Adrian Cox wrote:
> Unfortunately the kernel is already full of counting semaphores.
> Priority inheritance won't save you, as the task which is going to call
> up() need not be the same one that called down().
>
> Jamie Lokier's suggestion of raising priority when in the kernel doesn't
> help. You need to raise the priority of the task which is currently in
> userspace and will call up() next time it enters the kernel. You don't
> know which task that is.
Dear oh dear. I was under the impression that kernel semaphores are
supposed to be used as mutexes only -- there are other mechanisms for
signalling between processes.
Do any processes ever enter userspace holding a critical semaphore?
(Things like userspace signalling another userspace don't count -- it's
your own fault and your own problem if _that_ deadlocks).
-- Jamie
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