runtime: copy cpuprof code from Go 1.7 runtime

    
    This replaces runtime/cpuprof.goc with go/runtime/cpuprof.go and adjusts
    the supporting code in runtime/proc.c.
    
    This adds another case where the compiler needs to avoid heap allocation
    in the runtime package: when evaluating a method expression into a
    closure.  Implementing this required moving the relevant code from
    do_get_backend to do_flatten, so that I could easily add a temporary
    variable.  Doing that let me get rid of Bound_method_expression::do_lower.
    
    Reviewed-on: https://go-review.googlesource.com/31050

From-SVN: r241163

gcc/go/gofrontend/MERGE

-e3913d96fb024b916c87a4dc01f413523467ead9
+5f043fc2bf0f92a84a1f7da57acd79a61c9d2592
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

gcc/go/gofrontend/expressions.cc

@@ -3623,6 +3623,8 @@ Unsafe_type_conversion_expression::do_get_backend(Translate_context* context)
               || et->map_type() != NULL
               || et->channel_type() != NULL
 	      || et->is_nil_type());
+  else if (t->function_type() != NULL)
+    go_assert(et->points_to() != NULL);
   else
     go_unreachable();
 
@@ -6482,34 +6484,6 @@ Bound_method_expression::do_traverse(Traverse* traverse)
   return Expression::traverse(&this->expr_, traverse);
 }
 
-// Lower the expression.  If this is a method value rather than being
-// called, and the method is accessed via a pointer, we may need to
-// add nil checks.  Introduce a temporary variable so that those nil
-// checks do not cause multiple evaluation.
-
-Expression*
-Bound_method_expression::do_lower(Gogo*, Named_object*,
-				  Statement_inserter* inserter, int)
-{
-  // For simplicity we use a temporary for every call to an embedded
-  // method, even though some of them might be pure value methods and
-  // not require a temporary.
-  if (this->expr_->var_expression() == NULL
-      && this->expr_->temporary_reference_expression() == NULL
-      && this->expr_->set_and_use_temporary_expression() == NULL
-      && (this->method_->field_indexes() != NULL
-	  || (this->method_->is_value_method()
-	      && this->expr_->type()->points_to() != NULL)))
-    {
-      Temporary_statement* temp =
-	Statement::make_temporary(this->expr_->type(), NULL, this->location());
-      inserter->insert(temp);
-      this->expr_ = Expression::make_set_and_use_temporary(temp, this->expr_,
-							   this->location());
-    }
-  return this;
-}
-
 // Return the type of a bound method expression.  The type of this
 // object is simply the type of the method with no receiver.
 
@@ -6724,32 +6698,43 @@ bme_check_nil(const Method::Field_indexes* field_indexes, Location loc,
   return cond;
 }
 
-// Get the backend representation for a method value.
+// Flatten a method value into a struct with nil checks.  We can't do
+// this in the lowering phase, because if the method value is called
+// directly we don't need a thunk.  That case will have been handled
+// by Call_expression::do_lower, so if we get here then we do need a
+// thunk.
 
-Bexpression*
-Bound_method_expression::do_get_backend(Translate_context* context)
+Expression*
+Bound_method_expression::do_flatten(Gogo* gogo, Named_object*,
+				    Statement_inserter* inserter)
 {
-  Named_object* thunk = Bound_method_expression::create_thunk(context->gogo(),
+  Location loc = this->location();
+
+  Named_object* thunk = Bound_method_expression::create_thunk(gogo,
 							      this->method_,
 							      this->function_);
   if (thunk->is_erroneous())
     {
       go_assert(saw_errors());
-      return context->backend()->error_expression();
+      return Expression::make_error(loc);
     }
 
-  // FIXME: We should lower this earlier, but we can't lower it in the
-  // lowering pass because at that point we don't know whether we need
-  // to create the thunk or not.  If the expression is called, we
-  // don't need the thunk.
-
-  Location loc = this->location();
+  // Force the expression into a variable.  This is only necessary if
+  // we are going to do nil checks below, but it's easy enough to
+  // always do it.
+  Expression* expr = this->expr_;
+  if (!expr->is_variable())
+    {
+      Temporary_statement* etemp = Statement::make_temporary(NULL, expr, loc);
+      inserter->insert(etemp);
+      expr = Expression::make_temporary_reference(etemp, loc);
+    }
 
   // If the method expects a value, and we have a pointer, we need to
   // dereference the pointer.
 
   Named_object* fn = this->method_->named_object();
-  Function_type* fntype;
+  Function_type *fntype;
   if (fn->is_function())
     fntype = fn->func_value()->type();
   else if (fn->is_function_declaration())
@@ -6757,7 +6742,7 @@ Bound_method_expression::do_get_backend(Translate_context* context)
   else
     go_unreachable();
 
-  Expression* val = this->expr_;
+  Expression* val = expr;
   if (fntype->receiver()->type()->points_to() == NULL
       && val->type()->points_to() != NULL)
     val = Expression::make_unary(OPERATOR_MULT, val, loc);
@@ -6781,17 +6766,28 @@ Bound_method_expression::do_get_backend(Translate_context* context)
   vals->push_back(val);
 
   Expression* ret = Expression::make_struct_composite_literal(st, vals, loc);
-  ret = Expression::make_heap_expression(ret, loc);
 
-  // See whether the expression or any embedded pointers are nil.
+  if (!gogo->compiling_runtime() || gogo->package_name() != "runtime")
+    ret = Expression::make_heap_expression(ret, loc);
+  else
+    {
+      // When compiling the runtime, method closures do not escape.
+      // When escape analysis becomes the default, and applies to
+      // method closures, this should be changed to make it an error
+      // if a method closure escapes.
+      Temporary_statement* ctemp = Statement::make_temporary(st, ret, loc);
+      inserter->insert(ctemp);
+      ret = Expression::make_temporary_reference(ctemp, loc);
+      ret = Expression::make_unary(OPERATOR_AND, ret, loc);
+      ret->unary_expression()->set_does_not_escape();
+    }
+
+  // If necessary, check whether the expression or any embedded
+  // pointers are nil.
 
   Expression* nil_check = NULL;
-  Expression* expr = this->expr_;
   if (this->method_->field_indexes() != NULL)
     {
-      // Note that we are evaluating this->expr_ twice, but that is OK
-      // because in the lowering pass we forced it into a temporary
-      // variable.
       Expression* ref = expr;
       nil_check = bme_check_nil(this->method_->field_indexes(), loc, &ref);
       expr = ref;
@@ -6808,19 +6804,20 @@ Bound_method_expression::do_get_backend(Translate_context* context)
 	nil_check = Expression::make_binary(OPERATOR_OROR, nil_check, n, loc);
     }
 
-  Bexpression* bme = ret->get_backend(context);
   if (nil_check != NULL)
     {
-      Gogo* gogo = context->gogo();
-      Bexpression* crash =
-	gogo->runtime_error(RUNTIME_ERROR_NIL_DEREFERENCE,
-			    loc)->get_backend(context);
-      Btype* btype = ret->type()->get_backend(gogo);
-      Bexpression* bcheck = nil_check->get_backend(context);
-      bme = gogo->backend()->conditional_expression(btype, bcheck, crash,
-						    bme, loc);
-    }
-  return bme;
+      Expression* crash = gogo->runtime_error(RUNTIME_ERROR_NIL_DEREFERENCE,
+					      loc);
+      // Fix the type of the conditional expression by pretending to
+      // evaluate to RET either way through the conditional.
+      crash = Expression::make_compound(crash, ret, loc);
+      ret = Expression::make_conditional(nil_check, crash, ret, loc);
+    }
+
+  // RET is a pointer to a struct, but we want a function type.
+  ret = Expression::make_unsafe_cast(this->type(), ret, loc);
+
+  return ret;
 }
 
 // Dump ast representation of a bound method expression.

gcc/go/gofrontend/expressions.h

@@ -2888,7 +2888,7 @@ class Bound_method_expression : public Expression
   do_traverse(Traverse*);
 
   Expression*
-  do_lower(Gogo*, Named_object*, Statement_inserter*, int);
+  do_flatten(Gogo*, Named_object*, Statement_inserter*);
 
   Type*
   do_type();
@@ -2907,7 +2907,8 @@ class Bound_method_expression : public Expression
   }
 
   Bexpression*
-  do_get_backend(Translate_context*);
+  do_get_backend(Translate_context*)
+  { go_unreachable(); }
 
   void
   do_dump_expression(Ast_dump_context*) const;

libgo/Makefile.am

@@ -512,7 +512,6 @@ runtime_files = \
 	$(runtime_thread_files) \
 	runtime/yield.c \
 	$(rtems_task_variable_add_file) \
-	cpuprof.c \
 	go-iface.c \
 	lfstack.c \
 	malloc.c \

libgo/Makefile.in

@@ -261,9 +261,9 @@ am__objects_6 = go-append.lo go-assert.lo go-assert-interface.lo \
 	mcentral.lo $(am__objects_1) mfixalloc.lo mgc0.lo mheap.lo \
 	msize.lo $(am__objects_2) panic.lo parfor.lo print.lo proc.lo \
 	runtime.lo signal_unix.lo thread.lo $(am__objects_3) yield.lo \
-	$(am__objects_4) cpuprof.lo go-iface.lo lfstack.lo malloc.lo \
-	mprof.lo netpoll.lo rdebug.lo reflect.lo runtime1.lo \
-	sigqueue.lo time.lo $(am__objects_5)
+	$(am__objects_4) go-iface.lo lfstack.lo malloc.lo mprof.lo \
+	netpoll.lo rdebug.lo reflect.lo runtime1.lo sigqueue.lo \
+	time.lo $(am__objects_5)
 am_libgo_llgo_la_OBJECTS = $(am__objects_6)
 libgo_llgo_la_OBJECTS = $(am_libgo_llgo_la_OBJECTS)
 libgo_llgo_la_LINK = $(LIBTOOL) --tag=CC $(AM_LIBTOOLFLAGS) \
@@ -911,7 +911,6 @@ runtime_files = \
 	$(runtime_thread_files) \
 	runtime/yield.c \
 	$(rtems_task_variable_add_file) \
-	cpuprof.c \
 	go-iface.c \
 	lfstack.c \
 	malloc.c \
@@ -1547,7 +1546,6 @@ mostlyclean-compile:
 distclean-compile:
 	-rm -f *.tab.c
 
-@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/cpuprof.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/env_posix.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/getncpu-bsd.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/getncpu-irix.Plo@am__quote@

libgo/go/runtime/cpuprof.go

+// Copyright 2011 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.
+
+// CPU profiling.
+// Based on algorithms and data structures used in
+// http://code.google.com/p/google-perftools/.
+//
+// The main difference between this code and the google-perftools
+// code is that this code is written to allow copying the profile data
+// to an arbitrary io.Writer, while the google-perftools code always
+// writes to an operating system file.
+//
+// The signal handler for the profiling clock tick adds a new stack trace
+// to a hash table tracking counts for recent traces. Most clock ticks
+// hit in the cache. In the event of a cache miss, an entry must be
+// evicted from the hash table, copied to a log that will eventually be
+// written as profile data. The google-perftools code flushed the
+// log itself during the signal handler. This code cannot do that, because
+// the io.Writer might block or need system calls or locks that are not
+// safe to use from within the signal handler. Instead, we split the log
+// into two halves and let the signal handler fill one half while a goroutine
+// is writing out the other half. When the signal handler fills its half, it
+// offers to swap with the goroutine. If the writer is not done with its half,
+// we lose the stack trace for this clock tick (and record that loss).
+// The goroutine interacts with the signal handler by calling getprofile() to
+// get the next log piece to write, implicitly handing back the last log
+// piece it obtained.
+//
+// The state of this dance between the signal handler and the goroutine
+// is encoded in the Profile.handoff field. If handoff == 0, then the goroutine
+// is not using either log half and is waiting (or will soon be waiting) for
+// a new piece by calling notesleep(&p.wait).  If the signal handler
+// changes handoff from 0 to non-zero, it must call notewakeup(&p.wait)
+// to wake the goroutine. The value indicates the number of entries in the
+// log half being handed off. The goroutine leaves the non-zero value in
+// place until it has finished processing the log half and then flips the number
+// back to zero. Setting the high bit in handoff means that the profiling is over,
+// and the goroutine is now in charge of flushing the data left in the hash table
+// to the log and returning that data.
+//
+// The handoff field is manipulated using atomic operations.
+// For the most part, the manipulation of handoff is orderly: if handoff == 0
+// then the signal handler owns it and can change it to non-zero.
+// If handoff != 0 then the goroutine owns it and can change it to zero.
+// If that were the end of the story then we would not need to manipulate
+// handoff using atomic operations. The operations are needed, however,
+// in order to let the log closer set the high bit to indicate "EOF" safely
+// in the situation when normally the goroutine "owns" handoff.
+
+package runtime
+
+import (
+	"runtime/internal/atomic"
+	"unsafe"
+)
+
+const (
+	numBuckets      = 1 << 10
+	logSize         = 1 << 17
+	assoc           = 4
+	maxCPUProfStack = 64
+)
+
+type cpuprofEntry struct {
+	count uintptr
+	depth int
+	stack [maxCPUProfStack]uintptr
+}
+
+type cpuProfile struct {
+	on     bool    // profiling is on
+	wait   note    // goroutine waits here
+	count  uintptr // tick count
+	evicts uintptr // eviction count
+	lost   uintptr // lost ticks that need to be logged
+
+	// Active recent stack traces.
+	hash [numBuckets]struct {
+		entry [assoc]cpuprofEntry
+	}
+
+	// Log of traces evicted from hash.
+	// Signal handler has filled log[toggle][:nlog].
+	// Goroutine is writing log[1-toggle][:handoff].
+	log     [2][logSize / 2]uintptr
+	nlog    int
+	toggle  int32
+	handoff uint32
+
+	// Writer state.
+	// Writer maintains its own toggle to avoid races
+	// looking at signal handler's toggle.
+	wtoggle  uint32
+	wholding bool // holding & need to release a log half
+	flushing bool // flushing hash table - profile is over
+	eodSent  bool // special end-of-data record sent; => flushing
+}
+
+var (
+	cpuprofLock mutex
+	cpuprof     *cpuProfile
+
+	eod = [3]uintptr{0, 1, 0}
+)
+
+func setcpuprofilerate(hz int32) {
+	systemstack(func() {
+		setcpuprofilerate_m(hz)
+	})
+}
+
+// lostProfileData is a no-op function used in profiles
+// to mark the number of profiling stack traces that were
+// discarded due to slow data writers.
+func lostProfileData() {}
+
+// SetCPUProfileRate sets the CPU profiling rate to hz samples per second.
+// If hz <= 0, SetCPUProfileRate turns off profiling.
+// If the profiler is on, the rate cannot be changed without first turning it off.
+//
+// Most clients should use the runtime/pprof package or
+// the testing package's -test.cpuprofile flag instead of calling
+// SetCPUProfileRate directly.
+func SetCPUProfileRate(hz int) {
+	// Clamp hz to something reasonable.
+	if hz < 0 {
+		hz = 0
+	}
+	if hz > 1000000 {
+		hz = 1000000
+	}
+
+	lock(&cpuprofLock)
+	if hz > 0 {
+		if cpuprof == nil {
+			cpuprof = (*cpuProfile)(sysAlloc(unsafe.Sizeof(cpuProfile{}), &memstats.other_sys))
+			if cpuprof == nil {
+				print("runtime: cpu profiling cannot allocate memory\n")
+				unlock(&cpuprofLock)
+				return
+			}
+		}
+		if cpuprof.on || cpuprof.handoff != 0 {
+			print("runtime: cannot set cpu profile rate until previous profile has finished.\n")
+			unlock(&cpuprofLock)
+			return
+		}
+
+		cpuprof.on = true
+		// pprof binary header format.
+		// https://github.com/gperftools/gperftools/blob/master/src/profiledata.cc#L119
+		p := &cpuprof.log[0]
+		p[0] = 0                 // count for header
+		p[1] = 3                 // depth for header
+		p[2] = 0                 // version number
+		p[3] = uintptr(1e6 / hz) // period (microseconds)
+		p[4] = 0
+		cpuprof.nlog = 5
+		cpuprof.toggle = 0
+		cpuprof.wholding = false
+		cpuprof.wtoggle = 0
+		cpuprof.flushing = false
+		cpuprof.eodSent = false
+		noteclear(&cpuprof.wait)
+
+		setcpuprofilerate(int32(hz))
+	} else if cpuprof != nil && cpuprof.on {
+		setcpuprofilerate(0)
+		cpuprof.on = false
+
+		// Now add is not running anymore, and getprofile owns the entire log.
+		// Set the high bit in cpuprof.handoff to tell getprofile.
+		for {
+			n := cpuprof.handoff
+			if n&0x80000000 != 0 {
+				print("runtime: setcpuprofile(off) twice\n")
+			}
+			if atomic.Cas(&cpuprof.handoff, n, n|0x80000000) {
+				if n == 0 {
+					// we did the transition from 0 -> nonzero so we wake getprofile
+					notewakeup(&cpuprof.wait)
+				}
+				break
+			}
+		}
+	}
+	unlock(&cpuprofLock)
+}
+
+// add adds the stack trace to the profile.
+// It is called from signal handlers and other limited environments
+// and cannot allocate memory or acquire locks that might be
+// held at the time of the signal, nor can it use substantial amounts
+// of stack. It is allowed to call evict.
+//go:nowritebarrierrec
+func (p *cpuProfile) add(pc []uintptr) {
+	p.addWithFlushlog(pc, p.flushlog)
+}
+
+// addWithFlushlog implements add and addNonGo.
+// It is called from signal handlers and other limited environments
+// and cannot allocate memory or acquire locks that might be
+// held at the time of the signal, nor can it use substantial amounts
+// of stack. It may be called by a signal handler with no g or m.
+// It is allowed to call evict, passing the flushlog parameter.
+//go:nosplit
+//go:nowritebarrierrec
+func (p *cpuProfile) addWithFlushlog(pc []uintptr, flushlog func() bool) {
+	if len(pc) > maxCPUProfStack {
+		pc = pc[:maxCPUProfStack]
+	}
+
+	// Compute hash.
+	h := uintptr(0)
+	for _, x := range pc {
+		h = h<<8 | (h >> (8 * (unsafe.Sizeof(h) - 1)))
+		h += x * 41
+	}
+	p.count++
+
+	// Add to entry count if already present in table.
+	b := &p.hash[h%numBuckets]
+Assoc:
+	for i := range b.entry {
+		e := &b.entry[i]
+		if e.depth != len(pc) {
+			continue
+		}
+		for j := range pc {
+			if e.stack[j] != pc[j] {
+				continue Assoc
+			}
+		}
+		e.count++
+		return
+	}
+
+	// Evict entry with smallest count.
+	var e *cpuprofEntry
+	for i := range b.entry {
+		if e == nil || b.entry[i].count < e.count {
+			e = &b.entry[i]
+		}
+	}
+	if e.count > 0 {
+		if !p.evict(e, flushlog) {
+			// Could not evict entry. Record lost stack.
+			p.lost++
+			return
+		}
+		p.evicts++
+	}
+
+	// Reuse the newly evicted entry.
+	e.depth = len(pc)
+	e.count = 1
+	copy(e.stack[:], pc)
+}
+
+// evict copies the given entry's data into the log, so that
+// the entry can be reused.  evict is called from add, which
+// is called from the profiling signal handler, so it must not
+// allocate memory or block, and it may be called with no g or m.
+// It is safe to call flushlog. evict returns true if the entry was
+// copied to the log, false if there was no room available.
+//go:nosplit
+//go:nowritebarrierrec
+func (p *cpuProfile) evict(e *cpuprofEntry, flushlog func() bool) bool {
+	d := e.depth
+	nslot := d + 2
+	log := &p.log[p.toggle]
+	if p.nlog+nslot > len(log) {
+		if !flushlog() {
+			return false
+		}
+		log = &p.log[p.toggle]
+	}
+
+	q := p.nlog
+	log[q] = e.count
+	q++
+	log[q] = uintptr(d)
+	q++
+	copy(log[q:], e.stack[:d])
+	q += d
+	p.nlog = q
+	e.count = 0
+	return true
+}
+
+// flushlog tries to flush the current log and switch to the other one.
+// flushlog is called from evict, called from add, called from the signal handler,
+// so it cannot allocate memory or block. It can try to swap logs with
+// the writing goroutine, as explained in the comment at the top of this file.
+//go:nowritebarrierrec
+func (p *cpuProfile) flushlog() bool {
+	if !atomic.Cas(&p.handoff, 0, uint32(p.nlog)) {
+		return false
+	}
+	notewakeup(&p.wait)
+
+	p.toggle = 1 - p.toggle
+	log := &p.log[p.toggle]
+	q := 0
+	if p.lost > 0 {
+		lostPC := funcPC(lostProfileData)
+		log[0] = p.lost
+		log[1] = 1
+		log[2] = lostPC
+		q = 3
+		p.lost = 0
+	}
+	p.nlog = q
+	return true
+}
+
+// addNonGo is like add, but runs on a non-Go thread.
+// It can't do anything that might need a g or an m.
+// With this entry point, we don't try to flush the log when evicting an
+// old entry. Instead, we just drop the stack trace if we're out of space.
+//go:nosplit
+//go:nowritebarrierrec
+func (p *cpuProfile) addNonGo(pc []uintptr) {
+	p.addWithFlushlog(pc, func() bool { return false })
+}
+
+// getprofile blocks until the next block of profiling data is available
+// and returns it as a []byte. It is called from the writing goroutine.
+func (p *cpuProfile) getprofile() []byte {
+	if p == nil {
+		return nil
+	}
+
+	if p.wholding {
+		// Release previous log to signal handling side.
+		// Loop because we are racing against SetCPUProfileRate(0).
+		for {
+			n := p.handoff
+			if n == 0 {
+				print("runtime: phase error during cpu profile handoff\n")
+				return nil
+			}
+			if n&0x80000000 != 0 {
+				p.wtoggle = 1 - p.wtoggle
+				p.wholding = false
+				p.flushing = true
+				goto Flush
+			}
+			if atomic.Cas(&p.handoff, n, 0) {
+				break
+			}
+		}
+		p.wtoggle = 1 - p.wtoggle
+		p.wholding = false
+	}
+
+	if p.flushing {
+		goto Flush
+	}
+
+	if !p.on && p.handoff == 0 {
+		return nil
+	}
+
+	// Wait for new log.
+	notetsleepg(&p.wait, -1)
+	noteclear(&p.wait)
+
+	switch n := p.handoff; {
+	case n == 0:
+		print("runtime: phase error during cpu profile wait\n")
+		return nil
+	case n == 0x80000000:
+		p.flushing = true
+		goto Flush
+	default:
+		n &^= 0x80000000
+
+		// Return new log to caller.
+		p.wholding = true
+
+		return uintptrBytes(p.log[p.wtoggle][:n])
+	}
+
+	// In flush mode.
+	// Add is no longer being called. We own the log.
+	// Also, p.handoff is non-zero, so flushlog will return false.
+	// Evict the hash table into the log and return it.
+Flush:
+	for i := range p.hash {
+		b := &p.hash[i]
+		for j := range b.entry {
+			e := &b.entry[j]
+			if e.count > 0 && !p.evict(e, p.flushlog) {
+				// Filled the log. Stop the loop and return what we've got.
+				break Flush
+			}
+		}
+	}
+
+	// Return pending log data.
+	if p.nlog > 0 {
+		// Note that we're using toggle now, not wtoggle,
+		// because we're working on the log directly.
+		n := p.nlog
+		p.nlog = 0
+		return uintptrBytes(p.log[p.toggle][:n])
+	}
+
+	// Made it through the table without finding anything to log.
+	if !p.eodSent {
+		// We may not have space to append this to the partial log buf,
+		// so we always return a new slice for the end-of-data marker.
+		p.eodSent = true
+		return uintptrBytes(eod[:])
+	}
+
+	// Finally done. Clean up and return nil.
+	p.flushing = false
+	if !atomic.Cas(&p.handoff, p.handoff, 0) {
+		print("runtime: profile flush racing with something\n")
+	}
+	return nil
+}
+
+func uintptrBytes(p []uintptr) (ret []byte) {
+	pp := (*slice)(unsafe.Pointer(&p))
+	rp := (*slice)(unsafe.Pointer(&ret))
+
+	rp.array = pp.array
+	rp.len = pp.len * int(unsafe.Sizeof(p[0]))
+	rp.cap = rp.len
+
+	return
+}
+
+// CPUProfile returns the next chunk of binary CPU profiling stack trace data,
+// blocking until data is available. If profiling is turned off and all the profile
+// data accumulated while it was on has been returned, CPUProfile returns nil.
+// The caller must save the returned data before calling CPUProfile again.
+//
+// Most clients should use the runtime/pprof package or
+// the testing package's -test.cpuprofile flag instead of calling
+// CPUProfile directly.
+func CPUProfile() []byte {
+	return cpuprof.getprofile()
+}
+
+//go:linkname runtime_pprof_runtime_cyclesPerSecond runtime_pprof.runtime_cyclesPerSecond
+func runtime_pprof_runtime_cyclesPerSecond() int64 {
+	return tickspersecond()
+}

libgo/go/runtime/stubs.go

@@ -415,3 +415,16 @@ func startTheWorld() {
 func getMstats() *mstats {
 	return &memstats
 }
+
+// Temporary for gccgo until we port proc.go.
+func setcpuprofilerate_m(hz int32)
+
+// Temporary for gccgo until we port mem_GOOS.go.
+func sysAlloc(n uintptr, sysStat *uint64) unsafe.Pointer
+
+// Temporary for gccgo until we port proc.go, so that the C signal
+// handler can call into cpuprof.
+//go:linkname cpuprofAdd runtime.cpuprofAdd
+func cpuprofAdd(stk []uintptr) {
+	cpuprof.add(stk)
+}

libgo/runtime/cpuprof.goc

-// Copyright 2011 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.
-
-// CPU profiling.
-// Based on algorithms and data structures used in
-// http://code.google.com/p/google-perftools/.
-//
-// The main difference between this code and the google-perftools
-// code is that this code is written to allow copying the profile data
-// to an arbitrary io.Writer, while the google-perftools code always
-// writes to an operating system file.
-//
-// The signal handler for the profiling clock tick adds a new stack trace
-// to a hash table tracking counts for recent traces.  Most clock ticks
-// hit in the cache.  In the event of a cache miss, an entry must be 
-// evicted from the hash table, copied to a log that will eventually be
-// written as profile data.  The google-perftools code flushed the
-// log itself during the signal handler.  This code cannot do that, because
-// the io.Writer might block or need system calls or locks that are not
-// safe to use from within the signal handler.  Instead, we split the log
-// into two halves and let the signal handler fill one half while a goroutine
-// is writing out the other half.  When the signal handler fills its half, it
-// offers to swap with the goroutine.  If the writer is not done with its half,
-// we lose the stack trace for this clock tick (and record that loss).
-// The goroutine interacts with the signal handler by calling getprofile() to
-// get the next log piece to write, implicitly handing back the last log
-// piece it obtained.
-//
-// The state of this dance between the signal handler and the goroutine
-// is encoded in the Profile.handoff field.  If handoff == 0, then the goroutine
-// is not using either log half and is waiting (or will soon be waiting) for
-// a new piece by calling notesleep(&p->wait).  If the signal handler
-// changes handoff from 0 to non-zero, it must call notewakeup(&p->wait)
-// to wake the goroutine.  The value indicates the number of entries in the
-// log half being handed off.  The goroutine leaves the non-zero value in
-// place until it has finished processing the log half and then flips the number
-// back to zero.  Setting the high bit in handoff means that the profiling is over, 
-// and the goroutine is now in charge of flushing the data left in the hash table
-// to the log and returning that data.  
-//
-// The handoff field is manipulated using atomic operations.
-// For the most part, the manipulation of handoff is orderly: if handoff == 0
-// then the signal handler owns it and can change it to non-zero.  
-// If handoff != 0 then the goroutine owns it and can change it to zero.
-// If that were the end of the story then we would not need to manipulate
-// handoff using atomic operations.  The operations are needed, however,
-// in order to let the log closer set the high bit to indicate "EOF" safely
-// in the situation when normally the goroutine "owns" handoff.
-
-package runtime
-#include "runtime.h"
-#include "arch.h"
-#include "malloc.h"
-
-#include "array.h"
-typedef struct __go_open_array Slice;
-#define array __values
-#define len __count
-#define cap __capacity
-
-enum
-{
-	HashSize = 1<<10,
-	LogSize = 1<<17,
-	Assoc = 4,
-	MaxStack = 64,
-};
-
-typedef struct Profile Profile;
-typedef struct Bucket Bucket;
-typedef struct Entry Entry;
-
-struct Entry {
-	uintptr count;
-	uintptr depth;
-	uintptr stack[MaxStack];
-};
-
-struct Bucket {
-	Entry entry[Assoc];
-};
-
-struct Profile {
-	bool on;		// profiling is on
-	Note wait;		// goroutine waits here
-	uintptr count;		// tick count
-	uintptr evicts;		// eviction count
-	uintptr lost;		// lost ticks that need to be logged
-
-	// Active recent stack traces.
-	Bucket hash[HashSize];
-
-	// Log of traces evicted from hash.
-	// Signal handler has filled log[toggle][:nlog].
-	// Goroutine is writing log[1-toggle][:handoff].
-	uintptr log[2][LogSize/2];
-	uintptr nlog;
-	int32 toggle;
-	uint32 handoff;
-	
-	// Writer state.
-	// Writer maintains its own toggle to avoid races
-	// looking at signal handler's toggle.
-	uint32 wtoggle;
-	bool wholding;	// holding & need to release a log half
-	bool flushing;	// flushing hash table - profile is over
-	bool eod_sent;  // special end-of-data record sent; => flushing
-};
-
-static Lock lk;
-static Profile *prof;
-
-static void tick(uintptr*, int32);
-static void add(Profile*, uintptr*, int32);
-static bool evict(Profile*, Entry*);
-static bool flushlog(Profile*);
-
-static uintptr eod[3] = {0, 1, 0};
-
-// LostProfileData is a no-op function used in profiles
-// to mark the number of profiling stack traces that were
-// discarded due to slow data writers.
-static void
-LostProfileData(void)
-{
-}
-
-extern void runtime_SetCPUProfileRate(intgo)
-     __asm__ (GOSYM_PREFIX "runtime.SetCPUProfileRate");
-
-// SetCPUProfileRate sets the CPU profiling rate.
-// The user documentation is in debug.go.
-void
-runtime_SetCPUProfileRate(intgo hz)
-{
-	uintptr *p;
-	uintptr n;
-
-	// Clamp hz to something reasonable.
-	if(hz < 0)
-		hz = 0;
-	if(hz > 1000000)
-		hz = 1000000;
-
-	runtime_lock(&lk);
-	if(hz > 0) {
-		if(prof == nil) {
-			prof = runtime_SysAlloc(sizeof *prof, &mstats()->other_sys);
-			if(prof == nil) {
-				runtime_printf("runtime: cpu profiling cannot allocate memory\n");
-				runtime_unlock(&lk);
-				return;
-			}
-		}
-		if(prof->on || prof->handoff != 0) {
-			runtime_printf("runtime: cannot set cpu profile rate until previous profile has finished.\n");
-			runtime_unlock(&lk);
-			return;
-		}
-
-		prof->on = true;
-		p = prof->log[0];
-		// pprof binary header format.
-		// http://code.google.com/p/google-perftools/source/browse/trunk/src/profiledata.cc#117
-		*p++ = 0;  // count for header
-		*p++ = 3;  // depth for header
-		*p++ = 0;  // version number
-		*p++ = 1000000 / hz;  // period (microseconds)
-		*p++ = 0;
-		prof->nlog = p - prof->log[0];
-		prof->toggle = 0;
-		prof->wholding = false;
-		prof->wtoggle = 0;
-		prof->flushing = false;
-		prof->eod_sent = false;
-		runtime_noteclear(&prof->wait);
-
-		runtime_setcpuprofilerate(tick, hz);
-	} else if(prof != nil && prof->on) {
-		runtime_setcpuprofilerate(nil, 0);
-		prof->on = false;
-
-		// Now add is not running anymore, and getprofile owns the entire log.
-		// Set the high bit in prof->handoff to tell getprofile.
-		for(;;) {
-			n = prof->handoff;
-			if(n&0x80000000)
-				runtime_printf("runtime: setcpuprofile(off) twice");
-			if(runtime_cas(&prof->handoff, n, n|0x80000000))
-				break;
-		}
-		if(n == 0) {
-			// we did the transition from 0 -> nonzero so we wake getprofile
-			runtime_notewakeup(&prof->wait);
-		}
-	}
-	runtime_unlock(&lk);
-}
-
-static void
-tick(uintptr *pc, int32 n)
-{
-	add(prof, pc, n);
-}
-
-// add adds the stack trace to the profile.
-// It is called from signal handlers and other limited environments
-// and cannot allocate memory or acquire locks that might be
-// held at the time of the signal, nor can it use substantial amounts
-// of stack.  It is allowed to call evict.
-static void
-add(Profile *p, uintptr *pc, int32 n)
-{
-	int32 i, j;
-	uintptr h, x;
-	Bucket *b;
-	Entry *e;
-
-	if(n > MaxStack)
-		n = MaxStack;
-	
-	// Compute hash.
-	h = 0;
-	for(i=0; i<n; i++) {
-		h = h<<8 | (h>>(8*(sizeof(h)-1)));
-		x = pc[i];
-		h += x*31 + x*7 + x*3;
-	}
-	p->count++;
-
-	// Add to entry count if already present in table.
-	b = &p->hash[h%HashSize];
-	for(i=0; i<Assoc; i++) {
-		e = &b->entry[i];
-		if(e->depth != (uintptr)n)	
-			continue;
-		for(j=0; j<n; j++)
-			if(e->stack[j] != pc[j])
-				goto ContinueAssoc;
-		e->count++;
-		return;
-	ContinueAssoc:;
-	}
-
-	// Evict entry with smallest count.
-	e = &b->entry[0];
-	for(i=1; i<Assoc; i++)
-		if(b->entry[i].count < e->count)
-			e = &b->entry[i];
-	if(e->count > 0) {
-		if(!evict(p, e)) {
-			// Could not evict entry.  Record lost stack.
-			p->lost++;
-			return;
-		}
-		p->evicts++;
-	}
-	
-	// Reuse the newly evicted entry.
-	e->depth = n;
-	e->count = 1;
-	for(i=0; i<n; i++)
-		e->stack[i] = pc[i];
-}
-
-// evict copies the given entry's data into the log, so that
-// the entry can be reused.  evict is called from add, which
-// is called from the profiling signal handler, so it must not
-// allocate memory or block.  It is safe to call flushLog.
-// evict returns true if the entry was copied to the log,
-// false if there was no room available.
-static bool
-evict(Profile *p, Entry *e)
-{
-	int32 i, d, nslot;
-	uintptr *log, *q;
-	
-	d = e->depth;
-	nslot = d+2;
-	log = p->log[p->toggle];
-	if(p->nlog+nslot > nelem(p->log[0])) {
-		if(!flushlog(p))
-			return false;
-		log = p->log[p->toggle];
-	}
-	
-	q = log+p->nlog;
-	*q++ = e->count;
-	*q++ = d;
-	for(i=0; i<d; i++)
-		*q++ = e->stack[i];
-	p->nlog = q - log;
-	e->count = 0;
-	return true;
-}
-
-// flushlog tries to flush the current log and switch to the other one.
-// flushlog is called from evict, called from add, called from the signal handler,
-// so it cannot allocate memory or block.  It can try to swap logs with
-// the writing goroutine, as explained in the comment at the top of this file.
-static bool
-flushlog(Profile *p)
-{
-	uintptr *log, *q;
-
-	if(!runtime_cas(&p->handoff, 0, p->nlog))
-		return false;
-	runtime_notewakeup(&p->wait);
-
-	p->toggle = 1 - p->toggle;
-	log = p->log[p->toggle];
-	q = log;
-	if(p->lost > 0) {
-		*q++ = p->lost;
-		*q++ = 1;
-		*q++ = (uintptr)LostProfileData;
-		p->lost = 0;
-	}
-	p->nlog = q - log;
-	return true;
-}
-
-// getprofile blocks until the next block of profiling data is available
-// and returns it as a []byte.  It is called from the writing goroutine.
-Slice
-getprofile(Profile *p)
-{
-	uint32 i, j, n;
-	Slice ret;
-	Bucket *b;
-	Entry *e;
-
-	ret.array = nil;
-	ret.len = 0;
-	ret.cap = 0;
-	
-	if(p == nil)	
-		return ret;
-
-	if(p->wholding) {
-		// Release previous log to signal handling side.
-		// Loop because we are racing against SetCPUProfileRate(0).
-		for(;;) {
-			n = p->handoff;
-			if(n == 0) {
-				runtime_printf("runtime: phase error during cpu profile handoff\n");
-				return ret;
-			}
-			if(n & 0x80000000) {
-				p->wtoggle = 1 - p->wtoggle;
-				p->wholding = false;
-				p->flushing = true;
-				goto flush;
-			}
-			if(runtime_cas(&p->handoff, n, 0))
-				break;
-		}
-		p->wtoggle = 1 - p->wtoggle;
-		p->wholding = false;
-	}
-	
-	if(p->flushing)
-		goto flush;
-	
-	if(!p->on && p->handoff == 0)
-		return ret;
-
-	// Wait for new log.
-	runtime_notetsleepg(&p->wait, -1);
-	runtime_noteclear(&p->wait);
-
-	n = p->handoff;
-	if(n == 0) {
-		runtime_printf("runtime: phase error during cpu profile wait\n");
-		return ret;
-	}
-	if(n == 0x80000000) {
-		p->flushing = true;
-		goto flush;
-	}
-	n &= ~0x80000000;
-
-	// Return new log to caller.
-	p->wholding = true;
-
-	ret.array = (byte*)p->log[p->wtoggle];
-	ret.len = n*sizeof(uintptr);
-	ret.cap = ret.len;
-	return ret;
-
-flush:
-	// In flush mode.
-	// Add is no longer being called.  We own the log.
-	// Also, p->handoff is non-zero, so flushlog will return false.
-	// Evict the hash table into the log and return it.
-	for(i=0; i<HashSize; i++) {
-		b = &p->hash[i];
-		for(j=0; j<Assoc; j++) {
-			e = &b->entry[j];
-			if(e->count > 0 && !evict(p, e)) {
-				// Filled the log.  Stop the loop and return what we've got.
-				goto breakflush;
-			}
-		}
-	}
-breakflush:
-
-	// Return pending log data.
-	if(p->nlog > 0) {
-		// Note that we're using toggle now, not wtoggle,
-		// because we're working on the log directly.
-		ret.array = (byte*)p->log[p->toggle];
-		ret.len = p->nlog*sizeof(uintptr);
-		ret.cap = ret.len;
-		p->nlog = 0;
-		return ret;
-	}
-
-	// Made it through the table without finding anything to log.
-	if(!p->eod_sent) {
-		// We may not have space to append this to the partial log buf,
-		// so we always return a new slice for the end-of-data marker.
-		p->eod_sent = true;
-		ret.array = (byte*)eod;
-		ret.len = sizeof eod;
-		ret.cap = ret.len;
-		return ret;
-	}
-
-	// Finally done.  Clean up and return nil.
-	p->flushing = false;
-	if(!runtime_cas(&p->handoff, p->handoff, 0))
-		runtime_printf("runtime: profile flush racing with something\n");
-	return ret;  // set to nil at top of function
-}
-
-// CPUProfile returns the next cpu profile block as a []byte.
-// The user documentation is in debug.go.
-func CPUProfile() (ret Slice) {
-	ret = getprofile(prof);
-}

libgo/runtime/go-signal.c

@@ -156,6 +156,8 @@ runtime_sighandler (int sig, Siginfo *info,
 #ifdef SIGPROF
   if (sig == SIGPROF)
     {
+      /* FIXME: Handle m == NULL by calling something like gc's
+	 sigprofNonGo.  */
       if (m != NULL && gp != m->g0 && gp != m->gsignal)
 	runtime_sigprof ();
       return;

libgo/runtime/malloc.h

@@ -184,7 +184,8 @@ enum
 // SysFault marks a (already SysAlloc'd) region to fault
 // if accessed.  Used only for debugging the runtime.
 
-void*	runtime_SysAlloc(uintptr nbytes, uint64 *stat);
+void*	runtime_SysAlloc(uintptr nbytes, uint64 *stat)
+  __asm__ (GOSYM_PREFIX "runtime.sysAlloc");
 void	runtime_SysFree(void *v, uintptr nbytes, uint64 *stat);
 void	runtime_SysUnused(void *v, uintptr nbytes);
 void	runtime_SysUsed(void *v, uintptr nbytes);

libgo/runtime/proc.c

@@ -2686,11 +2686,8 @@ runtime_mcount(void)
 }
 
 static struct {
-	Lock;
-	void (*fn)(uintptr*, int32);
+	uint32 lock;
 	int32 hz;
-	uintptr pcbuf[TracebackMaxFrames];
-	Location locbuf[TracebackMaxFrames];
 } prof;
 
 static void System(void) {}
@@ -2703,8 +2700,11 @@ runtime_sigprof()
 	M *mp = g->m;
 	int32 n, i;
 	bool traceback;
+	uintptr pcbuf[TracebackMaxFrames];
+	Location locbuf[TracebackMaxFrames];
+	Slice stk;
 
-	if(prof.fn == nil || prof.hz == 0)
+	if(prof.hz == 0)
 		return;
 
 	if(mp == nil)
@@ -2718,12 +2718,6 @@ runtime_sigprof()
 	if(mp->mcache == nil)
 		traceback = false;
 
-	runtime_lock(&prof);
-	if(prof.fn == nil) {
-		runtime_unlock(&prof);
-		mp->mallocing--;
-		return;
-	}
 	n = 0;
 
 	if(runtime_atomicload(&runtime_in_callers) > 0) {
@@ -2735,34 +2729,44 @@ runtime_sigprof()
 	}
 
 	if(traceback) {
-		n = runtime_callers(0, prof.locbuf, nelem(prof.locbuf), false);
+		n = runtime_callers(0, locbuf, nelem(locbuf), false);
 		for(i = 0; i < n; i++)
-			prof.pcbuf[i] = prof.locbuf[i].pc;
+			pcbuf[i] = locbuf[i].pc;
 	}
 	if(!traceback || n <= 0) {
 		n = 2;
-		prof.pcbuf[0] = (uintptr)runtime_getcallerpc(&n);
+		pcbuf[0] = (uintptr)runtime_getcallerpc(&n);
 		if(mp->gcing || mp->helpgc)
-			prof.pcbuf[1] = (uintptr)GC;
+			pcbuf[1] = (uintptr)GC;
 		else
-			prof.pcbuf[1] = (uintptr)System;
+			pcbuf[1] = (uintptr)System;
+	}
+
+	if (prof.hz != 0) {
+		stk.__values = &pcbuf[0];
+		stk.__count = n;
+		stk.__capacity = n;
+
+		// Simple cas-lock to coordinate with setcpuprofilerate.
+		while (!runtime_cas(&prof.lock, 0, 1)) {
+			runtime_osyield();
+		}
+		if (prof.hz != 0) {
+			runtime_cpuprofAdd(stk);
+		}
+		runtime_atomicstore(&prof.lock, 0);
 	}
-	prof.fn(prof.pcbuf, n);
-	runtime_unlock(&prof);
+
 	mp->mallocing--;
 }
 
 // Arrange to call fn with a traceback hz times a second.
 void
-runtime_setcpuprofilerate(void (*fn)(uintptr*, int32), int32 hz)
+runtime_setcpuprofilerate_m(int32 hz)
 {
 	// Force sane arguments.
 	if(hz < 0)
 		hz = 0;
-	if(hz == 0)
-		fn = nil;
-	if(fn == nil)
-		hz = 0;
 
 	// Disable preemption, otherwise we can be rescheduled to another thread
 	// that has profiling enabled.
@@ -2773,10 +2777,12 @@ runtime_setcpuprofilerate(void (*fn)(uintptr*, int32), int32 hz)
 	// it would deadlock.
 	runtime_resetcpuprofiler(0);
 
-	runtime_lock(&prof);
-	prof.fn = fn;
+	while (!runtime_cas(&prof.lock, 0, 1)) {
+		runtime_osyield();
+	}
 	prof.hz = hz;
-	runtime_unlock(&prof);
+	runtime_atomicstore(&prof.lock, 0);
+
 	runtime_lock(&runtime_sched);
 	runtime_sched.profilehz = hz;
 	runtime_unlock(&runtime_sched);

libgo/runtime/runtime.h

@@ -417,7 +417,10 @@ void	runtime_freezetheworld(void);
 void	runtime_unwindstack(G*, byte*);
 void	runtime_sigprof();
 void	runtime_resetcpuprofiler(int32);
-void	runtime_setcpuprofilerate(void(*)(uintptr*, int32), int32);
+void	runtime_setcpuprofilerate_m(int32)
+     __asm__ (GOSYM_PREFIX "runtime.setcpuprofilerate_m");
+void	runtime_cpuprofAdd(Slice)
+     __asm__ (GOSYM_PREFIX "runtime.cpuprofAdd");
 void	runtime_usleep(uint32)
      __asm__ (GOSYM_PREFIX "runtime.usleep");
 int64	runtime_cputicks(void)

libgo/runtime/runtime1.goc

@@ -55,10 +55,6 @@ func getgoroot() (out String) {
 	out = runtime_getenv("GOROOT");
 }
 
-func runtime_pprof.runtime_cyclesPerSecond() (res int64) {
-	res = runtime_tickspersecond();
-}
-
 func sync.runtime_procPin() (p int) {
 	M *mp;