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    SubjectRe: [PATCH v8 14/19] locking/rwsem: Enable time-based spinning on reader-owned rwsem
    On Mon, May 20, 2019 at 04:59:13PM -0400, Waiman Long wrote:
    > +static inline void rwsem_set_nonspinnable(struct rw_semaphore *sem)
    > +{
    > + long owner = atomic_long_read(&sem->owner);
    > +
    > + while (owner & RWSEM_READER_OWNED) {
    > + if (owner & RWSEM_NONSPINNABLE)
    > + break;
    > + owner = atomic_long_cmpxchg(&sem->owner, owner,
    > + owner | RWSEM_NONSPINNABLE);
    > + }
    > +}

    --- a/kernel/locking/rwsem.c
    +++ b/kernel/locking/rwsem.c
    @@ -206,12 +206,13 @@ static inline void rwsem_set_nonspinnabl
    {
    long owner = atomic_long_read(&sem->owner);

    - while (owner & RWSEM_READER_OWNED) {
    + do {
    + if (!(owner & RWSEM_READER_OWNED))
    + break;
    if (owner & RWSEM_NONSPINNABLE)
    break;
    - owner = atomic_long_cmpxchg(&sem->owner, owner,
    - owner | RWSEM_NONSPINNABLE);
    - }
    + } while (!atomic_long_try_cmpxchg(&sem->owner, &owner,
    + owner | RWSEM_NONSPINNABLE));
    }

    /*
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