From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <af4b600c70d2c88d71c96e6b980e9e74@felloff.net>
Date: Thu,  5 Dec 2013 23:59:26 +0100
From: cinap_lenrek@felloff.net
To: 9fans@9fans.net
In-Reply-To: <27644fbad2e3cd6556717fb4f3ba7d1c@brasstown.quanstro.net>
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Subject: Re: [9fans] rio leak
Topicbox-Message-UUID: 930a0bc6-ead8-11e9-9d60-3106f5b1d025

i just tried something out. it appears that _schedexecwait()'s
purpose is to serve thredwaitchan():

          Threadwaitchan returns a channel of pointers to Waitmsg
          structures (see wait(2)). When an exec'ed process exits, a
          pointer to a Waitmsg is sent to this channel.  These Waitmsg
          structures have been allocated with malloc(2) and should be
          freed after use.

when threadwaitchan isnt used, we can rfork the execing child
with RFNOWAIT which will make the process doing the original
procexecl() not wait for the child.

i just tried this out with rio (and abaco) and it seems to work fine.

diff -r 42807d2e3f4b sys/src/libthread/main.c
--- a/sys/src/libthread/main.c	Thu Dec 05 22:43:44 2013 +0100
+++ b/sys/src/libthread/main.c	Fri Dec 06 23:50:34 2013 +0100
@@ -121,9 +121,10 @@
 int
 _schedexec(Execargs *e)
 {
-	int pid;
+	int pid, flag;

-	switch(pid = rfork(RFREND|RFNOTEG|RFFDG|RFMEM|RFPROC)){
+	flag = (_threadwaitchan == nil) ? RFNOWAIT : 0;
+	switch(pid = rfork(RFREND|RFNOTEG|RFFDG|RFMEM|RFPROC|flag)){
 	case 0:
 		efork(e);
 	default:

this is saving a couple of few processes. is it worth it?

--
cinap