Signal Request Not Reaching Child

[Horst Laumer]

In article <1990Nov26.214748.5977 at mdivax1.uucp>:


>A process (P) generates (and can kill) child processes.  Children are
>normally given a signal (kill -3) by P and kill themselves after cleaning
>up and acknowledging P's request.

>The problem is that (very rarely) a child process refuses to die.  No
>ack is sent to P.  When in this state, even kill -9 will not kill the
>child process.  However, the child process handles terminal i/o and if
>the terminal is shut off and on the child can be aborted.  This makes
>me think that the child is in a state where it cannot collect a software
>signal, perhaps because it is in the middle of a screen write or some
>terminal i/o.  Could this be the case?  What else could cause this?
>Work around solutions would also be appreciated.  Note: the terminal is
>set up in BLOCK mode, if that makes any difference.

>Thanks in advance for any suggestions/help.

This seams to be a general bug. At least in SysV, when kill(pid,SIGKILL)
doesn't work, this indicates that the recipient in in kernel mode and
executing (better: hanging) the code of a device driver the kernel relies
on (!). Since I do not know the process' job, assuming P knows the tty of
this child this may be worked around by having P close the line and send
the signal again.

hl
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