fix nagios' handling of nonblocking reads

[Henning Brauer]

nagios is doing reads on nonblocking fds incorrectly. easily
observable by using an alert script that sleeps for a long time,
nagios will consume all CPU time as long as the script runs.
the fix is to poll on EAGAIN instead of looping, of course. this has
the nice side effect of reducing overall CPU load caused by the nagios
process considerably.

$OpenBSD$
--- base/utils.c.orig	Fri Jan  9 14:20:10 2009
+++ base/utils.c	Fri Jan  9 14:28:24 2009
@@ -610,8 +610,16 @@ int my_system(char *cmd,int timeout,int *early_timeout
 				/* handle errors */
 				if(bytes_read==-1){
 					/* we encountered a recoverable error, so try again */
-					if(errno==EINTR || errno==EAGAIN)
+					if(errno==EINTR)
 						continue;
+					else if (errno == EAGAIN) {
+						struct pollfd	pfd;
+
+						pfd.fd = fd[0];
+						pfd.revents = POLLIN;
+						poll(&pfd, 1, -1);
+						continue;
+						}
 					else
 						break;
 					}


-- 
Henning Brauer, hb at bsws.de, henning at openbsd.org
BS Web Services, http://bsws.de
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