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    SubjectRe: [PATCH 1/19] MUTEX: Introduce simple mutex implementation
    On Sat, Dec 17, 2005 at 04:43:05PM -0700, Matthew Wilcox wrote:
    > I have a better example of something we currently get wrong that I
    > haven't heard any RT person worry about yet. If two tasks are sleeping
    > on the same semaphore, the one to be woken up will be the first one to
    > wait for it, not the highest-priority task.
    > Obviously, this was introduced by the wake-one semantics. But how to
    > fix it? Should we scan the entire queue looking for the best task to
    > wake? Should we try to maintain the wait list in priority order? Or
    > should we just not care? Should we document that we don't care? ;-)

    -rt deals with this using priority sorted wait queue and direct ownership
    hand off to the woken thread. It's working fine for now, but things like
    wake-all and company should probably be explored for various uses. A
    strict general purpose and RT usage of the Linux kernel have different
    performance characteristic and mutex selection at compile time should
    address things precisely.


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