During offlining, the concurrent rcutree_offline_cpu() can not be aware of each other through ->qsmaskinitnext. But cpu_dying_mask carries such information at that point and can be utilized. Besides, a trivial change which removes the redudant call to rcu_boost_kthread_setaffinity() in rcutree_dead_cpu() since rcutree_offline_cpu() can fully serve that purpose. Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx> Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx> Cc: David Woodhouse <dwmw@xxxxxxxxxxxx> Cc: Frederic Weisbecker <frederic@xxxxxxxxxx> Cc: Neeraj Upadhyay <quic_neeraju@xxxxxxxxxxx> Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> Cc: Lai Jiangshan <jiangshanlai@xxxxxxxxx> Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> Cc: "Jason A. Donenfeld" <Jason@xxxxxxxxx> To: rcu@xxxxxxxxxxxxxxx --- kernel/rcu/tree.c | 2 -- kernel/rcu/tree_plugin.h | 6 ++++++ 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 79aea7df4345..8a829b64f5b2 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2169,8 +2169,6 @@ int rcutree_dead_cpu(unsigned int cpu) return 0; WRITE_ONCE(rcu_state.n_online_cpus, rcu_state.n_online_cpus - 1); - /* Adjust any no-longer-needed kthreads. */ - rcu_boost_kthread_setaffinity(rnp, -1); // Stop-machine done, so allow nohz_full to disable tick. tick_dep_clear(TICK_DEP_BIT_RCU); return 0; diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index ef6d3ae239b9..e5afc63bd97f 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1243,6 +1243,12 @@ static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) cpu != outgoingcpu) cpumask_set_cpu(cpu, cm); cpumask_and(cm, cm, housekeeping_cpumask(HK_TYPE_RCU)); + /* + * For concurrent offlining, bit of qsmaskinitnext is not cleared yet. + * So resort to cpu_dying_mask, whose changes has already been visible. + */ + if (outgoingcpu != -1) + cpumask_andnot(cm, cm, cpu_dying_mask); if (cpumask_empty(cm)) cpumask_copy(cm, housekeeping_cpumask(HK_TYPE_RCU)); set_cpus_allowed_ptr(t, cm); -- 2.31.1
