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Commit 4df83742 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Ingo Molnar
Browse files

rcu: Convert rcutree to hotplug state machine 



Straight forward conversion to the state machine. Though the question arises
whether this needs really all these state transitions to work.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarAnna-Maria Gleixner <anna-maria@linutronix.de>
Reviewed-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160713153337.982013161@linutronix.de


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 15d7e3d3

include/linux/cpuhotplug.h

+3 −0
Original line number Diff line number Diff line
@@ -20,11 +20,13 @@ enum cpuhp_state { 
	CPUHP_X2APIC_PREPARE,

	CPUHP_SMPCFD_PREPARE,

	CPUHP_TIMERS_DEAD,

	CPUHP_RCUTREE_PREP,

	CPUHP_NOTIFY_PREPARE,

	CPUHP_BRINGUP_CPU,

	CPUHP_AP_IDLE_DEAD,

	CPUHP_AP_OFFLINE,

	CPUHP_AP_SCHED_STARTING,

	CPUHP_AP_RCUTREE_DYING,

	CPUHP_AP_IRQ_GIC_STARTING,

	CPUHP_AP_IRQ_GICV3_STARTING,

	CPUHP_AP_IRQ_HIP04_STARTING,
@@ -80,6 +82,7 @@ enum cpuhp_state { 
	CPUHP_AP_PERF_ARM_CCI_ONLINE,

	CPUHP_AP_PERF_ARM_CCN_ONLINE,

	CPUHP_AP_WORKQUEUE_ONLINE,

	CPUHP_AP_RCUTREE_ONLINE,

	CPUHP_AP_NOTIFY_ONLINE,

	CPUHP_AP_ONLINE_DYN,

	CPUHP_AP_ONLINE_DYN_END		= CPUHP_AP_ONLINE_DYN + 30,

include/linux/rcutiny.h

+7 −0
Original line number Diff line number Diff line
@@ -243,4 +243,11 @@ static inline void rcu_all_qs(void) 
	barrier(); /* Avoid RCU read-side critical sections leaking across. */

}



/* RCUtree hotplug events */

#define rcutree_prepare_cpu      NULL

#define rcutree_online_cpu       NULL

#define rcutree_offline_cpu      NULL

#define rcutree_dead_cpu         NULL

#define rcutree_dying_cpu        NULL



#endif /* __LINUX_RCUTINY_H */

include/linux/rcutree.h

+7 −0
Original line number Diff line number Diff line
@@ -111,4 +111,11 @@ bool rcu_is_watching(void); 


void rcu_all_qs(void);



/* RCUtree hotplug events */

int rcutree_prepare_cpu(unsigned int cpu);

int rcutree_online_cpu(unsigned int cpu);

int rcutree_offline_cpu(unsigned int cpu);

int rcutree_dead_cpu(unsigned int cpu);

int rcutree_dying_cpu(unsigned int cpu);



#endif /* __LINUX_RCUTREE_H */

kernel/cpu.c

+14 −0
Original line number Diff line number Diff line
@@ -1205,6 +1205,11 @@ static struct cpuhp_step cpuhp_bp_states[] = { 
		.startup = NULL,

		.teardown = timers_dead_cpu,

	},

	[CPUHP_RCUTREE_PREP] = {

		.name = "RCU-tree prepare",

		.startup = rcutree_prepare_cpu,

		.teardown = rcutree_dead_cpu,

	},

	/*

	 * Preparatory and dead notifiers. Will be replaced once the notifiers

	 * are converted to states.
@@ -1263,6 +1268,10 @@ static struct cpuhp_step cpuhp_ap_states[] = { 
		.startup		= sched_cpu_starting,

		.teardown		= sched_cpu_dying,

	},

	[CPUHP_AP_RCUTREE_DYING] = {

		.startup = NULL,

		.teardown = rcutree_dying_cpu,

	},

	/*

	 * Low level startup/teardown notifiers. Run with interrupts

	 * disabled. Will be removed once the notifiers are converted to
@@ -1296,6 +1305,11 @@ static struct cpuhp_step cpuhp_ap_states[] = { 
		.startup = workqueue_online_cpu,

		.teardown = workqueue_offline_cpu,

	},

	[CPUHP_AP_RCUTREE_ONLINE] = {

		.name = "RCU-tree online",

		.startup = rcutree_online_cpu,

		.teardown = rcutree_offline_cpu,

	},



	/*

	 * Online/down_prepare notifiers. Will be removed once the notifiers

kernel/rcu/tree.c

+52 −53
Original line number Diff line number Diff line
@@ -1073,11 +1073,11 @@ EXPORT_SYMBOL_GPL(rcu_is_watching); 
 * offline to continue to use RCU for one jiffy after marking itself

 * offline in the cpu_online_mask.  This leniency is necessary given the

 * non-atomic nature of the online and offline processing, for example,

 * the fact that a CPU enters the scheduler after completing the CPU_DYING

 * notifiers.

 * the fact that a CPU enters the scheduler after completing the teardown

 * of the CPU.

 *

 * This is also why RCU internally marks CPUs online during the

 * CPU_UP_PREPARE phase and offline during the CPU_DEAD phase.

 * This is also why RCU internally marks CPUs online during in the

 * preparation phase and offline after the CPU has been taken down.

 *

 * Disable checking if in an NMI handler because we cannot safely report

 * errors from NMI handlers anyway.
@@ -3806,12 +3806,58 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp) 
	raw_spin_unlock_irqrestore_rcu_node(rnp, flags);

}



static void rcu_prepare_cpu(int cpu)

int rcutree_prepare_cpu(unsigned int cpu)

{

	struct rcu_state *rsp;



	for_each_rcu_flavor(rsp)

		rcu_init_percpu_data(cpu, rsp);



	rcu_prepare_kthreads(cpu);

	rcu_spawn_all_nocb_kthreads(cpu);



	return 0;

}



static void rcutree_affinity_setting(unsigned int cpu, int outgoing)

{

	struct rcu_data *rdp = per_cpu_ptr(rcu_state_p->rda, cpu);



	rcu_boost_kthread_setaffinity(rdp->mynode, outgoing);

}



int rcutree_online_cpu(unsigned int cpu)

{

	sync_sched_exp_online_cleanup(cpu);

	rcutree_affinity_setting(cpu, -1);

	return 0;

}



int rcutree_offline_cpu(unsigned int cpu)

{

	rcutree_affinity_setting(cpu, cpu);

	return 0;

}





int rcutree_dying_cpu(unsigned int cpu)

{

	struct rcu_state *rsp;



	for_each_rcu_flavor(rsp)

		rcu_cleanup_dying_cpu(rsp);

	return 0;

}



int rcutree_dead_cpu(unsigned int cpu)

{

	struct rcu_state *rsp;



	for_each_rcu_flavor(rsp) {

		rcu_cleanup_dead_cpu(cpu, rsp);

		do_nocb_deferred_wakeup(per_cpu_ptr(rsp->rda, cpu));

	}

	return 0;

}



#ifdef CONFIG_HOTPLUG_CPU
@@ -3851,52 +3897,6 @@ void rcu_report_dead(unsigned int cpu) 
}

#endif



/*

 * Handle CPU online/offline notification events.

 */

int rcu_cpu_notify(struct notifier_block *self,

		   unsigned long action, void *hcpu)

{

	long cpu = (long)hcpu;

	struct rcu_data *rdp = per_cpu_ptr(rcu_state_p->rda, cpu);

	struct rcu_node *rnp = rdp->mynode;

	struct rcu_state *rsp;



	switch (action) {

	case CPU_UP_PREPARE:

	case CPU_UP_PREPARE_FROZEN:

		rcu_prepare_cpu(cpu);

		rcu_prepare_kthreads(cpu);

		rcu_spawn_all_nocb_kthreads(cpu);

		break;

	case CPU_ONLINE:

	case CPU_DOWN_FAILED:

		sync_sched_exp_online_cleanup(cpu);

		rcu_boost_kthread_setaffinity(rnp, -1);

		break;

	case CPU_DOWN_PREPARE:

		rcu_boost_kthread_setaffinity(rnp, cpu);

		break;

	case CPU_DYING:

	case CPU_DYING_FROZEN:

		for_each_rcu_flavor(rsp)

			rcu_cleanup_dying_cpu(rsp);

		break;

	case CPU_DEAD:

	case CPU_DEAD_FROZEN:

	case CPU_UP_CANCELED:

	case CPU_UP_CANCELED_FROZEN:

		for_each_rcu_flavor(rsp) {

			rcu_cleanup_dead_cpu(cpu, rsp);

			do_nocb_deferred_wakeup(per_cpu_ptr(rsp->rda, cpu));

		}

		break;

	default:

		break;

	}

	return NOTIFY_OK;

}



static int rcu_pm_notify(struct notifier_block *self,

			 unsigned long action, void *hcpu)

{
@@ -4208,10 +4208,9 @@ void __init rcu_init(void) 
	 * this is called early in boot, before either interrupts

	 * or the scheduler are operational.

	 */

	cpu_notifier(rcu_cpu_notify, 0);

	pm_notifier(rcu_pm_notify, 0);

	for_each_online_cpu(cpu)

		rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu);

		rcutree_prepare_cpu(cpu);

}



#include "tree_exp.h"