From ebdc2ebac8c2f9af09234e1486172b25a4af7136 Mon Sep 17 00:00:00 2001
From: Keith Randall <khr@google.com>
Date: Wed, 4 Mar 2015 16:20:19 -0800
Subject: [PATCH] Fix how goroutine arguments are handled.

runtime.goexit is the function that "lives" at the top of stack.  It
isn't really there, however.  It is just the return address used by
the outermost function of the goroutine.  It is just an assembly stub
that calls back into the runtime to deallocate the goroutine.

When the outermost goroutine function has arguments, the dumper
attributes them to runtime.goexit.  They aren't really there, however.
More specifically, they don't live in the outargs section of goexit's
frame.  They don't live in a frame, they are at the top of the
goroutine stack in their own little section.

runtime.goexit's "frame" is only one word in size, attributing the
goroutine's arguments to it causes a failure trying to read those
arguments out of the tiny frame.
---
 read/parser.go | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/read/parser.go b/read/parser.go
index a65e125..9275ef5 100644
--- a/read/parser.go
+++ b/read/parser.go
@@ -626,6 +626,29 @@ func rawRead(filename string) *Dump {
 			readUint64(r) // continpc
 			t.Name = readString(r)
 			t.Fields = readFields(r)
+			if t.Name == "runtime.goexit" {
+				// This is the function that "lives" at the top of stack.
+				// It isn't really there, however.  It is just the
+				// return address used by the outermost function of the
+				// goroutine.  It is just an assembly stub that calls
+				// back into the runtime to deallocate the goroutine.
+
+				// When the outermost goroutine function has arguments,
+				// the dumper attributes them to runtime.goexit.  They
+				// aren't really there, however.   More specifically,
+				// they don't live in the outargs section of goexit's
+				// frame.  They don't live in a frame, they are at the
+				// top of the goroutine stack in their own little section.
+
+				// runtime.goexit's "frame" is only one word in size,
+				// attributing the goroutine's arguments to it causes
+				// a failure trying to read those arguments out of
+				// the tiny frame.
+
+				// TODO: No frame is responsible for the goroutine's
+				// arguments.  How do we account for those roots?
+				t.Fields = nil
+			}
 			d.Frames = append(d.Frames, t)
 		case tagParams:
 			if readUint64(r) == 0 {