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    SubjectRe: [PATCH 1/2] sched/swait: allow swake_up() to return
    On Fri, Nov 10, 2017 at 03:10:17PM +0800, Peter Xu wrote:
    > I came to this when reading kvm_vcpu_wake_up(), so that only affects
    > some statistic which may not be that critical. However I don't know
    > whether there would be any other real use case that we would like to
    > know exactly whether a call to [s]wake_up() has really done something
    > or just returned with a NOP.
    >
    > Anyway, please let me know if you think the same change to wake_up()
    > would be meaningful, otherwise I can drop this patch and post another
    > KVM-only one to clean up the redundant callers of swait_active(),
    > since even if we dropped that list check in 35a2897c2a30, we'll do
    > that again in swake_up_locked().

    See commits:

    8cd641e3c7cb ("sched/wait: Add swq_has_sleeper()")
    5e0018b3e39e ("kvm: Serialize wq active checks in kvm_vcpu_wake_up()")


    In any case, I don't think we want the change you propose. The numbers
    don't mean much and there's no point in making all the callers in the
    kernel slower for it.

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