From: Dominik Vogt <dominik.vogt@gmx.de>
To: Zsh Users <zsh-users@zsh.org>
Subject: Frozen command substitution
Date: Sat, 11 Feb 2023 10:41:07 +0100 [thread overview]
Message-ID: <Y+dioiiAoWXaSGqw@localhost> (raw)
I have two long running scripts that do complex interaction with
the web browser, say "foo" which calls the subordinate script
"bar". The browser crashes once in a while and is restarted
automatically by some other script. Sometimes when this happens,
foo freezes in a call of bar and won't wake up anymore when bar
terminates:
-- foo --
while true; do
some-func
test some-condition && break
done
some-func () {
while true; do
R="$(bar ssome arguments)" <------- hangs in this line
test some condition && return 0
done
}
-- foo --
-- bar --
# some long-running loop
# ...
return 0
-- bar --
Ciao
Dominik ^_^ ^_^
--
So, foo calls bar in a loop. While bar is running, the browser is
restarted. bar detects this, finishes and exits with the "return
0". However, foo does not continue with the line after the
command substitution. A "ctrl-z" foollowed by "fg" does not help.
Sending it SIGUSR1 (which has a trap installed) wakes it up again.
In the process list:
$ pstree -a
...
<terminal>-+-zsh-+-foo
|-tee
+-zsh
(The whole stuff is calles with
"while true; do foo 2>&1 | tee foo.out; done".) /proc/<pid>/status says:
$ cat /proc/<pid>/status
...
State: S (sleeping)
Tgid: 13030
Ngid: 0
Pid: 13030
PPid: 24927
...
foo has a trap for "HUP" installed, and that's being called when
when I type "killall -HUP foo", so the shell is not dead. "ps"
lists the processes' status as "S+".
Dominik Vogt
next reply other threads:[~2023-02-11 9:41 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-11 9:41 Dominik Vogt [this message]
2023-02-11 17:02 ` Dominik Vogt
2023-02-11 17:36 ` Bart Schaefer
2023-02-11 20:28 ` Dominik Vogt
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