Can I use async and sync lock on same AsyncReaderWriterLock ?

[oruchreis]

Hi,
I saw both sync and async methods on AsyncReaderWriterLock. Can I use same lock object in both sync and async methods? I was using DotNext's AsyncReaderWriterLock, and I've figured out it doesn't wait if you call WriteLockAsync in a thread and then call ReadLock in another thread, also that question explains much more.
I've tested in a sample project and it works, but I want to ask and be sure if it works.

private static readonly AsyncReaderWriterLock _rwlock = new();
//Thread:1 with async using
using (await _rwlock.WriterLockAsync(token))
{}
//Thread:2 with sync using
using (_rwlock.UpgradeableReaderLock())
{
    using(_rwlock.WriterLock())
    {}
}

[timcassell]

Hi @oruchreis, sorry I didn't see this until now (I usually get notifications on this repo, not sure why I didn't for this discussion).

Yes, AsyncReaderWriterLock is designed to work with both async and sync on the same instance. It's not really recommended due to deadlock issues, but if you know for a fact that the sync calls will only happen on their own thread, that's exactly the situation it was designed to support.

[timcassell]

Btw, your upgradeable lock example is used incorrectly. It should look like this:

//Thread:2 with sync using
using (var upgradeableReaderKey = _rwlock.UpgradeableReaderLock())
{
    using(_rwlock.UpgradeToWriterLock(upgradeableReaderKey))
    {}
}

Otherwise, your normal _rwlock.WriterLock() causes a deadlock with the _rwlock.UpgradeableReaderLock().