VF50 linux process trying to close ttyLP2 hangs in lpuart_shutdown

Technical Support
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1

I’m using ofono 1.19 with a UART-attached modem. I often find that when I try to shut down the process it won’t respond, even to SIGKILL. It looks like it’s hanging in a driver function lpuart_shutdown.

# uname -r
4.4.14-v2.6b2+gefe965a
# echo $(cat /proc/$(pgrep ofono)/wchan)
lpuart_shutdown

I haven’t yet gotten a slimmed down test case, unfortunately. I’m assuming something else in the driver is holding the port lock.

Unfortunately the only mitigation I’ve found is a reboot; lsof doesn’t show the device open anymore, but another onofo instance can’t be started because the previous unkillable instance is still holding onto the dbus name.

2

Sorry! for the delay. Can you please provide some more details about the ofono configuration/setup to replicate the issue and also ofono v1.19 build details.

3

This is probably caused by the DMA wait queue. You probably hit a DMA edge case we fixed recently:

http://git.toradex.com/cgit/linux-toradex.git/commit/?h=toradex_vf_4.4-next&id=a650cbfc7e981ba24313da0338f4482bef514d44

This patch is not yet part of V2.6b2 or V2.6.1b1, it is only fixed in our latest V2.7 BSP release…

4

I will try incorporating this patch and see if the problem remains. Thank you.

5

The setup is ofono 1.19, but with a custom driver for a UART-attached u.blox SARA-350 module. Even if I gave you this code you would probably need a similar module to fully reproduce the case. If Stefan’s suggestion doesn’t help, I will try to create a simplified test case for further investigation. Thank you.

6

Since incorporating that patch the issue has not recurred. Thank you very much for pointing me to it.