test/t40f.c

   1 /* t40f.c
   2  *
   3  * Test timing
   4  *
   5  * Select works on regular files, (pseudo) terminal devices, streams-based
   6  * files, FIFOs, pipes, and sockets. This test verifies selecting with a time
   7  * out set.
   8  */
   9
  10 #include <stdio.h>
  11 #include <stdlib.h>
  12 #include <unistd.h>
  13 #include <sys/types.h>
  14 #include <sys/select.h>
  15 #include <sys/wait.h>
  16 #include <sys/time.h>
  17 #include <time.h>
  18 #include <errno.h>
  19 #include <string.h>
  20 #include <signal.h>
  21
  22 #include "common.h"
  23
  24 #define DO_HANDLEDATA 1
  25 #define DO_PAUSE 3
  26 #define DO_TIMEOUT 7
  27 #define DO_DELTA 0.5
  28 #define MAX_ERROR 5
  29 #define DELTA(x,y)  (x.tv_sec - y.tv_sec) * system_hz \
  30   + (x.tv_usec - y.tv_usec) * system_hz / 1000000
  31
  32 int got_signal = 0;
  33 int fd_ap[2];
  34
  35 int system_hz;
  36
  37 static void catch_signal(int sig_no) {
  38   got_signal = 1;
  39 }
  40
  41 static float compute_diff(struct timeval start, struct timeval end, float compare) {
  42   /* Compute time difference. It is assumed that the value of start <= end. */
  43   clock_t delta;
  44   int seconds, hundreths;
  45   float diff;
  46
  47   delta = DELTA(end, start); /* delta is in ticks */
  48   seconds = (int) (delta / system_hz);
  49   hundreths = (int) (delta * 100 / system_hz) - (seconds * 100);
  50
  51   diff = seconds + (hundreths / 100.0);
  52   diff -= compare;
  53   if(diff < 0) diff *= -1; /* Make diff a positive value */
  54
  55   return diff;
  56 }
  57
  58 static void do_child(void) {
  59   struct timeval tv;
  60
  61   /* Let the parent do initial read and write tests from and to the pipe. */
  62   tv.tv_sec = DO_PAUSE + DO_PAUSE + DO_PAUSE + 1;
  63   tv.tv_usec = 0;
  64   (void) select(0, NULL, NULL, NULL, &tv);
  65
  66   /* At this point the parent has a pending select with a DO_TIMEOUT timeout.
  67      We're going to interrupt by sending a signal */
  68   if(kill(getppid(), SIGUSR1) < 0) perror("Failed to send signal");
  69
  70   exit(0);
  71 }
  72
  73 static void do_parent(int child) {
  74   fd_set fds_read;
  75   struct timeval tv, start_time, end_time;
  76   int retval;
  77
  78   /* Install signal handler for SIGUSR1 */
  79   signal(SIGUSR1, catch_signal);
  80
  81   /* Parent and child share an anonymous pipe. Select for read and wait for the
  82    timeout to occur. We wait for DO_PAUSE seconds. Let's see if that's
  83    approximately right.*/
  84   FD_ZERO(&fds_read);
  85   FD_SET(fd_ap[0], &fds_read);
  86   tv.tv_sec = DO_PAUSE;
  87   tv.tv_usec = 0;
  88
  89   (void) gettimeofday(&start_time, NULL);   /* Record starting time */
  90   retval = select(fd_ap[0]+1, &fds_read, NULL, NULL, &tv);
  91   (void) gettimeofday(&end_time, NULL);     /* Record ending time */
  92
  93   /* Did we time out? */
  94   if(retval != 0) em(1, "Should have timed out");
  95
  96   /* Approximately right? The standard does not specify how precise the timeout
  97      should be. Instead, the granularity is implementation-defined. In this
  98      test we assume that the difference should be no more than half a second.*/
  99   if(compute_diff(start_time, end_time, DO_PAUSE) > DO_DELTA)
 100     em(2, "Time difference too large");
 101
 102   /* Let's wait for another DO_PAUSE seconds, expressed as microseconds */
 103   FD_ZERO(&fds_read);
 104   FD_SET(fd_ap[0], &fds_read);
 105   tv.tv_sec = 0;
 106   tv.tv_usec = DO_PAUSE * 1000000L;
 107
 108   (void) gettimeofday(&start_time, NULL);   /* Record starting time */
 109   retval = select(fd_ap[0]+1, &fds_read, NULL, NULL, &tv);
 110   (void) gettimeofday(&end_time, NULL);     /* Record ending time */
 111
 112   if(retval != 0) em(3, "Should have timed out");
 113   if(compute_diff(start_time, end_time, DO_PAUSE) > DO_DELTA)
 114     em(4, "Time difference too large");
 115
 116   /* Let's wait for another DO_PAUSE seconds, expressed in seconds and micro
 117      seconds. */
 118   FD_ZERO(&fds_read);
 119   FD_SET(fd_ap[0], &fds_read);
 120   tv.tv_sec = DO_PAUSE - 1;
 121   tv.tv_usec = (DO_PAUSE - tv.tv_sec) * 1000000L;
 122
 123   (void) gettimeofday(&start_time, NULL);   /* Record starting time */
 124   retval = select(fd_ap[0]+1, &fds_read, NULL, NULL, &tv);
 125   (void) gettimeofday(&end_time, NULL);     /* Record ending time */
 126
 127   if(retval != 0) em(5, "Should have timed out");
 128   if(compute_diff(start_time, end_time, DO_PAUSE) > DO_DELTA)
 129     em(6, "Time difference too large");
 130
 131   /* Finally, we test if our timeout is interrupted by a signal */
 132   FD_ZERO(&fds_read);
 133   FD_SET(fd_ap[0], &fds_read);
 134   tv.tv_sec = DO_TIMEOUT;
 135   tv.tv_usec = 0;
 136
 137   (void) gettimeofday(&start_time, NULL);   /* Record starting time */
 138   retval = select(fd_ap[0]+1, &fds_read, NULL, NULL, &tv);
 139   (void) gettimeofday(&end_time, NULL);     /* Record ending time */
 140
 141   if(retval != -1) em(7, "Should have been interrupted");
 142   if(compute_diff(start_time, end_time, DO_TIMEOUT) < DO_DELTA)
 143     em(8, "Failed to get interrupted by a signal");
 144
 145   if(!got_signal) em(9, "Failed to get interrupted by a signal");
 146
 147   waitpid(child, &retval, 0);
 148   exit(errct);
 149 }
 150
 151 int main(int argc, char **argv) {
 152   int forkres;
 153
 154   /* Retrieve actual system frequency. */
 155   system_hz = sysconf(_SC_CLK_TCK);
 156   /* Get subtest number */
 157   if(argc != 2) {
 158     printf("Usage: %s subtest_no\n", argv[0]);
 159     exit(-2);
 160   } else if(sscanf(argv[1], "%d", &subtest) != 1) {
 161     printf("Usage: %s subtest_no\n", argv[0]);
 162     exit(-2);
 163   }
 164
 165   /* Set up anonymous pipe */
 166   if(pipe(fd_ap) < 0) {
 167     perror("Could not create anonymous pipe");
 168     exit(-1);
 169   }
 170
 171   forkres = fork();
 172   if(forkres == 0) do_child();
 173   else if(forkres > 0)  do_parent(forkres);
 174   else { /* Fork failed */
 175     perror("Unable to fork");
 176     exit(-1);
 177   }
 178
 179   exit(-2); /* We're not supposed to get here. Both do_* routines should exit*/
 180
 181 }