This is a note to let you know that I've just added the patch titled
rcu: Introduce rcu_cpu_online()
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
rcu-introduce-rcu_cpu_online.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 4ab8ebcd72181f7baa6aba161c5c4366ae1c5b11
Author: Frederic Weisbecker <frederic@xxxxxxxxxx>
Date: Fri Oct 27 16:40:47 2023 +0200
rcu: Introduce rcu_cpu_online()
[ Upstream commit 2be4686d866ad5896f2bb94d82fe892197aea9c7 ]
Export the RCU point of view as to when a CPU is considered offline
(ie: when does RCU consider that a CPU is sufficiently down in the
hotplug process to not feature any possible read side).
This will be used by RCU-tasks whose vision of an offline CPU should
reasonably match the one of RCU core.
Fixes: cff9b2332ab7 ("kernel/sched: Modify initial boot task idle setup")
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index 98e13be411afd..3d1851f82dbb6 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -493,6 +493,7 @@ static inline void rcu_expedite_gp(void) { }
static inline void rcu_unexpedite_gp(void) { }
static inline void rcu_async_hurry(void) { }
static inline void rcu_async_relax(void) { }
+static inline bool rcu_cpu_online(int cpu) { return true; }
#else /* #ifdef CONFIG_TINY_RCU */
bool rcu_gp_is_normal(void); /* Internal RCU use. */
bool rcu_gp_is_expedited(void); /* Internal RCU use. */
@@ -502,6 +503,7 @@ void rcu_unexpedite_gp(void);
void rcu_async_hurry(void);
void rcu_async_relax(void);
void rcupdate_announce_bootup_oddness(void);
+bool rcu_cpu_online(int cpu);
#ifdef CONFIG_TASKS_RCU_GENERIC
void show_rcu_tasks_gp_kthreads(void);
#else /* #ifdef CONFIG_TASKS_RCU_GENERIC */
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 92a090e161865..9af42eae1ba38 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -4139,6 +4139,13 @@ static bool rcu_rdp_cpu_online(struct rcu_data *rdp)
return !!(rdp->grpmask & rcu_rnp_online_cpus(rdp->mynode));
}
+bool rcu_cpu_online(int cpu)
+{
+ struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
+
+ return rcu_rdp_cpu_online(rdp);
+}
+
#if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU)
/*
