Is there a way to synchronously check if a Mutex is unlocked kotlinlang #coroutines

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Title

s

Seri

05/12/2020, 8:01 PM

Is there a way to synchronously check if a Mutex is unlocked and run a block of code under it? Similar to

Mutex.withLock { ... }

, but with calls while the Mutex is locked being discarded instead of suspending.

o

octylFractal

05/12/2020, 8:13 PM

is

tryLock

not good enough?

if you really want a `tryWithLock`:

inline fun <T : Any> Mutex.tryWithLock(owner: Any? = null, action: () -> T): T? {
    return if (tryLock(owner)) {
        try {
            action()
        } finally {
            unlock(owner)
        }
    } else {
        null
    }
}

explicitly forbids

null

because it's the failure signal here, you can change that up if you want

s

Seri

05/12/2020, 8:21 PM

My issue with tryLock was that it didn’t immediately run the block, so there was a race condition.

That tryWithLock extension method is what I was thinking about writing, nice!

o

octylFractal

05/12/2020, 8:21 PM

I don't get what the race condition is here? if

tryLock

returns

true

, you got the exclusive lock -- nothing can interrupt it

s

Seri

05/12/2020, 8:23 PM

I think I had the synchronous bits mixed up in my head, I was imagining the following at first:

if (!mutex.isLocked) {
    mutex.withLock { ... }
}

Looking back at that, I can see the flaw

o

octylFractal

05/12/2020, 8:24 PM

yea, there's a race condition there -- but I think

tryLock

should work

s

Seri

05/12/2020, 8:24 PM

👍

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