[PHP-DEV] Help please: child processes are not killed when PHP is done

[O'Neil Delpratt]

Hi All,

I am experiencing a strange behaviour in my PHP extension. My setup: Ubuntu LTS 
16, Apache 2.4, PHP 7.0.30 (tested with PHP 7.1.17) and latest Saxon-HE/C 64bit.

Observed behaviour is that Apache spawns a couple of child processes as soon as 
Saxon is invoked. Problem is that those child processes are not killed when PHP 
is done.

Code
<?php
// output current PID and number of threads
$pid = getmypid();
$child_threads = trim(`ls /proc/{$pid}/task | wc -l`);

echo "&lt;pre&gt;";
echo "Process ID :$pid".PHP_EOL;
echo "Number of threads: $child_threads".PHP_EOL;
echo str_repeat("-", 20).PHP_EOL;

$sax = new Saxon\SaxonProcessor();

// output number of threads again
$child_threads = trim(`ls /proc/{$pid}/task | wc -l`).PHP_EOL;
echo "Number of threads: $child_threads".PHP_EOL;
/>


Gives the output:

Process ID: 5591 Number of threads: 1 ——————— Number of threads: 9

Running that code snippet, I see that additional 9 child threads are running, 
but they stay alive until I manually kill them.

Source code of php extension: 
https://dev.saxonica.com/repos/archive/opensource/latest9.8/hec/Saxon.C.API/php7_saxon.cpp
 
<https://dev.saxonica.com/repos/archive/opensource/latest9.8/hec/Saxon.C.API/php7_saxon.cpp>