Re: [ros-dev] Re: [ros-svn] [ion] 20554: - Fix shamefully dangerously broken Work Thread/Queue/Item implementation:

[Alex Ionescu]

Hartmut Birr wrote:

>  Alex Ionescu wrote:
>   
>
> >  Hartmut Birr wrote:
> >
> >     
> >
> > >  Hi,
> > >
> > > there are three places in the kernel, which does remove wait blocks.
> > > They are in KiAbortWaitThread, KiInsertQueue and KiBlockThread. Only in
> > > KiBlockThread, Thread->WaitBlockList is  set to NULL. Is this the
> > > problem?
> > >
> > > - Hartmut
> > >  
> > >
> > >       
> > >  
> > Hi,
> >
> > I have been reading Windows Internals II and Windows Internals 4th
> > Edition and I see that the wait blocks are actually supposed to be a
> > circular list... so there should never really be any "NULL". It's
> > possible I based some previous code on this knowledge, which is now
> > conflicting with the ROS implementation of a null-terminated list. I
> > will change the wait code to use circular lists as documented and post
> > a patch.
> >
> > Best regards,
> > Alex Ionescu
> >
> >     
> >  
> I think, the real problem isn't if the list is NULL terminated or if the
> WaitBlockList entry from thread is NULL. 
>  
Hmm perhaps not, but it's still an issue I'm going to tackle tonight 
(last time I tried it failed for mysterious reasons).

>  The real problem is,
> KiAbortWaitThread is called for a thread which does not waiting.
>   
>  
Ok, since this happened after my worker thread patch and they use kernel 
queues, I reviewed their implementation and found a number of important 
flaws.. wether or not they cause this problem I can't tell for sure, but 
I've also added a debug print before the KeAbortWaitThread call... let 
me know if this patch fixes anything or if the dprint shoes that the 
thread isn't really waiting.

>  - Hartmut
>
> ____________________________
>  
Best regards,
Alex Ionescu