Re: [Queue-developers] queued and defunct processes

[Mike C. <da...@ix...>]

On Sat, May 12, 2001 at 11:24:32PM -0700, Mike Castle wrote:
> I think I may have narrowed it down.
> 
> It *appears* that if queued receives a SIGCHLD while inside netfread,
> things aren't properly processed.  The fact that a SIGCHLD was received is
> either somehow lost, OR things hang out in netfread for a long time.


Well, I'm still not sure about the above, however, I *did* observe the
following:

Queue_nonblocking_rw(), as used by the getloadavg routine, really mucks
things up as well.  As the following extract from the log shows, the
handling of a SIGCHLD can be delayed by at least a minute.  (A few extra
timestamps were put into place just to be sure).

thune.mrc-home.org[8602]: timestamp:    "Sun May 13 00:05:01"
thune.mrc-home.org[8602]: handle.c chldsigh():
        pid 8604: signal 17.
thune.mrc-home.org[8602]: exit at Sun May 13 00:05:01 2001
 from handle.c:1997   <<< my extra stuff
thune.mrc-home.org[7817]: timestamp:    "Sun May 13 00:05:01"
thune.mrc-home.org[7817]: queued queued.c sigchld(): SIGCHLD.
qlib.c Queue_count_the_signal(): signal 17: 14.
qlib.c Queue_nonblocking_rw(): select()ing on fd 8 for 61 seconds...
thune.mrc-home.org[7817]: timestamp:    "Sun May 13 00:06:02"
qlib.c Queue_nonblocking_rw(): timed out read()ing 4 bytes from fd 8.
qlib.c Queue_nonblocking_rw(): failed to read() 4 bytes (done 0) on fd 8,
giving
 up.
qlib.c Queue_net_rw(): failed to get 1 4-byte items on fd 8; got 0 bytes.
wakeup.c getrldavg(): failed to fread() from fd 8.
wakeup.c getrldavg(): close(8).
wakeup.c getrldavg(): ### failed to get load from mars.mrc-home.org
             ### returning 1.00e+08 as rejection designator.
thune.mrc-home.org[7817]: queued queued.c runqueue_b():
        queue is running max number of jobs = 2
thune.mrc-home.org[7817]: queued queued.c main() child:
        SIGCHLD flag set; running waitforchild()...
thune.mrc-home.org[7817]: queued queued.c waitforchild():
        wait exit pid=8627, stat=00, cpu=1.6
thune.mrc-home.org[7817]: queued queued.c waitforchild(): Sun May 13
00:06:02 2001

Note that PID 8602 exited at 00:05:01, and the SIGCHLD was received by 7817.
However, it wasn't even able to be processed for another 61 seconds, (both
according to the comment from nonblocking_rw and the time stamp from when
waitforchild was finally entered.

Still trying to work out WHY mars is in such a state....

mrc
-- 
       Mike Castle       Life is like a clock:  You can work constantly
  da...@ix...  and be right all the time, or not work at all
www.netcom.com/~dalgoda/ and be right at least twice a day.  -- mrc
    We are all of us living in the shadow of Manhattan.  -- Watchmen