[PATCH RFC tip/core/rcu 6/9] locking/percpu-rwsem: Make use of the rcu_sync infrastructure

From: Oleg Nesterov Currently down_write/up_write calls synchronize_sched_expedited() twice, which is evil. Change this code to rely on rcu-sync primitives. This avoids the _expedited "big hammer", and this can be faster in the contended case or even in the case when a single thread does

[PATCH RFC tip/core/rcu 6/9] locking/percpu-rwsem: Make use of the rcu_sync infrastructure

From: Oleg Nesterov o...@redhat.com Currently down_write/up_write calls synchronize_sched_expedited() twice, which is evil. Change this code to rely on rcu-sync primitives. This avoids the _expedited big hammer, and this can be faster in the contended case or even in the case when a single