What is the reason to deprecate Lock in swoole 4.4 ?

[abbychau]

I found 废弃Lock模块，废弃原因：在协程模式下加锁可能存在问题，可使用chan实现协程版本的锁.

What is the concrete reason? or what are the error instances?

[matyhtf]

Bad Case:

<?php
$lock = new Swoole\Lock();
$c = 2;

while ($c--) {
    go(function () use ($lock) {
        $lock->lock();
        Co::sleep(1);
        $lock->unlock();
    });
}

[matyhtf]

This will cause a deadlock

[abbychau]

Thanks. I try to elaborate. Please tell me if I am wrong.

I think the problem is because of Co::sleep, Locks are across the threads, a thread sleep could be more suitable. However, this will block the second creation of Coroutine, which is not the expected behavior.

after reading

static void sleep_timeout(swTimer *timer, swTimer_node *tnode)
{
    ((Coroutine *) tnode->data)->resume();
}

int System::sleep(double sec)
{
    Coroutine* co = Coroutine::get_current_safe();
    if (swTimer_add(&SwooleG.timer, (long) (sec * 1000), 0, co, sleep_timeout) == NULL)
    {
        return -1;
    }
    co->yield();
    return 0;
}

the yield may not be resumed after the next coroutine comes in.

[huanghantao]

@abbychau 死锁的原因是Swoole的协程是在同一个线程里面跑，也就是说，这个线程把自己给锁住了。如果未来Swoole的协程可以在不同的线程里面跑，应该是不会死锁的。

[huanghantao]

@abbychau Swoole以后应该是会提供协程锁

[abbychau]

@abbychau 死锁的原因是Swoole的协程是在同一个线程里面跑，也就是说，这个线程把自己给锁住了。如果未来Swoole的协程可以在不同的线程里面跑，应该是不会死锁的。

I think so too.

[abbychau]

@abbychau Swoole以后应该是会提供协程锁

This will be very cool. 😎 kotlinx implemented it.