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    SubjectRe: RT Mutex patch and tester [PREEMPT_RT]
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    On Thu, Jan 12, 2006 at 01:54:23PM +0100, Esben Nielsen wrote:
    > turnstiles? What is that?

    http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/kern/subr_turnstile.c

    Please, read. Now tell me or not if that looks familiar ? :)

    Moving closer an implementation is arguable, but it is something that
    should be considered somewhat since folks in both the Solaris (and
    FreeBSD) communities have given a lot more consideration to these issues.

    The stack allocated objects are fine for now. Priority inheritance
    chains should never get long with a fine grained kernel, so the use
    of a stack allocated object and migrating pi-ed waiters should not
    be a major real world issue in Linux yet.

    Folks should also consider using an adaptive spin in the __grab_lock() (sp?)
    related loops as a possible way of optimizing away the immediate blocks.
    FreeBSD actually checks the owner of a lock aacross another processor
    to see if it's actively running, "current", and will block or wait if
    it's running or not respectively. It's pretty trivial code, so it's
    not a big issue to implement. This is ignoring the CPU local storage
    issues.

    bill

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