Re: [ros-dev] Race Condition?

[Alex Ionescu]

Aliberti Emanuele wrote:

>   Hi Eric
>
> >   Most of these issues should get fixed by the
> > attached patch. It 
> >  replaces the
> >  hive locks and hive list lock (executive resources) by a global registry
> >  lock. The result is that only a single thread can modify the registry.
> >   
> >  
>  what is the general criterion (if one exists) one should use when 
>  choosing a synchronization object to use in kernel mode code?
>
>  I ask you this question, because a possible race condition was 
>  reported by Gé in the LPC code.
>  As a preliminary step in fixing that, I introduced a FAST_MUTEX to 
>  queue threads that use the LPC facility.
>  Now I see that you use an ERESOURCE to fix the same problem in the CM.
>
>  Emanuele
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>  
Hi,

FAST_MUTEX cannot be shared, it's always exclusive, while ERESOURCE can 
be exclusive or shared.
It's usually a waste of resources to use an ERESOURCE if you want the 
locking to be exclusive, but since we need to support shared access as 
well, ERESOURCE is a good choice. It's commonly used for Read/Writing to 
disk (ie, registry).

Best regards,
Alex Ionescu