Adds eshutdown(2) to allow programs to stop event processing before exiting.

There is currently no way for programs using event(2) to stop event processing.
Device files and memory are held by the library.  This prevents programs using
event(2) from returning to console mode cleanly without exiting.

This patch adds eshutdown(2) to provide that function.  Existing programs using
event(2) should not be affected by this change.  I have recompiled and run
clock(1) and tweak(1) for testing, both of which behave unchanged.

Updated to fix style(6) violations.

Notes:
Sat Mar 22 18:39:39 EDT 2008 geoff
    would it suffice to make ekill() in /sys/src/libdraw/event.c
    documented and non-static?

Thu Apr 10 19:26:30 EDT 2008 geoff
    This is just not the Plan 9 way of doing things.
    vim is a mistake to begin with and we don't need shell escapes.


Reference: /n/sources/patch/sorry/eshutdown2
Date: Thu Mar 20 08:44:08 CET 2008
Signed-off-by: stefanha@gmail.com
Reviewed-by: geoff

--- /sys/include/event.h	Thu Mar 20 08:42:40 2008
+++ /sys/include/event.h	Thu Mar 20 08:42:32 2008
@@ -44,6 +44,7 @@
  * Events
  */
 extern void	 einit(ulong);
+extern void	 eshutdown(void);
 extern ulong	 estart(ulong, int, int);
 extern ulong	 estartfn(ulong, int, int, int (*fn)(int, Event*, uchar*, int));
 extern ulong	 etimer(ulong, int);
--- /sys/src/libdraw/event.c	Thu Mar 20 08:42:59 2008
+++ /sys/src/libdraw/event.c	Sun Mar 23 23:02:44 2008
@@ -10,7 +10,7 @@
 struct Slave
 {
 	int	pid;
-	Ebuf	*head;		/* ueue of messages for this descriptor */
+	Ebuf	*head;		/* queue of messages for this descriptor */
 	Ebuf	*tail;
 	int	(*fn)(int, Event*, uchar*, int);
 };
@@ -22,6 +22,8 @@
 	uchar	buf[EMAXMSG];
 };
 
+enum { Noexit, Exiting };
+
 static	Slave	eslave[MAXSLAVE];
 static	int	Skeyboard = -1;
 static	int	Smouse = -1;
@@ -31,15 +33,18 @@
 static	int	nslave;
 static	int	parentpid;
 static	int	epipe[2];
+
+static	int	mousefd;
+static	int	cursorfd;
+static	int	consfd;
+static	int	ctlfd;
+
 static	int	eforkslave(ulong);
 static	void	extract(void);
 static	void	ekill(void);
 static	int	enote(void *, char *);
-static	int	mousefd;
-static	int	cursorfd;
 
-static
-Ebuf*
+static Ebuf*
 ebread(Slave *s)
 {
 	Ebuf *eb;
@@ -228,13 +233,15 @@
 void
 einit(ulong keys)
 {
-	int ctl, fd;
+	int firstinit;
 	char buf[256];
 
+	firstinit = (parentpid == 0);
 	parentpid = getpid();
 	if(pipe(epipe) < 0)
 		drawerror(display, "events: einit pipe");
-	atexit(ekill);
+	if(firstinit)
+		atexit(ekill);
 	atnotify(enote, 1);
 	snprint(buf, sizeof buf, "%s/mouse", display->devdir);
 	mousefd = open(buf, ORDWR|OCEXEC);
@@ -246,17 +253,17 @@
 		drawerror(display, "einit: can't open cursor\n");
 	if(keys&Ekeyboard){
 		snprint(buf, sizeof buf, "%s/cons", display->devdir);
-		fd = open(buf, OREAD);
-		if(fd < 0)
+		consfd = open(buf, OREAD);
+		if(consfd < 0)
 			drawerror(display, "events: can't open console");
 		snprint(buf, sizeof buf, "%s/consctl", display->devdir);
-		ctl = open("/dev/consctl", OWRITE|OCEXEC);
-		if(ctl < 0)
+		ctlfd = open("/dev/consctl", OWRITE|OCEXEC);
+		if(ctlfd < 0)
 			drawerror(display, "events: can't open consctl");
-		write(ctl, "rawon", 5);
+		write(ctlfd, "rawon", 5);
 		for(Skeyboard=0; Ekeyboard & ~(1<<Skeyboard); Skeyboard++)
 			;
-		ekeyslave(fd);
+		ekeyslave(consfd);
 	}
 	if(keys&Emouse){
 		estart(Emouse, mousefd, 1+4*12);
@@ -266,6 +273,59 @@
 }
 
 static void
+edoshutdown(int exiting)
+{
+	int i, nalive;
+	Ebuf *eb, *next;
+	Waitmsg *wm;
+
+	atnotify(enote, 0);
+	close(epipe[0]);
+	close(epipe[1]);
+	epipe[0] = epipe[1] = -1;
+	for(i = 0; i < nslave; i++){
+		if(parentpid == eslave[i].pid)
+			continue;		/* don't kill myself */
+		postnote(PNPROC, eslave[i].pid, "die");
+	}
+	/*
+	 * returning leaves mousefd open so that the display is closed
+	 * before the kernel closes mousefd.
+	 * this ensures that rio redraws the console.
+	 */
+	if(exiting)
+		return;
+
+	nalive = nslave;
+	while(nalive > 0 && (wm = wait()) != nil) {
+		for(i = 0; i < nslave; i++)
+			if(eslave[i].pid == wm->pid)
+				nalive--;
+		free(wm);
+	}
+	for(i = 0; i < nslave; i++){
+		for(eb = eslave[i].head; eb; eb = next){
+			next = eb->next;
+			free(eb);
+		}
+		memset(&eslave[i], 0, sizeof(eslave[i]));
+	}
+	write(ctlfd, "rawoff", 6);
+	close(ctlfd);
+	close(consfd);
+	close(cursorfd);
+	close(mousefd);
+	nslave = 0;
+	Skeyboard = Smouse = Stimer = ctlfd = consfd = cursorfd = mousefd = -1;
+}
+
+void
+eshutdown(void)
+{
+	edoshutdown(Noexit);
+}
+
+static void
 extract(void)
 {
 	Slave *s;
@@ -372,22 +432,15 @@
 		}
 		return 0;
 	}
-	close(epipe[0]);
-	epipe[0] = -1;
-	close(epipe[1]);
-	epipe[1] = -1;
-	for(i=0; i<nslave; i++){
-		if(pid == eslave[i].pid)
-			continue;	/* don't kill myself */
-		postnote(PNPROC, eslave[i].pid, "die");
-	}
+	edoshutdown(Exiting);
 	return 0;
 }
 
 static void
 ekill(void)
 {
-	enote(0, 0);
+	if(epipe[0] != -1)
+		enote(0, 0);
 }
 
 Mouse
--- /sys/src/ape/lib/draw/libc.h	Thu Mar 20 08:43:13 2008
+++ /sys/src/ape/lib/draw/libc.h	Thu Mar 20 08:43:06 2008
@@ -126,6 +126,7 @@
 #define readn _READN
 #define mallocz _MALLOCZ
 #define iounit	_IOUNIT
+#define wait _WAIT
 
 /* assume being called as in event.c */
 #define postnote(x, pid, msg) kill(pid, SIGTERM)