/*
 * Copyright (c) 1996 Regents of the University of Michigan.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that this notice is preserved and that due credit is given
 * to the University of Michigan at Ann Arbor. The name of the University
 * may not be used to endorse or promote products derived from this
 * software without specific prior written permission. This software
 * is provided ``as is'' without express or implied warranty.
 */

/*
 * ldap_pvt_thread_sleep.c - allow a thread to sleep without putting
 * the whole process (e.g. pod under lwp) to sleep.
 *
 * Contains platform-specific code to allow this:
 *
 * Under non-preemptive threads packages like SunOS lwp, tsleep() adds
 * the thread to a list of sleepers.  The lwp_scheduler process takes
 * care of resuming suspended threads.
 *
 * Under a fully-preemptive threads package, like Solaris threads,
 * tsleep just calls sleep(), and there is no scheduler thread.  Life
 * is so much simpler...
 */

#include "portable.h"

#include <stdio.h>
#include <stdlib.h>
#include <ac/unistd.h>			/* get sleep() */

#include "ldap_pvt_thread.h"

#if !defined( HAVE_LWP )

/*
 * Here we assume we have fully preemptive threads and that sleep()
 * does the right thing.
 */
unsigned int
ldap_pvt_thread_sleep(
	unsigned int interval
)
{
	sleep( interval );
	return 0;
}

#else

unsigned int
ldap_pvt_thread_sleep(
	unsigned int interval
)
{
	thread_t		mylwp;
	tl_t		*t, *nt;
	time_t		now;


	if ( lwp_self( &mylwp ) < 0 ) {
		return -1;
	}

	time( &now );

	mon_enter( &sglob->tsl_mon );

	if ( sglob->tsl_list != NULL ) {
		for ( t = sglob->tsl_list; t != NULL; t = t->tl_next ) {
			if ( SAMETHREAD( t->tl_tid, mylwp )) {
				/* We're already sleeping? */
				t->tl_wake = now + interval;
				mon_exit( &sglob->tsl_mon );
				lwp_suspend( mylwp );
				return 0;
			}
		}
	}

	nt = (tl_t *) malloc( sizeof( tl_t ));

	nt->tl_next = sglob->tsl_list;
	nt->tl_wake = now + interval;
	nt->tl_tid = mylwp;
	sglob->tsl_list = nt;

	mon_exit( &sglob->tsl_mon );

	lwp_suspend( mylwp );
	return 0;
}

/*
 * The lwp_scheduler thread periodically checks to see if any threads
 * are due to be resumed.  If there are, it resumes them.  Otherwise,
 * it computes the lesser of ( 1 second ) or ( the minimum time until
 * a thread need to be resumed ) and puts itself to sleep for that amount
 * of time.
 */
void
lwp_scheduler(
	int		stackno
)
{
	time_t			now, min;
	struct timeval		interval;
	tl_t			*t;

	while ( !sglob->slurpd_shutdown ) {
		mon_enter( &sglob->tsl_mon );

		time( &now );
		min = 0L;
		if ( sglob->tsl_list != NULL ) {
			for ( t = sglob->tsl_list; t != NULL; t = t->tl_next ) {
				if (( t->tl_wake  > 0L ) && ( t->tl_wake < now )) {
					lwp_resume( t->tl_tid );
					t->tl_wake = 0L;
				}

				if (( t->tl_wake > now ) && ( t->tl_wake < min )) {
					min =  t->tl_wake;
				}
			}
		}

		mon_exit( &sglob->tsl_mon );

		interval.tv_usec = 0L;
		if ( min == 0L ) {
			interval.tv_sec = 1L;
		} else {
			interval.tv_sec = min;
		}

		lwp_sleep( &interval );
	}

	mon_enter( &sglob->tsl_mon );

	for ( t = sglob->tsl_list; t != NULL; t = t->tl_next ) {
		lwp_resume( t->tl_tid );
	}

	mon_exit( &sglob->tsl_mon );

	free_stack( stackno );
}

#endif /* HAVE_LWP */