dbwrap_watch: Don't alert ourselves, fix raw.oplock.batch26 race

This fixes the following flaky test:

UNEXPECTED(failure): samba3.raw.oplock.batch26(nt4_dc)
REASON: Exception: Exception: (../../source4/torture/raw/oplock.c:3718): wrong value for break_info.count got 0x2 - should be 0x1

You can reproduce it with two small msleeps, which means it's a race
condition:

diff --git a/source3/smbd/open.c b/source3/smbd/open.c
index 20b5a3e294c..126c7fc021d 100644
--- a/source3/smbd/open.c
+++ b/source3/smbd/open.c
@@ -1917,6 +1917,14 @@ NTSTATUS send_break_message(struct messaging_context *msg_ctx,
 	DATA_BLOB blob;
 	NTSTATUS status;

+	{
+		static bool sent = false;
+		if (sent) {
+			smb_msleep(500);
+		}
+		sent = true;
+	}
+
 	if (DEBUGLVL(10)) {
 		struct server_id_buf buf;
 		DBG_DEBUG("Sending break message to %s\n",
diff --git a/source3/smbd/oplock.c b/source3/smbd/oplock.c
index b3da84b1269..d9c4dbb9487 100644
--- a/source3/smbd/oplock.c
+++ b/source3/smbd/oplock.c
@@ -858,6 +858,8 @@ static void process_oplock_break_message(struct messaging_context *msg_ctx,
 	uint16_t break_to;
 	bool break_needed = true;

+	smb_msleep(100);
+
 	msg = talloc(talloc_tos(), struct oplock_break_message);
 	if (msg == NULL) {
 		DBG_WARNING("talloc failed\n");

15a8af075a2 introduced a bug where we immediately wake up ourselves
after doing a watch_send, leading to two inter-smbd oplock break
messages for this case. In theory, this should not matter, as in the
oplock break handler in the destination smbd we check

(fsp->sent_oplock_break != NO_BREAK_SENT)

so that the break does not get sent twice. However, with the above two
sleeps the oplock holding client could send out its oplock downgrade
while the second inter-smbd break messages was on its way.

The real fix would be to note in the share mode array that the
inter-smbd message has already been sent, but as other users of
dbwrap_watched_watch_send might also be affected by this bug, this fix
should be sufficient to get rid of this flaky test.

Unfortunately, dbwrap_watch.c is now pretty complex and needs some
serious refactoring to become understandable again. But that's
something for another day, sorry.

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>

0 files changed, 0 insertions, 0 deletions