Fix for interesting resource constraint condition. When all opens are

level 2 and a request for open with no oplock is received then the
smbd should send *synchronous* break messages, not asynchronous,
otherwise it spins very rapidly, releasing the lock, sending the
'break to none' messages and then re-acquiring the lock before
any other process has a chance to get the lock and remove it's own
oplock (at least on linux).
Jeremy.
(This used to be commit d1e8991a76a57b7d96dd7db3c1d9bbf5b28da88e)

3 files changed, 22 insertions, 17 deletions

diff --git a/source3/include/smb.h b/source3/include/smb.h
index 3ca8d32289..8138555539 100644
--- a/source3/include/smb.h
+++ b/source3/include/smb.h
@@ -1512,15 +1512,17 @@ extern int chain_size;
  *  +----+--------+-------+--------+---------+
  */
 
-#define OPLOCK_BREAK_CMD 0x1
 #define OPLOCK_BREAK_PID_OFFSET 2
 #define OPLOCK_BREAK_DEV_OFFSET (OPLOCK_BREAK_PID_OFFSET + sizeof(pid_t))
 #define OPLOCK_BREAK_INODE_OFFSET (OPLOCK_BREAK_DEV_OFFSET + sizeof(SMB_DEV_T))
 #define OPLOCK_BREAK_FILEID_OFFSET (OPLOCK_BREAK_INODE_OFFSET + sizeof(SMB_INO_T))
 #define OPLOCK_BREAK_MSG_LEN (OPLOCK_BREAK_FILEID_OFFSET + sizeof(unsigned long))
 
+/* Message types */
+#define OPLOCK_BREAK_CMD 0x1
 #define KERNEL_OPLOCK_BREAK_CMD 0x2
 #define LEVEL_II_OPLOCK_BREAK_CMD 0x3
+#define ASYNC_LEVEL_II_OPLOCK_BREAK_CMD 0x4
 
 /*
  * Capabilities abstracted for different systems.
diff --git a/source3/smbd/open.c b/source3/smbd/open.c
index 5c3359fc6b..29048bca02 100644
--- a/source3/smbd/open.c
+++ b/source3/smbd/open.c
@@ -585,7 +585,7 @@ dev = %x, inode = %.0f\n", *p_oplock_request, share_entry->op_type, fname, (unsi
 				/* Oplock break - unlock to request it. */
 				unlock_share_entry(conn, dev, inode);
 				
-				opb_ret = request_oplock_break(share_entry);
+				opb_ret = request_oplock_break(share_entry, False);
 				
 				/* Now relock. */
 				lock_share_entry(conn, dev, inode);
diff --git a/source3/smbd/oplock.c b/source3/smbd/oplock.c
index 14b243b36e..f5c19bcf62 100644
--- a/source3/smbd/oplock.c
+++ b/source3/smbd/oplock.c
@@ -368,6 +368,7 @@ BOOL process_local_message(char *buffer, int buf_size)
 
 		case OPLOCK_BREAK_CMD:
 		case LEVEL_II_OPLOCK_BREAK_CMD:
+		case ASYNC_LEVEL_II_OPLOCK_BREAK_CMD:
 
 			/* Ensure that the msg length is correct. */
 			if(msg_len != OPLOCK_BREAK_MSG_LEN) {
@@ -438,14 +439,14 @@ oplocks. Returning success.\n"));
 	}
 
 	/* 
-	 * Do the appropriate reply - none in the kernel or level II case.
+	 * Do the appropriate reply - none in the kernel or async level II case.
 	 */
 
-	if(SVAL(msg_start,OPBRK_MESSAGE_CMD_OFFSET) == OPLOCK_BREAK_CMD) {
+	if(break_cmd_type == OPLOCK_BREAK_CMD || break_cmd_type == LEVEL_II_OPLOCK_BREAK_CMD) {
 		struct sockaddr_in toaddr;
 
 		/* Send the message back after OR'ing in the 'REPLY' bit. */
-		SSVAL(msg_start,OPBRK_MESSAGE_CMD_OFFSET,OPLOCK_BREAK_CMD | CMD_REPLY);
+		SSVAL(msg_start,OPBRK_MESSAGE_CMD_OFFSET,break_cmd_type | CMD_REPLY);
 
 		memset((char *)&toaddr,'\0',sizeof(toaddr));
 		toaddr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
@@ -902,7 +903,7 @@ Send an oplock break message to another smbd process. If the oplock is held
 by the local smbd then call the oplock break function directly.
 ****************************************************************************/
 
-BOOL request_oplock_break(share_mode_entry *share_entry)
+BOOL request_oplock_break(share_mode_entry *share_entry, BOOL async)
 {
 	char op_break_msg[OPLOCK_BREAK_MSG_LEN];
 	struct sockaddr_in addr_out;
@@ -912,6 +913,7 @@ BOOL request_oplock_break(share_mode_entry *share_entry)
 	SMB_DEV_T dev = share_entry->dev;
 	SMB_INO_T inode = share_entry->inode;
 	unsigned long file_id = share_entry->share_file_id;
+	uint16 break_cmd_type;
 
 	if(pid == share_entry->pid) {
 		/* We are breaking our own oplock, make sure it's us. */
@@ -942,11 +944,12 @@ dev = %x, inode = %.0f, file_id = %lu and no fsp found !\n",
 	/* We need to send a OPLOCK_BREAK_CMD message to the port in the share mode entry. */
 
 	if (LEVEL_II_OPLOCK_TYPE(share_entry->op_type)) {
-		SSVAL(op_break_msg,OPBRK_MESSAGE_CMD_OFFSET,LEVEL_II_OPLOCK_BREAK_CMD);
+		break_cmd_type = async ? ASYNC_LEVEL_II_OPLOCK_BREAK_CMD : LEVEL_II_OPLOCK_BREAK_CMD;
 	} else {
-		SSVAL(op_break_msg,OPBRK_MESSAGE_CMD_OFFSET,OPLOCK_BREAK_CMD);
+		break_cmd_type = OPLOCK_BREAK_CMD;
 	}
 
+	SSVAL(op_break_msg,OPBRK_MESSAGE_CMD_OFFSET,break_cmd_type);
 	memcpy(op_break_msg+OPLOCK_BREAK_PID_OFFSET,(char *)&pid,sizeof(pid));
 	memcpy(op_break_msg+OPLOCK_BREAK_DEV_OFFSET,(char *)&dev,sizeof(dev));
 	memcpy(op_break_msg+OPLOCK_BREAK_INODE_OFFSET,(char *)&inode,sizeof(inode));
@@ -959,7 +962,7 @@ dev = %x, inode = %.0f, file_id = %lu and no fsp found !\n",
 	addr_out.sin_family = AF_INET;
    
 	if( DEBUGLVL( 3 ) ) {
-		dbgtext( "request_oplock_break: sending a oplock break message to " );
+		dbgtext( "request_oplock_break: sending a %s oplock break message to ", async ? "asynchronous" : "synchronous" );
 		dbgtext( "pid %d on port %d ", (int)share_entry->pid, share_entry->op_port );
 		dbgtext( "for dev = %x, inode = %.0f, file_id = %lu\n",
             (unsigned int)dev, (double)inode, file_id );
@@ -972,19 +975,19 @@ dev = %x, inode = %.0f, file_id = %lu and no fsp found !\n",
 			dbgtext( "break message to pid %d ", (int)share_entry->pid );
 			dbgtext( "on port %d ", share_entry->op_port );
 			dbgtext( "for dev = %x, inode = %.0f, file_id = %lu\n",
-          (unsigned int)dev, (double)inode, file_id );
+				(unsigned int)dev, (double)inode, file_id );
 			dbgtext( "Error was %s\n", strerror(errno) );
 		}
 		return False;
 	}
 
 	/*
-	 * If we just sent a message to a level II oplock share entry then
+	 * If we just sent a message to a level II oplock share entry in async mode then
 	 * we are done and may return.
 	 */
 
-	if (LEVEL_II_OPLOCK_TYPE(share_entry->op_type)) {
-		DEBUG(3,("request_oplock_break: sent break message to level II entry.\n"));
+	if (LEVEL_II_OPLOCK_TYPE(share_entry->op_type) && async) {
+		DEBUG(3,("request_oplock_break: sent async break message to level II entry.\n"));
 		return True;
 	}
 
@@ -1039,10 +1042,10 @@ dev = %x, inode = %.0f, file_id = %lu and no fsp found !\n",
 		reply_msg_start = &op_break_reply[OPBRK_CMD_HEADER_LEN];
 
 		/*
-		 * Test to see if this is the reply we are awaiting.
+		 * Test to see if this is the reply we are awaiting (ie. the one we sent with the CMD_REPLY flag OR'ed in).
 		 */
 		if((SVAL(reply_msg_start,OPBRK_MESSAGE_CMD_OFFSET) & CMD_REPLY) &&
-			((SVAL(reply_msg_start,OPBRK_MESSAGE_CMD_OFFSET) & ~CMD_REPLY) == OPLOCK_BREAK_CMD) &&
+			((SVAL(reply_msg_start,OPBRK_MESSAGE_CMD_OFFSET) & ~CMD_REPLY) == break_cmd_type) &&
 			(reply_from_port == share_entry->op_port) && 
 			(memcmp(&reply_msg_start[OPLOCK_BREAK_PID_OFFSET], &op_break_msg[OPLOCK_BREAK_PID_OFFSET],
 				OPLOCK_BREAK_MSG_LEN - OPLOCK_BREAK_PID_OFFSET) == 0)) {
@@ -1185,8 +1188,8 @@ void release_level_2_oplocks_on_change(files_struct *fsp)
 			 * message.
 			 */
 
-			DEBUG(10,("release_level_2_oplocks_on_change: breaking remote oplock.\n"));
-			request_oplock_break(share_entry);
+			DEBUG(10,("release_level_2_oplocks_on_change: breaking remote oplock (async).\n"));
+			request_oplock_break(share_entry, True);
 		}
 	}