From f589bf01ca9f0409b3ac40c1ec8a17ef71c0a498 Mon Sep 17 00:00:00 2001
From: Christian Schneider
Date: Fri, 14 Aug 2009 13:13:17 +0000
Subject: Close a lock race when lock expires, check existance of file in
 _waitforlock

---
 it_url.class | 25 +++++++++++--------------
 1 file changed, 11 insertions(+), 14 deletions(-)

diff --git a/it_url.class b/it_url.class
index 692f825..5393de9 100644
--- a/it_url.class
+++ b/it_url.class
@@ -407,7 +407,7 @@ function get_cache($p = array())
 		{
 			# Wait for file currently being transferred
 			EDC('getcache', "wait", $p['url'], $path);
-			$result = it_url::_waitforlock($path, $p);
+			$result = it_url::_waitforlockedfile($path, $p);
 		}
 	}
 	else
@@ -455,7 +455,7 @@ function get_cache($p = array())
 			{
 				# Wait for file currently being processed
 				EDC('getcache', "processwait", $p['url'], $path);
-				$result = it_url::_waitforlock($path, $p);
+				$result = it_url::_waitforlockedfile($path, $p);
 			}
 		}
 	}
@@ -500,11 +500,8 @@ function _expired($path, $maxage)
  */
 function _lock($path)
 {
-	# expire forgotten locks
-	if (($mtime = @filemtime("$path.lock")) && (time() - $mtime > 30))
-		@unlink("$path.lock");
-
-	return @fopen("$path.lock", EDC('nocache') ? "w" : "x");
+	$force = EDC('nocache') || (($mtime = @filemtime("$path.lock")) && (time() - $mtime > 30)); # expire forgotten locks
+	return @fopen("$path.lock", $force ? "w" : "x");
 }
 
 /**
@@ -519,26 +516,26 @@ function _unlock($path, $lock)
 }
 
 /**
- * Wait for lock on a file to be released
- * @param $path File to wait for lock
+ * Wait for file which is currently locked
+ * @param $path File to wait for
  * @param $p Wait parameters, see @get_cache
- * @return Whether lock was released within timeout
+ * @return Whether lock was released within timeout and file is still there
  */
-function _waitforlock($path, $p)
+function _waitforlockedfile($path, $p)
 {
 	$sleeptime = 0.1; # seconds to wait per pass
 
 	# wait until cache is ready, then read from cache
-	for ($maxpasses = $p['timeout'] / $sleeptime, $passes = 0; ($result = file_exists("$path.lock")) && ($passes < $maxpasses); ++$passes)
+	for ($maxpasses = $p['timeout'] / $sleeptime, $passes = 0; ($lockedbyother = file_exists("$path.lock")) && ($passes < $maxpasses); ++$passes)
 	{
 		usleep($sleeptime * 1000000);
 		clearstatcache();
 	}
 
-	if ($result && $p['safety'] == 1)
+	if ($lockedbyother && $p['safety'] == 1)
 		it::error(($passes < $maxpasses ? "error getting url" : "timeout") . " in it_url::get_cache(): url={$p['url']}, passes=$passes, maxpasses=$maxpasses, path={$p['path']}");
 
-	return !$result;
+	return !$lockedbyother && file_exists($path);
 }
 
 /**
-- 
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