Messages in this thread Patch in this message | | | From | Frederic Weisbecker <> | Subject | [PATCH 07/10] rcu: Temporarily assume that nohz full CPUs might not be NOCB | Date | Wed, 13 May 2020 18:47:11 +0200 |
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So far nohz_full CPUs had to be nocb. This requirement may change temporarily as we are working on preparing RCU to be able to toggle the nocb state of a CPU. Once that is done and nohz_full can be toggled as well dynamically, we'll restore that initial requirement.
Thus for now as a temporary state, make rcu_nohz_full_cpu() aware of nohz_full CPUs that are not nocb so that they can handle the callbacks locally.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Cc: Paul E. McKenney <paulmck@kernel.org> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Lai Jiangshan <jiangshanlai@gmail.com> Cc: Joel Fernandes <joel@joelfernandes.org> --- kernel/rcu/tree.c | 2 +- kernel/rcu/tree.h | 2 +- kernel/rcu/tree_plugin.h | 7 ++++--- 3 files changed, 6 insertions(+), 5 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index cc95419f6491..74b6798309ef 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3223,7 +3223,7 @@ static int rcu_pending(int user) return 1; /* Is this a nohz_full CPU in userspace or idle? (Ignore RCU if so.) */ - if ((user || rcu_is_cpu_rrupt_from_idle()) && rcu_nohz_full_cpu()) + if ((user || rcu_is_cpu_rrupt_from_idle()) && rcu_nohz_full_cpu(rdp)) return 0; /* Is the RCU core waiting for a quiescent state from this CPU? */ diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index 9dc2ec021da5..4b9643d9f5e0 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -451,7 +451,7 @@ do { \ #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ static void rcu_bind_gp_kthread(void); -static bool rcu_nohz_full_cpu(void); +static bool rcu_nohz_full_cpu(struct rcu_data *rdp); static void rcu_dynticks_task_enter(void); static void rcu_dynticks_task_exit(void); diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 43ecc047af26..f19e81e0c691 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -2532,13 +2532,14 @@ static void show_rcu_nocb_state(struct rcu_data *rdp) * The idea is to avoid waking up RCU core processing on such a * CPU unless the grace period has extended for too long. * - * This code relies on the fact that all NO_HZ_FULL CPUs are also - * CONFIG_RCU_NOCB_CPU CPUs. + * This code relies on the fact that NO_HZ_FULL CPUs might not + * be CONFIG_RCU_NOCB_CPU CPUs (temporary development state). */ -static bool rcu_nohz_full_cpu(void) +static bool rcu_nohz_full_cpu(struct rcu_data *rdp) { #ifdef CONFIG_NO_HZ_FULL if (tick_nohz_full_cpu(smp_processor_id()) && + rcu_segcblist_is_offloaded(&rdp->cblist) && (!rcu_gp_in_progress() || ULONG_CMP_LT(jiffies, READ_ONCE(rcu_state.gp_start) + HZ))) return true; -- 2.25.0
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