Description:
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I have a PHP page that opens a UDP socket and listens for data (blocking on socket_recvfrom). When the socket recieves a packet, the script echoes a message and finishes. This works fine, but when two instances of this page are running (both blocking on socket_recvfrom), Apache (2.2.4) stops responding to any new requests (even for non-php pages) until one of them gets unblocked. The same problem occurs with other blocking socket functions (such as socket_accept and socket_read with TCP sockets).

Reproduction instructions:
1. open a browser window to udp_recv.php?port=11111. it sits there "loading" since PHP is waiting for socket data.
2. open another browser window to udp_recv.php?port=22222.
3 (the problem). open another browser window and point it to index.html or any other url on the server. it just sits there "loading".
4. in a command prompt, type "perl udp_send.pl 11111" to send 'hello' to the first php script's udp socket, causing it to finish. Suddenly, the third request completes.

Reproduce code:
---------------
udp_recv.php:

<?php
$listener = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
socket_bind($listener, gethostbyname('localhost'), $_GET['port']) or exit('error on bind');
$len = socket_recvfrom($listener, $data, 2048, 0, $host, $port);
echo "$len bytes recieved from $host:$port: $data\n";
?>

udp_send.pl:

use strict; use Socket;
socket(SOCKET, PF_INET, SOCK_DGRAM, getprotobyname('udp')) or die "socket: $!";
send(SOCKET, 'hello', 0, sockaddr_in(shift, inet_aton('localhost'))) or die "send: $!";


Expected result:
----------------
I expect Apache to continue to accept and handle new web page requests while the two PHP pages are blocking on socket functions.

Actual result:
--------------
Once there are two PHP pages blocking on socket functions, all subsequent requests (even for non-php URIs) appear as "loading" in the browser until one of the PHP scripts unblocks.

Note: If the third request is for a PHP page containing an error_log() at the very beginning, then the logfile output is not generated as long as the first two pages are blocking (suggesting that Apache isn't getting around to starting PHP during this time).