usr/src/cmd/stat/common/common.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 /*
  22  * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  23  * Use is subject to license terms.
  24  */
  25
  26 #include "statcommon.h"
  27
  28 #include <stdarg.h>
  29 #include <signal.h>
  30 #include <errno.h>
  31 #include <string.h>
  32 #include <stdlib.h>
  33
  34 extern char *cmdname;
  35 extern int caught_cont;
  36
  37 /*PRINTFLIKE2*/
  38 void
  39 fail(int do_perror, char *message, ...)
  40 {
  41         va_list args;
  42         int save_errno = errno;
  43
  44         va_start(args, message);
  45         (void) fprintf(stderr, "%s: ", cmdname);
  46         (void) vfprintf(stderr, message, args);
  47         va_end(args);
  48         if (do_perror)
  49                 (void) fprintf(stderr, ": %s", strerror(save_errno));
  50         (void) fprintf(stderr, "\n");
  51         exit(2);
  52 }
  53
  54 /*
  55  * Sleep until *wakeup + interval, keeping cadence where desired
  56  *
  57  * *wakeup -    The time we last wanted to wake up. Updated.
  58  * interval -   We want to sleep until *wakeup + interval
  59  * forever -    Running for infinite periods, so cadence not important
  60  * *caught_cont - Global set by signal handler if we got a SIGCONT
  61  */
  62 void
  63 sleep_until(hrtime_t *wakeup, hrtime_t interval, int forever,
  64     int *caught_cont)
  65 {
  66         hrtime_t now, pause, pause_left;
  67         struct timespec pause_tv;
  68         int status;
  69
  70         now = gethrtime();
  71         pause = *wakeup + interval - now;
  72
  73         if (pause <= 0 || pause < (interval / 4))
  74                 if (forever || *caught_cont) {
  75                         /* Reset our cadence (see comment below) */
  76                         *wakeup = now + interval;
  77                         pause = interval;
  78                 } else {
  79                         /*
  80                          * If we got here, then the time between the
  81                          * output we just did, and the scheduled time
  82                          * for the next output is < 1/4 of our requested
  83                          * interval AND the number of intervals has been
  84                          * requested AND we have never caught a SIGCONT
  85                          * (so we have never been suspended).  In this
  86                          * case, we'll try to stay to the desired
  87                          * cadence, and we will pause for 1/2 the normal
  88                          * interval this time.
  89                          */
  90                         pause = interval / 2;
  91                         *wakeup += interval;
  92                 }
  93         else
  94                 *wakeup += interval;
  95         if (pause < 1000)
  96                 /* Near enough */
  97                 return;
  98
  99         /* Now do the actual sleep */
 100         pause_left = pause;
 101         do {
 102                 pause_tv.tv_sec = pause_left / NANOSEC;
 103                 pause_tv.tv_nsec = pause_left % NANOSEC;
 104                 status = nanosleep(&pause_tv, NULL);
 105                 if (status < 0)
 106                         if (errno == EINTR) {
 107                                 now = gethrtime();
 108                                 pause_left = *wakeup - now;
 109                                 if (pause_left < 1000)
 110                                         /* Near enough */
 111                                         return;
 112                         } else {
 113                                 fail(1, "nanosleep failed");
 114                         }
 115         } while (status != 0);
 116 }
 117
 118 /*
 119  * Signal handler - so we can be aware of SIGCONT
 120  */
 121 void
 122 cont_handler(int sig_number)
 123 {
 124         /* Re-set the signal handler */
 125         (void) signal(sig_number, cont_handler);
 126         caught_cont = 1;
 127 }