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

[Andrei Alexandrescu]

On 5/30/12 9:43 AM, Regan Heath wrote:
> On Wed, 30 May 2012 17:00:43 +0100, Andrei Alexandrescu
> <SeeWebsiteForEmail at erdani.org> wrote:
>
>> On 5/30/12 5:32 AM, Regan Heath wrote:
>>> On Wed, 30 May 2012 10:21:00 +0100, deadalnix <deadalnix at gmail.com>
>>> wrote:
>>>> You don't want to synchronize on ANY object. You want to synchronize
>>>> on explicit mutexes.
>>>
>>> +1 .. this is the key point/issue.
>>
>> TDPL's design only allows for entire synchronized classes (not
>> separate synchronized and unsynchronized methods), which pair mutexes
>> with the data they protect. This is more restrictive than exposing
>> mutexes, but in a good way. We use such a library artifact in C++ at
>> Facebook all the time, to great success.
>
> Can you call pass them to a synchronized statement? i.e.
>
> TDPLStyleSynchClass a = new TDPLStyleSynchClass();
> synchronized(a) {
> }

Yes. Well I recommend acquiring the text! :o)

> ... because, if you can, then you're exposing the mutex.

No.

>> People shouldn't create designs that have synchronized classes
>> referring to one another naively. Designing with mutexes (explicit or
>> implicit) will always create the possibility of deadlock, so examples
>> how that could happen are easy to come across.
>
> True. But in my Example 1

Your example 1 should not compile.

>> TDPL improves on deadlocks by introducing synchronized statements with
>> more than one argument, see 13.15.
>
> Is there anywhere I can see this online? (for free :p)

http://goo.gl/ZhPM2

>> The implicit mutexes used by synchronized classes are recursive.
>
> :) why would you want anything else.

Efficiency.


Andrei