Don't emit a spurious EVFILT_PROC event with no fflags set on process exit

if NOTE_EXIT is not being monitored.  The rationale is that a listener
should only get an event for exit() if they registered interest via
NOTE_EXIT.  This matches the behavior on OS X.
- Don't save the exit status on process exit unless NOTE_EXIT is being
  monitored.
- Add an internal EV_DROP flag that requests kqueue_scan() to free the
  knote without signalling it to userland and use this when a process
  exits but the fflags in the knote is zero.

Reviewed by:	jmg
MFC after:	1 month

1 files changed, 1 insertions, 0 deletions

diff --git a/sys/sys/event.h b/sys/sys/event.h
index 707fbed..1066e36 100644
--- a/sys/sys/event.h
+++ b/sys/sys/event.h
@@ -76,6 +76,7 @@ struct kevent {
 #define EV_DISPATCH	0x0080		/* disable event after reporting */
 
 #define EV_SYSFLAGS	0xF000		/* reserved by system */
+#define	EV_DROP		0x1000		/* note should be dropped */
 #define EV_FLAG1	0x2000		/* filter-specific flag */
 
 /* returned values */