From: David Kastrup <dak@gnu.org>
To: Andreas Schwab <schwab@suse.de>
Cc: Sam Steingold <sds@gnu.org>, emacs-devel@gnu.org
Subject: Re: busyloop in sigchld_handler
Date: Mon, 12 Mar 2007 20:34:43 +0100 [thread overview]
Message-ID: <85ejnumf1o.fsf@lola.goethe.zz> (raw)
In-Reply-To: <jeejnub6se.fsf@sykes.suse.de> (Andreas Schwab's message of "Mon\, 12 Mar 2007 20\:28\:33 +0100")
Andreas Schwab <schwab@suse.de> writes:
> Sam Steingold <sds@gnu.org> writes:
>
>> I don't know the details, but the kernel obviously has to do SOMETHING
>> when the child process terminates: it has to notice the state change so
>> that wait3 in emacs will return "yes, the child is dead" instead of
>> "nothing for you yet". The busyloop prevents the kernel from doing
>> anything for some time.
>
> But the busyloop does not happen when there is nothing to do, it only
> happens when wait3 is interrupted. A zero return will cause the handler
> to return immediately.
>
>> Now, it might be better to remove the WNOHANG option instead (except that
>> signal handlers are not supposed to hang),
>
> If you don't use WNOHANG you open up a race where several processes may
> have their status changed, but only one signal is sent (non-realtime
> signals are not queued).
How does WNOHANG protect against that? It does not prevent
scheduling, and it certainly does not prevent parallel execution on
multi-processor machines.
I should think that we need to prepare against this anyway.
--
David Kastrup, Kriemhildstr. 15, 44793 Bochum
next prev parent reply other threads:[~2007-03-12 19:34 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-11 18:33 busyloop in sigchld_handler Sam Steingold
2007-03-11 19:39 ` Kim F. Storm
2007-03-11 19:43 ` David Kastrup
2007-03-11 19:51 ` Sam Steingold
2007-03-11 20:42 ` Kim F. Storm
2007-03-11 21:06 ` Sam Steingold
2007-03-11 21:14 ` Eli Zaretskii
2007-03-11 21:17 ` Sam Steingold
2007-03-11 21:51 ` Eli Zaretskii
2007-03-11 22:21 ` Sam Steingold
2007-03-12 4:24 ` Richard Stallman
2007-03-12 7:00 ` David Kastrup
2007-03-13 2:43 ` Richard Stallman
2007-03-11 22:27 ` Andreas Schwab
2007-03-11 22:30 ` Kim F. Storm
2007-03-12 17:37 ` Andreas Schwab
2007-03-12 17:53 ` Sam Steingold
2007-03-12 18:45 ` Andreas Schwab
2007-03-12 18:57 ` Sam Steingold
2007-03-12 19:28 ` Andreas Schwab
2007-03-12 19:34 ` David Kastrup [this message]
2007-03-12 21:36 ` Andreas Schwab
2007-03-13 7:29 ` David Kastrup
2007-03-13 9:29 ` Andreas Schwab
2007-03-13 22:19 ` David Kastrup
2007-03-13 22:28 ` Andreas Schwab
2007-03-13 22:54 ` David Kastrup
2007-03-13 23:17 ` Andreas Schwab
2007-03-14 7:06 ` David Kastrup
2007-03-14 9:24 ` Kim F. Storm
2007-03-14 10:00 ` David Kastrup
2007-03-14 10:22 ` Andreas Schwab
2007-03-14 10:52 ` David Kastrup
2007-03-14 11:01 ` Andreas Schwab
2007-03-14 11:12 ` David Kastrup
2007-03-14 12:29 ` Andreas Schwab
2007-03-14 10:01 ` Andreas Schwab
2007-03-14 13:15 ` Kim F. Storm
2007-03-14 13:41 ` Andreas Schwab
2007-03-14 14:10 ` Kim F. Storm
2007-03-14 14:12 ` Andreas Schwab
2007-03-14 15:02 ` Kim F. Storm
2007-03-14 16:34 ` Andreas Schwab
2007-03-16 9:34 ` Kim F. Storm
2007-03-16 9:59 ` Andreas Schwab
2007-03-14 3:24 ` Richard Stallman
2007-03-14 17:34 ` David Kastrup
2007-03-26 1:47 ` YAMAMOTO Mitsuharu
2007-03-26 2:02 ` Sam Steingold
2007-03-26 2:17 ` YAMAMOTO Mitsuharu
2007-03-28 10:02 ` Kim F. Storm
2007-03-28 15:19 ` Chong Yidong
2007-03-28 15:25 ` Andreas Schwab
2007-03-28 15:33 ` Kim F. Storm
2007-03-28 15:37 ` Andreas Schwab
2007-03-28 20:18 ` Kim F. Storm
2007-03-29 17:59 ` Richard Stallman
2007-03-28 15:30 ` Alfred M. Szmidt
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