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    SubjectRe: [PATCH-tip 04/22] locking/rwsem: Remove arch specific rwsem files
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    On 02/07/2019 02:36 PM, Peter Zijlstra wrote:
    > On Thu, Feb 07, 2019 at 02:07:08PM -0500, Waiman Long wrote:
    >
    >> +static inline int __down_read_trylock(struct rw_semaphore *sem)
    >> +{
    >> + long tmp;
    >> +
    >> + while ((tmp = atomic_long_read(&sem->count)) >= 0) {
    >> + if (tmp == atomic_long_cmpxchg_acquire(&sem->count, tmp,
    >> + tmp + RWSEM_ACTIVE_READ_BIAS)) {
    >> + return 1;
    >> + }
    >> + }
    > Nah, you're supposed to write that like:
    >
    > for (;;) {
    > val = atomic_long_cond_read_relaxed(&sem->count, VAL < 0);
    > if (atomic_long_try_cmpxchg_acquire(&sem->count, &val,
    > val + RWSEM_ACTIVE_READ_BIAS))
    > break;
    > }
    >

    Ah, you are right. I just took it directly from the current generic
    asm.h file and didn't pay much attention to it. I will fix that in the
    next iteration.

    >> + return 0;
    >> +}
    >
    > Anyway, yuck, you're keeping all that BIAS nonsense :/ I was so hoping
    > for a rwsem implementation without that impenetrable crap.

    Well, I am going to take out all the BIAS handling in a later patch.
    This one is just for removing the architecture specific files.

    I can't change the rwsem count encoding before I take out all the arch
    specific files.

    Cheers,
    Longman

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