Jack Pham wrote:
> Hi Thinh, Ferry,
>
> On Tue, Oct 20, 2020 at 10:58:31PM +0000, Thinh Nguyen wrote:
>> Thinh Nguyen wrote:
>>> Hi,
>>>
>>> Ferry Toth wrote:
>>>> Op 20-10-2020 om 14:32 schreef Felipe Balbi:
>>>>> Hi,
>>>>>
>>>>> Ferry Toth <fntoth@xxxxxxxxx> 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).
> But only for dwc3 right? In general do other UDC drivers provide
> synchronous behavior? It does states clearly in the kerneldoc for
> usb_ep_dequeue() that the completion is asynchronous. From
> drivers/usb/gadget/udc/core.c:
>
> * If the request is still active on the endpoint, it is dequeued and
> * eventually its completion routine is called (with status -ECONNRESET);
> * else a negative error code is returned. This routine is asynchronous,
> * that is, it may return before the completion routine runs.
>
> Alternatively, could we not fix up u_audio.c to deal with this?
The issue is in u_audio.c. But I want to confirm my suspicion about
whether the oops that Ferry is due to this (most likely it is).
We don't want to apply this as a workaround and mask the issue in audio.c.
>
> diff --git a/drivers/usb/gadget/function/u_audio.c b/drivers/usb/gadget/function/u_audio.c
> index 56906d15fb55..f08f036d520e 100644
> --- a/drivers/usb/gadget/function/u_audio.c
> +++ b/drivers/usb/gadget/function/u_audio.c
> @@ -89,7 +89,12 @@ static void u_audio_iso_complete(struct usb_ep *ep, struct usb_request *req)
> struct snd_uac_chip *uac = prm->uac;
>
> /* i/f shutting down */
> - if (!prm->ep_enabled || req->status == -ESHUTDOWN)
> + if (!prm->ep_enabled) {
> + usb_ep_free_request(ep, req);
> + return;
> + }
> +
> + if (req->status == -ESHUTDOWN)
> return;
>
> /*
> @@ -352,7 +357,6 @@ 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;
> }
> }
>
> Jack
Yes, the u_audio.c needs to do something like that.
BR,
Thinh
