/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (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 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#include "umem_base.h"
#include "vmem_base.h"

#include <sys/ccompile.h>

#include <signal.h>

/*ARGSUSED*/
static void * __NORETURN
umem_update_thread(void *arg)
{
        struct timeval now;
        int in_update = 0;

        (void) mutex_lock(&umem_update_lock);

        ASSERT(umem_update_thr == thr_self());
        ASSERT(umem_st_update_thr == 0);

        for (;;) {
                umem_process_updates();

                if (in_update) {
                        in_update = 0;
                        /*
                         * we wait until now to set the next update time
                         * so that the updates are self-throttling
                         */
                        (void) gettimeofday(&umem_update_next, NULL);
                        umem_update_next.tv_sec += umem_reap_interval;
                }

                switch (umem_reaping) {
                case UMEM_REAP_DONE:
                case UMEM_REAP_ADDING:
                        break;

                case UMEM_REAP_ACTIVE:
                        umem_reap_next = gethrtime() +
                            (hrtime_t)umem_reap_interval * NANOSEC;
                        umem_reaping = UMEM_REAP_DONE;
                        break;

                default:
                        ASSERT(umem_reaping == UMEM_REAP_DONE ||
                            umem_reaping == UMEM_REAP_ADDING ||
                            umem_reaping == UMEM_REAP_ACTIVE);
                        break;
                }

                (void) gettimeofday(&now, NULL);
                if (now.tv_sec > umem_update_next.tv_sec ||
                    (now.tv_sec == umem_update_next.tv_sec &&
                    now.tv_usec >= umem_update_next.tv_usec)) {
                        /*
                         * Time to run an update
                         */
                        (void) mutex_unlock(&umem_update_lock);

                        vmem_update(NULL);
                        /*
                         * umem_cache_update can use umem_add_update to
                         * request further work.  The update is not complete
                         * until all such work is finished.
                         */
                        umem_cache_applyall(umem_cache_update);

                        (void) mutex_lock(&umem_update_lock);
                        in_update = 1;
                        continue;       /* start processing immediately */
                }

                /*
                 * if there is no work to do, we wait until it is time for
                 * next update, or someone wakes us.
                 */
                if (umem_null_cache.cache_unext == &umem_null_cache) {
                        int cancel_state;
                        timespec_t abs_time;
                        abs_time.tv_sec = umem_update_next.tv_sec;
                        abs_time.tv_nsec = umem_update_next.tv_usec * 1000;

                        (void) pthread_setcancelstate(PTHREAD_CANCEL_DISABLE,
                            &cancel_state);
                        (void) cond_timedwait(&umem_update_cv,
                            &umem_update_lock, &abs_time);
                        (void) pthread_setcancelstate(cancel_state, NULL);
                }
        }
        /* LINTED no return statement */
}

int
umem_create_update_thread(void)
{
        sigset_t sigmask, oldmask;
        thread_t newthread;

        ASSERT(MUTEX_HELD(&umem_update_lock));
        ASSERT(umem_update_thr == 0);

        /*
         * The update thread handles no signals
         */
        (void) sigfillset(&sigmask);
        (void) thr_sigsetmask(SIG_BLOCK, &sigmask, &oldmask);

        /*
         * drop the umem_update_lock; we cannot hold locks acquired in
         * pre-fork handler while calling thr_create or thr_continue().
         */

        (void) mutex_unlock(&umem_update_lock);

        if (thr_create(NULL, 0, umem_update_thread, NULL,
            THR_BOUND | THR_DAEMON | THR_DETACHED | THR_SUSPENDED,
            &newthread) == 0) {
                (void) thr_sigsetmask(SIG_SETMASK, &oldmask, NULL);
                (void) thr_setname(newthread, "umem_update");

                (void) mutex_lock(&umem_update_lock);
                /*
                 * due to the locking in umem_reap(), only one thread can
                 * ever call umem_create_update_thread() at a time.  This
                 * must be the case for this code to work.
                 */

                ASSERT(umem_update_thr == 0);
                umem_update_thr = newthread;
                (void) mutex_unlock(&umem_update_lock);
                (void) thr_continue(newthread);
                (void) mutex_lock(&umem_update_lock);

                return (1);
        } else { /* thr_create failed */
                (void) thr_sigsetmask(SIG_SETMASK, &oldmask, NULL);
                (void) mutex_lock(&umem_update_lock);
        }
        return (0);
}