synchronized (this[.classinfo]) in druntime and phobos

[Andrei Alexandrescu]

On 5/30/12 9:23 AM, Alex Rønne Petersen wrote:
> On 30-05-2012 18:14, Andrei Alexandrescu wrote:
>> This is news to me. How do you publicly access the mutex of a
>> synchronized class object?
>
> Generally in two ways:
>
> 1) synchronized (obj)

This is not accessing the mutex for arbitrary operations.

> 2) obj.__monitor

All symbols starting with two underscores are reserved by the 
implementation.

> (1) accesses it in order to actually do locking, but if obj is an
> instantiation of a class that uses the this reference internally for
> locking, you end up with potential deadlocks.

Deadlocks are endemic to mutex-based programming and are not avoided 
inherently or preferentially by the alternative you discussed (exposing 
unrestricted mutex).

> Therefore, you can say
> that obj's mutex is exposed.

Nothing could stop one, but that claim is incorrect.


Andrei