D.2.7.8 Offline a CPU
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D.2.7.8 Offline a CPU

CPU-offline events cause rcu_cpu_notify() to invoke rcu_offline_cpu(), which in turn invokes __rcu_offline_cpu() on both the rcu and the rcu_bh instances of the data structures. This function clears the outgoing CPU's bits so that future grace periods will not expect this CPU to announce quiescent states, and further invokes cpu_quiet() in order to announce the offline-induced extended quiescent state. This work is performed with the global ->onofflock held in order to prevent interference with concurrent grace-period initialization.

Quick Quiz D.16: But the other reason to hold ->onofflock is to prevent multiple concurrent online/offline operations, right? End Quick Quiz