runtime: simplify stack traces

Make the stack traces more readable for new
Go programmers while preserving their utility for old hands.

- Change status number [4] to string.
- Elide frames in runtime package (internal details).
- Swap file:line and arguments.
- Drop 'created by' for main goroutine.
- Show goroutines in order of allocation:
  implies main goroutine first if nothing else.

There is no option to get the extra frames back.
Uncomment 'return 1' at the bottom of symtab.c.

$ 6.out
throw: all goroutines are asleep - deadlock!

goroutine 1 [chan send]:
main.main()
       /Users/rsc/g/go/src/pkg/runtime/x.go:22 +0x8a

goroutine 2 [select (no cases)]:
main.sel()
       /Users/rsc/g/go/src/pkg/runtime/x.go:11 +0x18
created by main.main
       /Users/rsc/g/go/src/pkg/runtime/x.go:19 +0x23

goroutine 3 [chan receive]:
main.recv(0xf8400010a0, 0x0)
       /Users/rsc/g/go/src/pkg/runtime/x.go:15 +0x2e
created by main.main
       /Users/rsc/g/go/src/pkg/runtime/x.go:20 +0x50

goroutine 4 [chan receive (nil chan)]:
main.recv(0x0, 0x0)
       /Users/rsc/g/go/src/pkg/runtime/x.go:15 +0x2e
created by main.main
       /Users/rsc/g/go/src/pkg/runtime/x.go:21 +0x66
$

$ 6.out index
panic: runtime error: index out of range

goroutine 1 [running]:
main.main()
        /Users/rsc/g/go/src/pkg/runtime/x.go:25 +0xb9
$

$ 6.out nil
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x0 pc=0x22ca]

goroutine 1 [running]:
main.main()
        /Users/rsc/g/go/src/pkg/runtime/x.go:28 +0x211
$

$ 6.out panic
panic: panic

goroutine 1 [running]:
main.main()
        /Users/rsc/g/go/src/pkg/runtime/x.go:30 +0x101
$

R=golang-dev, qyzhai, n13m3y3r, r
CC=golang-dev
https://golang.org/cl/4907048

1 files changed, 43 insertions, 5 deletions

diff --git a/src/pkg/runtime/proc.c b/src/pkg/runtime/proc.c
index dd42675c2a..3a431ef35e 100644
--- a/src/pkg/runtime/proc.c
+++ b/src/pkg/runtime/proc.c
@@ -250,6 +250,40 @@ runtime·goexit(void)
 }
 
 void
+runtime·goroutineheader(G *g)
+{
+	int8 *status;
+
+	switch(g->status) {
+	case Gidle:
+		status = "idle";
+		break;
+	case Grunnable:
+		status = "runnable";
+		break;
+	case Grunning:
+		status = "running";
+		break;
+	case Gsyscall:
+		status = "syscall";
+		break;
+	case Gwaiting:
+		if(g->waitreason)
+			status = g->waitreason;
+		else
+			status = "waiting";
+		break;
+	case Gmoribund:
+		status = "moribund";
+		break;
+	default:
+		status = "???";
+		break;
+	}
+	runtime·printf("goroutine %d [%s]:\n", g->goid, status);
+}
+
+void
 runtime·tracebackothers(G *me)
 {
 	G *g;
@@ -257,7 +291,8 @@ runtime·tracebackothers(G *me)
 	for(g = runtime·allg; g != nil; g = g->alllink) {
 		if(g == me || g->status == Gdead)
 			continue;
-		runtime·printf("\ngoroutine %d [%d]:\n", g->goid, g->status);
+		runtime·printf("\n");
+		runtime·goroutineheader(g);
 		runtime·traceback(g->sched.pc, g->sched.sp, 0, g);
 	}
 }
@@ -1073,15 +1108,18 @@ runtime·newproc1(byte *fn, byte *argp, int32 narg, int32 nret, void *callerpc)
 	schedlock();
 
 	if((newg = gfget()) != nil){
-		newg->status = Gwaiting;
 		if(newg->stackguard - StackGuard != newg->stack0)
 			runtime·throw("invalid stack in newg");
 	} else {
 		newg = runtime·malg(StackMin);
-		newg->status = Gwaiting;
-		newg->alllink = runtime·allg;
-		runtime·allg = newg;
+		if(runtime·lastg == nil)
+			runtime·allg = newg;
+		else
+			runtime·lastg->alllink = newg;
+		runtime·lastg = newg;
 	}
+	newg->status = Gwaiting;
+	newg->waitreason = "new goroutine";
 
 	sp = newg->stackbase;
 	sp -= siz;