At CPU offline time, we must handle any pending wakeup for the nocb_gp kthread linked to the outgoing CPU. Now we are making sure of that twice: 1) From rcu_report_dead() when the outgoing CPU makes the very last local cleanups by itself before switching offline. 2) From rcutree_dead_cpu(). Here the offlining CPU has gone and is truly now offline. Another CPU takes care of post-portem cleaning up and check if the offline CPU had pending wakeup. Both ways are fine but we have to choose one or the other because we don't need to repeat that action. Simply benefit from cache locality and keep only the first solution.
Unified · Split
| @@ -2471,9 +2471,6 @@ int rcutree_dead_cpu(unsigned int cpu) · 2470 unmodified lines | |||
| 2471 | WRITE_ONCE(rcu_state.n_online_cpus, rcu_state.n_online_cpus - 1); | 2471 | WRITE_ONCE(rcu_state.n_online_cpus, rcu_state.n_online_cpus - 1); |
| 2472 | /* Adjust any no-longer-needed kthreads. */ | 2472 | /* Adjust any no-longer-needed kthreads. */ |
| 2473 | rcu_boost_kthread_setaffinity(rnp, -1); | 2473 | rcu_boost_kthread_setaffinity(rnp, -1); |
| 2474 | /* Do any needed no-CB deferred wakeups from this CPU. */ | ||
| 2475 | do_nocb_deferred_wakeup(per_cpu_ptr(&rcu_data, cpu)); | ||
| 2476 | |||
| 2477 | // Stop-machine done, so allow nohz_full to disable tick. | 2474 | // Stop-machine done, so allow nohz_full to disable tick. |
| 2478 | tick_dep_clear(TICK_DEP_BIT_RCU); | 2475 | tick_dep_clear(TICK_DEP_BIT_RCU); |
| 2479 | return 0; | 2476 | return 0; |