* [BUG?] "wait <PID>" sometimes confused with multiple childs
@ 2018-03-12 13:23 ` Antoine C.
2018-03-12 14:19 ` Peter Stephenson
0 siblings, 1 reply; 2+ messages in thread
From: Antoine C. @ 2018-03-12 13:23 UTC (permalink / raw)
To: zsh-workers
Hello,
I have a problem with a script starting several subshells in background then checking their return code. It looks like the "wait <PID>" builtin is sometimes returning the error code of another child.
Here is a script reproducing this behavior. Several childs are started in a first loop with predefined return code, their PID saved, then we wait for each of them in a second loop and check their RC:
------start-----
#!/bin/zsh
while true; do
pids=()
for task in {1..16} ; do
( sleep .1 ; exit $task ) &
pids+=($!)
# uncomment to prevent bug
#sleep .1
done
for task in {1..16} ; do
wait $pids[task]
rc=$?
if (( rc != task )) ; then
echo " FAIL $pids[task]" $rc $task
fi
done
echo "done $pids"
done
------end-----
On my machine, I have many "FAIL ..." printed, around 1 "FAIL" every 2 "done".
If we comment out the "sleep" above, no more fails are printed. I also tried with bash (with a few syntax changes), and it is always working as expected.
Is it a bug or am I missing something?
Antoine
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [BUG?] "wait <PID>" sometimes confused with multiple childs
2018-03-12 13:23 ` [BUG?] "wait <PID>" sometimes confused with multiple childs Antoine C.
@ 2018-03-12 14:19 ` Peter Stephenson
0 siblings, 0 replies; 2+ messages in thread
From: Peter Stephenson @ 2018-03-12 14:19 UTC (permalink / raw)
To: Antoine C., zsh-workers
On Mon, 12 Mar 2018 14:23:59 +0100
Antoine C. <acalando@free.fr> wrote:
> I have a problem with a script starting several subshells in
> background then checking their return code. It looks like the "wait
> <PID>" builtin is sometimes returning the error code of another child.
>
> Is it a bug or am I missing something?
It's a bug. You hit a race where we record the status but don't
read it back properly.
Thanks, I had no problem investigating with that script.
pws
diff --git a/Src/jobs.c b/Src/jobs.c
index 503618f..330ee6b 100644
--- a/Src/jobs.c
+++ b/Src/jobs.c
@@ -2289,8 +2289,11 @@ bin_fg(char *name, char **argv, Options ops, int func)
*/
retval = waitforpid(pid, 1);
}
- if (retval == 0)
- retval = lastval2;
+ if (retval == 0) {
+ if ((retval = getbgstatus(pid)) < 0) {
+ retval = lastval2;
+ }
+ }
} else if ((retval = getbgstatus(pid)) < 0) {
zwarnnam(name, "pid %d is not a child of this shell", pid);
/* presumably lastval2 doesn't tell us a heck of a lot? */
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2018-03-12 14:26 UTC | newest]
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2018-03-12 13:23 ` [BUG?] "wait <PID>" sometimes confused with multiple childs Antoine C.
2018-03-12 14:19 ` Peter Stephenson
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