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rcu: Introduce rcu_cpu_online()

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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@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
This commit is contained in:
Frederic Weisbecker 2023-10-27 16:40:47 +02:00
parent 85d68222dd
commit 2be4686d86
2 changed files with 9 additions and 0 deletions
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2
kernel/rcu/rcu.h
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@ -500,6 +500,7 @@ 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. */
@ -509,6 +510,7 @@ 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 */

7
kernel/rcu/tree.c
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@ -4216,6 +4216,13 @@ 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)
/*