From 3bcb6e5e80cb05cecaddd866d4b15b428334b9aa Mon Sep 17 00:00:00 2001
From: Sepherosa Ziehau <sephe@dragonflybsd.org>
Date: Fri, 23 Sep 2011 14:23:53 +0800
Subject: [PATCH] kevent: Restore old EV_EOF semantics

- EV_EOF should be set when the other side closed the connection, even
  if there are data pending in the read buffer (the old semantics).
- EV_NODATA is added to indicate there are no more data pending in the
  buffer and EOF is detected (EV_EOF is also set in this situation).

Kernel code now tests EV_NODATA instead of EV_EOF, since EV_NODATA
delivers the information which was delivered by the EV_EOF before
this commit.

DragonFly-Bug: http://bugs.dragonflybsd.org/issue1998
---
 sys/dev/misc/cmx/cmx.c          |  2 +-
 sys/dev/misc/kbd/kbd.c          |  3 ++-
 sys/dev/video/bktr/bktr_os.c    |  2 +-
 sys/dev/video/cxm/cxm.c         |  2 +-
 sys/kern/kern_event.c           |  2 +-
 sys/kern/sys_generic.c          |  8 ++++----
 sys/kern/sys_pipe.c             | 14 ++++++++------
 sys/kern/tty.c                  |  2 +-
 sys/kern/tty_pty.c              |  4 ++--
 sys/kern/uipc_socket.c          | 12 +++++++-----
 sys/sys/event.h                 |  1 +
 sys/vfs/devfs/devfs_core.c      |  2 +-
 sys/vfs/fifofs/fifo_vnops.c     | 10 ++++++----
 sys/vfs/gnu/ext2fs/ext2_vnops.c |  6 +++---
 sys/vfs/hammer/hammer_vnops.c   |  6 +++---
 sys/vfs/tmpfs/tmpfs_vnops.c     |  6 +++---
 sys/vfs/ufs/ufs_vnops.c         |  6 +++---
 17 files changed, 48 insertions(+), 40 deletions(-)

diff --git a/sys/dev/misc/cmx/cmx.c b/sys/dev/misc/cmx/cmx.c
index 9174fae457..815590cedb 100644
--- a/sys/dev/misc/cmx/cmx.c
+++ b/sys/dev/misc/cmx/cmx.c
@@ -702,7 +702,7 @@ cmx_filter_read(struct knote *kn, long hint)
         uint8_t bsr = 0;
 
         if (sc == NULL || sc->dying) {
-		kn->kn_flags |= EV_EOF;
+		kn->kn_flags |= (EV_EOF | EV_NODATA);
                 return (1);
 	}
 
diff --git a/sys/dev/misc/kbd/kbd.c b/sys/dev/misc/kbd/kbd.c
index b39133ef42..3c9ecc57f4 100644
--- a/sys/dev/misc/kbd/kbd.c
+++ b/sys/dev/misc/kbd/kbd.c
@@ -924,7 +924,8 @@ genkbdfilter(struct knote *kn, long hint)
 	sc = dev->si_drv1;
         kbd = kbd_get_keyboard(KBD_INDEX(dev));
 	if ((sc == NULL) || (kbd == NULL) || !KBD_IS_VALID(kbd)) {
-		kn->kn_flags |= EV_EOF;	/* the keyboard has gone */
+		/* The keyboard has gone */
+		kn->kn_flags |= (EV_EOF | EV_NODATA);
 		ready = 1;
 	} else {
 		if (sc->gkb_q_length > 0)
diff --git a/sys/dev/video/bktr/bktr_os.c b/sys/dev/video/bktr/bktr_os.c
index 07240752db..710cedccf1 100644
--- a/sys/dev/video/bktr/bktr_os.c
+++ b/sys/dev/video/bktr/bktr_os.c
@@ -772,7 +772,7 @@ bktr_filter(struct knote *kn, long hint)
 
 	if (bktr == NULL) {
 		/* the device is no longer valid/functioning */
-		kn->kn_flags |= EV_EOF;
+		kn->kn_flags |= (EV_EOF | EV_NODATA);
 		return (1);
 	}
 
diff --git a/sys/dev/video/cxm/cxm.c b/sys/dev/video/cxm/cxm.c
index ed83036b83..2b9ee89ece 100644
--- a/sys/dev/video/cxm/cxm.c
+++ b/sys/dev/video/cxm/cxm.c
@@ -2954,7 +2954,7 @@ cxm_filter(struct knote *kn, long hint)
 
 	if (sc == NULL) {
 		/* the device is no longer valid/functioning */
-		kn->kn_flags |= EV_EOF;
+		kn->kn_flags |= (EV_EOF | EV_NODATA);
 		return (1);
 	}
 
diff --git a/sys/kern/kern_event.c b/sys/kern/kern_event.c
index bd5ac9a3d9..f475cf13a1 100644
--- a/sys/kern/kern_event.c
+++ b/sys/kern/kern_event.c
@@ -300,7 +300,7 @@ filt_proc(struct knote *kn, long hint)
 			kn->kn_data = p->p_xstat;
 			kn->kn_ptr.p_proc = NULL;
 		}
-		kn->kn_flags |= (EV_EOF | EV_ONESHOT); 
+		kn->kn_flags |= (EV_EOF | EV_NODATA | EV_ONESHOT); 
 		return (1);
 	}
 
diff --git a/sys/kern/sys_generic.c b/sys/kern/sys_generic.c
index 050813df4c..42cbc3bf0d 100644
--- a/sys/kern/sys_generic.c
+++ b/sys/kern/sys_generic.c
@@ -1375,12 +1375,12 @@ poll_copyout(void *arg, struct kevent *kevp, int count, int *res)
 			case EVFILT_READ:
 #if 0
 				/*
-				 * EOF on the read side can indicate a
+				 * NODATA on the read side can indicate a
 				 * half-closed situation and not necessarily
 				 * a disconnect, so depend on the user
 				 * issuing a read() and getting 0 bytes back.
 				 */
-				if (kevp[i].flags & EV_EOF)
+				if (kevp[i].flags & EV_NODATA)
 					pfd->revents |= POLLHUP;
 #endif
 				if (pfd->events & POLLIN)
@@ -1397,7 +1397,7 @@ poll_copyout(void *arg, struct kevent *kevp, int count, int *res)
 				 * In this case a disconnect is implied even
 				 * for a half-closed (write side) situation.
 				 */
-				if (kevp[i].flags & EV_EOF) {
+				if (kevp[i].flags & EV_NODATA) {
 					pfd->revents |= POLLHUP;
 				} else {
 					if (pfd->events & POLLOUT)
@@ -1408,7 +1408,7 @@ poll_copyout(void *arg, struct kevent *kevp, int count, int *res)
 				break;
 			case EVFILT_EXCEPT:
 				/*
-				 * EV_EOF should never be tagged for this
+				 * EV_NODATA should never be tagged for this
 				 * filter.
 				 */
 				if (pfd->events & POLLPRI)
diff --git a/sys/kern/sys_pipe.c b/sys/kern/sys_pipe.c
index 5f14a90e12..9a36d75279 100644
--- a/sys/kern/sys_pipe.c
+++ b/sys/kern/sys_pipe.c
@@ -1243,10 +1243,12 @@ filt_piperead(struct knote *kn, long hint)
 
 	kn->kn_data = rpipe->pipe_buffer.windex - rpipe->pipe_buffer.rindex;
 
-	/*
-	 * Only set EOF if all data has been exhausted
-	 */
-	if ((rpipe->pipe_state & PIPE_REOF) && kn->kn_data == 0) {
+	if (rpipe->pipe_state & PIPE_REOF) {
+		/*
+		 * Only set NODATA if all data has been exhausted
+		 */
+		if (kn->kn_data == 0)
+			kn->kn_flags |= EV_NODATA;
 		kn->kn_flags |= EV_EOF; 
 		ready = 1;
 	}
@@ -1270,7 +1272,7 @@ filt_pipewrite(struct knote *kn, long hint)
 
 	kn->kn_data = 0;
 	if (wpipe == NULL) {
-		kn->kn_flags |= EV_EOF;
+		kn->kn_flags |= (EV_EOF | EV_NODATA);
 		return (1);
 	}
 
@@ -1278,7 +1280,7 @@ filt_pipewrite(struct knote *kn, long hint)
 	lwkt_gettoken(&wpipe->pipe_wlock);
 
 	if (wpipe->pipe_state & PIPE_WEOF) {
-		kn->kn_flags |= EV_EOF; 
+		kn->kn_flags |= (EV_EOF | EV_NODATA);
 		ready = 1;
 	}
 
diff --git a/sys/kern/tty.c b/sys/kern/tty.c
index e616e1c4dd..21af56005a 100644
--- a/sys/kern/tty.c
+++ b/sys/kern/tty.c
@@ -1354,7 +1354,7 @@ filt_ttyread(struct knote *kn, long hint)
 	lwkt_gettoken(&tty_token);
 	kn->kn_data = ttnread(tp);
 	if (ISSET(tp->t_state, TS_ZOMBIE)) {
-		kn->kn_flags |= EV_EOF;
+		kn->kn_flags |= (EV_EOF | EV_NODATA);
 		lwkt_reltoken(&tty_token);
 		return (1);
 	}
diff --git a/sys/kern/tty_pty.c b/sys/kern/tty_pty.c
index cd553daace..99337f1c7d 100644
--- a/sys/kern/tty_pty.c
+++ b/sys/kern/tty_pty.c
@@ -890,7 +890,7 @@ filt_ptcread (struct knote *kn, long hint)
 
 	lwkt_gettoken(&tty_token);
 	if ((tp->t_state & TS_ZOMBIE) || (pti->pt_flags & PF_SCLOSED)) {
-		kn->kn_flags |= EV_EOF;
+		kn->kn_flags |= (EV_EOF | EV_NODATA);
 		lwkt_reltoken(&tty_token);
 		return (1);
 	}
@@ -916,7 +916,7 @@ filt_ptcwrite (struct knote *kn, long hint)
 
 	lwkt_gettoken(&tty_token);
 	if (tp->t_state & TS_ZOMBIE) {
-		kn->kn_flags |= EV_EOF;
+		kn->kn_flags |= (EV_EOF | EV_NODATA);
 		lwkt_reltoken(&tty_token);
 		return (1);
 	}
diff --git a/sys/kern/uipc_socket.c b/sys/kern/uipc_socket.c
index 204ff48a49..b20eb28d04 100644
--- a/sys/kern/uipc_socket.c
+++ b/sys/kern/uipc_socket.c
@@ -1811,10 +1811,12 @@ filt_soread(struct knote *kn, long hint)
 	}
 	kn->kn_data = so->so_rcv.ssb_cc;
 
-	/*
-	 * Only set EOF if all data has been exhausted.
-	 */
-	if ((so->so_state & SS_CANTRCVMORE) && kn->kn_data == 0) {
+	if (so->so_state & SS_CANTRCVMORE) {
+		/*
+		 * Only set NODATA if all data has been exhausted.
+		 */
+		if (kn->kn_data == 0)
+			kn->kn_flags |= EV_NODATA;
 		kn->kn_flags |= EV_EOF; 
 		kn->kn_fflags = so->so_error;
 		return (1);
@@ -1845,7 +1847,7 @@ filt_sowrite(struct knote *kn, long hint)
 
 	kn->kn_data = ssb_space(&so->so_snd);
 	if (so->so_state & SS_CANTSENDMORE) {
-		kn->kn_flags |= EV_EOF; 
+		kn->kn_flags |= (EV_EOF | EV_NODATA);
 		kn->kn_fflags = so->so_error;
 		return (1);
 	}
diff --git a/sys/sys/event.h b/sys/sys/event.h
index 396fdabc31..c39a6e7155 100644
--- a/sys/sys/event.h
+++ b/sys/sys/event.h
@@ -88,6 +88,7 @@ struct kevent {
 /* returned values */
 #define EV_EOF		0x8000		/* EOF detected */
 #define EV_ERROR	0x4000		/* error, data contains errno */
+#define EV_NODATA	0x1000		/* EOF and no more data */
 
 /*
  * data/hint flags for EVFILT_{READ|WRITE}, shared with userspace
diff --git a/sys/vfs/devfs/devfs_core.c b/sys/vfs/devfs/devfs_core.c
index 65f90f759d..f5ddfe5406 100644
--- a/sys/vfs/devfs/devfs_core.c
+++ b/sys/vfs/devfs/devfs_core.c
@@ -2305,7 +2305,7 @@ devfs_cdev_unlock(cdev_t dev)
 static int
 devfs_detached_filter_eof(struct knote *kn, long hint)
 {
-	kn->kn_flags |= EV_EOF;
+	kn->kn_flags |= (EV_EOF | EV_NODATA);
 	return (1);
 }
 
diff --git a/sys/vfs/fifofs/fifo_vnops.c b/sys/vfs/fifofs/fifo_vnops.c
index 0c572ad9d9..22e2a5a4aa 100644
--- a/sys/vfs/fifofs/fifo_vnops.c
+++ b/sys/vfs/fifofs/fifo_vnops.c
@@ -422,12 +422,14 @@ filt_fiforead(struct knote *kn, long hint)
 
 	lwkt_gettoken(&vp->v_token);
 	kn->kn_data = so->so_rcv.ssb_cc;
-	if ((so->so_state & SS_ISDISCONNECTED) && kn->kn_data == 0) {
+	if (so->so_state & SS_ISDISCONNECTED) {
+		if (kn->kn_data == 0)
+			kn->kn_flags |= EV_NODATA;
 		kn->kn_flags |= EV_EOF;
 		lwkt_reltoken(&vp->v_token);
 		return (1);
 	}
-	kn->kn_flags &= ~EV_EOF;
+	kn->kn_flags &= ~(EV_EOF | EV_NODATA);
 	lwkt_reltoken(&vp->v_token);
 	return (kn->kn_data > 0);
 }
@@ -452,11 +454,11 @@ filt_fifowrite(struct knote *kn, long hint)
 	lwkt_gettoken(&vp->v_token);
 	kn->kn_data = ssb_space(&so->so_snd);
 	if (so->so_state & SS_ISDISCONNECTED) {
-		kn->kn_flags |= EV_EOF;
+		kn->kn_flags |= (EV_EOF | EV_NODATA);
 		lwkt_reltoken(&vp->v_token);
 		return (1);
 	}
-	kn->kn_flags &= ~EV_EOF;
+	kn->kn_flags &= ~(EV_EOF | EV_NODATA);
 	lwkt_reltoken(&vp->v_token);
 	return (kn->kn_data >= so->so_snd.ssb_lowat);
 }
diff --git a/sys/vfs/gnu/ext2fs/ext2_vnops.c b/sys/vfs/gnu/ext2fs/ext2_vnops.c
index c04dbaaad7..790ed9a747 100644
--- a/sys/vfs/gnu/ext2fs/ext2_vnops.c
+++ b/sys/vfs/gnu/ext2fs/ext2_vnops.c
@@ -1989,7 +1989,7 @@ filt_ext2read(struct knote *kn, long hint)
 	 * the knote for deletion.
 	 */
 	if (hint == NOTE_REVOKE) {
-		kn->kn_flags |= (EV_EOF | EV_ONESHOT);
+		kn->kn_flags |= (EV_EOF | EV_NODATA | EV_ONESHOT);
 		return (1);
 	}
         off = ip->i_size - kn->kn_fp->f_offset;
@@ -2008,7 +2008,7 @@ filt_ext2write(struct knote *kn, long hint)
 	 * the knote for deletion.
 	 */
 	if (hint == NOTE_REVOKE)
-		kn->kn_flags |= (EV_EOF | EV_ONESHOT);
+		kn->kn_flags |= (EV_EOF | EV_NODATA | EV_ONESHOT);
 
         kn->kn_data = 0;
         return (1);
@@ -2020,7 +2020,7 @@ filt_ext2vnode(struct knote *kn, long hint)
 	if (kn->kn_sfflags & hint)
 		kn->kn_fflags |= hint;
 	if (hint == NOTE_REVOKE) {
-		kn->kn_flags |= EV_EOF;
+		kn->kn_flags |= (EV_EOF | EV_NODATA);
 		return (1);
 	}
 	return (kn->kn_fflags != 0);
diff --git a/sys/vfs/hammer/hammer_vnops.c b/sys/vfs/hammer/hammer_vnops.c
index 533cc249eb..e5101d721a 100644
--- a/sys/vfs/hammer/hammer_vnops.c
+++ b/sys/vfs/hammer/hammer_vnops.c
@@ -3661,7 +3661,7 @@ filt_hammerread(struct knote *kn, long hint)
 	off_t off;
 
 	if (hint == NOTE_REVOKE) {
-		kn->kn_flags |= (EV_EOF | EV_ONESHOT);
+		kn->kn_flags |= (EV_EOF | EV_NODATA | EV_ONESHOT);
 		return(1);
 	}
 	lwkt_gettoken(&hmp->fs_token);	/* XXX use per-ip-token */
@@ -3677,7 +3677,7 @@ static int
 filt_hammerwrite(struct knote *kn, long hint)
 {
 	if (hint == NOTE_REVOKE)
-		kn->kn_flags |= (EV_EOF | EV_ONESHOT);
+		kn->kn_flags |= (EV_EOF | EV_NODATA | EV_ONESHOT);
 	kn->kn_data = 0;
 	return (1);
 }
@@ -3688,7 +3688,7 @@ filt_hammervnode(struct knote *kn, long hint)
 	if (kn->kn_sfflags & hint)
 		kn->kn_fflags |= hint;
 	if (hint == NOTE_REVOKE) {
-		kn->kn_flags |= EV_EOF;
+		kn->kn_flags |= (EV_EOF | EV_NODATA);
 		return (1);
 	}
 	return (kn->kn_fflags != 0);
diff --git a/sys/vfs/tmpfs/tmpfs_vnops.c b/sys/vfs/tmpfs/tmpfs_vnops.c
index c2ea751d3d..c740d46b37 100644
--- a/sys/vfs/tmpfs/tmpfs_vnops.c
+++ b/sys/vfs/tmpfs/tmpfs_vnops.c
@@ -1579,7 +1579,7 @@ filt_tmpfsread(struct knote *kn, long hint)
 	off_t off;
 
 	if (hint == NOTE_REVOKE) {
-		kn->kn_flags |= (EV_EOF | EV_ONESHOT);
+		kn->kn_flags |= (EV_EOF | EV_NODATA | EV_ONESHOT);
 		return(1);
 	}
 
@@ -1605,7 +1605,7 @@ static int
 filt_tmpfswrite(struct knote *kn, long hint)
 {
 	if (hint == NOTE_REVOKE)
-		kn->kn_flags |= (EV_EOF | EV_ONESHOT);
+		kn->kn_flags |= (EV_EOF | EV_NODATA | EV_ONESHOT);
 	kn->kn_data = 0;
 	return (1);
 }
@@ -1616,7 +1616,7 @@ filt_tmpfsvnode(struct knote *kn, long hint)
 	if (kn->kn_sfflags & hint)
 		kn->kn_fflags |= hint;
 	if (hint == NOTE_REVOKE) {
-		kn->kn_flags |= EV_EOF;
+		kn->kn_flags |= (EV_EOF | EV_NODATA);
 		return (1);
 	}
 	return (kn->kn_fflags != 0);
diff --git a/sys/vfs/ufs/ufs_vnops.c b/sys/vfs/ufs/ufs_vnops.c
index 65fdd6d1ec..427bfaa6f7 100644
--- a/sys/vfs/ufs/ufs_vnops.c
+++ b/sys/vfs/ufs/ufs_vnops.c
@@ -2181,7 +2181,7 @@ filt_ufsread(struct knote *kn, long hint)
 	 * the knote for deletion.
 	 */
 	if (hint == NOTE_REVOKE) {
-		kn->kn_flags |= (EV_EOF | EV_ONESHOT);
+		kn->kn_flags |= (EV_EOF | EV_NODATA | EV_ONESHOT);
 		return (1);
 	}
 
@@ -2201,7 +2201,7 @@ filt_ufswrite(struct knote *kn, long hint)
 	 * the knote for deletion.
 	 */
 	if (hint == NOTE_REVOKE)
-		kn->kn_flags |= (EV_EOF | EV_ONESHOT);
+		kn->kn_flags |= (EV_EOF | EV_NODATA | EV_ONESHOT);
 
         kn->kn_data = 0;
         return (1);
@@ -2213,7 +2213,7 @@ filt_ufsvnode(struct knote *kn, long hint)
 	if (kn->kn_sfflags & hint)
 		kn->kn_fflags |= hint;
 	if (hint == NOTE_REVOKE) {
-		kn->kn_flags |= EV_EOF;
+		kn->kn_flags |= (EV_EOF | EV_NODATA);
 		return (1);
 	}
 	return (kn->kn_fflags != 0);
-- 
2.41.0