Re: Question about 2 gp8psk patches I noticed, and possible bug.

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Hi Mauro,

Unfortunately the patch doesn't seem to have solved the problem. I do
have the kernel recompiled with debug enabled though per your irc msg.
dmesg gives me:

[   70.741073] usbcore: deregistering interface driver dvb_usb_gp8psk
[   70.741165] ------------[ cut here ]------------
[   70.741172] WARNING: CPU: 1 PID: 2119 at kernel/module.c:1108
module_put+0x67/0x80
[   70.741174] Modules linked in: dvb_usb_gp8psk(-) dvb_usb dvb_core
nvidia_drm(PO) nvidia_modeset(PO) snd_hda_codec_hdmi snd_hda_intel
snd_hda_codec snd_hwdep snd_hda_core snd_pcm snd_timer snd soundcore
nvidia(PO)
[   70.741186] CPU: 1 PID: 2119 Comm: rmmod Tainted: P           O
4.8.4-build.2 #1
[   70.741187] Hardware name: MSI MS-7309/MS-7309, BIOS V1.12 02/23/2009
[   70.741189]  00000000 c12c15f0 00000000 00000000 c103fc7a c161ecc0
00000001 00000847
[   70.741194]  c161e50f 00000454 c10a4b87 c10a4b87 00000009 fb090cc0
00000000 00000000
[   70.741197]  f4e72000 c103fd43 00000009 00000000 00000000 c10a4b87
fb08f6a0 c10a58fa
[   70.741202] Call Trace:
[   70.741206]  [<c12c15f0>] ? dump_stack+0x44/0x64
[   70.741209]  [<c103fc7a>] ? __warn+0xfa/0x120
[   70.741211]  [<c10a4b87>] ? module_put+0x67/0x80
[   70.741213]  [<c10a4b87>] ? module_put+0x67/0x80
[   70.741215]  [<c103fd43>] ? warn_slowpath_null+0x23/0x30
[   70.741217]  [<c10a4b87>] ? module_put+0x67/0x80
[   70.741221]  [<fb08f6a0>] ? gp8psk_fe_set_frontend+0x460/0x460
[dvb_usb_gp8psk]
[   70.741223]  [<c10a58fa>] ? symbol_put_addr+0x2a/0x50
[   70.741225]  [<fb08e04e>] ? gp8psk_usb_disconnect+0x4e/0x90 [dvb_usb_gp8psk]
[   70.741229]  [<c13da272>] ? usb_unbind_interface+0x62/0x250
[   70.741233]  [<c1551f3f>] ? _raw_spin_unlock_irqrestore+0xf/0x30
[   70.741235]  [<c1372ea4>] ? __pm_runtime_idle+0x44/0x70
[   70.741239]  [<c1369a68>] ? __device_release_driver+0x78/0x120
[   70.741241]  [<c136a297>] ? driver_detach+0x87/0x90
[   70.741243]  [<c13695d8>] ? bus_remove_driver+0x38/0x90
[   70.741245]  [<c13d9608>] ? usb_deregister+0x58/0xb0
[   70.741248]  [<c10a5eb0>] ? SyS_delete_module+0x130/0x1f0
[   70.741251]  [<c1036200>] ? __do_page_fault+0x1a0/0x440
[   70.741253]  [<c1000fa5>] ? exit_to_usermode_loop+0x85/0x90
[   70.741254]  [<c10013f0>] ? do_fast_syscall_32+0x80/0x130
[   70.741257]  [<c1552403>] ? sysenter_past_esp+0x40/0x6a
[   70.741259] ---[ end trace a387b7eddb538bfb ]---
[   70.743654] dvb-usb: Genpix SkyWalker-2 DVB-S receiver successfully
deinitialized and disconnected.


I read the Bug Hunting url but it's still not clear to me which line
from that dmesg text I should be focused on. It would suggest the
first line (dump_stack+0x44/0x64) but you pointed to
gp8psk_fe_set_frontend so I'm not sure what to do next. When I go into
gdb I see:

gdb $(find /lib/modules/$(uname -r) -name dvb-usb-gp8psk.ko)
...
Reading symbols from
/lib/modules/4.8.4-build.2/kernel/drivers/media/usb/dvb-usb/dvb-usb-gp8psk.ko...(no
debugging symbols found)...done.
(gdb)

gdb /usr/src/linux/vmlinux
...
Reading symbols from /usr/src/linux/vmlinux...done.
(gdb)
(gdb)

"No debugging symbols found" doesn't sound good, but DEBUG is enabled:

$ grep "^CONFIG_DEBUG" /usr/src/linux/.config
CONFIG_DEBUG_RODATA=y
CONFIG_DEBUG_INFO=y
CONFIG_DEBUG_FS=y
CONFIG_DEBUG_KERNEL=y
CONFIG_DEBUG_MEMORY_INIT=y
CONFIG_DEBUG_PREEMPT=y
CONFIG_DEBUG_BUGVERBOSE=y



On Tue, Nov 8, 2016 at 9:55 AM, Mauro Carvalho Chehab
<mchehab@xxxxxxxxxxxxxxxx> wrote:
> Em Sat, 5 Nov 2016 19:24:58 -0700
> VDR User <user.vdr@xxxxxxxxx> escreveu:
>
>> I have
>> several different Genpix devices that use the gp8psk driver and in all
>> cases the following happens when I unload it:
>>
>> [494896.234616] usbcore: deregistering interface driver dvb_usb_gp8psk
>> [494896.234712] ------------[ cut here ]------------
>> [494896.234719] WARNING: CPU: 1 PID: 28102 at kernel/module.c:1108
>> module_put+0x57/0x70
>> [494896.234720] Modules linked in: dvb_usb_gp8psk(-) dvb_usb dvb_core
>> nvidia_drm(PO) nvidia_modeset(PO) snd_hda_codec_hdmi snd_hda_intel
>> snd_hda_codec snd_hwdep snd_hda_core snd_pcm snd_timer snd soundcore
>> nvidia(PO) [last unloaded: rc_core]
>> [494896.234732] CPU: 1 PID: 28102 Comm: rmmod Tainted: P        WC O
>>  4.8.4-build.1 #1
>> [494896.234733] Hardware name: MSI MS-7309/MS-7309, BIOS V1.12 02/23/2009
>> [494896.234735]  00000000 c12ba080 00000000 00000000 c103ed6a c1616014
>> 00000001 00006dc6
>> [494896.234739]  c1615862 00000454 c109e8a7 c109e8a7 00000009 ffffffff
>> 00000000 f13f6a10
>> [494896.234743]  f5f5a600 c103ee33 00000009 00000000 00000000 c109e8a7
>> f80ca4d0 c109f617
>> [494896.234746] Call Trace:
>> [494896.234753]  [<c12ba080>] ? dump_stack+0x44/0x64
>> [494896.234756]  [<c103ed6a>] ? __warn+0xfa/0x120
>> [494896.234758]  [<c109e8a7>] ? module_put+0x57/0x70
>> [494896.234760]  [<c109e8a7>] ? module_put+0x57/0x70
>> [494896.234762]  [<c103ee33>] ? warn_slowpath_null+0x23/0x30
>> [494896.234763]  [<c109e8a7>] ? module_put+0x57/0x70
>> [494896.234766]  [<f80ca4d0>] ? gp8psk_fe_set_frontend+0x460/0x460
>> [dvb_usb_gp8psk]
>> [494896.234769]  [<c109f617>] ? symbol_put_addr+0x27/0x50
>> [494896.234771]  [<f80bc9ca>] ?
>> dvb_usb_adapter_frontend_exit+0x3a/0x70 [dvb_usb]
>> [494896.234773]  [<f80bb3bf>] ? dvb_usb_exit+0x2f/0xd0 [dvb_usb]
>> [494896.234776]  [<c13d03bc>] ? usb_disable_endpoint+0x7c/0xb0
>> [494896.234778]  [<f80bb48a>] ? dvb_usb_device_exit+0x2a/0x50 [dvb_usb]
>> [494896.234780]  [<c13d2882>] ? usb_unbind_interface+0x62/0x250
>> [494896.234782]  [<c136b514>] ? __pm_runtime_idle+0x44/0x70
>> [494896.234785]  [<c13620d8>] ? __device_release_driver+0x78/0x120
>> [494896.234787]  [<c1362907>] ? driver_detach+0x87/0x90
>> [494896.234789]  [<c1361c48>] ? bus_remove_driver+0x38/0x90
>> [494896.234791]  [<c13d1c18>] ? usb_deregister+0x58/0xb0
>> [494896.234793]  [<c109fbb0>] ? SyS_delete_module+0x130/0x1f0
>> [494896.234796]  [<c1055654>] ? task_work_run+0x64/0x80
>> [494896.234798]  [<c1000fa5>] ? exit_to_usermode_loop+0x85/0x90
>> [494896.234800]  [<c10013f0>] ? do_fast_syscall_32+0x80/0x130
>> [494896.234803]  [<c1549f43>] ? sysenter_past_esp+0x40/0x6a
>> [494896.234805] ---[ end trace 6ebc60ef3981792f ]---
>> [494896.235890] dvb-usb: Genpix SkyWalker-2 DVB-S receiver
>> successfully deinitialized and disconnected.
>
> I suspect that this is due to a race condition at device unregister.
> could you please try the enclosed patch?
>
> gp8psk: unregister gp8psk-fe early
>
> Letting gp8psk-fe to unregister late can cause race issues.
>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx>
>
>
> diff --git a/drivers/media/usb/dvb-usb/gp8psk.c b/drivers/media/usb/dvb-usb/gp8psk.c
> index 2829e3082d15..04ea2bbbe5ae 100644
> --- a/drivers/media/usb/dvb-usb/gp8psk.c
> +++ b/drivers/media/usb/dvb-usb/gp8psk.c
> @@ -270,6 +270,32 @@ static int gp8psk_usb_probe(struct usb_interface *intf,
>         return ret;
>  }
>
> +static void gp8psk_usb_disconnect(struct usb_interface *intf)
> +{
> +       struct dvb_usb_device *d = usb_get_intfdata(intf);
> +       struct dvb_usb_adapter *adap;
> +       int i, n;
> +
> +       /*
> +        * As gsp8psk-fe can call back this driver, in order to do URB
> +        * transfers, we need to manually exit the frontend earlier.
> +        */
> +       for (n = 0; n < d->num_adapters_initialized; n++) {
> +               adap = &d->adapter[n];
> +               i = adap->num_frontends_initialized - 1;
> +
> +               for (; i >= 0; i--) {
> +                       if (adap->fe_adap[i].fe != NULL) {
> +                               dvb_unregister_frontend(adap->fe_adap[i].fe);
> +                               dvb_frontend_detach(adap->fe_adap[i].fe);
> +                       }
> +               }
> +               adap->num_frontends_initialized = 0;
> +       }
> +
> +       dvb_usb_device_exit(intf);
> +}
> +
>  static struct usb_device_id gp8psk_usb_table [] = {
>             { USB_DEVICE(USB_VID_GENPIX, USB_PID_GENPIX_8PSK_REV_1_COLD) },
>             { USB_DEVICE(USB_VID_GENPIX, USB_PID_GENPIX_8PSK_REV_1_WARM) },
> @@ -338,7 +364,7 @@ static struct dvb_usb_device_properties gp8psk_properties = {
>  static struct usb_driver gp8psk_usb_driver = {
>         .name           = "dvb_usb_gp8psk",
>         .probe          = gp8psk_usb_probe,
> -       .disconnect = dvb_usb_device_exit,
> +       .disconnect     = gp8psk_usb_disconnect,
>         .id_table       = gp8psk_usb_table,
>  };
>
--
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