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 #define DO_HANDLEDATA 1
  23 #define DO_PAUSE 3
  24 #define DO_TIMEOUT 7
  25 #define DO_DELTA 0.5
  26 #define MAX_ERROR 5
  27 #define DELTA(x,y)  (x.tv_sec - y.tv_sec) * CLOCKS_PER_SEC \
  28   + (x.tv_usec - y.tv_usec) * CLOCKS_PER_SEC / 1000000
  29
  30 int errct = 0, subtest = -1, got_signal = 0;
  31 int fd_ap[2];
  32
  33 void catch_signal(int sig_no) {
  34   got_signal = 1;
  35 }
  36
  37 void e(int n, char *s) {
  38   printf("Subtest %d, error %d, %s\n", subtest, n, s);
  39
  40   if (errct++ > MAX_ERROR) {
  41     printf("Too many errors; test aborted\n");
  42     exit(errct);
  43   }
  44 }
  45
  46 float compute_diff(struct timeval start, struct timeval end, float compare) {
  47   /* Compute time difference. It is assumed that the value of start <= end. */
  48   clock_t delta;
  49   int seconds, hundreths;
  50   float diff;
  51
  52   delta = DELTA(end, start); /* delta is in ticks */
  53   seconds = (int) (delta / CLOCKS_PER_SEC);
  54   hundreths = (int) (delta * 100 / CLOCKS_PER_SEC) - (seconds * 100);
  55
  56   diff = seconds + (hundreths / 100.0);
  57   diff -= compare;
  58   if(diff < 0) diff *= -1; /* Make diff a positive value */
  59
  60   return diff;
  61 }
  62
  63 void do_child(void) {
  64   struct timeval tv;
  65
  66   /* Let the parent do initial read and write tests from and to the pipe. */
  67   tv.tv_sec = DO_PAUSE + DO_PAUSE + DO_PAUSE + 1;
  68   tv.tv_usec = 0;
  69   (void) select(0, NULL, NULL, NULL, &tv);
  70
  71   /* At this point the parent has a pending select with a DO_TIMEOUT timeout.
  72      We're going to interrupt by sending a signal */
  73   if(kill(getppid(), SIGUSR1) < 0) perror("Failed to send signal");
  74
  75   exit(0);
  76 }
  77
  78 void do_parent(int child) {
  79   fd_set fds_read;
  80   struct timeval tv, start_time, end_time;
  81   int retval;
  82
  83   /* Install signal handler for SIGUSR1 */
  84   signal(SIGUSR1, catch_signal);
  85
  86   /* Parent and child share an anonymous pipe. Select for read and wait for the
  87    timeout to occur. We wait for DO_PAUSE seconds. Let's see if that's
  88    approximately right.*/
  89   FD_ZERO(&fds_read);
  90   FD_SET(fd_ap[0], &fds_read);
  91   tv.tv_sec = DO_PAUSE;
  92   tv.tv_usec = 0;
  93
  94   (void) gettimeofday(&start_time, NULL);   /* Record starting time */
  95   retval = select(fd_ap[0]+1, &fds_read, NULL, NULL, &tv);
  96   (void) gettimeofday(&end_time, NULL);     /* Record ending time */
  97
  98   /* Did we time out? */
  99   if(retval != 0) e(1, "Should have timed out");
 100
 101   /* Approximately right? The standard does not specify how precise the timeout
 102      should be. Instead, the granularity is implementation-defined. In this
 103      test we assume that the difference should be no more than half a second.*/
 104   if(compute_diff(start_time, end_time, DO_PAUSE) > DO_DELTA)
 105     e(2, "Time difference too large");
 106
 107   /* Let's wait for another DO_PAUSE seconds, expressed as microseconds */
 108   FD_ZERO(&fds_read);
 109   FD_SET(fd_ap[0], &fds_read);
 110   tv.tv_sec = 0;
 111   tv.tv_usec = DO_PAUSE * 1000000L;
 112
 113   (void) gettimeofday(&start_time, NULL);   /* Record starting time */
 114   retval = select(fd_ap[0]+1, &fds_read, NULL, NULL, &tv);
 115   (void) gettimeofday(&end_time, NULL);     /* Record ending time */
 116
 117   if(retval != 0) e(3, "Should have timed out");
 118   if(compute_diff(start_time, end_time, DO_PAUSE) > DO_DELTA)
 119     e(4, "Time difference too large");
 120
 121   /* Let's wait for another DO_PAUSE seconds, expressed in seconds and micro
 122      seconds. */
 123   FD_ZERO(&fds_read);
 124   FD_SET(fd_ap[0], &fds_read);
 125   tv.tv_sec = DO_PAUSE - 1;
 126   tv.tv_usec = (DO_PAUSE - tv.tv_sec) * 1000000L;
 127
 128   (void) gettimeofday(&start_time, NULL);   /* Record starting time */
 129   retval = select(fd_ap[0]+1, &fds_read, NULL, NULL, &tv);
 130   (void) gettimeofday(&end_time, NULL);     /* Record ending time */
 131
 132   if(retval != 0) e(5, "Should have timed out");
 133   if(compute_diff(start_time, end_time, DO_PAUSE) > DO_DELTA)
 134     e(6, "Time difference too large");
 135
 136   /* Finally, we test if our timeout is interrupted by a signal */
 137   FD_ZERO(&fds_read);
 138   FD_SET(fd_ap[0], &fds_read);
 139   tv.tv_sec = DO_TIMEOUT;
 140   tv.tv_usec = 0;
 141
 142   (void) gettimeofday(&start_time, NULL);   /* Record starting time */
 143   retval = select(fd_ap[0]+1, &fds_read, NULL, NULL, &tv);
 144   (void) gettimeofday(&end_time, NULL);     /* Record ending time */
 145
 146   if(retval != -1) e(7, "Should have been interrupted");
 147   if(compute_diff(start_time, end_time, DO_TIMEOUT) < DO_DELTA)
 148     e(8, "Failed to get interrupted by a signal");
 149
 150   if(!got_signal) e(9, "Failed to get interrupted by a signal");
 151
 152   waitpid(child, &retval, 0);
 153   exit(errct);
 154 }
 155
 156 int main(int argc, char **argv) {
 157   int forkres;
 158
 159   /* Get subtest number */
 160   if(argc != 2) {
 161     printf("Usage: %s subtest_no\n", argv[0]);
 162     exit(-2);
 163   } else if(sscanf(argv[1], "%d", &subtest) != 1) {
 164     printf("Usage: %s subtest_no\n", argv[0]);
 165     exit(-2);
 166   }
 167
 168   /* Set up anonymous pipe */
 169   if(pipe(fd_ap) < 0) {
 170     perror("Could not create anonymous pipe");
 171     exit(-1);
 172   }
 173
 174   forkres = fork();
 175   if(forkres == 0) do_child();
 176   else if(forkres > 0)  do_parent(forkres);
 177   else { /* Fork failed */
 178     perror("Unable to fork");
 179     exit(-1);
 180   }
 181
 182   exit(-2); /* We're not supposed to get here. Both do_* routines should exit*/
 183
 184 }