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ratrace: various improvements

error handling, serialize exits, close reader filedescriptors,
fix channel types, embedd the string buffer in the Msg struct.

--- a/sys/src/cmd/ratrace.c

+++ b/sys/src/cmd/ratrace.c

@@ -4,7 +4,6 @@

 enum {

 	Stacksize	= 8*1024,

-	Bufsize		= 8*1024,

 };

 Channel *out;

@@ -14,49 +13,63 @@

 typedef struct Msg Msg;

 struct Msg {

-	char	*buf;

 	int	pid;

+	char	buf[8*1024];

 };

+typedef struct Reader Reader;

+struct Reader {

+	int	pid;

+

+	int	tfd;

+	int	cfd;

+

+	Msg*	msg;

+};

+

 void

-die(char *s)

+die(Reader *r)

 {

-	fprint(2, "%s\n", s);

-	exits(s);

+	Msg *s;

+

+	s = r->msg;

+	snprint(s->buf, sizeof(s->buf), " = %r\n");

+	s->pid = r->pid;

+	sendp(quit, s);

+	close(r->tfd);

+	close(r->cfd);

+	threadexits(nil);

 }

 void

-cwrite(int fd, char *path, char *cmd, int len)

+cwrite(Reader *r, char *cmd)

 {

-	if (write(fd, cmd, len) < len) {

-		fprint(2, "cwrite: %s: failed %d bytes: %r\n", path, len);

-		sendp(quit, nil);

-		threadexits(nil);

-	}

+	if (write(r->cfd, cmd, strlen(cmd)) < 0)

+		die(r);

 }

 void

 reader(void *v)

 {

-	int cfd, tfd, forking = 0, pid, newpid;

-	char *ctl, *truss;

+	int forking = 0, newpid;

+	Reader r;

 	Msg *s;

-	pid = (int)(uintptr)v;

-	ctl = smprint("/proc/%d/ctl", pid);

-	if ((cfd = open(ctl, OWRITE)) < 0)

-		die(smprint("%s: %r", ctl));

-	truss = smprint("/proc/%d/syscall", pid);

-	if ((tfd = open(truss, OREAD)) < 0)

-		die(smprint("%s: %r", truss));

+	r.pid = (int)(uintptr)v;

+	r.tfd = r.cfd = -1;

-	cwrite(cfd, ctl, "stop", 4);

-	cwrite(cfd, truss, "startsyscall", 12);

+	r.msg = s = mallocz(sizeof(Msg), 1);

+	snprint(s->buf, sizeof(s->buf), "/proc/%d/ctl", r.pid);

+	if ((r.cfd = open(s->buf, OWRITE)) < 0)

+		die(&r);

+	snprint(s->buf, sizeof(s->buf), "/proc/%d/syscall", r.pid);

+	if ((r.tfd = open(s->buf, OREAD)) < 0)

+		die(&r);

-	s = mallocz(sizeof(Msg) + Bufsize, 1);

-	s->pid = pid;

-	s->buf = (char *)&s[1];

-	while(pread(tfd, s->buf, Bufsize - 1, 0) > 0){

+	cwrite(&r, "stop");

+	cwrite(&r, "startsyscall");

+

+	while(pread(r.tfd, s->buf, sizeof(s->buf)-1, 0) > 0){

 		if (forking && s->buf[1] == '=' && s->buf[3] != '-') {

 			forking = 0;

 			newpid = strtol(&s->buf[3], 0, 0);

@@ -82,14 +95,13 @@

 			}

 			free(rf);

 		}

+		s->pid = r.pid;

 		sendp(out, s);

-		cwrite(cfd, truss, "startsyscall", 12);

-		s = mallocz(sizeof(Msg) + Bufsize, 1);

-		s->pid = pid;

-		s->buf = (char *)&s[1];

+

+		r.msg = s = mallocz(sizeof(Msg), 1);

+		cwrite(&r, "startsyscall");

 	}

-	sendp(quit, nil);

-	threadexitsall(nil);

+	die(&r);

 }

 void

@@ -103,7 +115,7 @@

 	a[0].op = CHANRCV;

 	a[0].c = quit;

-	a[0].v = nil;

+	a[0].v = &s;

 	a[1].op = CHANRCV;

 	a[1].c = out;

 	a[1].v = &s;

@@ -112,19 +124,16 @@

 	a[2].v = nil;

 	a[3].op = CHANEND;

-	for(;;)

+	while(nread > 0){

 		switch(alt(a)){

 		case 0:

 			nread--;

-			if(nread <= 0)

-				goto done;

-			break;

 		case 1:

 			if(s->pid != lastpid){

 				lastpid = s->pid;

 				fprint(2, s->buf[1]=='='? "\n%d ...": "\n", lastpid);

 			}

-			fprint(2, "%s", s->buf);

+			write(2, s->buf, strlen(s->buf));

 			free(s);

 			break;

 		case 2:

@@ -131,8 +140,7 @@

 			nread++;

 			break;

 		}

-done:

-	exits(nil);

+	}

 }

 void

@@ -139,7 +147,7 @@

 usage(void)

 {

 	fprint(2, "Usage: ratrace [-c cmd [arg...]] | [pid]\n");

-	exits("usage");

+	threadexits("usage");

 }

 void

@@ -185,9 +193,9 @@

 		pid = atoi(argv[1]);

 	}

-	out   = chancreate(sizeof(char*), 0);

-	quit  = chancreate(sizeof(char*), 0);

-	forkc = chancreate(sizeof(ulong *), 0);

+	out   = chancreate(sizeof(Msg*), 0);

+	quit  = chancreate(sizeof(Msg*), 0);

+	forkc = chancreate(sizeof(void*), 0);

 	nread++;

 	procrfork(writer, (void*)pid, Stacksize, 0);

 	reader((void*)pid);