2016-04-19 6:01 GMT+03:00 Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>: > 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. > Hello, > What uart # (0-5) are you using? I am using uart5 (ttyS5). > Are you using not-yet-mainline patches to 8250 driver (like for gpio modem control)? No, I use vanilla 4.6-rc3 (and 4.5 behaviour is the same). > > >>>> 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. As Jiri said, CLOCAL prevents open() from blocking. However, my uart doesn't have any modem control pins in device tree only rts/cts. > > 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 >>> >> >> >> > -- With best regards, Matwey V. Kornilov. Sternberg Astronomical Institute, Lomonosov Moscow State University, Russia 119991, Moscow, Universitetsky pr-k 13, +7 (495) 9392382 -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
