000 ffffffffa051eea0 ffff8800ca369278
> > > >   ffffffffa051a068 ffff8800c0a18090 ffffffff810dfb47 0000000000000000
> > > >  Call Trace:
> > > >   [<ffffffff810055ac>] dump_trace+0x8c/0x340
> > > >   [<ffffffff81005903>] show_stack_log_lvl+0xa3/0x190
> > > >   [<ffffffff81007061>] show_stack+0x21/0x50
> > > >   [<ffffffff81664f12>] dump_stack+0x47/0x67
> > > >   [<ffffffff81062381>] warn_slowpath_common+0x81/0xb0
> > > >   [<ffffffff810dfb47>] module_put+0xc7/0xd0
> > > >   [<ffffffffa04d98d1>] dvb_usb_adapter_frontend_exit+0x41/0x60 [dvb_usb]
> > > >   [<ffffffffa04d8451>] dvb_usb_exit+0x31/0xa0 [dvb_usb]
> > > >   [<ffffffffa04d84fb>] dvb_usb_device_exit+0x3b/0x50 [dvb_usb]
> > > >   [<ffffffff814cefad>] usb_unbind_interface+0x1ed/0x2c0
> > > >   [<ffffffff8145ceae>] __device_release_driver+0x7e/0x100
> > > >   [<ffffffff8145cf52>] device_release_driver+0x22/0x30
> > > >   [<ffffffff814cf13d>] usb_forced_unbind_intf+0x2d/0x60
> > > >   [<ffffffff814cf3c3>] usb_suspend+0x73/0x130
> > > >   [<ffffffff814bd453>] usb_dev_freeze+0x13/0x20
> > > >   [<ffffffff81468fca>] dpm_run_callback+0x4a/0x150
> > > >   [<ffffffff81469c81>] __device_suspend+0x121/0x350
> > > >   [<ffffffff81469ece>] async_suspend+0x1e/0xa0
> > > >   [<ffffffff81081e63>] async_run_entry_fn+0x43/0x150
> > > >   [<ffffffff81079e72>] process_one_work+0x142/0x3f0
> > > >   [<ffffffff8107a234>] worker_thread+0x114/0x460
> > > >   [<ffffffff8107f3b1>] kthread+0xc1/0xe0
> > > >   [<ffffffff8166b77c>] ret_from_fork+0x7c/0xb0
> > > > 
> > > > So something went wrong in module refcount, which likely leads to
> > > > disabling the device and returning -ENODEV in the end.
> > > > 
> > > > Does this ring a bell to you guys?
> > > > 
> > > > The hardware details and logs are found in the URL below:
> > > >   https://bugzilla.novell.com/show_bug.cgi?id=916577
> > > 
> > > I wonder whether no one hits the same problem...?
> > 
> > Hi Takashi,
> > 
> > There were no recent changes at dvb-usb core or at the dtt200u.c driver.
> > So, I don't think that the regression was caused by a change at the media
> > subsystem. Yet, we've added some patches to fix suspend/resume at the
> > DVB core, but they basically add a new set of optional callbacks. So, it
> > should not cause any regression.
> > 
> > The changeset in question is 59d7889ae49f6e3e9d9cff8c0de7ad95d9ca068b.
>  
> Hm, is this commit really merged between 3.18 and 3.19?
> 
> > From those messages:
> > 
> > 2015-02-06T15:30:47.468258+01:00 linux-z24t kernel: [  150.552119] dvb-usb: downloading firmware from file 'dvb-usb-wt220u-fc03.fw'
> > 2015-02-06T15:30:47.468827+01:00 linux-z24t mtp-probe: checking bus 1, device 5: "/sys/devices/pci0000:00/0000:00:1d.7/usb1/1-4"
> > 2015-02-06T15:30:47.879878+01:00 linux-z24t mtp-probe: bus: 1, device: 5 was not an MTP device
> > 2015-02-06T15:30:47.880192+01:00 linux-z24t kernel: [  151.992993] usb 1-4: USB disconnect, device number 5
> > 2015-02-06T15:30:47.880839+01:00 linux-z24t kernel: [  151.993076] dvb-usb: generic DVB-USB module successfully deinitialized and disconnected.
> > 
> > I _suspect_ that dvb_usb_download_firmware() failed to load the firmware
> > file.
> > 
> > That problem actually looks like a recently discovered issue:t
> > request_firmware() fails during resume on some systems. What
> > seems to happen in this case is that the media drivers are resumed
> > _before_ mounting the partition where the firmware file is hosted.
> > 
> > Yet, in this case, it should be printing:
> > 	"did not find the firmware file."
> 
> Right.  This makes me wonder, too.
> 
> > I would add a test patch in order to print the return code from
> > dvb_usb_download_firmware(), in order to see if it succeeds or
> > not, e. g. something like the patch below, and then try to narrow
> > down where it is failing, assuming that the new message will be printed.
> > 
> > If nothing gets printed, then I would try to discover why the USB
> > stack disconnected the device. Perhaps an ehci/xhci bug?
> 
> OK, I'll give a test kernel to report.

The patched kernel didn't show the message.  So it's not about the
firmware load failure, apparently.  Any other point to check?


Takashi