Commit 395a2f09 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Define rcu_all_qs() only in !PREEMPT builds 



Now that rcu_all_qs() is used only in !PREEMPT builds, move it to
tree_plugin.h so that it is defined only in those builds.  This in
turn means that rcu_momentary_dyntick_idle() is only used in !PREEMPT
builds, but it is simply marked __maybe_unused in order to keep it
near the rest of the dyntick-idle code.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 4d232dfe

include/linux/rcutree.h

+2 −0
Original line number Diff line number Diff line
@@ -66,7 +66,9 @@ void rcu_scheduler_starting(void); 
extern int rcu_scheduler_active __read_mostly;

void rcu_end_inkernel_boot(void);

bool rcu_is_watching(void);

#ifndef CONFIG_PREEMPT

void rcu_all_qs(void);

#endif



/* RCUtree hotplug events */

int rcutree_prepare_cpu(unsigned int cpu);

kernel/rcu/tree.c

+1 −40
Original line number Diff line number Diff line
@@ -356,7 +356,7 @@ bool rcu_eqs_special_set(int cpu) 
 *

 * The caller must have disabled interrupts and must not be idle.

 */

static void rcu_momentary_dyntick_idle(void)

static void __maybe_unused rcu_momentary_dyntick_idle(void)

{

	struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);

	int special;
@@ -381,45 +381,6 @@ static int rcu_is_cpu_rrupt_from_idle(void) 
	       __this_cpu_read(rcu_dynticks.dynticks_nmi_nesting) <= 1;

}



/*

 * Register an urgently needed quiescent state.  If there is an

 * emergency, invoke rcu_momentary_dyntick_idle() to do a heavy-weight

 * dyntick-idle quiescent state visible to other CPUs, which will in

 * some cases serve for expedited as well as normal grace periods.

 * Either way, register a lightweight quiescent state.

 *

 * The barrier() calls are redundant in the common case when this is

 * called externally, but just in case this is called from within this

 * file.

 *

 */

void rcu_all_qs(void)

{

	unsigned long flags;



	if (!raw_cpu_read(rcu_dynticks.rcu_urgent_qs))

		return;

	preempt_disable();

	/* Load rcu_urgent_qs before other flags. */

	if (!smp_load_acquire(this_cpu_ptr(&rcu_dynticks.rcu_urgent_qs))) {

		preempt_enable();

		return;

	}

	this_cpu_write(rcu_dynticks.rcu_urgent_qs, false);

	barrier(); /* Avoid RCU read-side critical sections leaking down. */

	if (unlikely(raw_cpu_read(rcu_dynticks.rcu_need_heavy_qs))) {

		local_irq_save(flags);

		rcu_momentary_dyntick_idle();

		local_irq_restore(flags);

	}

	if (unlikely(raw_cpu_read(rcu_data.cpu_no_qs.b.exp)))

		rcu_qs();

	this_cpu_inc(rcu_dynticks.rcu_qs_ctr);

	barrier(); /* Avoid RCU read-side critical sections leaking up. */

	preempt_enable();

}

EXPORT_SYMBOL_GPL(rcu_all_qs);



#define DEFAULT_RCU_BLIMIT 10     /* Maximum callbacks per rcu_do_batch. */

static long blimit = DEFAULT_RCU_BLIMIT;

#define DEFAULT_RCU_QHIMARK 10000 /* If this many pending, ignore blimit. */

kernel/rcu/tree_plugin.h

+39 −0
Original line number Diff line number Diff line
@@ -947,6 +947,45 @@ static void rcu_qs(void) 
	rcu_report_exp_rdp(this_cpu_ptr(&rcu_data));

}



/*

 * Register an urgently needed quiescent state.  If there is an

 * emergency, invoke rcu_momentary_dyntick_idle() to do a heavy-weight

 * dyntick-idle quiescent state visible to other CPUs, which will in

 * some cases serve for expedited as well as normal grace periods.

 * Either way, register a lightweight quiescent state.

 *

 * The barrier() calls are redundant in the common case when this is

 * called externally, but just in case this is called from within this

 * file.

 *

 */

void rcu_all_qs(void)

{

	unsigned long flags;



	if (!raw_cpu_read(rcu_dynticks.rcu_urgent_qs))

		return;

	preempt_disable();

	/* Load rcu_urgent_qs before other flags. */

	if (!smp_load_acquire(this_cpu_ptr(&rcu_dynticks.rcu_urgent_qs))) {

		preempt_enable();

		return;

	}

	this_cpu_write(rcu_dynticks.rcu_urgent_qs, false);

	barrier(); /* Avoid RCU read-side critical sections leaking down. */

	if (unlikely(raw_cpu_read(rcu_dynticks.rcu_need_heavy_qs))) {

		local_irq_save(flags);

		rcu_momentary_dyntick_idle();

		local_irq_restore(flags);

	}

	if (unlikely(raw_cpu_read(rcu_data.cpu_no_qs.b.exp)))

		rcu_qs();

	this_cpu_inc(rcu_dynticks.rcu_qs_ctr);

	barrier(); /* Avoid RCU read-side critical sections leaking up. */

	preempt_enable();

}

EXPORT_SYMBOL_GPL(rcu_all_qs);



/*

 * Note a PREEMPT=n context switch.  The caller must have disabled interrupts.

 */