[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