Arguments

Description

Wait for an RCU-preempt grace period, but expedite it. The basic idea is to IPI all non-idle non-nohz online CPUs. The IPI handler checks whether the CPU is in an RCU-preempt critical section, and if so, it sets a flag that causes the outermost rcu_read_unlock to report the quiescent state. On the other hand, if the CPU is not in an RCU read-side critical section, the IPI handler reports the quiescent state immediately.

Although this is a greate improvement over previous expedited implementations, it is still unfriendly to real-time workloads, so is thus not recommended for any sort of common-case code. In fact, if you are using synchronize_rcu_expedited in a loop, please restructure your code to batch your updates, and then Use a single synchronize_rcu instead.