Re: BUG with linux 5.9.0 with dwc3 in gadget mode

From: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
To: Ferry Toth <fntoth@gmail.com>,
	"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>
Cc: "felipe.balbi-VuQAYsv1563Yd54FQh9/CA-XMD5yJDbdMReXY1tMh2IBg@public.gmane.org"
	 <felipe.balbi-VuQAYsv1563Yd54FQh9/CA-XMD5yJDbdMReXY1tMh2IBg@public.gmane.org>,
	Heikki Krogerus <heikki.krogerus@linux.intel.com>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Subject: Re: BUG with linux 5.9.0 with dwc3 in gadget mode
Date: Wed, 21 Oct 2020 19:50:05 +0000	[thread overview]
Message-ID: <aad327a8-95bc-40ec-abf7-ad216a02fad0@synopsys.com> (raw)
In-Reply-To: <2b6586e6-528c-86e8-9d92-0061bc44866d@gmail.com>

Ferry Toth wrote:
> Op 21-10-2020 om 00:58 schreef Thinh Nguyen:
>> Thinh Nguyen wrote:
>>> Hi,
>>>
>>> Ferry Toth wrote:
>>>> Op 20-10-2020 om 14:32 schreef Felipe Balbi:
>>>>> Hi,
>>>>>
>>>>> Ferry Toth <fntoth@gmail.com> writes:
>>>>>
>>>>> 8< snip
>>>>>
>>>>>>>> [   12.657416] CR2: 0000000100000000
>>>>>>>> [   12.660729] ---[ end trace 9b92dea6da33c71e ]---
>>>>>>> It this something you can reproduce on your end? Ferry, can you get
>>>>>>> dwc3
>>>>>>> trace logs when this happens? ftrace_dump_on_oops may help here.
>>>>>> I will do that tonight. Is flipping on ftrace_dump_on_oops
>>>>>> sufficient or
>>>>>> do I need to do more?
>>>>> you'd have to enable dwc3 trace events first ;-)
>>>>>
>>>>>> BTW after posting this I found in host mode dwc3 is not working
>>>>>> properly
>>>>>> either. No oops, but no driver get loaded on device plug in.
>>>>> okay
>>>>>
>>>> Ehem, you maybe only me to enable /dwc3/dwc3_ep_dequeue/enable:
>>>>
>>>> root@edison:/boot# uname -a
>>>> Linux edison 5.9.0-edison-acpi-standard #1 SMP Mon Oct 19 20:17:04 UTC
>>>> 2020 x86_64 x86_64 x86_64 GNU/Linux
>>>> root@edison:/boot# echo 1 >
>>>> /sys/kernel/debug/tracing/events/dwc3/dwc3_ep_dequeue/enable
>>>> root@edison:/boot# echo 1 > /proc/sys/kernel/ftrace_dump_on_oops
>>>> root@edison:/boot#
>>>> root@edison:/boot# [ 2608.585323] BUG: kernel NULL pointer
>>>> dereference, address: 0000000000000000
>>>> [ 2608.592288] #PF: supervisor read access in kernel mode
>>>> [ 2608.597419] #PF: error_code(0x0000) - not-present page
>>>> [ 2608.602549] PGD 0 P4D 0
>>>> [ 2608.605090] Oops: 0000 [#1] SMP PTI
>>>> [ 2608.608580] CPU: 1 PID: 733 Comm: irq/15-dwc3 Not tainted
>>>> 5.9.0-edison-acpi-standard #1
>>>> [ 2608.616571] Hardware name: Intel Corporation Merrifield/BODEGA BAY,
>>>> BIOS 542 2015.01.21:18.19.48
>>>> [ 2608.625356] RIP: 0010:dwc3_gadget_ep_dequeue+0x41/0x1c0
>>>> [ 2608.630580] Code: e9 51 01 00 00 4c 8d a3 30 01 00 00 4c 89 e7 e8
>>>> 15 e6 42 00 49 8b 4e 48 49 89 c5 49 8d 46 48 48 8d 51 a0 48 39 c8 75
>>>> 0f eb 2e <48> 8b 4a 60 48 8d 51 a0 48 39 c8 74 21 48 39 d5 75 ee 45 31
>>>> f6 4c
>>>> [ 2608.649320] RSP: 0018:ffffa838002a7c40 EFLAGS: 00010087
>>>> [ 2608.654543] RAX: ffff9a5f4609c048 RBX: ffff9a5f46f48028 RCX:
>>>> 0000000000000000
>>>> [ 2608.661666] RDX: ffffffffffffffa0 RSI: 0000000000000008 RDI:
>>>> ffff9a5f46f48158
>>>> [ 2608.668790] RBP: ffff9a5f7bd09b40 R08: 00000000000002d8 R09:
>>>> ffff9a5f7dd6a000
>>>> [ 2608.675913] R10: ffffa838002a7d90 R11: ffff9a5f46f48300 R12:
>>>> ffff9a5f46f48158
>>>> [ 2608.683039] R13: 0000000000000046 R14: ffff9a5f4609c000 R15:
>>>> ffff9a5f7ad77e00
>>>> [ 2608.690165] FS:  0000000000000000(0000) GS:ffff9a5f7e300000(0000)
>>>> knlGS:0000000000000000
>>>> [ 2608.698244] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>> [ 2608.703980] CR2: 0000000000000000 CR3: 000000003780a000 CR4:
>>>> 00000000001006e0
>>>> [ 2608.711102] Call Trace:
>>>> [ 2608.713561]  usb_ep_dequeue+0x19/0x80
>>>> [ 2608.717234]  u_audio_stop_capture+0x54/0x9a [u_audio]
>>>> [ 2608.722289]  afunc_set_alt+0x73/0x80 [usb_f_uac2]
>>> I took a look at how the audio function is handling switching alternate
>>> setting and dequeuing endpoints, and I think I found the issue.
>>>
>>> Here's a snippet of the free_ep() code in u_audio.c:
>>>
>>> static inline void free_ep(struct uac_rtd_params *prm, struct usb_ep
>>> *ep)
>>> {
>>>      .....
>>>          for (i = 0; i < params->req_number; i++) {
>>>                  if (prm->ureq[i].req) {
>>>                          usb_ep_dequeue(ep, prm->ureq[i].req);
>>>                          usb_ep_free_request(ep, prm->ureq[i].req);
>>>                          prm->ureq[i].req = NULL;
>>>                  }
>>>          }
>>>    ....
>>>
>>>
>>> usb_ep_dequeue() can be asynchronous. The dwc3 still has ownership of
>>> the request until it gives back the request. Freeing the request
>>> immediately here will cause a problem.
>>
>> To confirm my suspicion, can you try this and see if you still get oops?
>>
>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>> index eec8e9a9e3ed..b66eb24ec070 100644
>> --- a/drivers/usb/dwc3/gadget.c
>> +++ b/drivers/usb/dwc3/gadget.c
>> @@ -2031,6 +2031,7 @@ static int dwc3_gadget_ep_dequeue(struct usb_ep
>> *ep,
>>                          list_for_each_entry_safe(r, t,
>> &dep->started_list, list)
>>                                  dwc3_gadget_move_cancelled_request(r);
>>   +                      
>> dwc3_gadget_ep_cleanup_cancelled_requests(dep);
>>                          goto out;
>>                  }
>>          }
>>
>>
>> This will make usb_ep_dequeue() synchronous. (Note that this is not
>> tested).
>
> Unfortunately, it doesn't work. The trace changes to:
> root@edison:~# [  104.418264] BUG: kernel NULL pointer dereference,
> address: 0000000000000000
> [  104.425227] #PF: supervisor instruction fetch in kernel mode
> [  104.430877] #PF: error_code(0x0010) - not-present page
> [  104.436007] PGD 0 P4D 0
> [  104.438547] Oops: 0010 [#1] SMP PTI
> [  104.442039] CPU: 1 PID: 605 Comm: irq/15-dwc3 Not tainted
> 5.9.0-edison-acpi-standard #1
> [  104.450027] Hardware name: Intel Corporation Merrifield/BODEGA BAY,
> BIOS 542 2015.01.21:18.19.48
> [  104.458802] RIP: 0010:0x0
> [  104.461425] Code: Bad RIP value.
> [  104.464649] RSP: 0018:ffffae584034fbf8 EFLAGS: 00010046
> [  104.469870] RAX: 0000000000000000 RBX: ffff8c198608a028 RCX:
> ffff8c19bb87fa00
> [  104.476993] RDX: 00000000ffffff94 RSI: ffff8c19bafa54e0 RDI:
> ffff8c198609ee00
> [  104.484118] RBP: ffff8c19bafa54e0 R08: 0000000000000046 R09:
> 0000000000000238
> [  104.491241] R10: 000000000000002c R11: ffff8c19bcf62490 R12:
> ffff8c198609ee00
> [  104.498366] R13: ffff8c198608a028 R14: 0000000000000002 R15:
> ffff8c19bb8ff000
> [  104.505493] FS:  0000000000000000(0000) GS:ffff8c19be300000(0000)
> knlGS:0000000000000000
> [  104.513572] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [  104.519309] CR2: ffffffffffffffd6 CR3: 000000002e80a000 CR4:
> 00000000001006e0
> [  104.526432] Call Trace:
> [  104.528892]  dwc3_gadget_giveback+0xbf/0x120
> [  104.533169]  __dwc3_gadget_ep_disable+0xc5/0x250
> [  104.537789]  dwc3_gadget_ep_disable+0x3d/0xd0
> [  104.542149]  usb_ep_disable+0x1d/0x80
> [  104.545823]  u_audio_stop_capture+0x87/0x9a [u_audio]
> [  104.550880]  afunc_set_alt+0x73/0x80 [usb_f_uac2]
> [  104.555594]  composite_setup+0x20f/0x1b20 [libcomposite]
> [  104.560912]  ? configfs_composite_setup+0x6b/0x90 [libcomposite]
> [  104.566921]  configfs_composite_setup+0x6b/0x90 [libcomposite]
> [  104.572752]  dwc3_ep0_delegate_req+0x24/0x40
> [  104.577022]  dwc3_ep0_interrupt+0x40a/0x9d8
> [  104.581205]  dwc3_thread_interrupt+0x880/0xf70
>

Oops, looks like I can't make it synchronous this way. Can you try
Jack's change to the u_audio.c instead?

Thanks,
Thinh