bug symfony#27670 [Cache] Fix locking on Solaris (nicolas-grekas)

This PR was merged into the 4.2-dev branch.

Discussion
----------

[Cache] Fix locking on Solaris

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

As reported on symfony#27668, the descriptor must be writeable on Solaris to get an exclusive lock.

Commits
-------

43da583 [Cache] Fix locking on Solaris

Author: nicolas-grekas

src/Symfony/Component/Cache/LockRegistry.php

@@ -64,9 +64,11 @@ public static function setFiles(array $files): array
         $previousFiles = self::$files;
         self::$files = $files;
 
-        foreach (self::$openedFiles as $k => $file) {
-            flock($file, LOCK_UN);
-            fclose($file);
+        foreach (self::$openedFiles as $file) {
+            if ($file) {
+                flock($file, LOCK_UN);
+                fclose($file);
+            }
         }
         self::$openedFiles = self::$lockedFiles = array();
 
@@ -112,19 +114,24 @@ function (CacheItemPoolInterface $pool, CacheItemInterface $item, $value, float
             flock($lock, LOCK_SH);
         } finally {
             flock($lock, LOCK_UN);
-            self::$lockedFiles[$key] = false;
+            unset(self::$lockedFiles[$key]);
         }
 
         return false;
     }
 
     private static function open(int $key)
     {
-        if ($h = self::$openedFiles[$key] ?? null) {
+        if (null !== $h = self::$openedFiles[$key] ?? null) {
             return $h;
         }
-        if ($h = fopen(self::$files[$key], 'rb')) {
-            return self::$openedFiles[$key] = $h;
+        set_error_handler(function () {});
+        try {
+            $h = fopen(self::$files[$key], 'r+');
+        } finally {
+            restore_error_handler();
         }
+
+        self::$openedFiles[$key] = $h ?: @fopen(self::$files[$key], 'r');
     }
 }