Mutex.withLock uses owner parameter for checks but doesn't state equality contract in docs

[baltiyskiy]

Mutex.withLock() states that owner is an "optional owner token for debugging". However, it really uses it for consistency checks, e.g. curOwner !== owner in lockSuspend. This means that owner must be unique for each invocation of withLock(), otherwise one will get a cryptic IllegalStateException: Already locked by <owner>. The problem is that this contract isn't stated in the docs. Another problem is that using a debugging token for consistency checks doesn't look like a good idea.

[elizarov]

So what change do you propose to make?

[baltiyskiy]

Either update the docs to state that owner must be unique for each concurrent invocation, or don't use it for consistency checks.

There are cases where "debugging token" is naturally derived from the operation that wants to take the lock, but its description can be non-unique. One might say that this is a problem with debugging, but in fact logging might use some other means to provide context, e.g. coroutines-aware context propagation.

[qwwdfsad]

This means that owner must be unique for each invocation of withLock()

It does not. It should be unique for overlapping concurrent operations.

Either update the docs to state that owner must be unique for each concurrent invocation

Actually, withLock was the only method where this limitation has not been noticed