bug #45737 [Lock] SemaphoreStore catching exception from sem_get (Triplkrypl)

nicolas-grekas · nicolas-grekas · commit 172bf0fc7407 · 2022-03-18T16:35:42.000+01:00
This PR was merged into the 4.4 branch. Discussion ---------- [Lock] SemaphoreStore catching exception from sem_get | Q | A | ------------- | --- | Branch? | 4.4 | Bug fix? | yes | New feature? | no | Deprecations? | no We use on project symfony/lock and I found exception in our monitoring from `sem_get` PHP function. Function `sem_get` is called before `sem_acquire` so resource is not locked and `sem_get` function call can run in same time as some code with locked resource in another process where removing semaphpore going on by function `sem_remove`. PHP: 7.4.13 symfony/lock: 5.3.4 Exceptions: `Symfony\Component\Lock\Exception\LockAcquiringException` Failed to acquire the "some_our_resource_key" lock. `ErrorException` sem_get(): failed for key 0xffffffffb8cf1ec4: Identifier removed Commits ------- 53f473f ignoring exception from sem_get in SemaphoreStore Lock component, preventing of error: identifier removed
diff --git a/src/Symfony/Component/Lock/Store/SemaphoreStore.php b/src/Symfony/Component/Lock/Store/SemaphoreStore.php
@@ -64,12 +64,12 @@ private function lock(Key $key, bool $blocking)
         }
 
         $keyId = unpack('i', md5($key, true))[1];
-        $resource = sem_get($keyId);
-        $acquired = @sem_acquire($resource, !$blocking);
+        $resource = @sem_get($keyId);
+        $acquired = $resource && @sem_acquire($resource, !$blocking);
 
         while ($blocking && !$acquired) {
-            $resource = sem_get($keyId);
-            $acquired = @sem_acquire($resource);
+            $resource = @sem_get($keyId);
+            $acquired = $resource && @sem_acquire($resource);
         }
 
         if (!$acquired) {

Original file line number	Diff line number	Diff line change
`@@ -64,12 +64,12 @@ private function lock(Key $key, bool $blocking)`
`64`	`64`	`}`
`65`	`65`
`66`	`66`	`$keyId = unpack('i', md5($key, true))[1];`
`67`		`- $resource = sem_get($keyId);`
`68`		`- $acquired = @sem_acquire($resource, !$blocking);`
	`67`	`+ $resource = @sem_get($keyId);`
	`68`	`+ $acquired = $resource && @sem_acquire($resource, !$blocking);`
`69`	`69`
`70`	`70`	`while ($blocking && !$acquired) {`
`71`		`- $resource = sem_get($keyId);`
`72`		`- $acquired = @sem_acquire($resource);`
	`71`	`+ $resource = @sem_get($keyId);`
	`72`	`+ $acquired = $resource && @sem_acquire($resource);`
`73`	`73`	`}`
`74`	`74`
`75`	`75`	`if (!$acquired) {`