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[ticket/9061] Fixed a race condition in queue locking.

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Changed queue locking to cover all queue file operations,
in particular the check for queue file existince and
inclusion of queue file must be done under one lock.

Also refactored queue locking and unlocking into separate
methods.

PHPBB3-9061
This commit is contained in:
Oleg Pudeyev 2010-04-20 06:53:52 -04:00 committed by Chris Smith
parent cb3cf71805
commit 01ef46a510
1 changed files with 62 additions and 19 deletions
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81
phpBB/includes/functions_messenger.php
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@ -631,6 +631,58 @@ class queue
$this->data[$object]['data'][] = $scope;
}
/**
* Obtains exclusive lock on queue cache file.
* Returns resource representing the lock
*/
function lock()
{
// For systems that can't have two processes opening
// one file for writing simultaneously
if (file_exists($this->cache_file . '.lock'))
{
$mode = 'rb';
}
else
{
$mode = 'wb';
}
$lock_fp = @fopen($this->cache_file . '.lock', $mode);
// Two processes may attempt to create lock file at the same time.
// Have the losing process try opening the lock file again for reading
// on the assumption that the winning process created it
if (!$lock_fp && $mode == 'wb')
{
// Assign to $mode for the check in chmod below
$mode = 'rb';
$lock_fp = @fopen($this->cache_file . '.lock', $mode);
}
if ($lock_fp && $mode == 'wb')
{
// Only need to set mode when the lock file is written
@chmod($this->cache_file . '.lock', 0666);
}
if ($lock_fp)
{
@flock($lock_fp, LOCK_EX);
}
return $lock_fp;
}
/**
* Releases lock on queue cache file, using resource obtained from lock()
*/
function unlock($lock_fp)
{
// lock() will return null if opening lock file, and thus locking, failed.
// Accept null values here so that client code does not need to check them
if ($lock_fp)
{
@flock($lock_fp, LOCK_UN);
fclose($lock_fp);
}
}
/**
* Process queue
* Using lock file
@ -639,24 +691,16 @@ class queue
{
global $db, $config, $phpEx, $phpbb_root_path, $user;
$lock_fp = $this->lock();
set_config('last_queue_run', time(), true);
// Delete stale lock file
if (file_exists($this->cache_file . '.lock') && !file_exists($this->cache_file))
if (!file_exists($this->cache_file) || filemtime($this->cache_file) > time() - $config['queue_interval'])
{
@unlink($this->cache_file . '.lock');
$this->unlock($lock_fp);
return;
}
if (!file_exists($this->cache_file) || (file_exists($this->cache_file . '.lock') && filemtime($this->cache_file) > time() - $config['queue_interval']))
{
return;
}
$fp = @fopen($this->cache_file . '.lock', 'wb');
fclose($fp);
@chmod($this->cache_file . '.lock', 0777);
include($this->cache_file);
foreach ($this->queue_data as $object => $data_ary)
@ -713,6 +757,7 @@ class queue
break;
default:
$this->unlock($lock_fp);
return;
}
@ -738,8 +783,6 @@ class queue
if (!$result)
{
@unlink($this->cache_file . '.lock');
messenger::error('EMAIL', $err_msg);
continue 2;
}
@ -783,16 +826,14 @@ class queue
{
if ($fp = @fopen($this->cache_file, 'wb'))
{
@flock($fp, LOCK_EX);
fwrite($fp, "<?php\nif (!defined('IN_PHPBB')) exit;\n\$this->queue_data = unserialize(" . var_export(serialize($this->queue_data), true) . ");\n\n?>");
@flock($fp, LOCK_UN);
fclose($fp);
phpbb_chmod($this->cache_file, CHMOD_READ | CHMOD_WRITE);
}
}
@unlink($this->cache_file . '.lock');
$this->unlock($lock_fp);
}
/**
@ -805,6 +846,8 @@ class queue
return;
}
$lock_fp = $this->lock();
if (file_exists($this->cache_file))
{
include($this->cache_file);
@ -824,13 +867,13 @@ class queue
if ($fp = @fopen($this->cache_file, 'w'))
{
@flock($fp, LOCK_EX);
fwrite($fp, "<?php\nif (!defined('IN_PHPBB')) exit;\n\$this->queue_data = unserialize(" . var_export(serialize($this->data), true) . ");\n\n?>");
@flock($fp, LOCK_UN);
fclose($fp);
phpbb_chmod($this->cache_file, CHMOD_READ | CHMOD_WRITE);
}
$this->unlock($lock_fp);
}
}