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Commit 7fdefc10 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Break up rcu_gp_kthread() into subfunctions 



Then rcu_gp_kthread() function is too large and furthermore needs to
have the force_quiescent_state() code pulled in.  This commit therefore
breaks up rcu_gp_kthread() into rcu_gp_init() and rcu_gp_cleanup().

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
parent c856bafa

kernel/rcutree.c

+135 −115
Original line number Diff line number Diff line
@@ -1028,37 +1028,20 @@ rcu_start_gp_per_cpu(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_dat 
}



/*

 * Body of kthread that handles grace periods.

 * Initialize a new grace period.

 */

static int __noreturn rcu_gp_kthread(void *arg)

static int rcu_gp_init(struct rcu_state *rsp)

{

	unsigned long gp_duration;

	struct rcu_data *rdp;

	struct rcu_node *rnp;

	struct rcu_state *rsp = arg;



	for (;;) {

	struct rcu_node *rnp = rcu_get_root(rsp);



		/* Handle grace-period start. */

		rnp = rcu_get_root(rsp);

		for (;;) {

			wait_event_interruptible(rsp->gp_wq, rsp->gp_flags);

			if (rsp->gp_flags)

				break;

			flush_signals(current);

		}

	raw_spin_lock_irq(&rnp->lock);

	rsp->gp_flags = 0;

		rdp = this_cpu_ptr(rsp->rda);



	if (rcu_gp_in_progress(rsp)) {

			/*

			 * A grace period is already in progress, so

			 * don't start another one.

			 */

		/* Grace period already in progress, don't start another.  */

		raw_spin_unlock_irq(&rnp->lock);

			cond_resched();

			continue;

		return 0;

	}



	if (rsp->fqs_active) {
@@ -1068,8 +1051,7 @@ static int __noreturn rcu_gp_kthread(void *arg) 
		 */

		rsp->fqs_need_gp = 1;

		raw_spin_unlock_irq(&rnp->lock);

			cond_resched();

			continue;

		return 0;

	}



	/* Advance to a new grace period and initialize state. */
@@ -1086,17 +1068,20 @@ static int __noreturn rcu_gp_kthread(void *arg) 


	/*

	 * Set the quiescent-state-needed bits in all the rcu_node

		 * structures for all currently online CPUs in breadth-first

		 * order, starting from the root rcu_node structure.

		 * This operation relies on the layout of the hierarchy

		 * within the rsp->node[] array.  Note that other CPUs will

		 * access only the leaves of the hierarchy, which still

		 * indicate that no grace period is in progress, at least

		 * until the corresponding leaf node has been initialized.

		 * In addition, we have excluded CPU-hotplug operations.

	 * structures for all currently online CPUs in breadth-first order,

	 * starting from the root rcu_node structure, relying on the layout

	 * of the tree within the rsp->node[] array.  Note that other CPUs

	 * will access only the leaves of the hierarchy, thus seeing that no

	 * grace period is in progress, at least until the corresponding

	 * leaf node has been initialized.  In addition, we have excluded

	 * CPU-hotplug operations.

	 *

	 * The grace period cannot complete until the initialization

	 * process finishes, because this kthread handles both.

	 */

	rcu_for_each_node_breadth_first(rsp, rnp) {

		raw_spin_lock_irq(&rnp->lock);

		rdp = this_cpu_ptr(rsp->rda);

		rcu_preempt_check_blocked_tasks(rnp);

		rnp->qsmask = rnp->qsmaskinit;

		rnp->gpnum = rsp->gpnum;
@@ -1117,19 +1102,18 @@ static int __noreturn rcu_gp_kthread(void *arg) 
	rsp->fqs_state = RCU_SIGNAL_INIT;

	raw_spin_unlock_irq(&rnp->lock);

	put_online_cpus();



		/* Handle grace-period end. */

		rnp = rcu_get_root(rsp);

		for (;;) {

			wait_event_interruptible(rsp->gp_wq,

						 !ACCESS_ONCE(rnp->qsmask) &&

						 !rcu_preempt_blocked_readers_cgp(rnp));

			if (!ACCESS_ONCE(rnp->qsmask) &&

			    !rcu_preempt_blocked_readers_cgp(rnp))

				break;

			flush_signals(current);

	return 1;

}



/*

 * Clean up after the old grace period.

 */

static int rcu_gp_cleanup(struct rcu_state *rsp)

{

	unsigned long gp_duration;

	struct rcu_data *rdp;

	struct rcu_node *rnp = rcu_get_root(rsp);



	raw_spin_lock_irq(&rnp->lock);

	gp_duration = jiffies - rsp->gp_start;

	if (gp_duration > rsp->gp_max)
@@ -1150,6 +1134,7 @@ static int __noreturn rcu_gp_kthread(void *arg) 
	 * callbacks are waiting on the grace period that just now

	 * completed.

	 */

	rdp = this_cpu_ptr(rsp->rda);

	if (*rdp->nxttail[RCU_WAIT_TAIL] == NULL) {

		raw_spin_unlock_irq(&rnp->lock);
@@ -1175,6 +1160,41 @@ static int __noreturn rcu_gp_kthread(void *arg) 
	if (cpu_needs_another_gp(rsp, rdp))

		rsp->gp_flags = 1;

	raw_spin_unlock_irq(&rnp->lock);

	return 1;

}



/*

 * Body of kthread that handles grace periods.

 */

static int __noreturn rcu_gp_kthread(void *arg)

{

	struct rcu_state *rsp = arg;

	struct rcu_node *rnp = rcu_get_root(rsp);



	for (;;) {



		/* Handle grace-period start. */

		for (;;) {

			wait_event_interruptible(rsp->gp_wq, rsp->gp_flags);

			if (rsp->gp_flags && rcu_gp_init(rsp))

				break;

			cond_resched();

			flush_signals(current);

		}



		/* Handle grace-period end. */

		rnp = rcu_get_root(rsp);

		for (;;) {

			wait_event_interruptible(rsp->gp_wq,

						 !ACCESS_ONCE(rnp->qsmask) &&

						 !rcu_preempt_blocked_readers_cgp(rnp));

			if (!ACCESS_ONCE(rnp->qsmask) &&

			    !rcu_preempt_blocked_readers_cgp(rnp) &&

			    rcu_gp_cleanup(rsp))

				break;

			cond_resched();

			flush_signals(current);

		}

	}

}