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SubjectFrequent dwc3 crashes on suspend or reboot since 5.0-rc1
Hey all,
Since the 5.0 merge window opened, I've been tripping on frequent
dwc3 crashes on reboot and suspend, which I've added an example to the
bottom of this mail.

I've dug in a little bit and sort of have a sense of whats going on.

In ffs_epfile_io():
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/usb/gadget/function/f_fs.c#n1065

The completion done is setup on the stack:
DECLARE_COMPLETION_ONSTACK(done);

Then later we setup a request and queue it:
req->context = &done;
...
ret = usb_ep_queue(ep->ep, req, GFP_ATOMIC);

Then wait for it:
if (unlikely(wait_for_completion_interruptible(&done))) {
/*
* To avoid race condition with ffs_epfile_io_complete,
* dequeue the request first then check
* status. usb_ep_dequeue API should guarantee no race
* condition with req->complete callback.
*/
usb_ep_dequeue(ep->ep, req);
interrupted = ep->status < 0;
}

The problem is, that we end up being interrupted, supposedly dequeue
the request, and exit.

But then (or in parallel) the irq triggers and we try calling
complete() on the context pointer which points to now random stack
space, which results in the panic.

It seems like something is wrong with usb_ep_dequeue not really
stopping the irq from happening?

If I revert all the changes to dwc3 back to 4.20, I don't see the issue.

I'll do some bisection to try to narrow things down, but I wanted to
see if this was a known issue or if anyone had immediate ideas as to
what might be wrong.

thanks
-john

[ 36.911170] Unable to handle kernel paging request at virtual
address ffffff801153d660
[ 36.912769] Unable to handle kernel paging request at virtual
address ffffff800004b564
[ 36.919881] Mem abort info:
[ 36.919884] ESR = 0x96000047
[ 36.919888] Exception class = DABT (current EL), IL = 32 bits
[ 36.919890] SET = 0, FnV = 0
[ 36.919895] EA = 0, S1PTW = 0
[ 36.927875] Mem abort info:
[ 36.935718] Data abort info:
[ 36.935721] ISV = 0, ISS = 0x00000047
[ 36.935723] CM = 0, WnR = 1
[ 36.935730] swapper pgtable: 4k pages, 39-bit VAs, pgdp = 00000000f1b819ef
[ 36.935733] [ffffff801153d660] pgd=000000021ffff803,
pud=000000021ffff803, pmd=000000021fffb803, pte=0000000000000000
[ 36.935744] Internal error: Oops: 96000047 [#1] PREEMPT SMP
[ 36.935748] Modules linked in:
[ 36.938552] ESR = 0x86000006
[ 36.941601] CPU: 0 PID: 2656 Comm: irq/69-dwc3 Tainted: G S
4.20.0-10778-gadc8369 #210
[ 36.941603] Hardware name: HiKey960 (DT)
[ 36.941610] pstate: 00400085 (nzcv daIf +PAN -UAO)
[ 36.947554] Exception class = IABT (current EL), IL = 32 bits
[ 36.950594] pc : queued_spin_lock_slowpath+0x1cc/0x2c8
[ 36.950601] lr : queued_spin_lock_slowpath+0xd0/0x2c8
[ 36.950603] sp : ffffff8011e13be0
[ 36.950607] x29: ffffff8011e13be0 x28: 0000000000000000
[ 36.950611] x27: ffffff801186d000 x26: ffffff8010159000
[ 36.950615] x25: ffffff801186d000 x24: ffffffc218be36e8
[ 36.950619] x23: ffffff801186e910 x22: 0000000000040000
[ 36.950622] x21: ffffffc21f71b640 x20: ffffff801153d000
[ 36.950626] x19: ffffff8011e1bbe8 x18: 0000000000000000
[ 36.950629] x17: 00000000100eb564 x16: 00000000100eb564
[ 36.950633] x15: 0000000000000000 x14: ffffff801187cf80
[ 36.950636] x13: 000000420e1de000 x12: 0000000034d4d91d
[ 36.950640] x11: 0000000000000000 x10: 0000000000000a20
[ 36.950643] x9 : ffffff8011e13d10 x8 : ffffffc218874c00
[ 36.950646] x7 : 0000000000000000 x6 : ffffff801186db08
[ 36.950650] x5 : 0000000000000000 x4 : 0000000000000000
[ 36.950653] x3 : ffffffc21f71b640 x2 : 0000000000000000
[ 36.950656] x1 : ffffff801153d660 x0 : ffffffc21f71b648
[ 36.950663] Process irq/69-dwc3 (pid: 2656, stack limit = 0x00000000b627af93)
[ 36.950666] Call trace:
[ 36.950670] queued_spin_lock_slowpath+0x1cc/0x2c8
[ 36.950681] _raw_spin_lock_irqsave+0x64/0x78
[ 36.950692] complete+0x28/0x70
[ 36.950703] ffs_epfile_io_complete+0x3c/0x50
[ 36.950713] usb_gadget_giveback_request+0x34/0x108
[ 36.950721] dwc3_gadget_giveback+0x50/0x68
[ 36.950723] dwc3_thread_interrupt+0x358/0x1488
[ 36.950731] irq_thread_fn+0x30/0x88
[ 36.950734] irq_thread+0x114/0x1b0
[ 36.950739] kthread+0x104/0x130
[ 36.950747] ret_from_fork+0x10/0x1c
[ 36.950755] Code: 91190281 8b021021 f860dae2 91002060 (f8226823)
[ 36.953901] SET = 0, FnV = 0
[ 36.956685] ---[ end trace 3d13dc405c1e8aa7 ]---
[ 36.965704] Kernel panic - not syncing: Fatal exception
[ 36.966372] EA = 0, S1PTW = 0
[ 36.973246] SMP: stopping secondary CPUs
[ 36.983855] Kernel Offset: disabled
[ 36.983860] CPU features: 0x002,21882004
[ 36.983861] Memory Limit: none
[ 37.210976] Rebooting in 5 seconds..

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