source: mainline/libc/generic/time.c@ bf9afa07

/*
 * Copyright (C) 2006 Ondrej Palkovsky
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */ 

#include <sys/time.h>
#include <unistd.h>
#include <ipc/ipc.h>
#include <stdio.h>
#include <arch/barrier.h>
#include <unistd.h>
#include <atomic.h>
#include <futex.h>

#include <sysinfo.h>
#include <as.h>
#include <ddi.h>

/* Pointers to public variables with time */
struct {
        volatile sysarg_t seconds1;
        volatile sysarg_t useconds;
        volatile sysarg_t seconds2;
} *ktime = NULL;


/** POSIX gettimeofday
 *
 * The time variables are memory mapped(RO) from kernel, which updates
 * them periodically. As it is impossible to read 2 values atomically, we
 * use a trick: First read a seconds, then read microseconds, then
 * read seconds again. If a second elapsed in the meantime, read
 * useconds again. This provides assurance, that at least the
 * sequence of subsequent gettimeofday calls is ordered.
 */
int gettimeofday(struct timeval *tv, struct timezone *tz)
{
        void *mapping;
        sysarg_t s1, s2;
        sysarg_t rights;
        int res;

        if (!ktime) {
                mapping = as_get_mappable_page(PAGE_SIZE);
                /* Get the mapping of kernel clock */
                res = ipc_call_sync_3(PHONE_NS, IPC_M_AS_AREA_RECV, 
                                      mapping, PAGE_SIZE, 0,
                                      NULL,&rights,NULL);
                if (res) {
                        printf("Failed to initialize timeofday memarea\n");
                        _exit(1);
                }
                if (rights != (AS_AREA_READ | AS_AREA_CACHEABLE)) {
                        printf("Received bad rights on time area: %X\n",
                               rights);
                        as_area_destroy(mapping);
                        _exit(1);
                }
                ktime = mapping;
        }
        if (tz) {
                tz->tz_minuteswest = 0;
                tz->tz_dsttime = DST_NONE;
        }

        s2 = ktime->seconds2;
        read_barrier();
        tv->tv_usec = ktime->useconds;
        read_barrier();
        s1 = ktime->seconds1;
        if (s1 != s2) {
                tv->tv_usec = 0;
                tv->tv_sec = s1 > s2 ? s1 : s2;
        } else
                tv->tv_sec = s1;

        return 0;
}

/** Wait unconditionally for specified microseconds */
void usleep(unsigned long usec)
{
        atomic_t futex = FUTEX_INITIALIZER;

        futex_initialize(&futex,0);
        futex_down_timeout(&futex, usec, 0);
}