Implement kqueue(2) for procdesc(4).

kqueue(2) already supports EVFILT_PROC. Add an EVFILT_PROCDESC that
behaves the same, but operates on a procdesc(4) instead. Only implement
NOTE_EXIT for now. The nice thing about NOTE_EXIT is that it also
returns the exit status of the process, meaning that we can now obtain
this value, even if pdwait4(2) is still unimplemented.

Notes:

- Simply reuse EVFILT_NETDEV for EVFILT_PROCDESC. As both of these will
  be used on totally different descriptor types, this should not clash.

- Let procdesc_kqops_event() reuse the same structure as filt_proc().
  The only difference is that procdesc_kqops_event() should also be able
  to deal with the case where the process was already terminated after
  registration. Simply test this when hint == 0.

- Fix some style(9) issues in filt_proc() to keep it consistent with the
  newly added procdesc_kqops_event().

- Save the exit status of the process in pd->pd_xstat, as we cannot pick
  up the proctree_lock from within procdesc_kqops_event().

Discussed on:	arch@
Reviewed by:	kib@

1 files changed, 2 insertions, 2 deletions

diff --git a/sys/sys/event.h b/sys/sys/event.h
index 3b765c0..1f27c4d 100644
--- a/sys/sys/event.h
+++ b/sys/sys/event.h
@@ -38,7 +38,7 @@
 #define EVFILT_PROC		(-5)	/* attached to struct proc */
 #define EVFILT_SIGNAL		(-6)	/* attached to struct proc */
 #define EVFILT_TIMER		(-7)	/* timers */
-/*	EVFILT_NETDEV		(-8)	   no longer supported */
+#define EVFILT_PROCDESC		(-8)	/* attached to process descriptors */
 #define EVFILT_FS		(-9)	/* filesystem events */
 #define EVFILT_LIO		(-10)	/* attached to lio requests */
 #define EVFILT_USER		(-11)	/* User events */
@@ -120,7 +120,7 @@ struct kevent {
 #define	NOTE_REVOKE	0x0040			/* vnode access was revoked */
 
 /*
- * data/hint flags for EVFILT_PROC, shared with userspace
+ * data/hint flags for EVFILT_PROC and EVFILT_PROCDESC, shared with userspace
  */
 #define	NOTE_EXIT	0x80000000		/* process exited */
 #define	NOTE_FORK	0x40000000		/* process forked */