[Qemu-devel] qemu-system-x86_64: hw/usb/core.c:720: usb_ep_get: Assertion `dev != NULL' failed

[Guenter Roeck]

Hi,

I have seen the following problem several times recently. This is with qemu-4.0.

qemu-system-x86_64: hw/usb/core.c:720: usb_ep_get: Assertion `dev != NULL' 
failed

Backtrace gives me the following call path.

main_loop()
  main_loop_wait()
    glib_pollfds_poll()
      aio_ctx_dispatch()
        aio_dispatch()
          aio_bh_poll()
            ehci_work_bh()
              ehci_advance_async_state()
                ehci_advance_state()
                  ehci_execute()
                    usb_ep_get()

The problem always happens during shutdown, maybe once every 100 boots.
It seems to be more likely to happen when the system is under heavy load.

...
umount: devtmpfs busy - remounted read-only
[   49.018682] EXT4-fs (sda): re-mounted. Opts: (null)
[   49.028052] sd 6:0:0:0: [sda] Synchronizing SCSI cache
qemu-system-x86_64: hw/usb/core.c:733: usb_ep_get: Assertion `dev != NULL' 
failed.

Essentially that means that p->queue->dev is NULL in ehci_execute().

Has anyone else seen this problem ? Any idea what I can do to debug
this further ?

Thanks,
Guenter