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On 1/16/15 10:32 AM, Dr. Werner Fink wrote:
> On Fri, Jan 16, 2015 at 09:22:36AM -0500, Chet Ramey wrote:
>> On 1/13/15 4:29 AM, Dr. Werner Fink wrote:
>>
>>>>> Bash Version: 4.3
>>>>> Patch Level: 33
>>>>> Release Status: release
>>>>>
>>>>> Description:
>>>>> Named fifo's causing hanging bash scripts like
>>>>>
>>>>> while IFS="|" read a b c ; do
>>>>> [shell code]
>>>>> done < <(shell code)
>>>>>
>>>>> can cause random hangs of the bash. An strace shows that the
>>>>> bash
>>>>> stays in wait4()
>>>>
>>>> And when you attach to one of the hanging bash processes using gdb, what
>>>> does the stack traceback look like?
>>>
>>> Yes (and sorry for the wrong email address as this was done on a clean
>>> virtual sysstem)
>>>
>>> there are two hanging bash processes together with the find command:
>>>
>>> werner 19062 0.8 0.0 11864 2868 ttyS0 S+ 10:21 0:00 bash -x
>>> /tmp/brp-25-symlink
>>> werner 19063 0.0 0.0 11860 1920 ttyS0 S+ 10:21 0:00 bash -x
>>> /tmp/brp-25-symlink
>>> werner 19064 0.2 0.0 16684 2516 ttyS0 S+ 10:21 0:00 find .
>>> -type l -printf %p|%h|%l n
>>>
>>> the gdb -p 19062 and gdb -p 19063 show
>>>
>>> (gdb) bt
>>> #0 0x00007f530818a65c in waitpid () from /lib64/libc.so.6
>>> #1 0x000000000042b233 in waitchld (block=block@entry=1, wpid=19175) at
>>> jobs.c:3235
>>> #2 0x000000000042c6da in wait_for (pid=pid@entry=19175) at jobs.c:2496
>>
>> What do ps and gdb tell you about pid 19175 (and the corresponding pid in
>> the call to waitchld in the other traceback)? Running, terminated, reaped,
>> other?
>
> d136:~ # ps 10942
> PID TTY STAT TIME COMMAND
> d136:~ #
>
> ... the process does not exists anymore. I guess that this could belong to
> the sed commands of the script.
This is why I need to be able to reproduce it. If the process got reaped,
when would it have happened and why would the call to wait_for() have
found a valid CHILD struct for it? The whole loop runs with SIGCHLD
blocked, so it's not as if the signal handler could have reaped the
child out from under it. I have questions but no way to find answers.
- --
``The lyf so short, the craft so long to lerne.'' - Chaucer
``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU c...@case.edu http://cnswww.cns.cwru.edu/~chet/
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