totally rewrote the async signal, notification and oplock notification

handling in Samba. This was needed due to several limitations and
races in the previous code - as a side effect the new code is much
cleaner :)

in summary:

- changed sys_select() to avoid a signal/select race condition. It is a
  rare race but once we have signals doing notification and oplocks it
  is important.

- changed our main processing loop to take advantage of the new
  sys_select semantics

- split the notify code into implementaion dependent and general
  parts. Added the following structure that defines an implementation:

struct cnotify_fns {
	void * (*register_notify)(connection_struct *conn, char *path, uint32 flags);
	BOOL (*check_notify)(connection_struct *conn, uint16 vuid, char *path, uint32 flags, void *data, time_t t);
	void (*remove_notify)(void *data);
};


then I wrote two implementations, one using hash/poll (like our old
code) and the other using the new Linux kernel change notify. It
should be easy to add other change notify implementations by creating
a sructure of the above type.

- fixed a bug in change notify where we were returning the wrong error
  code.

- rewrote the core change notify code to be much simpler

- moved to real-time signals for leases and change notify

Amazingly, it all seems to work. I was very surprised!
(This used to be commit 44766c39e0027c762bee8b33b12c621c109a3267)

1 files changed, 17 insertions, 12 deletions

diff --git a/source3/smbd/oplock_linux.c b/source3/smbd/oplock_linux.c
index 46290683d2..de2a4300a7 100644
--- a/source3/smbd/oplock_linux.c
+++ b/source3/smbd/oplock_linux.c
@@ -29,7 +29,7 @@ extern int DEBUGLEVEL;
 
 static unsigned signals_received;
 static unsigned signals_processed;
-static int fd_pending; /* the fd of the current pending SIGIO */
+static int fd_pending; /* the fd of the current pending signal */
 
 #ifndef F_SETLEASE
 #define F_SETLEASE	1024
@@ -43,14 +43,19 @@ static int fd_pending; /* the fd of the current pending SIGIO */
 #define CAP_LEASE 28
 #endif
 
+#ifndef RT_SIGNAL_LEASE
+#define RT_SIGNAL_LEASE 33
+#endif
+
 /****************************************************************************
-handle a SIGIO, incrementing the signals_received and blocking SIGIO
+handle a LEASE signal, incrementing the signals_received and blocking the signal
 ****************************************************************************/
-static void sigio_handler(int signal, siginfo_t *info, void *unused)
+static void signal_handler(int signal, siginfo_t *info, void *unused)
 {
+	BlockSignals(True, signal);
 	fd_pending = info->si_fd;
 	signals_received++;
-	BlockSignals(True, SIGIO);
+	sys_select_signal();
 }
 
 /****************************************************************************
@@ -150,7 +155,7 @@ dev = %x, inode = %.0f\n", (unsigned int)dev, (double)inode ));
 	/* now we can receive more signals */
 	fd_pending = -1;
 	signals_processed++;
-	BlockSignals(False, SIGIO);
+	BlockSignals(False, RT_SIGNAL_LEASE);
      
 	return True;
 }
@@ -213,16 +218,16 @@ static BOOL linux_kernel_oplock_parse(char *msg_start, int msg_len, SMB_INO_T *i
 {
 	/* Ensure that the msg length is correct. */
 	if (msg_len != KERNEL_OPLOCK_BREAK_MSG_LEN) {
-		DEBUG(0,("process_local_message: incorrect length for KERNEL_OPLOCK_BREAK_CMD (was %d, \
-should be %d).\n", msg_len, KERNEL_OPLOCK_BREAK_MSG_LEN));
+		DEBUG(0,("incorrect length for KERNEL_OPLOCK_BREAK_CMD (was %d, should be %d).\n", 
+			 msg_len, KERNEL_OPLOCK_BREAK_MSG_LEN));
 		return False;
 	}
 
         memcpy((char *)inode, msg_start+KERNEL_OPLOCK_BREAK_INODE_OFFSET, sizeof(*inode));
         memcpy((char *)dev, msg_start+KERNEL_OPLOCK_BREAK_DEV_OFFSET, sizeof(*dev));
 
-        DEBUG(5,("process_local_message: kernel oplock break request for \
-file dev = %x, inode = %.0f\n", (unsigned int)*dev, (double)*inode));
+        DEBUG(5,("kernel oplock break request for file dev = %x, inode = %.0f\n", 
+		 (unsigned int)*dev, (double)*inode));
 
 	return True;
 }
@@ -264,10 +269,10 @@ struct kernel_oplocks *linux_init_kernel_oplocks(void)
 	}
 
         act.sa_handler = NULL;
-        act.sa_sigaction = sigio_handler;
+        act.sa_sigaction = signal_handler;
         act.sa_flags = SA_SIGINFO;
-        if (sigaction(SIGIO, &act, NULL) != 0) {
-		DEBUG(0,("Failed to setup SIGIO handler\n"));
+        if (sigaction(RT_SIGNAL_LEASE, &act, NULL) != 0) {
+		DEBUG(0,("Failed to setup RT_SIGNAL_LEASE handler\n"));
 		return NULL;
         }