X-Git-Url: https://git.ozlabs.org/?p=ccan;a=blobdiff_plain;f=ccan%2Ftdb%2Ftools%2Fstarvation.c;fp=ccan%2Ftdb%2Ftools%2Fstarvation.c;h=5f8c23d1b9a50d4b423c86b3a74d03933b76b855;hp=0000000000000000000000000000000000000000;hb=ee9f03894bdeedc4888ff3cd2ddae083e1b65d96;hpb=bb4b8b6b32f34faf27b1c8e2b380f2df84810693

diff --git a/ccan/tdb/tools/starvation.c b/ccan/tdb/tools/starvation.c
new file mode 100644
index 00000000..5f8c23d1
--- /dev/null
+++ b/ccan/tdb/tools/starvation.c
@@ -0,0 +1,138 @@
+/* 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;
+}