+/* Demonstrate starvation of tdb_lockall */
+#include <ccan/tdb/tdb.h>
+#include <err.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <time.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/time.h>
+
+static void usage(const char *extra)
+{
+ errx(1, "%s%s"
+ "Usage: starvation [lockall|gradual] <num> <worktime-in-ms>\n"
+ " Each locker holds lock for between 1/2 and 1 1/2 times\n"
+ " worktime, then sleeps for one second.\n\n"
+ " Main process tries tdb_lockall or tdb_lockall_gradual.",
+ extra ? extra : "", extra ? "\n" : "");
+}
+
+static void run_and_sleep(struct tdb_context *tdb, int parentfd, unsigned time)
+{
+ char c;
+ struct timespec hold;
+ unsigned rand, randtime;
+ TDB_DATA key;
+
+ key.dptr = (void *)&rand;
+ key.dsize = sizeof(rand);
+
+ while (read(parentfd, &c, 1) != 0) {
+ /* Lock a random key. */
+ rand = random();
+ if (tdb_chainlock(tdb, key) != 0)
+ errx(1, "chainlock failed: %s", tdb_errorstr(tdb));
+
+ /* Hold it for some variable time. */
+ randtime = time / 2 + (random() % time);
+ hold.tv_sec = randtime / 1000;
+ hold.tv_nsec = (randtime % 1000) * 1000000;
+ nanosleep(&hold, NULL);
+
+ if (tdb_chainunlock(tdb, key) != 0)
+ errx(1, "chainunlock failed: %s", tdb_errorstr(tdb));
+
+ /* Wait for a second without the lock. */
+ sleep(1);
+ }
+ exit(0);
+}
+
+static void logfn(struct tdb_context *tdb,
+ enum tdb_debug_level level,
+ const char *fmt, ...)
+{
+ va_list ap;
+
+ va_start(ap, fmt);
+ vfprintf(stderr, fmt, ap);
+ va_end(ap);
+}
+
+int main(int argc, char *argv[])
+{
+ int (*lockall)(struct tdb_context *);
+ unsigned int num, worktime, i;
+ int pfd[2];
+ struct tdb_context *tdb;
+ struct tdb_logging_context log = { logfn, NULL };
+ struct timeval start, end, duration;
+
+ if (argc != 4)
+ usage(NULL);
+
+ if (strcmp(argv[1], "lockall") == 0)
+ lockall = tdb_lockall;
+ else if (strcmp(argv[1], "gradual") == 0)
+ lockall = tdb_lockall_gradual;
+ else
+ usage("Arg1 should be 'lockall' or 'gradual'");
+
+ num = atoi(argv[2]);
+ worktime = atoi(argv[3]);
+
+ if (!num || !worktime)
+ usage("Number of threads and worktime must be non-zero");
+
+ if (pipe(pfd) != 0)
+ err(1, "Creating pipe");
+
+ tdb = tdb_open_ex("/tmp/starvation.tdb", 10000, TDB_DEFAULT,
+ O_RDWR|O_CREAT|O_TRUNC, 0600, &log, NULL);
+ if (!tdb)
+ err(1, "Opening tdb /tmp/starvation.tdb");
+
+ for (i = 0; i < num; i++) {
+ switch (fork()) {
+ case 0:
+ close(pfd[1]);
+ fcntl(pfd[0], F_SETFL,
+ fcntl(pfd[0], F_GETFL)|O_NONBLOCK);
+ srandom(getpid() + i);
+ if (tdb_reopen(tdb) != 0)
+ err(1, "Reopening tdb %s", tdb_name(tdb));
+
+ run_and_sleep(tdb, pfd[0], worktime);
+ case -1:
+ err(1, "forking");
+ }
+ /* Stagger the children. */
+ usleep(random() % (1000000 / num));
+ }
+
+ close(pfd[0]);
+ sleep(1);
+ gettimeofday(&start, NULL);
+ if (lockall(tdb) != 0)
+ errx(1, "lockall failed: %s", tdb_errorstr(tdb));
+ gettimeofday(&end, NULL);
+
+ duration.tv_sec = end.tv_sec - start.tv_sec;
+ duration.tv_usec = end.tv_usec - start.tv_usec;
+ if (duration.tv_usec < 0) {
+ --duration.tv_sec;
+ duration.tv_usec += 1000000;
+ }
+
+ if (tdb_unlockall(tdb) != 0)
+ errx(1, "unlockall failed: %s", tdb_errorstr(tdb));
+ tdb_close(tdb);
+ unlink("/tmp/starvation.tdb");
+
+ printf("Took %lu.%06lu seconds\n", duration.tv_sec, duration.tv_usec);
+ return 0;
+}
projects / ccan / commitdiff