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SubjectRe: [patch V5 34/72] locking/rwlock: Provide RT variant
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On 2021/8/16 5:28, Thomas Gleixner wrote:
> From: Thomas Gleixner <tglx@linutronix.de>
>
> Similar to rw_semaphores on RT the rwlock substitution is not writer fair
> because it's not feasible to have a writer inherit it's priority to
> multiple readers. Readers blocked on a writer follow the normal rules of
> priority inheritance. Like RT spinlocks RT rwlocks are state preserving
> across the slow lock operations (contended case).
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
> V5: Add missing might_sleep() and fix lockdep init (Sebastian)
> ---
> include/linux/rwlock_rt.h | 140 ++++++++++++++++++++++++++++++++++++++++
> include/linux/rwlock_types.h | 49 ++++++++++----
> include/linux/spinlock_rt.h | 2
> kernel/Kconfig.locks | 2
> kernel/locking/spinlock.c | 7 ++
> kernel/locking/spinlock_debug.c | 5 +
> kernel/locking/spinlock_rt.c | 131 +++++++++++++++++++++++++++++++++++++
> 7 files changed, 323 insertions(+), 13 deletions(-)
> create mode 100644 include/linux/rwlock_rt.h
> ---
.....
> +
> +int __sched rt_rwlock_is_contended(rwlock_t *rwlock)
> +{
> + return rw_base_is_contended(&rwlock->rwbase);
> +}
> +EXPORT_SYMBOL(rt_rwlock_is_contended);
> +

rt_rwlock_is_conted() exported but not declared in the header file?
Is this a special design or a mistake?

Thanks
Xiaoming Ni

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