> Yes, this is classic priority inversion. It is here now, today with
> semaphors which are held by code that blocks. If the code doesn't
> block, why not use a spin lock? If it does, well the problem is here
Because eg. other code that holds the semaphore needs to sleep
> now. I suppose we could set a preempt disable around a semaphore if it
> makes you feel better. It doesn't fix the problem if the task blocks
It would make me feel better, but it would defeat the purpose.
There's a lot of code holding semaphores.
> AND it is legal to block while holding a preemption lock.
But it's easier to fix. If you can preempt only by explicitely
sleeping, you can beat priority invasion by changing basically
only wake_up. If you can be preempted at random, you need to know
who holds a semaphore.
Regards
Oliver
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