Index: includes/common.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/common.inc,v
retrieving revision 1.1209
diff -u -p -r1.1209 common.inc
--- includes/common.inc	20 Aug 2010 01:17:51 -0000	1.1209
+++ includes/common.inc	20 Aug 2010 22:46:04 -0000
@@ -3210,42 +3210,52 @@ function drupal_build_css_cache($css) {
     $uri = $map[$key];
   }

-  if (empty($uri) || !file_exists($uri)) {
-    // Build aggregate CSS file.
-    foreach ($css as $stylesheet) {
-      // Only 'file' stylesheets can be aggregated.
-      if ($stylesheet['type'] == 'file') {
-        $contents = drupal_load_stylesheet($stylesheet['data'], TRUE);
-        // Return the path to where this CSS file originated from.
-        $base = base_path() . dirname($stylesheet['data']) . '/';
-        _drupal_build_css_path(NULL, $base);
-        // Prefix all paths within this CSS file, ignoring external and absolute paths.
-        $data .= preg_replace_callback('/url\(\s*[\'"]?(?![a-z]+:|\/+)([^\'")]+)[\'"]?\s*\)/i', '_drupal_build_css_path', $contents);
+  $lock_acquire_attempts = 0;
+  do {
+    if (empty($uri) || !file_exists($uri)) {
+      if ($lock_acquired = lock_acquire('css_files')) {
+        // Build aggregate CSS file.
+        foreach ($css as $stylesheet) {
+          // Only 'file' stylesheets can be aggregated.
+          if ($stylesheet['type'] == 'file') {
+            $contents = drupal_load_stylesheet($stylesheet['data'], TRUE);
+            // Return the path to where this CSS file originated from.
+            $base = base_path() . dirname($stylesheet['data']) . '/';
+            _drupal_build_css_path(NULL, $base);
+            // Prefix all paths within this CSS file, ignoring external and absolute paths.
+            $data .= preg_replace_callback('/url\([\'"]?(?![a-z]+:|\/+)([^\'")]+)[\'"]?\)/i', '_drupal_build_css_path', $contents);
+          }
+        }
+
+        // Per the W3C specification at http://www.w3.org/TR/REC-CSS2/cascade.html#at-import,
+        // @import rules must proceed any other style, so we move those to the top.
+        $regexp = '/@import[^;]+;/i';
+        preg_match_all($regexp, $data, $matches);
+        $data = preg_replace($regexp, '', $data);
+        $data = implode('', $matches[0]) . $data;
+
+        // Prefix filename to prevent blocking by firewalls which reject files
+        // starting with "ad*".
+        $filename = 'css_' . drupal_hash_base64($data) . '.css';
+        // Create the css/ within the files folder.
+        $csspath = 'public://css';
+        $uri = $csspath . '/' . $filename;
+        // Create the CSS file.
+        file_prepare_directory($csspath, FILE_CREATE_DIRECTORY);
+        if (!file_exists($uri) && !file_unmanaged_save_data($data, $uri, FILE_EXISTS_REPLACE)) {
+          return FALSE;
+        }
+        // Save the updated map.
+        $map[$key] = $uri;
+        variable_set('drupal_css_cache_files', $map);
+        lock_release('css_files');
+      }
+      else {
+        lock_wait();
       }
     }
-
-    // Per the W3C specification at http://www.w3.org/TR/REC-CSS2/cascade.html#at-import,
-    // @import rules must proceed any other style, so we move those to the top.
-    $regexp = '/@import[^;]+;/i';
-    preg_match_all($regexp, $data, $matches);
-    $data = preg_replace($regexp, '', $data);
-    $data = implode('', $matches[0]) . $data;
-
-    // Prefix filename to prevent blocking by firewalls which reject files
-    // starting with "ad*".
-    $filename = 'css_' . drupal_hash_base64($data) . '.css';
-    // Create the css/ within the files folder.
-    $csspath = 'public://css';
-    $uri = $csspath . '/' . $filename;
-    // Create the CSS file.
-    file_prepare_directory($csspath, FILE_CREATE_DIRECTORY);
-    if (!file_exists($uri) && !file_unmanaged_save_data($data, $uri, FILE_EXISTS_REPLACE)) {
-      return FALSE;
-    }
-    // Save the updated map.
-    $map[$key] = $uri;
-    variable_set('drupal_css_cache_files', $map);
   }
+  while (!file_exists($uri) && $lock_acquired === FALSE && ++$lock_acquire_attempts < 5);
   return $uri;
 }

@@ -4421,28 +4431,38 @@ function drupal_build_js_cache($files) {
     $uri = $map[$key];
   }

-  if (empty($uri) || !file_exists($uri)) {
-    // Build aggregate JS file.
-    foreach ($files as $path => $info) {
-      if ($info['preprocess']) {
-        // Append a ';' and a newline after each JS file to prevent them from running together.
-        $contents .= file_get_contents($path) . ";\n";
-      }
-    }
-    // Prefix filename to prevent blocking by firewalls which reject files
-    // starting with "ad*".
-    $filename = 'js_' . drupal_hash_base64($contents) . '.js';
-    // Create the js/ within the files folder.
-    $jspath = 'public://js';
-    $uri = $jspath . '/' . $filename;
-    // Create the JS file.
-    file_prepare_directory($jspath, FILE_CREATE_DIRECTORY);
-    if (!file_unmanaged_save_data($contents, $uri, FILE_EXISTS_REPLACE)) {
-      return FALSE;
+  $lock_acquire_attempts = 0;
+  do {
+    if (empty($uri) || !file_exists($uri)) {
+      if ($lock_acquired = lock_acquire('js_files')) {
+        // Build aggregate JS file.
+        foreach ($files as $path => $info) {
+          if ($info['preprocess']) {
+            // Append a ';' and a newline after each JS file to prevent them from running together.
+            $contents .= file_get_contents($path) . ";\n";
+          }
+        }
+        // Prefix filename to prevent blocking by firewalls which reject files
+        // starting with "ad*".
+        $filename = 'js_' . drupal_hash_base64($contents) . '.js';
+        // Create the js/ within the files folder.
+        $jspath = 'public://js';
+        $uri = $jspath . '/' . $filename;
+        // Create the JS file.
+        file_prepare_directory($jspath, FILE_CREATE_DIRECTORY);
+        if (!file_unmanaged_save_data($contents, $uri, FILE_EXISTS_REPLACE)) {
+          return FALSE;
+        }
+        $map[$key] = $uri;
+        variable_set('drupal_js_cache_files', $map);
+        lock_release('js_files');
+      }
+      else {
+        lock_wait();
+      }
     }
-    $map[$key] = $uri;
-    variable_set('drupal_js_cache_files', $map);
   }
+  while (!file_exists($uri) && $lock_acquired === FALSE && ++$lock_acquire_attempts < 5);
   return $uri;
 }