/*

 * CDDL HEADER START

 *

 * The contents of this file are subject to the terms of the

 * Common Development and Distribution License, Version 1.0 only

 * (the "License").  You may not use this file except in compliance

 * with the License.

 *

 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE

 * or http://www.opensolaris.org/os/licensing.

 * See the License for the specific language governing permissions

 * and limitations under the License.

 *

 * When distributing Covered Code, include this CDDL HEADER in each

 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.

 * If applicable, add the following below this CDDL HEADER, with the

 * fields enclosed by brackets "[]" replaced with your own identifying

 * information: Portions Copyright [yyyy] [name of copyright owner]

 *

 * CDDL HEADER END

 */

/*

 * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.

 * Use is subject to license terms.

 */

#pragma ident	"%Z%%M%	%I%	%E% SMI"

#include <sys/types.h>

#include <sys/param.h>

#include <sys/var.h>

#include <sys/thread.h>

#include <sys/cpuvar.h>

#include <sys/kstat.h>

#include <sys/uadmin.h>

#include <sys/systm.h>

#include <sys/errno.h>

#include <sys/cmn_err.h>

#include <sys/procset.h>

#include <sys/processor.h>

#include <sys/debug.h>

#include <sys/cyclic.h>

#include <sys/pool_pset.h>

/*

 * cpu_intr_on - determine whether the CPU is participating

 * in I/O interrupts.

 */

int

cpu_intr_on(cpu_t *cp)

{

	ASSERT(MUTEX_HELD(&cpu_lock));

	return ((cp->cpu_flags & CPU_ENABLE) != 0);

}

/*

 * Return the next on-line CPU handling interrupts.

 */

cpu_t *

cpu_intr_next(cpu_t *cp)

{

	cpu_t	*c;

	ASSERT(MUTEX_HELD(&cpu_lock));

	c = cp->cpu_next_onln;

	while (c != cp) {

		if (cpu_intr_on(c)) {

			return (c);

		}

		c = c->cpu_next_onln;

	}

	return (NULL);

}

/*

 * cpu_intr_count - count how many CPUs are handling I/O interrupts.

 */

int

cpu_intr_count(cpu_t *cp)

{

	cpu_t	*c;

	int	count = 0;

	ASSERT(MUTEX_HELD(&cpu_lock));

	c = cp;

	do {

		if (cpu_intr_on(c)) {

			++count;

		}

	} while ((c = c->cpu_next) != cp);

	return (count);

}

/*

 * Enable I/O interrupts on this CPU, if they are disabled.

 */

void

cpu_intr_enable(cpu_t *cp)

{

	ASSERT(MUTEX_HELD(&cpu_lock));

	if (!cpu_intr_on(cp)) {

		cpu_enable_intr(cp);

		cpu_set_state(cp);

	}

}

/*

 * cpu_intr_disable - redirect I/O interrupts targetted at this CPU.

 *

 * semantics: We check the count of CPUs that are accepting

 * interrupts, because it's stupid to take the last CPU out

 * of I/O interrupt participation. This also permits the

 * p_online syscall to fail gracefully in uniprocessor configurations

 * without having to perform any special platform-specific operations.

 */

int

cpu_intr_disable(cpu_t *cp)

{

	int	e = EBUSY;

	ASSERT(MUTEX_HELD(&cpu_lock));

	if ((cpu_intr_count(cp) > 1) && (cpu_intr_next(cp) != NULL)) {

		if (cpu_intr_on(cp)) {

			/*

			 * Juggle away cyclics, but don't fail if we don't

			 * manage to juggle all of them away; we want to allow

			 * CPU-bound cyclics to continue to fire on the

			 * sheltered CPU.

			 */

			(void) cyclic_juggle(cp);

			e = cpu_disable_intr(cp);

		}

	}

	if (e == 0)

		cpu_set_state(cp);

	return (e);

}