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    SubjectRe: [RFC] sched: make callers check lock contention for cond_resched_lock()
    On Thu, 03 May 2012 10:35:27 +0200
    Peter Zijlstra <> wrote:

    > On Thu, 2012-05-03 at 17:12 +0900, Takuya Yoshikawa wrote:
    > >
    > > Although we can do that using spin_is_contended() and cond_resched(),
    > > changing cond_resched_lock() to satisfy such a need is another option.
    > >
    > Yeah, not a pretty patch. Changing all cond_resched_lock() sites just to
    > change one and in such an ugly way too.
    > So what's the impact of making spin_needbreak() work for !PREEMPT?

    Although the real use case is out of this RFC patch, we are now discussing
    a case in which we may hold a spin_lock for long time, ms order, depending
    on workload; and in that case, other threads -- VCPU threads -- should be
    given higher priority for that problematic lock.

    I wanted to hear whether other users also have similar needs. If so, it
    may be worth making the API a bit more generic.

    But I could not find a clean solution for that. Do you think that using
    spin_is_contended() directly is the way to go?


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