Re: kern/12534 (Processes can hang at exit-time on ttyout)

[Andreas Gustafsson <gson%gson.org@localhost>]

The following reply was made to PR kern/12534; it has been noted by GNATS.

From: Andreas Gustafsson <gson%gson.org@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: kern/12534 (Processes can hang at exit-time on ttyout)
Date: Wed, 20 Aug 2014 11:18:29 +0300

 I'm suffering from what looks like kern/12534 on NetBSD 6.1.3/amd64.
 When I connect to the serial console of another system using tip(1)
 over a com(4) port, sometimes the tip process hangs indefinitely while
 exiting:
 
  UID   PID  PPID CPU PRI NI   VSZ   RSS WCHAN   STAT TTY         TIME COMMAND
    0 12964     1   0   0  0     0     0 -       DE   pts/4-   0:00.00 (tip)
 
 Kernel stack trace of the tip process from ddb:
 
   trace: pid 12964 lid 1 at 0xfffffe8000078850
   sleepq_block() at netbsd:sleepq_block+0xad
   cv_timedwait_sig() at netbsd:cv_timedwait_sig+0xaa
   ttysleep() at netbsd:ttysleep+0x55
   ttywait() at netbsd:ttywait+0x5c
   ttywflush() at netbsd:ttywflush+0x11
   ttylclose() at netbsd:ttylclose+0x17
   comclose() at netbsd:comclose+0x62
   cdev_close() at netbsd:cdev_close+0x6a
   spec_close() at netbsd:spec_close+0x106
   VOP_CLOSE() at netbsd:VOP_CLOSE+0x33
   vn_close() at netbsd:vn_close+0x4e
   closef() at netbsd:closef+0x4a
   fd_free() at netbsd:fd_free+0xba
   exit1() at netbsd:exit1+0xf9
   sys_exit() at netbsd:sys_exit+0x3e
   syscall() at netbsd:syscall+0xc4
 
 Unplugging and replugging the serial port resolves the situation (I'm
 mentioning this because it may offer some clue as to the cause of the
 bug, not to suggest that it is an acceptable work-around - for an
 unattended system, it clearly isn't).
 -- 
 Andreas Gustafsson, gson%gson.org@localhost