rcu: Standardize explicit CPU-hotplug calls

rcu_report_dead() and rcutree_migrate_callbacks() have their headers in
rcupdate.h while those are pure rcutree calls, like the other CPU-hotplug
functions.

Also rcu_cpu_starting() and rcu_report_dead() have different naming
conventions while they mirror each other's effects.

Fix the headers and propose a naming that relates both functions and
aligns with the prefix of other rcutree CPU-hotplug functions.

Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>

Documentation/RCU/Design/Expedited-Grace-Periods/Expedited-Grace-Periods.rst

@@ -181,7 +181,7 @@ operations is carried out at several levels:
    of this wait (or series of waits, as the case may be) is to permit a
    concurrent CPU-hotplug operation to complete.
 #. In the case of RCU-sched, one of the last acts of an outgoing CPU is
-   to invoke ``rcu_report_dead()``, which reports a quiescent state for
+   to invoke ``rcutree_report_cpu_dead()``, which reports a quiescent state for
    that CPU. However, this is likely paranoia-induced redundancy.
 
 +-----------------------------------------------------------------------+

Documentation/RCU/Design/Memory-Ordering/TreeRCU-gp-fqs.svg

@@ -1135,7 +1135,7 @@
        font-weight="bold"
        font-size="192"
        id="text202-7-5-3-27-6-5"
-       style="font-size:192px;font-style:normal;font-weight:bold;text-anchor:start;fill:#000000;stroke-width:0.025in;font-family:Courier">rcu_report_dead()</text>
+       style="font-size:192px;font-style:normal;font-weight:bold;text-anchor:start;fill:#000000;stroke-width:0.025in;font-family:Courier">rcutree_report_cpu_dead()</text>
     <text
        xml:space="preserve"
        x="3745.7725"
@@ -1256,7 +1256,7 @@
        font-style="normal"
        y="3679.27"
        x="-3804.9949"
-       xml:space="preserve">rcu_cpu_starting()</text>
+       xml:space="preserve">rcutree_report_cpu_starting()</text>
     <g
        style="fill:none;stroke-width:0.025in"
        id="g3107-7-5-0"

Documentation/RCU/Design/Memory-Ordering/TreeRCU-gp.svg

@@ -3274,7 +3274,7 @@
          font-weight="bold"
          font-size="192"
          id="text202-7-5-3-27-6-5"
-         style="font-size:192px;font-style:normal;font-weight:bold;text-anchor:start;fill:#000000;stroke-width:0.025in;font-family:Courier">rcu_report_dead()</text>
+         style="font-size:192px;font-style:normal;font-weight:bold;text-anchor:start;fill:#000000;stroke-width:0.025in;font-family:Courier">rcutree_report_cpu_dead()</text>
       <text
          xml:space="preserve"
          x="3745.7725"
@@ -3395,7 +3395,7 @@
          font-style="normal"
          y="3679.27"
          x="-3804.9949"
-         xml:space="preserve">rcu_cpu_starting()</text>
+         xml:space="preserve">rcutree_report_cpu_starting()</text>
       <g
          style="fill:none;stroke-width:0.025in"
          id="g3107-7-5-0"

Documentation/RCU/Design/Memory-Ordering/TreeRCU-hotplug.svg

@@ -607,7 +607,7 @@
        font-weight="bold"
        font-size="192"
        id="text202-7-5-3-27-6"
-       style="font-size:192px;font-style:normal;font-weight:bold;text-anchor:start;fill:#000000;stroke-width:0.025in;font-family:Courier">rcu_report_dead()</text>
+       style="font-size:192px;font-style:normal;font-weight:bold;text-anchor:start;fill:#000000;stroke-width:0.025in;font-family:Courier">rcutree_report_cpu_dead()</text>
     <text
        xml:space="preserve"
        x="3745.7725"
@@ -728,7 +728,7 @@
        font-style="normal"
        y="3679.27"
        x="-3804.9949"
-       xml:space="preserve">rcu_cpu_starting()</text>
+       xml:space="preserve">rcutree_report_cpu_starting()</text>
     <g
        style="fill:none;stroke-width:0.025in"
        id="g3107-7-5-0"

Documentation/RCU/Design/Requirements/Requirements.rst

@@ -1955,12 +1955,12 @@ if offline CPUs block an RCU grace period for too long.
 
 An offline CPU's quiescent state will be reported either:
 
-1.  As the CPU goes offline using RCU's hotplug notifier (rcu_report_dead()).
+1.  As the CPU goes offline using RCU's hotplug notifier (rcutree_report_cpu_dead()).
 2.  When grace period initialization (rcu_gp_init()) detects a
     race either with CPU offlining or with a task unblocking on a leaf
     ``rcu_node`` structure whose CPUs are all offline.
 
-The CPU-online path (rcu_cpu_starting()) should never need to report
+The CPU-online path (rcutree_report_cpu_starting()) should never need to report
 a quiescent state for an offline CPU.  However, as a debugging measure,
 it does emit a warning if a quiescent state was not already reported
 for that CPU.

arch/arm64/kernel/smp.c

@@ -215,7 +215,7 @@ asmlinkage notrace void secondary_start_kernel(void)
 	if (system_uses_irq_prio_masking())
 		init_gic_priority_masking();
 
-	rcu_cpu_starting(cpu);
+	rcutree_report_cpu_starting(cpu);
 	trace_hardirqs_off();
 
 	/*
@@ -401,7 +401,7 @@ void __noreturn cpu_die_early(void)
 
 	/* Mark this CPU absent */
 	set_cpu_present(cpu, 0);
-	rcu_report_dead();
+	rcutree_report_cpu_dead();
 
 	if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
 		update_cpu_boot_status(CPU_KILL_ME);

arch/powerpc/kernel/smp.c

@@ -1629,7 +1629,7 @@ void start_secondary(void *unused)
 
 	smp_store_cpu_info(cpu);
 	set_dec(tb_ticks_per_jiffy);
-	rcu_cpu_starting(cpu);
+	rcutree_report_cpu_starting(cpu);
 	cpu_callin_map[cpu] = 1;
 
 	if (smp_ops->setup_cpu)

arch/s390/kernel/smp.c

@@ -898,7 +898,7 @@ static void smp_start_secondary(void *cpuvoid)
 	S390_lowcore.restart_flags = 0;
 	restore_access_regs(S390_lowcore.access_regs_save_area);
 	cpu_init();
-	rcu_cpu_starting(cpu);
+	rcutree_report_cpu_starting(cpu);
 	init_cpu_timer();
 	vtime_init();
 	vdso_getcpu_init();

arch/x86/kernel/smpboot.c

@@ -288,7 +288,7 @@ static void notrace start_secondary(void *unused)
 
 	cpu_init();
 	fpu__init_cpu();
-	rcu_cpu_starting(raw_smp_processor_id());
+	rcutree_report_cpu_starting(raw_smp_processor_id());
 	x86_cpuinit.early_percpu_clock_init();
 
 	ap_starting();

include/linux/interrupt.h

@@ -566,7 +566,7 @@ enum
  *
  * _ RCU:
  * 	1) rcutree_migrate_callbacks() migrates the queue.
- * 	2) rcu_report_dead() reports the final quiescent states.
+ * 	2) rcutree_report_cpu_dead() reports the final quiescent states.
  *
  * _ IRQ_POLL: irq_poll_cpu_dead() migrates the queue
  */

include/linux/rcupdate.h

@@ -122,8 +122,6 @@ static inline void call_rcu_hurry(struct rcu_head *head, rcu_callback_t func)
 void rcu_init(void);
 extern int rcu_scheduler_active;
 void rcu_sched_clock_irq(int user);
-void rcu_report_dead(void);
-void rcutree_migrate_callbacks(int cpu);
 
 #ifdef CONFIG_TASKS_RCU_GENERIC
 void rcu_init_tasks_generic(void);

include/linux/rcutiny.h

@@ -171,6 +171,6 @@ static inline void rcu_all_qs(void) { barrier(); }
 #define rcutree_offline_cpu      NULL
 #define rcutree_dead_cpu         NULL
 #define rcutree_dying_cpu        NULL
-static inline void rcu_cpu_starting(unsigned int cpu) { }
+static inline void rcutree_report_cpu_starting(unsigned int cpu) { }
 
 #endif /* __LINUX_RCUTINY_H */

include/linux/rcutree.h

@@ -110,7 +110,7 @@ void rcu_all_qs(void);
 /* RCUtree hotplug events */
 int rcutree_prepare_cpu(unsigned int cpu);
 int rcutree_online_cpu(unsigned int cpu);
-void rcu_cpu_starting(unsigned int cpu);
+void rcutree_report_cpu_starting(unsigned int cpu);
 
 #ifdef CONFIG_HOTPLUG_CPU
 int rcutree_dead_cpu(unsigned int cpu);
@@ -122,4 +122,9 @@ int rcutree_offline_cpu(unsigned int cpu);
 #define rcutree_offline_cpu NULL
 #endif
 
+void rcutree_migrate_callbacks(int cpu);
+
+/* Called from hotplug and also arm64 early secondary boot failure */
+void rcutree_report_cpu_dead(void);
+
 #endif /* __LINUX_RCUTREE_H */

kernel/cpu.c

@@ -1388,10 +1388,10 @@ void cpuhp_report_idle_dead(void)
 	struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 
 	BUG_ON(st->state != CPUHP_AP_OFFLINE);
-	rcu_report_dead();
+	rcutree_report_cpu_dead();
 	st->state = CPUHP_AP_IDLE_DEAD;
 	/*
-	 * We cannot call complete after rcu_report_dead() so we delegate it
+	 * We cannot call complete after rcutree_report_cpu_dead() so we delegate it
 	 * to an online cpu.
 	 */
 	smp_call_function_single(cpumask_first(cpu_online_mask),
@@ -1617,7 +1617,7 @@ void notify_cpu_starting(unsigned int cpu)
 	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 	enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
 
-	rcu_cpu_starting(cpu);	/* Enables RCU usage on this CPU. */
+	rcutree_report_cpu_starting(cpu);	/* Enables RCU usage on this CPU. */
 	cpumask_set_cpu(cpu, &cpus_booted_once_mask);
 
 	/*

kernel/rcu/tree.c

@@ -4216,7 +4216,7 @@ bool rcu_lockdep_current_cpu_online(void)
 	rdp = this_cpu_ptr(&rcu_data);
 	/*
 	 * Strictly, we care here about the case where the current CPU is
-	 * in rcu_cpu_starting() and thus has an excuse for rdp->grpmask
+	 * in rcutree_report_cpu_starting() and thus has an excuse for rdp->grpmask
 	 * not being up to date. So arch_spin_is_locked() might have a
 	 * false positive if it's held by some *other* CPU, but that's
 	 * OK because that just means a false *negative* on the warning.
@@ -4445,8 +4445,10 @@ int rcutree_online_cpu(unsigned int cpu)
  * from the incoming CPU rather than from the cpuhp_step mechanism.
  * This is because this function must be invoked at a precise location.
  * This incoming CPU must not have enabled interrupts yet.
+ *
+ * This mirrors the effects of rcutree_report_cpu_dead().
  */
-void rcu_cpu_starting(unsigned int cpu)
+void rcutree_report_cpu_starting(unsigned int cpu)
 {
 	unsigned long mask;
 	struct rcu_data *rdp;
@@ -4500,8 +4502,10 @@ void rcu_cpu_starting(unsigned int cpu)
  * Note that this function is special in that it is invoked directly
  * from the outgoing CPU rather than from the cpuhp_step mechanism.
  * This is because this function must be invoked at a precise location.
+ *
+ * This mirrors the effect of rcutree_report_cpu_starting().
  */
-void rcu_report_dead(void)
+void rcutree_report_cpu_dead(void)
 {
 	unsigned long flags;
 	unsigned long mask;
@@ -5072,7 +5076,7 @@ void __init rcu_init(void)
 	pm_notifier(rcu_pm_notify, 0);
 	WARN_ON(num_online_cpus() > 1); // Only one CPU this early in boot.
 	rcutree_prepare_cpu(cpu);
-	rcu_cpu_starting(cpu);
+	rcutree_report_cpu_starting(cpu);
 	rcutree_online_cpu(cpu);
 
 	/* Create workqueue for Tree SRCU and for expedited GPs. */