For what it's worth, I also see this upon occasion on Scientific Linux 6.3 with 5.3.
Luckily, it doesn't seem to happen during the boot process (though my servers have LOM access, it's a pain to SSH into the actual console or use a Java applet while remotely rebooting). I suspect there's a race going on, as it seems that not all of the prior php-fpm processes have quit yet when this occurs.
My workaround is to (as root):
# pkill php-fpm && pkill -9 php-fpm
This attempts to gracefully quit anything that can be (such as the service command that's trying to spawn processes), and forcefully quit anything that's hung. It "works", but it also seems that a bit of patience also does the trick.
This also seems to happen more on servers with busier (in terms of PHP usage) sites, and with multiple php-fpm pools. I haven't really investigated it fully, but it's not unique to EL5 or PHP 5.4. I suspect it's also not unique to Remi's build, but that people on e.g. Fedora don't really do "servery" stuff and it doesn't get noticed as much. In the "servery" world, php-fpm is still a scary new thing.
For what it's worth, this is what shows up on the "service php-fpm restart" terminal after the first kill command, quoted above:
Starting php-fpm: /sbin/service: line 66: 19476 Terminated env -i PATH="$PATH" TERM="$TERM" "${SERVICEDIR}/${SERVICE}" ${OPTIONS}
And the obligatory additional information:
$ lsb_release -d && uname -srvmpio && php-fpm -v && repoquery --installed -i php-fpm
Description: Scientific Linux release 6.3 (Carbon)
Linux 2.6.32-279.2.1.el6.x86_64 #1 SMP Thu Jul 19 16:08:55 CDT 2012 x86_64 x86_64 x86_64 GNU/Linux
PHP 5.3.16 (fpm-fcgi) (built: Aug 16 2012 13:52:44)
Copyright (c) 1997-2009 The PHP Group
Zend Engine v2.3.0, Copyright (c) 1998-2012 Zend Technologies
with Xdebug v2.1.4, Copyright (c) 2002-2012, by Derick Rethans
Name : php-fpm
Version : 5.3.16
Release : 1.el6.remi
Architecture: x86_64
Size : 3392329
Packager : http://blog.famillecollet.com/
Group : Development/Languages
URL : I had to delete php's link, since the forum complained about it. Sigh.
Repository : installed
Summary : PHP FastCGI Process Manager
Source : php-5.3.16-1.el6.remi.src.rpm
Description :
PHP-FPM (FastCGI Process Manager) is an alternative PHP FastCGI
implementation with some additional features useful for sites of
any size, especially busier sites.
EDIT: I just updated a host that experiences the issue quite often (the same one I gave the uname and such for) to 5.4.6 from remi-test, and I can't make it happen again. That's the joy of intermittent bugs, eh? I'll update again if I can get it to reproduce with 5.4.