Re: DVB suspend/resume regression on 3.19

[Shuah Khan]

On Fri, Feb 13, 2015 at 8:12 AM, Takashi Iwai <tiwai@xxxxxxx> 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@xxxxxxx> 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.
>> > >

Hi Takashi and Mauro,

Looking at the stack trace usb_forced_unbind_intf() gets called from
usb_suspend(). Looks like the suspend path in  unbind_no_pm_drivers_interfaces()
determines the driver doesn't have suspend/resume support and goes to
usb_forced_unbind_intf().

At this point forced unbinding results in release the driver via
usb_driver_release_interface().

It is worth looking into if the driver indeed has suspend/resume
routines?

-- Shuah

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