synchronization mechanisms

[Monica Puig-Pey]

Hello!
As I told you in previous questions I'm developing drivers using the 
2.6.31-11-rt patch under ubuntu 10.04.
It is very important for me to know about which real time 
synchronization mechanisms do I have.
I found the RT-mutexes, with priority inherintance, the plists (priority 
lists) and now I'm looking for more information about semaphores. I 
haven't found anything relevant in the code that I could know that they 
work well under real time, having a priority queue of tasks waiting on 
it. So I've made an easy example where I have 3 kernel threads with 
different priorities each (60,70,80) in the semaphore queue. Then I see 
is always the most priority kthread who wakes up the first. Good! It 
seems to work as a RT semaphore!
In my code I have an error. I can use down_interruptible but I can't use 
down_killable. Why is it?
Could anybody give me some help about semaphores in the rt-patch and 
about any other synchronization mechanism thought for real time?

Thanks a lot

Mónica
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