git.ozlabs.org Git - ccan/blob - ccan/tdb/tools/starvation.c

   1 /* Demonstrate starvation of tdb_lockall */
   2 #include <ccan/tdb/tdb.h>
   3 #include <err.h>
   4 #include <unistd.h>
   5 #include <fcntl.h>
   6 #include <time.h>
   7 #include <stdlib.h>
   8 #include <stdbool.h>
   9 #include <stdarg.h>
  10 #include <stdio.h>
  11 #include <string.h>
  12 #include <sys/time.h>
  13
  14 static void usage(const char *extra)
  15 {
  16         errx(1, "%s%s"
  17              "Usage: starvation [lockall|gradual] <num> <worktime-in-ms>\n"
  18              "  Each locker holds lock for between 1/2 and 1 1/2 times\n"
  19              "  worktime, then sleeps for one second.\n\n"
  20              "  Main process tries tdb_lockall or tdb_lockall_gradual.",
  21              extra ? extra : "", extra ? "\n" : "");
  22 }
  23
  24 static void run_and_sleep(struct tdb_context *tdb, int parentfd, unsigned time)
  25 {
  26         char c;
  27         struct timespec hold;
  28         unsigned rand, randtime;
  29         TDB_DATA key;
  30
  31         key.dptr = (void *)&rand;
  32         key.dsize = sizeof(rand);
  33
  34         while (read(parentfd, &c, 1) != 0) {
  35                 /* Lock a random key. */
  36                 rand = random();
  37                 if (tdb_chainlock(tdb, key) != 0)
  38                         errx(1, "chainlock failed: %s", tdb_errorstr(tdb));
  39
  40                 /* Hold it for some variable time. */
  41                 randtime = time / 2 + (random() % time);
  42                 hold.tv_sec = randtime / 1000;
  43                 hold.tv_nsec = (randtime % 1000) * 1000000;
  44                 nanosleep(&hold, NULL);
  45
  46                 if (tdb_chainunlock(tdb, key) != 0)
  47                         errx(1, "chainunlock failed: %s", tdb_errorstr(tdb));
  48
  49                 /* Wait for a second without the lock. */
  50                 sleep(1);
  51         }
  52         exit(0);
  53 }
  54
  55 static void logfn(struct tdb_context *tdb,
  56                   enum tdb_debug_level level,
  57                   const char *fmt, ...)
  58 {
  59            va_list ap;
  60
  61            va_start(ap, fmt);
  62            vfprintf(stderr, fmt, ap);
  63            va_end(ap);
  64 }
  65
  66 int main(int argc, char *argv[])
  67 {
  68         int (*lockall)(struct tdb_context *);
  69         unsigned int num, worktime, i;
  70         int pfd[2];
  71         struct tdb_context *tdb;
  72         struct tdb_logging_context log = { logfn, NULL };
  73         struct timeval start, end, duration;
  74
  75         if (argc != 4)
  76                 usage(NULL);
  77
  78         if (strcmp(argv[1], "lockall") == 0)
  79                 lockall = tdb_lockall;
  80         else if (strcmp(argv[1], "gradual") == 0)
  81                 lockall = tdb_lockall_gradual;
  82         else
  83                 usage("Arg1 should be 'lockall' or 'gradual'");
  84
  85         num = atoi(argv[2]);
  86         worktime = atoi(argv[3]);
  87
  88         if (!num || !worktime)
  89                 usage("Number of threads and worktime must be non-zero");
  90
  91         if (pipe(pfd) != 0)
  92                 err(1, "Creating pipe");
  93
  94         tdb = tdb_open_ex("/tmp/starvation.tdb", 10000, TDB_DEFAULT,
  95                           O_RDWR|O_CREAT|O_TRUNC, 0600, &log, NULL);
  96         if (!tdb)
  97                 err(1, "Opening tdb /tmp/starvation.tdb");
  98
  99         for (i = 0; i < num; i++) {
 100                 switch (fork()) {
 101                 case 0:
 102                         close(pfd[1]);
 103                         fcntl(pfd[0], F_SETFL,
 104                               fcntl(pfd[0], F_GETFL)|O_NONBLOCK);
 105                         srandom(getpid() + i);
 106                         if (tdb_reopen(tdb) != 0)
 107                                 err(1, "Reopening tdb %s", tdb_name(tdb));
 108
 109                         run_and_sleep(tdb, pfd[0], worktime);
 110                 case -1:
 111                         err(1, "forking");
 112                 }
 113                 /* Stagger the children. */
 114                 usleep(random() % (1000000 / num));
 115         }
 116
 117         close(pfd[0]);
 118         sleep(1);
 119         gettimeofday(&start, NULL);
 120         if (lockall(tdb) != 0)
 121                 errx(1, "lockall failed: %s", tdb_errorstr(tdb));
 122         gettimeofday(&end, NULL);
 123
 124         duration.tv_sec = end.tv_sec - start.tv_sec;
 125         duration.tv_usec = end.tv_usec - start.tv_usec;
 126         if (duration.tv_usec < 0) {
 127                 --duration.tv_sec;
 128                 duration.tv_usec += 1000000;
 129         }
 130
 131         if (tdb_unlockall(tdb) != 0)
 132                 errx(1, "unlockall failed: %s", tdb_errorstr(tdb));
 133         tdb_close(tdb);
 134         unlink("/tmp/starvation.tdb");
 135
 136         printf("Took %lu.%06lu seconds\n", duration.tv_sec, duration.tv_usec);
 137         return 0;
 138 }