UvDriver: stop the loop from timer callbacks for libuv < 1.45

.php-cs-fixer.dist.php

@@ -47,6 +47,7 @@ public function getRules(): array
                     'uv_now',
                     'uv_run',
                     'uv_poll_init_socket',
+                    'uv_stop',
                     'uv_timer_init',
                     'uv_timer_start',
                     'uv_timer_stop',

src/EventLoop/Driver/UvDriver.php

@@ -14,11 +14,39 @@
 
 final class UvDriver extends AbstractDriver
 {
+    private static ?bool $libuvStopWorkaround = null;
+
     public static function isSupported(): bool
     {
         return \extension_loaded("uv");
     }
 
+    private static function getLibuvVersion(): ?string
+    {
+        \ob_start();
+        \phpinfo(\INFO_MODULES);
+        $info = (string) \ob_get_clean();
+
+        if (\preg_match('/libuv Version[^0-9]+([0-9.]+)/', $info, $matches)) {
+            return $matches[1];
+        }
+
+        return null;
+    }
+
+    private static function needsStopWorkaround(): bool
+    {
+        if (self::$libuvStopWorkaround === null) {
+            // libuv < 1.45 runs the due timers before polling in UV_RUN_ONCE, then polls with the timeout of the
+            // next timer: without one, it blocks until an I/O event while another handle keeps the loop alive.
+            // If we can't determine the version, assume it is a newer version including the fix.
+            $libuvVersion = self::getLibuvVersion();
+            self::$libuvStopWorkaround = $libuvVersion !== null && \version_compare($libuvVersion, '1.45', '<');
+        }
+
+        return self::$libuvStopWorkaround;
+    }
+
     /** @var resource|\UVLoop A uv_loop resource created with uv_loop_new() */
     private $handle;
     /** @var array<string, resource> */
@@ -35,6 +63,8 @@
     {
         parent::__construct();
 
+        $stopWorkaround = self::needsStopWorkaround();
+
         $this->handle = \uv_loop_new();
 
         /** @psalm-suppress UnusedClosureParam */
@@ -50,7 +80,7 @@
 
                     $flags |= $callback->invokable ? $this->getStreamCallbackFlags($callback) : 0;
                 }
                 \uv_poll_start($event, $flags, $this->ioCallback);
             }
 
             foreach ($callbacks as $callback) {
@@ -58,7 +88,7 @@
 
                 // $events is ORed with 4 to trigger callback if no events are indicated (0) or on UV_DISCONNECT (4).
                 // http://docs.libuv.org/en/v1.x/poll.html
                 if (!($this->getStreamCallbackFlags($callback) & $events || ($events | 4) === 4)) {
                     continue;
                 }
 
@@ -66,12 +96,16 @@
             }
         };
 
-        $this->timerCallback = function ($event): void {
+        $this->timerCallback = function ($event) use ($stopWorkaround): void {
             $callback = $this->uvCallbacks[(int) $event][0];
 
             \assert($callback instanceof TimerCallback);
 
             $this->enqueueCallback($callback);
+
+            if ($stopWorkaround) {
+                \uv_stop($this->handle);
+            }
         };
 
         $this->signalCallback = function ($event): void {
@@ -159,9 +193,9 @@
                 $streamId = (int) $callback->stream;
 
                 if (isset($this->streams[$streamId])) {
                     $event = $this->streams[$streamId];
                 } elseif (isset($this->events[$id])) {
                     $event = $this->streams[$streamId] = $this->events[$id];
                 } else {
                     /** @psalm-suppress TooManyArguments */
                     $event = $this->streams[$streamId] = \uv_poll_init_socket($this->handle, $callback->stream);

test/Driver/UvDriverTest.php

@@ -26,4 +26,45 @@ public function testSupported(): void
     {
         self::assertTrue(UvDriver::isSupported());
     }
+
+    /**
+     * Short timers with another referenced watcher: on libuv < 1.45, a timer due when the driver entered its
+     * blocking run left the loop blocked forever. Run in a child process, killed if it hangs.
+     */
+    public function testShortTimersWithASignalWatcher(): void
+    {
+        $code = <<<'PHP'
+            require $argv[1];
+            $loop = new Revolt\EventLoop\Driver\UvDriver();
+            Revolt\EventLoop::setDriver($loop);
+            Revolt\EventLoop::onSignal(\defined('SIGUSR2') ? SIGUSR2 : 31, static fn () => null);
+            for ($i = 0; $i < 3000; $i++) {
+                $suspension = Revolt\EventLoop::getSuspension();
+                Revolt\EventLoop::delay(0.001, $suspension->resume(...));
+                $suspension->suspend();
+            }
+            echo 'done';
+            PHP;
+
+        $process = \proc_open(
+            [\PHP_BINARY, '-r', $code, '--', __DIR__ . '/../../vendor/autoload.php'],
+            [1 => ['pipe', 'w'], 2 => ['pipe', 'w']],
+            $pipes,
+        );
+        self::assertIsResource($process);
+
+        $deadline = \hrtime(true) + 30_000_000_000;
+        while (\proc_get_status($process)['running'] && \hrtime(true) < $deadline) {
+            \usleep(50_000);
+        }
+        $running = \proc_get_status($process)['running'];
+        if ($running) {
+            \proc_terminate($process, 9);
+        }
+        $output = \stream_get_contents($pipes[1]) . \stream_get_contents($pipes[2]);
+        \proc_close($process);
+
+        self::assertFalse($running, "3000 delays of 1 ms didn't complete in 30 seconds: $output");
+        self::assertSame('done', $output);
+    }
 }