Re: 4.6-rc3 hung at tty_port_block_til_ready+0x11c/0x2a0

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On 04/18/2016 07:18 AM, Matwey V. Kornilov wrote:
> 2016-04-18 9:55 GMT+03:00 Jiri Slaby <jslaby@xxxxxxx>:
>> On 04/17/2016, 02:33 PM, Matwey V. Kornilov wrote:
>>> Hello,
>>>
>>> When running 4.6-rc3 (please find used config attached) on BeagleBone Black with 8250_omap serial driver I see the following hung.

What uart # (0-5) are you using?
Are you using not-yet-mainline patches to 8250 driver (like for gpio modem control)?


>>> When test application a.out run twice (test.c source code attached here) the following happens:
>>>
>>> # ./a.out # ./a.out
>>> (hung here, may be interrupted with Ctrl-C)
>>>
>>> Trace from echo t > /proc/sysrq-trigger is the following:
>>>
>>> апр 17 12:29:23 nohostname kernel: a.out           S c0c3544c     0   922    882 0x00000000
>>> апр 17 12:29:23 nohostname kernel: [<c0c3544c>] (__schedule) from [<c0c3597c>] (schedule+0x5c/0xd0)
>>> апр 17 12:29:23 nohostname kernel: [<c0c3597c>] (schedule) from [<c0794820>] (tty_port_block_til_ready+0x11c/0x2a0)
>>> апр 17 12:29:23 nohostname kernel: [<c0794820>] (tty_port_block_til_ready) from [<c07abfb0>] (uart_open+0x11c/0x158)
>> ...
>>>
>>> I don't think that open() user-space call should be blocked under such circumstances, so I think that this is rather an issue within the kernel.
>>> I've found that the effect dissapears when termios calls are dropped from test.c

Assuming you are _not_ using gpio modem control, this shouldn't happen
because the driver should report TIOCM_CAR always on if DCD is not
pinned out for exactly this reason.

IOW, could be driver bug.

Regards,
Peter Hurley


>> I suppose the memset in the program cleared CLOCAL and the subsequent
>> open waits for carrier...
>>
> 
> The same program doesn't hang when fdti_sio based /dev/ttyUSB is being used.
> 
>> thanks,
>> --
>> js
>> suse labs
>>
> 
> 
> 

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