Neaten tdb to sync with samba version of locking fix.

Also, actually test locking, rather than just lock count (bit me in samba fix)

ccan/tdb/lock.c

@@ -304,17 +304,18 @@ int tdb_transaction_lock(struct tdb_context *tdb, int ltype)
 	if (tdb->global_lock.count) {
 		return 0;
 	}
-	if (tdb->have_transaction_lock) {
-		tdb->have_transaction_lock++;
+	if (tdb->transaction_lock_count > 0) {
+		tdb->transaction_lock_count++;
 		return 0;
 	}
+
 	if (tdb->methods->tdb_brlock(tdb, TRANSACTION_LOCK, ltype, 
 				     F_SETLKW, 0, 1) == -1) {
 		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_lock: failed to get transaction lock\n"));
 		tdb->ecode = TDB_ERR_LOCK;
 		return -1;
 	}
-	tdb->have_transaction_lock++;
+	tdb->transaction_lock_count++;
 	return 0;
 }
 
@@ -323,13 +324,19 @@ int tdb_transaction_lock(struct tdb_context *tdb, int ltype)
  */
 int tdb_transaction_unlock(struct tdb_context *tdb)
 {
+	int ret;
 	if (tdb->global_lock.count) {
 		return 0;
 	}
-	if (--tdb->have_transaction_lock) {
+	if (tdb->transaction_lock_count > 1) {
+		tdb->transaction_lock_count--;
 		return 0;
 	}
-	return tdb->methods->tdb_brlock(tdb, TRANSACTION_LOCK, F_UNLCK, F_SETLKW, 0, 1);
+	ret = tdb->methods->tdb_brlock(tdb, TRANSACTION_LOCK, F_UNLCK, F_SETLKW, 0, 1);
+	if (ret == 0) {
+		tdb->transaction_lock_count = 0;
+	}
+	return ret;
 }
 
 

ccan/tdb/tdb_private.h

@@ -215,7 +215,7 @@ struct tdb_context {
 	struct tdb_transaction *transaction;
 	int page_size;
 	int max_dead_records;
-	int have_transaction_lock;
+	int transaction_lock_count;
 	int tracefd;
 	volatile sig_atomic_t *interrupt_sig_ptr;
 };

ccan/tdb/test/external-transaction.c

@@ -0,0 +1,107 @@
+#include "external-transaction.h"
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <err.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <limits.h>
+#include <string.h>
+#include <ccan/tdb/tdb.h>
+
+static volatile sig_atomic_t alarmed;
+static void do_alarm(int signum)
+{
+	alarmed++;
+}
+
+static int do_transaction(const char *name)
+{
+	TDB_DATA k = { .dptr = (void *)"a", .dsize = 1 };
+	TDB_DATA d = { .dptr = (void *)"b", .dsize = 1 };
+	struct tdb_context *tdb = tdb_open(name, 0, 0, O_RDWR, 0);
+
+	if (!tdb)
+		return -1;
+
+	alarmed = 0;
+	tdb_setalarm_sigptr(tdb, &alarmed);
+
+	alarm(1);
+	if (tdb_transaction_start(tdb) != 0)
+		goto maybe_alarmed;
+
+	if (tdb_store(tdb, k, d, 0) != 0) {
+		tdb_transaction_cancel(tdb);
+		tdb_close(tdb);
+		return -2;
+	}
+
+	if (tdb_transaction_commit(tdb) == 0) {
+		tdb_delete(tdb, k);
+		tdb_close(tdb);
+		return 1;
+	}
+
+	tdb_delete(tdb, k);
+maybe_alarmed:
+	tdb_close(tdb);
+	if (alarmed)
+		return 0;
+	return -3;
+}
+
+
+/* Do this before doing any tdb stuff.  Return handle, or -1. */
+int prepare_external_agent(void)
+{
+	int pid;
+	int command[2], response[2];
+	struct sigaction act = { .sa_handler = do_alarm };
+	char name[PATH_MAX];
+
+	if (pipe(command) != 0 || pipe(response) != 0)
+		return -1;
+
+	pid = fork();
+	if (pid < 0)
+		return -1;
+
+	if (pid != 0) {
+		close(command[0]);
+		close(response[1]);
+		/* FIXME: Make fds consective. */
+		dup2(command[1]+1, response[1]);
+		return command[1];
+	}
+
+	close(command[1]);
+	close(response[0]);
+	sigaction(SIGALRM, &act, NULL);
+
+	while (read(command[0], name, sizeof(name)) != 0) {
+		int result = do_transaction(name);
+		if (write(response[1], &result, sizeof(result))
+		    != sizeof(result))
+			err(1, "Writing response");
+	}
+	exit(0);
+}
+
+/* Ask the external agent to try to do a transaction. */
+bool external_agent_transaction(int handle, const char *tdbname)
+{
+	int res;
+
+	if (write(handle, tdbname, strlen(tdbname)+1)
+	    != strlen(tdbname)+1)
+		err(1, "Writing to agent");
+
+	if (read(handle+1, &res, sizeof(res)) != sizeof(res))
+		err(1, "Reading from agent");
+
+	if (res > 1)
+		errx(1, "Agent returned %u\n", res);
+
+	return res;
+}

ccan/tdb/test/external-transaction.h

@@ -0,0 +1,11 @@
+#ifndef TDB_TEST_EXTERNAL_TRANSACTION_H
+#define TDB_TEST_EXTERNAL_TRANSACTION_H
+#include <stdbool.h>
+
+/* Do this before doing any tdb stuff.  Return handle, or -1. */
+int prepare_external_agent(void);
+
+/* Ask the external agent to try to do a transaction. */
+bool external_agent_transaction(int handle, const char *tdbname);
+
+#endif /* TDB_TEST_EXTERNAL_TRANSACTION_H */

ccan/tdb/test/run-nested-traverse.c

@@ -12,6 +12,9 @@
 #include <stdlib.h>
 #include <stdbool.h>
 #include <err.h>
+#include "external-transaction.h"
+
+static int agent;
 
 static bool correct_key(TDB_DATA key)
 {
@@ -38,11 +41,11 @@ static int traverse1(struct tdb_context *tdb, TDB_DATA key, TDB_DATA data,
 {
 	ok1(correct_key(key));
 	ok1(correct_data(data));
-	ok1(tdb->have_transaction_lock);
+	ok1(!external_agent_transaction(agent, tdb_name(tdb)));
 	tdb_traverse(tdb, traverse2, NULL);
 
 	/* That should *not* release the transaction lock! */
-	ok1(tdb->have_transaction_lock);
+	ok1(!external_agent_transaction(agent, tdb_name(tdb)));
 	return 0;
 }
 
@@ -51,12 +54,17 @@ int main(int argc, char *argv[])
 	struct tdb_context *tdb;
 	TDB_DATA key, data;
 
-	plan_tests(14);
-	tdb = tdb_open("/tmp/test.tdb", 1024, TDB_CLEAR_IF_FIRST,
+	plan_tests(15);
+	agent = prepare_external_agent();
+	if (agent < 0)
+		err(1, "preparing agent");
+
+	tdb = tdb_open("/tmp/test3.tdb", 1024, TDB_CLEAR_IF_FIRST,
 		       O_CREAT|O_TRUNC|O_RDWR, 0600);
 	ok1(tdb);
 
-	/* Tickle bug on appending zero length buffer to zero length buffer. */
+	ok1(external_agent_transaction(agent, tdb_name(tdb)));
+
 	key.dsize = strlen("hi");
 	key.dptr = (void *)"hi";
 	data.dptr = (void *)"world";

ccan/tdb/test/run-traverse-in-transaction.c

@@ -12,6 +12,9 @@
 #include <stdlib.h>
 #include <stdbool.h>
 #include <err.h>
+#include "external-transaction.h"
+
+static int agent;
 
 static bool correct_key(TDB_DATA key)
 {
@@ -38,12 +41,15 @@ int main(int argc, char *argv[])
 	struct tdb_context *tdb;
 	TDB_DATA key, data;
 
-	plan_tests(12);
-	tdb = tdb_open("/tmp/test.tdb", 1024, TDB_CLEAR_IF_FIRST,
+	plan_tests(13);
+	agent = prepare_external_agent();
+	if (agent < 0)
+		err(1, "preparing agent");
+
+	tdb = tdb_open("/tmp/test2.tdb", 1024, TDB_CLEAR_IF_FIRST,
 		       O_CREAT|O_TRUNC|O_RDWR, 0600);
 	ok1(tdb);
 
-	/* Tickle bug on appending zero length buffer to zero length buffer. */
 	key.dsize = strlen("hi");
 	key.dptr = (void *)"hi";
 	data.dptr = (void *)"world";
@@ -51,18 +57,21 @@ int main(int argc, char *argv[])
 
 	ok1(tdb_store(tdb, key, data, TDB_INSERT) == 0);
 
+	ok1(external_agent_transaction(agent, tdb_name(tdb)));
+
 	ok1(tdb_transaction_start(tdb) == 0);
-	ok(tdb->have_transaction_lock, "Transaction lock in transaction");
+	ok1(!external_agent_transaction(agent, tdb_name(tdb)));
 	tdb_traverse(tdb, traverse, NULL);
 
 	/* That should *not* release the transaction lock! */
-	ok(tdb->have_transaction_lock, "Transaction lock after traverse");
+	ok1(!external_agent_transaction(agent, tdb_name(tdb)));
 	tdb_traverse_read(tdb, traverse, NULL);
 
 	/* That should *not* release the transaction lock! */
-	ok(tdb->have_transaction_lock, "Transaction lock after traverse_read");
+	ok1(!external_agent_transaction(agent, tdb_name(tdb)));
 	ok1(tdb_transaction_commit(tdb) == 0);
-	ok(!tdb->have_transaction_lock, "Transaction unlock");
+	/* Now we should be fine. */
+	ok1(external_agent_transaction(agent, tdb_name(tdb)));
 
 	tdb_close(tdb);