Implement Go threads. Implement a general event system

including breakpoints and Go thread create/exit.

R=rsc
APPROVED=rsc
DELTA=751  (729 added, 6 deleted, 16 changed)
OCL=34345
CL=34351

6 files changed, 750 insertions, 19 deletions

diff --git a/usr/austin/ogle/event.go b/usr/austin/ogle/event.go
new file mode 100644
index 000000000..dee1ba58e
--- /dev/null
+++ b/usr/austin/ogle/event.go
@@ -0,0 +1,294 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ogle
+
+import (
+	"fmt";
+	"os";
+	"ptrace";
+)
+
+/*
+ * Hooks and events
+ */
+
+// An EventHandler is a function that takes an event and returns a
+// response to that event and possibly an error.  If an event handler
+// returns an error, the process stops and no other handlers for that
+// event are executed.
+type EventHandler func(e Event) (EventAction, os.Error)
+
+// An EventAction is an event handler's response to an event.  If all
+// of an event's handlers execute without returning errors, their
+// results are combined as follows: If any handler returned
+// EAContinue, then the process resumes (without returning from
+// WaitStop); otherwise, if any handler returned EAStop, the process
+// remains stopped; otherwise, if all handlers returned EADefault, the
+// process resumes.  A handler may return EARemoveSelf bit-wise or'd
+// with any other action to indicate that the handler should be
+// removed from the hook.
+type EventAction int
+
+const (
+	EARemoveSelf EventAction = 0x100;
+	EADefault    EventAction = iota;
+	EAStop;
+	EAContinue;
+)
+
+// A EventHook allows event handlers to be added and removed.
+type EventHook interface {
+	AddHandler(EventHandler);
+	RemoveHandler(EventHandler);
+	NumHandler() int;
+	handle(e Event) (EventAction, os.Error);
+	String() string;
+}
+
+// EventHook is almost, but not quite, suitable for user-defined
+// events.  If we want user-defined events, make EventHook a struct,
+// special-case adding and removing handlers in breakpoint hooks, and
+// provide a public interface for posting events to hooks.
+
+type Event interface {
+	Process() *Process;
+	Thread() *Thread;
+	String() string;
+}
+
+type commonHook struct {
+	// Head of handler chain
+	head *handler;
+	// Number of non-internal handlers
+	len int;
+}
+
+type handler struct {
+	eh EventHandler;
+	// True if this handler must be run before user-defined
+	// handlers in order to ensure correctness.
+	internal bool;
+	// True if this handler has been removed from the chain.
+	removed bool;
+	next *handler;
+}
+
+func (h *commonHook) AddHandler(eh EventHandler) {
+	h.addHandler(eh, false);
+}
+
+func (h *commonHook) addHandler(eh EventHandler, internal bool) {
+	// Ensure uniqueness of handlers
+	h.RemoveHandler(eh);
+
+	if !internal {
+		h.len++;
+	}
+	// Add internal handlers to the beginning
+	if internal || h.head == nil {
+		h.head = &handler{eh, internal, false, h.head};
+		return;
+	}
+	// Add handler after internal handlers
+	// TODO(austin) This should probably go on the end instead
+	prev := h.head;
+	for prev.next != nil && prev.internal {
+		prev = prev.next;
+	}
+	prev.next = &handler{eh, internal, false, prev.next};
+}
+
+func (h *commonHook) RemoveHandler(eh EventHandler) {
+	plink := &h.head;
+	for l := *plink; l != nil; plink, l = &l.next, l.next {
+		if l.eh == eh {
+			if !l.internal {
+				h.len--;
+			}
+			l.removed = true;
+			*plink = l.next;
+			break;
+		}
+	}
+}
+
+func (h *commonHook) NumHandler() int {
+	return h.len;
+}
+
+func (h *commonHook) handle(e Event) (EventAction, os.Error) {
+	action := EADefault;
+	plink := &h.head;
+	for l := *plink; l != nil; plink, l = &l.next, l.next {
+		if l.removed {
+			continue;
+		}
+		a, err := l.eh(e);
+		if a & EARemoveSelf == EARemoveSelf {
+			if !l.internal {
+				h.len--;
+			}
+			l.removed = true;
+			*plink = l.next;
+			a &^= EARemoveSelf;
+		}
+		if err != nil {
+			return EAStop, err;
+		}
+		if a > action {
+			action = a;
+		}
+	}
+	return action, nil;
+}
+
+type commonEvent struct {
+	// The process of this event
+	p *Process;
+	// The thread of this event.
+	t *Thread;
+}
+
+func (e *commonEvent) Process() *Process {
+	return e.p;
+}
+
+func (e *commonEvent) Thread() *Thread {
+	return e.t;
+}
+
+/*
+ * Standard event handlers
+ */
+
+// EventPrint is a standard event handler that prints events as they
+// occur.  It will not cause the process to stop.
+func EventPrint(ev Event) (EventAction, os.Error) {
+	// TODO(austin) Include process name here?
+	fmt.Fprintf(os.Stderr, "*** %v\n", ev.String());
+	return EADefault, nil;
+}
+
+// EventStop is a standard event handler that causes the process to stop.
+func EventStop(ev Event) (EventAction, os.Error) {
+	return EAStop, nil;
+}
+
+/*
+ * Breakpoints
+ */
+
+type breakpointHook struct {
+	commonHook;
+	p *Process;
+	pc ptrace.Word;
+}
+
+// A Breakpoint event occurs when a process reaches a particular
+// program counter.  When this event is handled, the current thread
+// will be the thread that reached the program counter.
+type Breakpoint struct {
+	commonEvent;
+	osThread ptrace.Thread;
+	pc ptrace.Word;
+}
+
+func (h *breakpointHook) AddHandler(eh EventHandler) {
+	h.addHandler(eh, false);
+}
+
+func (h *breakpointHook) addHandler(eh EventHandler, internal bool) {
+	// We register breakpoint events lazily to avoid holding
+	// references to breakpoints without handlers.  Be sure to use
+	// the "canonical" breakpoint if there is one.
+	if cur, ok := h.p.breakpointHooks[h.pc]; ok {
+		h = cur;
+	}
+	oldhead := h.head;
+	h.commonHook.addHandler(eh, internal);
+	if oldhead == nil && h.head != nil {
+		h.p.proc.AddBreakpoint(h.pc);
+		h.p.breakpointHooks[h.pc] = h;
+	}
+}
+
+func (h *breakpointHook) RemoveHandler(eh EventHandler) {
+	oldhead := h.head;
+	h.commonHook.RemoveHandler(eh);
+	if oldhead != nil && h.head == nil {
+		h.p.proc.RemoveBreakpoint(h.pc);
+		h.p.breakpointHooks[h.pc] = nil, false;
+	}
+}
+
+func (h *breakpointHook) String() string {
+	// TODO(austin) Include process name?
+	// TODO(austin) Use line:pc or at least sym+%#x
+	return fmt.Sprintf("breakpoint at %#x", h.pc);
+}
+
+func (b *Breakpoint) PC() ptrace.Word {
+	return b.pc;
+}
+
+func (b *Breakpoint) String() string {
+	// TODO(austin) Include process name and thread
+	// TODO(austin) Use line:pc or at least sym+%#x
+	return fmt.Sprintf("breakpoint at %#x", b.pc);
+}
+
+/*
+ * Thread create/exit
+ */
+
+type threadCreateHook struct {
+	commonHook;
+}
+
+func (h *threadCreateHook) String() string {
+	return "thread create";
+}
+
+// A ThreadCreate event occurs when a process creates a new Go thread.
+// When this event is handled, the current thread will be the newly
+// created thread.
+type ThreadCreate struct {
+	commonEvent;
+	parent *Thread;
+}
+
+// Parent returns the thread that created this thread.  May be nil if
+// this event is the creation of the first thread.
+func (e *ThreadCreate) Parent() *Thread {
+	return e.parent;
+}
+
+func (e *ThreadCreate) String() string {
+	// TODO(austin) Include process name
+	if e.parent == nil {
+		return fmt.Sprintf("%v created", e.t);
+	}
+	return fmt.Sprintf("%v created by %v", e.t, e.parent);
+}
+
+type threadExitHook struct {
+	commonHook;
+}
+
+func (h *threadExitHook) String() string {
+	return "thread exit";
+}
+
+// A ThreadExit event occurs when a Go thread exits.
+type ThreadExit struct {
+	commonEvent;
+}
+
+func (e *ThreadExit) String() string {
+	// TODO(austin) Include process name
+	//return fmt.Sprintf("%v exited", e.t);
+	// For debugging purposes
+	return fmt.Sprintf("thread %#x exited", e.t.g.addr().base);
+}
diff --git a/usr/austin/ogle/frame.go b/usr/austin/ogle/frame.go
index 4a4fd9a43..522c263b1 100644
--- a/usr/austin/ogle/frame.go
+++ b/usr/austin/ogle/frame.go
@@ -47,7 +47,7 @@ func NewFrame(g remoteStruct) *Frame {
 	// figure out if it's on an OS thread or not.  However, this
 	// is difficult because the state isn't updated atomically
 	// with scheduling changes.
-	for _, t := range p.Threads() {
+	for _, t := range p.proc.Threads() {
 		regs, err := t.Regs();
 		if err != nil {
 			// TODO(austin) What to do?
@@ -182,6 +182,8 @@ func (f *Frame) Outer() *Frame {
 		return nil;
 	}
 
+	// TODO(austin) Register this frame for shoot-down.
+
 	f.outer = prepareFrame(pc, sp, f.stk, f);
 	return f.outer;
 }
diff --git a/usr/austin/ogle/process.go b/usr/austin/ogle/process.go
index 9dc5bc909..f1e7524b4 100644
--- a/usr/austin/ogle/process.go
+++ b/usr/austin/ogle/process.go
@@ -6,9 +6,11 @@ package ogle
 
 import (
 	"eval";
+	"fmt";
+	"log";
+	"os";
 	"ptrace";
 	"reflect";
-	"os";
 	"sym";
 )
 
@@ -37,17 +39,33 @@ func (e ProcessNotStopped) String() string {
 	return "process not stopped";
 }
 
+// An UnknownThread error is an internal error representing an
+// unrecognized G structure pointer.
+type UnknownThread struct {
+	OSThread ptrace.Thread;
+	GoThread ptrace.Word;
+}
+
+func (e UnknownThread) String() string {
+	return fmt.Sprintf("internal error: unknown thread (G %#x)", e.GoThread);
+}
+
+// A NoCurrentThread error occurs when no thread is currently selected
+// in a process (or when there are no threads in a process).
+type NoCurrentThread struct {}
+
+func (e NoCurrentThread) String() string {
+	return "no current thread";
+}
+
 // A Process represents a remote attached process.
 type Process struct {
 	Arch;
-	ptrace.Process;
+	proc ptrace.Process;
 
 	// The symbol table of this process
 	syms *sym.GoSymTable;
 
-	// Current frame, or nil if the current thread is not stopped
-	frame *Frame;
-
 	// A possibly-stopped OS thread, or nil
 	threadCache ptrace.Thread;
 
@@ -62,24 +80,76 @@ type Process struct {
 
 	// Globals from the sys package (or from no package)
 	sys struct {
-		lessstack, goexit, newproc, deferproc *sym.TextSym;
+		lessstack, goexit, newproc, deferproc, newprocreadylocked *sym.TextSym;
+		allg remotePtr;
+		g0 remoteStruct;
 	};
+
+	// Event queue
+	posted []Event;
+	pending []Event;
+	event Event;
+
+	// Event hooks
+	breakpointHooks map[ptrace.Word] *breakpointHook;
+	threadCreateHook *threadCreateHook;
+	threadExitHook *threadExitHook;
+
+	// Current thread, or nil if there are no threads
+	curThread *Thread;
+
+	// Threads by the address of their G structure
+	threads map[ptrace.Word] *Thread;
 }
 
+/*
+ * Process creation
+ */
+
 // NewProcess constructs a new remote process around a ptrace'd
 // process, an architecture, and a symbol table.
-func NewProcess(proc ptrace.Process, arch Arch, syms *sym.GoSymTable) *Process {
+func NewProcess(proc ptrace.Process, arch Arch, syms *sym.GoSymTable) (*Process, os.Error) {
 	p := &Process{
 		Arch: arch,
-		Process: proc,
+		proc: proc,
 		syms: syms,
 		types: make(map[ptrace.Word] *remoteType),
+		breakpointHooks: make(map[ptrace.Word] *breakpointHook),
+		threadCreateHook: new(threadCreateHook),
+		threadExitHook: new(threadExitHook),
+		threads: make(map[ptrace.Word] *Thread),
 	};
 
-	// TODO(austin) Set p.frame if proc is stopped
-
+	// Fill in remote runtime
 	p.bootstrap();
-	return p;
+
+	switch {
+	case p.sys.allg.addr().base == 0:
+		return nil, FormatError("failed to find runtime symbol 'allg'");
+	case p.sys.g0.addr().base == 0:
+		return nil, FormatError("failed to find runtime symbol 'g0'");
+	case p.sys.newprocreadylocked == nil:
+		return nil, FormatError("failed to find runtime symbol 'newprocreadylocked'");
+	case p.sys.goexit == nil:
+		return nil, FormatError("failed to find runtime symbol 'sys.goexit'");
+	}
+
+	// Get current threads
+	p.threads[p.sys.g0.addr().base] = &Thread{p.sys.g0, nil, false};
+	g := p.sys.allg.Get();
+	for g != nil {
+		gs := g.(remoteStruct);
+		fmt.Printf("*** Found thread at %#x\n", gs.addr().base);
+		p.threads[gs.addr().base] = &Thread{gs, nil, false};
+		g = gs.Field(p.f.G.Alllink).(remotePtr).Get();
+	}
+	p.selectSomeThread();
+
+	// Create internal breakpoints to catch new and exited threads
+	p.OnBreakpoint(ptrace.Word(p.sys.newprocreadylocked.Entry())).(*breakpointHook).addHandler(readylockedBP, true);
+	p.OnBreakpoint(ptrace.Word(p.sys.goexit.Entry())).(*breakpointHook).addHandler(goexitBP, true);
+
+	return p, nil;
 }
 
 // NewProcessElf constructs a new remote process around a ptrace'd
@@ -99,7 +169,7 @@ func NewProcessElf(proc ptrace.Process, elf *sym.Elf) (*Process, os.Error) {
 	default:
 		return nil, UnknownArchitecture(elf.Machine);
 	}
-	return NewProcess(proc, arch, syms), nil;
+	return NewProcess(proc, arch, syms);
 }
 
 // bootstrap constructs the runtime structure of a remote process.
@@ -154,16 +224,39 @@ func (p *Process) bootstrap() {
 	p.sys.goexit = globalFn("goexit");
 	p.sys.newproc = globalFn("sys·newproc");
 	p.sys.deferproc = globalFn("sys·deferproc");
+	p.sys.newprocreadylocked = globalFn("newprocreadylocked");
+	if allg := p.syms.SymFromName("allg"); allg != nil {
+		p.sys.allg = remotePtr{remote{ptrace.Word(allg.Common().Value), p}, p.runtime.G};
+	}
+	if g0 := p.syms.SymFromName("g0"); g0 != nil {
+		p.sys.g0 = p.runtime.G.mk(remote{ptrace.Word(g0.Common().Value), p}).(remoteStruct);
+	}
+}
+
+func (p *Process) selectSomeThread() {
+	// Once we have friendly thread ID's, there might be a more
+	// reasonable behavior for this.
+	p.curThread = nil;
+	for _, t := range p.threads {
+		if !t.isG0() {
+			p.curThread = t;
+			return;
+		}
+	}
 }
 
-func (p *Process) someStoppedThread() ptrace.Thread {
+/*
+ * Process memory
+ */
+
+func (p *Process) someStoppedOSThread() ptrace.Thread {
 	if p.threadCache != nil {
 		if _, err := p.threadCache.Stopped(); err == nil {
 			return p.threadCache;
 		}
 	}
 
-	for _, t := range p.Threads() {
+	for _, t := range p.proc.Threads() {
 		if _, err := t.Stopped(); err == nil {
 			p.threadCache = t;
 			return t;
@@ -173,7 +266,7 @@ func (p *Process) someStoppedThread() ptrace.Thread {
 }
 
 func (p *Process) Peek(addr ptrace.Word, out []byte) (int, os.Error) {
-	thr := p.someStoppedThread();
+	thr := p.someStoppedOSThread();
 	if thr == nil {
 		return 0, ProcessNotStopped{};
 	}
@@ -181,7 +274,7 @@ func (p *Process) Peek(addr ptrace.Word, out []byte) (int, os.Error) {
 }
 
 func (p *Process) Poke(addr ptrace.Word, b []byte) (int, os.Error) {
-	thr := p.someStoppedThread();
+	thr := p.someStoppedOSThread();
 	if thr == nil {
 		return 0, ProcessNotStopped{};
 	}
@@ -191,3 +284,225 @@ func (p *Process) Poke(addr ptrace.Word, b []byte) (int, os.Error) {
 func (p *Process) peekUintptr(addr ptrace.Word) ptrace.Word {
 	return ptrace.Word(mkUintptr(remote{addr, p}).(remoteUint).Get());
 }
+
+/*
+ * Events
+ */
+
+// OnBreakpoint returns the hook that is run when the program reaches
+// the given program counter.
+func (p *Process) OnBreakpoint(pc ptrace.Word) EventHook {
+	if bp, ok := p.breakpointHooks[pc]; ok {
+		return bp;
+	}
+	// The breakpoint will register itself when a handler is added
+	return &breakpointHook{commonHook{nil, 0}, p, pc};
+}
+
+// OnThreadCreate returns the hook that is run when a Go thread is created.
+func (p *Process) OnThreadCreate() EventHook {
+	return p.threadCreateHook;
+}
+
+// OnThreadExit returns the hook 
+func (p *Process) OnThreadExit() EventHook {
+	return p.threadExitHook;
+}
+
+// osThreadToThread looks up the Go thread running on an OS thread.
+func (p *Process) osThreadToThread(t ptrace.Thread) (*Thread, os.Error) {
+	regs, err := t.Regs();
+	if err != nil {
+		return nil, err;
+	}
+	g := p.G(regs);
+	gt, ok := p.threads[g];
+	if !ok {
+		return nil, UnknownThread{t, g};
+	}
+	return gt, nil;
+}
+
+// causesToEvents translates the stop causes of the underlying process
+// into an event queue.
+func (p *Process) causesToEvents() ([]Event, os.Error) {
+	// Count causes we're interested in
+	nev := 0;
+	for _, t := range p.proc.Threads() {
+		if c, err := t.Stopped(); err == nil {
+			switch c := c.(type) {
+			case ptrace.Breakpoint:
+				nev++;
+			case ptrace.Signal:
+				// TODO(austin)
+				//nev++;
+			}
+		}
+	}
+
+	// Translate causes to events
+	events := make([]Event, nev);
+	i := 0;
+	for _, t := range p.proc.Threads() {
+		if c, err := t.Stopped(); err == nil {
+			switch c := c.(type) {
+			case ptrace.Breakpoint:
+				gt, err := p.osThreadToThread(t);
+				if err != nil {
+					return nil, err;
+				}
+				events[i] = &Breakpoint{commonEvent{p, gt}, t, ptrace.Word(c)};
+				i++;
+			case ptrace.Signal:
+				// TODO(austin)
+			}
+		}
+	}
+
+	return events, nil;
+}
+
+// postEvent appends an event to the posted queue.  These events will
+// be processed before any currently pending events.
+func (p *Process) postEvent(ev Event) {
+	n := len(p.posted);
+	m := n*2;
+	if m == 0 {
+		m = 4;
+	}
+	posted := make([]Event, n+1, m);
+	for i, p := range p.posted {
+		posted[i] = p;
+	}
+	posted[n] = ev;
+	p.posted = posted;
+}
+
+// processEvents processes events in the event queue until no events
+// remain, a handler returns EAStop, or a handler returns an error.
+// It returns either EAStop or EAContinue and possibly an error.
+func (p *Process) processEvents() (EventAction, os.Error) {
+	var ev Event;
+	for len(p.posted) > 0 {
+		ev, p.posted = p.posted[0], p.posted[1:len(p.posted)];
+		action, err := p.processEvent(ev);
+		if action == EAStop {
+			return action, err;
+		}
+	}
+
+	for len(p.pending) > 0 {
+		ev, p.pending = p.pending[0], p.pending[1:len(p.pending)];
+		action, err := p.processEvent(ev);
+		if action == EAStop {
+			return action, err;
+		}
+	}
+
+	return EAContinue, nil;
+}
+
+// processEvent processes a single event, without manipulating the
+// event queues.  It returns either EAStop or EAContinue and possibly
+// an error.
+func (p *Process) processEvent(ev Event) (EventAction, os.Error) {
+	p.event = ev;
+
+	var action EventAction;
+	var err os.Error;
+	switch ev := p.event.(type) {
+	case *Breakpoint:
+		hook, ok := p.breakpointHooks[ev.pc];
+		if !ok {
+			break;
+		}
+		p.curThread = ev.Thread();
+		action, err = hook.handle(ev);
+
+	case *ThreadCreate:
+		p.curThread = ev.Thread();
+		action, err = p.threadCreateHook.handle(ev);
+
+	case *ThreadExit:
+		action, err = p.threadExitHook.handle(ev);
+
+	default:
+		log.Crashf("Unknown event type %T in queue", p.event);
+	}
+
+	if err != nil {
+		return EAStop, err;
+	} else if action == EAStop {
+		return EAStop, nil;
+	}
+	return EAContinue, nil;
+}
+
+// Event returns the last event that caused the process to stop.  This
+// may return nil if the process has never been stopped by an event.
+//
+// TODO(austin) Return nil if the user calls p.Stop()?
+func (p *Process) Event() Event {
+	return p.event;
+}
+
+/*
+ * Process control
+ */
+
+// TODO(austin) Cont, WaitStop, and Stop.  Need to figure out how
+// event handling works with these.  Originally I did it only in
+// WaitStop, but if you Cont and there are pending events, then you
+// have to not actually continue and wait until a WaitStop to process
+// them, even if the event handlers will tell you to continue.  We
+// could handle them in both Cont and WaitStop to avoid this problem,
+// but it's still weird if an event happens after the Cont and before
+// the WaitStop that the handlers say to continue from.  Or we could
+// handle them on a separate thread.  Then obviously you get weird
+// asynchrony things, like prints while the user it typing a command,
+// but that's not necessarily a bad thing.
+
+// ContWait resumes process execution and waits for an event to occur
+// that stops the process.
+func (p *Process) ContWait() os.Error {
+	for {
+		a, err := p.processEvents();
+		if err != nil {
+			return err;
+		} else if a == EAStop {
+			break;
+		}
+		err = p.proc.Continue();
+		if err != nil {
+			return err;
+		}
+		err = p.proc.WaitStop();
+		if err != nil {
+			return err;
+		}
+		for _, t := range p.threads {
+			t.resetFrame();
+		}
+		p.pending, err = p.causesToEvents();
+		if err != nil {
+			return err;
+		}
+	}
+	return nil;
+}
+
+// Out selects the caller frame of the current frame.
+func (p *Process) Out() os.Error {
+	if p.curThread == nil {
+		return NoCurrentThread{};
+	}
+	return p.curThread.Out();
+}
+
+// In selects the frame called by the current frame.
+func (p *Process) In() os.Error {
+	if p.curThread == nil {
+		return NoCurrentThread{};
+	}
+	return p.curThread.In();
+}
diff --git a/usr/austin/ogle/rruntime.go b/usr/austin/ogle/rruntime.go
index e0a654691..758f1c708 100644
--- a/usr/austin/ogle/rruntime.go
+++ b/usr/austin/ogle/rruntime.go
@@ -110,20 +110,24 @@ type rt1ArrayType struct {
  * See $GOROOT/src/pkg/runtime/runtime.h
  */
 
+// Fields beginning with _ are only for padding
+
 type rt1Stktop struct {
 	stackguard uintptr;
 	stackbase *rt1Stktop;
 	gobuf rt1Gobuf;
+	_args uint32;
+	_fp uintptr;
 }
 
 type rt1Gobuf struct {
 	sp uintptr;
 	pc uintptr;
 	g *rt1G;
+	r0 uintptr;
 }
 
 type rt1G struct {
-	// Fields beginning with _ are only for padding
 	_stackguard uintptr;
 	stackbase *rt1Stktop;
 	_defer uintptr;
@@ -133,6 +137,7 @@ type rt1G struct {
 	alllink *rt1G;
 	_param uintptr;
 	status int16;
+	// Incomplete
 }
 
 var rt1GStatus = runtimeGStatus{
@@ -193,7 +198,7 @@ type runtimeIndexes struct {
 		Sp, Pc, G int;
 	};
 	G struct {
-		Stackbase, Sched, Status int;
+		Stackbase, Sched, Status, Alllink int;
 	};
 }
 
diff --git a/usr/austin/ogle/rtype.go b/usr/austin/ogle/rtype.go
index 856594936..5bca923ce 100644
--- a/usr/austin/ogle/rtype.go
+++ b/usr/austin/ogle/rtype.go
@@ -54,6 +54,7 @@ func newManualType(t eval.Type, arch Arch) *remoteType {
 		basicType(eval.Uint8Type,   mkUint8,   1, 0);
 		basicType(eval.Uint32Type,  mkUint32,  4, 0);
 		basicType(eval.UintptrType, mkUintptr, arch.PtrSize(), 0);
+		basicType(eval.Int16Type,   mkInt16,   2, 0);
 		basicType(eval.Int32Type,   mkInt32,   4, 0);
 		basicType(eval.IntType,     mkInt,     arch.IntSize(), 0);
 		basicType(eval.StringType,  mkString,  arch.PtrSize() + arch.IntSize(), arch.PtrSize());
diff --git a/usr/austin/ogle/thread.go b/usr/austin/ogle/thread.go
new file mode 100644
index 000000000..888d01eff
--- /dev/null
+++ b/usr/austin/ogle/thread.go
@@ -0,0 +1,114 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ogle
+
+import (
+	"fmt";
+	"os";
+	"ptrace";
+)
+
+// A Thread represents a Go thread.
+type Thread struct {
+	g remoteStruct;
+	frame *Frame;
+	dead bool;
+}
+
+func (t *Thread) String() string {
+	if t.dead {
+		return "<dead thread>";
+	}
+	// TODO(austin) Give threads friendly ID's
+	return fmt.Sprintf("thread %#x", t.g.addr().base);
+}
+
+// isG0 returns true if this thread if the internal idle thread
+func (t *Thread) isG0() bool {
+	return t.g.addr().base == t.g.r.p.sys.g0.addr().base;
+}
+
+func (t *Thread) resetFrame() {
+	// TODO(austin) NewFrame can abort
+	// TODO(austin) Reuse any live part of the current frame stack
+	// so existing references to Frame's keep working.
+	t.frame = NewFrame(t.g);
+}
+
+// Out selects the caller frame of the current frame.
+func (t *Thread) Out() os.Error {
+	// TODO(austin) Outer can abort
+	f := t.frame.Outer();
+	if f != nil {
+		t.frame = f;
+	}
+	return nil;
+}
+
+// In selects the frame called by the current frame.
+func (t *Thread) In() os.Error {
+	f := t.frame.Inner();
+	if f != nil {
+		t.frame = f;
+	}
+	return nil;
+}
+
+func readylockedBP(ev Event) (EventAction, os.Error) {
+	b := ev.(*Breakpoint);
+	p := b.Process();
+
+	// The new g is the only argument to this function, so the
+	// stack will have the return address, then the G*.
+	regs, err := b.osThread.Regs();
+	if err != nil {
+		return EAStop, err;
+	}
+	sp := regs.SP();
+	addr := sp + ptrace.Word(p.PtrSize());
+	arg := remotePtr{remote{addr, p}, p.runtime.G};
+	g := arg.Get();
+	if g == nil {
+		return EAStop, UnknownThread{b.osThread, 0};
+	}
+	gs := g.(remoteStruct);
+	t := &Thread{gs, nil, false};
+	p.threads[gs.addr().base] = t;
+
+	// Enqueue thread creation event
+	parent := b.Thread();
+	if parent.isG0() {
+		parent = nil;
+	}
+	p.postEvent(&ThreadCreate{commonEvent{p, t}, parent});
+
+	// If we don't have any thread selected, select this one
+	if p.curThread == nil {
+		p.curThread = t;
+	}
+
+	return EADefault, nil;
+}
+
+func goexitBP(ev Event) (EventAction, os.Error) {
+	b := ev.(*Breakpoint);
+	p := b.Process();
+
+	t := b.Thread();
+	t.dead = true;
+
+	addr := t.g.addr().base;
+	p.threads[addr] = nil, false;
+
+	// Enqueue thread exit event
+	p.postEvent(&ThreadExit{commonEvent{p, t}});
+
+	// If we just exited our selected thread, selected another
+	if p.curThread == t {
+		p.selectSomeThread();
+	}
+
+	return EADefault, nil;
+}