[phobos] parallelism segfaults

[Sean Kelly]

A regular collection is run.

Sent from my iPhone

On Sep 14, 2011, at 4:36 AM, David Simcha <dsimcha at gmail.com> wrote:

> On 9/14/2011 1:04 AM, Sean Kelly wrote:
>> On Sep 13, 2011, at 11:59 AM, Martin Nowak wrote:
>> 
>>> I've had a look the core dumps from the sometimes failing std.parallelism test.
>>> The issue is one of having daemon threads running while the GC is unmapping memory.
>>> Usually this goes unnoticed because the parallelism threads wait in a work queue condition.
>>> Sometimes a daemon thread is awakening from it's GC suspend handler after memory was already
>>> freed. This issue is already mentioned in a comment at gc_term.
>>> 
>>> 
>>> Thread  obj = Thread.getThis();
>>> 
>>> ...
>>> suspend
>>> ...
>>> 
>>> if( obj&&  !obj.m_lock ) //<- segfault
>>> 
>>> 
>>> I think we should bluntly kill daemon threads after thread_joinAll.
>> One issue with this is that if these threads held any locks accessed during later parts of the cleanup (the GC lock, module-level locks accessed in static dtors, etc), the app could hang instead of shutting down cleanly.  If the threads are forcibly terminated then it would really have to be after these cleanup steps occurred, but by then Bad Things could already be happening because module dtors have been run and the GC is terminated.
>> 
>> Since daemon threads are an explicit choice made by the user, I hope that they have also considered how to notify them to terminate cleanly (as one does in C/C++ where daemon threads are the default).  The best thing is really to build this into the relevant module dtor.  There's also Runtime.isHalting if someone can present a case to un-deprecate it.
>> _______________________________________________
>> phobos mailing list
>> phobos at puremagic.com
>> http://lists.puremagic.com/mailman/listinfo/phobos
>> 
> 
> Is the finalizer guaranteed to be called on all GC-allocated class instances before program termination, or is a regular collection cycle just run?
> _______________________________________________
> phobos mailing list
> phobos at puremagic.com
> http://lists.puremagic.com/mailman/listinfo/phobos