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)

2 files changed, 4 insertions, 109 deletions

diff --git a/source3/lib/debug.c b/source3/lib/debug.c
index 675c2d8cfc..a388956d42 100644
--- a/source3/lib/debug.c
+++ b/source3/lib/debug.c
@@ -132,6 +132,8 @@ void sig_usr2( int sig )
 
   DEBUG( 0, ( "Got SIGUSR2; set debug level to %d.\n", DEBUGLEVEL ) );
 
+  sys_select_signal();
+
 #if !defined(HAVE_SIGACTION)
   CatchSignal( SIGUSR2, SIGNAL_CAST sig_usr2 );
 #endif
@@ -154,6 +156,8 @@ void sig_usr1( int sig )
 
   DEBUG( 0, ( "Got SIGUSR1; set debug level to %d.\n", DEBUGLEVEL ) );
 
+  sys_select_signal();
+
 #if !defined(HAVE_SIGACTION)
   CatchSignal( SIGUSR1, SIGNAL_CAST sig_usr1 );
 #endif
diff --git a/source3/lib/system.c b/source3/lib/system.c
index 46b01b747a..479bce1965 100644
--- a/source3/lib/system.c
+++ b/source3/lib/system.c
@@ -39,115 +39,6 @@ extern int DEBUGLEVEL;
 */
 
 
-/*******************************************************************
-this replaces the normal select() system call
-return if some data has arrived on one of the file descriptors
-return -1 means error
-********************************************************************/
-#ifndef HAVE_SELECT
-static int pollfd(int fd)
-{
-  int     r=0;
-
-#ifdef HAS_RDCHK
-  r = rdchk(fd);
-#elif defined(TCRDCHK)
-  (void)ioctl(fd, TCRDCHK, &r);
-#else
-  (void)ioctl(fd, FIONREAD, &r);
-#endif
-
-  return(r);
-}
-
-int sys_select(int maxfd, fd_set *fds,struct timeval *tval)
-{
-  fd_set fds2;
-  int counter=0;
-  int found=0;
-
-  FD_ZERO(&fds2);
-
-  while (1) 
-  {
-    int i;
-    for (i=0;i<maxfd;i++) {
-      if (FD_ISSET(i,fds) && pollfd(i)>0) {
-        found++;
-        FD_SET(i,&fds2);
-      }
-    }
-
-    if (found) {
-      memcpy((void *)fds,(void *)&fds2,sizeof(fds2));
-      return(found);
-    }
-      
-    if (tval && tval->tv_sec < counter) return(0);
-      sleep(1);
-      counter++;
-  }
-}
-
-#else /* !NO_SELECT */
-int sys_select(int maxfd, fd_set *fds,struct timeval *tval)
-{
-#ifdef USE_POLL
-  struct pollfd pfd[256];
-  int i;
-  int maxpoll;
-  int timeout;
-  int pollrtn;
-
-  maxpoll = 0;
-  for( i = 0; i < maxfd; i++) {
-    if(FD_ISSET(i,fds)) {
-      struct pollfd *pfdp = &pfd[maxpoll++];
-      pfdp->fd = i;
-      pfdp->events = POLLIN;
-      pfdp->revents = 0;
-    }
-  }
-
-  timeout = (tval != NULL) ? (tval->tv_sec * 1000) + (tval->tv_usec/1000) :
-                -1;
-  errno = 0;
-  pollrtn = poll( &pfd[0], maxpoll, timeout);
-
-  FD_ZERO(fds);
-
-  for( i = 0; i < maxpoll; i++)
-    if( pfd[i].revents & POLLIN )
-      FD_SET(pfd[i].fd,fds);
-
-  return pollrtn;
-#else /* USE_POLL */
-
-  struct timeval t2;
-  int selrtn;
-
-  if (tval) memcpy((void *)&t2,(void *)tval,sizeof(t2));
-  errno = 0;
-  selrtn = select(maxfd,SELECT_CAST fds,NULL,NULL,tval?&t2:NULL);
-
-  return(selrtn);
-}
-#endif /* USE_POLL */
-#endif /* NO_SELECT */
-
-/*******************************************************************
-similar to sys_select() but catch EINTR and continue
-this is what sys_select() used to do in Samba
-********************************************************************/
-int sys_select_intr(int maxfd, fd_set *fds,struct timeval *tval)
-{
-	int ret;
-	do {
-		ret = sys_select(maxfd, fds, tval);
-	} while (ret == -1 && errno == EINTR);
-	return ret;
-}
-
 
 /*******************************************************************
  A wrapper for usleep in case we don't have one.