flock() blocks entire event loop (not just current coroutine)

[YanGusik]

Context

I'm working on a Laravel adapter for TrueAsync (similar to Laravel Octane but using native TrueAsync primitives — Scope/Context instead of container cloning).

During testing I found that flock(LOCK_EX) on a contested file freezes the entire event loop, not just the waiting coroutine.

Expected behavior (per docs on proc_close()):

"blocks the current coroutine until the process exits—other coroutines continue running"

I expected flock() to behave the same way — suspend only the waiting coroutine while the scheduler continues running others.

---

Reproduction

<?php
use Async\Scope;
use function Async\delay;
use function Async\timeout;

$lockFile = '/tmp/trueasync_flock_test.txt';
file_put_contents($lockFile, '');
$start = microtime(true);

function ms(float $start): string {
    return str_pad((int)round((microtime(true) - $start) * 1000), 5) . 'ms';
}

// Ticker in root scope — heartbeat of the event loop
$rootScope = new Scope();
$rootScope->spawn(function () use ($start) {
    for ($i = 1; $i <= 12; $i++) {
        delay(100);
        echo "[ticker]  " . ms($start) . "\n";
    }
});

// Holder in isolated scope — acquires lock, holds 500ms
$holderScope = new Scope();
$holderScope->spawn(function () use ($start, $lockFile) {
    delay(150);
    $f = fopen($lockFile, 'w');
    flock($f, LOCK_EX);
    echo "[holder]  " . ms($start) . " — acquired LOCK_EX, holding 500ms...\n";
    delay(500);
    flock($f, LOCK_UN);
    fclose($f);
    echo "[holder]  " . ms($start) . " — released\n";
});

// Waiter in isolated scope — tries to acquire same lock
$waiterScope = new Scope();
$waiterScope->spawn(function () use ($start, $lockFile) {
    delay(200);
    echo "[waiter]  " . ms($start) . " — waiting for LOCK_EX...\n";
    $f = fopen($lockFile, 'w');
    flock($f, LOCK_EX); // entire event loop freezes here
    echo "[waiter]  " . ms($start) . " — acquired\n";
    flock($f, LOCK_UN);
    fclose($f);
});

$rootScope->awaitCompletion(timeout(5000));

Actual output:

[ticker]   100ms
[holder]   150ms — acquired LOCK_EX, holding 500ms...
[waiter]   200ms — waiting for LOCK_EX...
                   ← hangs forever, Ctrl+C required

Ticker stops completely. Holder's delay(500) never fires. All three scopes are frozen.

---

How this manifests in Laravel

Laravel's FileSessionHandler::write() calls file_put_contents($path, $data, LOCK_EX).

With concurrent requests and delay() in a route handler, multiple coroutines hit session write simultaneously — lock contention freezes the entire server.

file_put_contents itself is in the async function list, but the LOCK_EX flag internally calls flock() which is not async-wrapped.

---

Question

Is flock() planned to be covered with async support (similar to how proc_close() blocks only the current coroutine)?

This is critical for framework adapters since file-based sessions, cache drivers, and file locks are common in Laravel/Symfony.

[EdmondDantes]

It was done: https://github.com/true-async/php-async/releases/tag/v0.6.2