Re: [Xenomai-core] Pending ownership and resource stealing

[Philippe Gerum <rpm@xenomai.org>]

Gilles Chanteperdrix wrote:
> Philippe Gerum wrote:
>  > prio(task1) > prio(task2)
>  > 
>  > 1. task1 grabs a resource
>  > 2. task1 sleeps for some time
>  > 3. task2 blocks requesting the resource
>  > 4. task1 wakes up from the sleep and releases the resource to task2
>  > 5. task1 wants the resource back immediately and calls 
>  > xnsynch_sleep_on() since the ownership has been transferred to task2 
>  > since step 4.
>  > 6a. old way: task1 would block and task2 would run anyway, with a PIP 
>  > boost, blocking task1 until the resource is released
>  > 6b. new way: task1 steals the resource previously granted to task2 
>  > directly from xnsynch_sleep_on(), but doing so, nobody downstream has 
>  > had a chance to update any skin-specific data, such as an additional 
>  > "owner" field.
> 
> Posix skin mutexes work the new way without calling xnsynch_sleep_on, so
> probably need fixing.
> 

I don't see any additional information maintained by the skin, aside of 
the sem->count field, so that should be ok as it is. Is there anything 
else recorded for tracking the current ownership of a sem-mutex object?

-- 

Philippe.