runtime: use cgo traceback for SIGPROF

If we collected a cgo traceback when entering the SIGPROF signal
handler, record it as part of the profiling stack trace.

This serves as the promised test for https://golang.org/cl/21055 .

Change-Id: I5f60cd6cea1d9b7c3932211483a6bfab60ed21d2
Reviewed-on: https://go-review.googlesource.com/22650
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

1 files changed, 96 insertions, 0 deletions

diff --git a/src/runtime/testdata/testprogcgo/pprof.go b/src/runtime/testdata/testprogcgo/pprof.go
new file mode 100644
index 0000000000..04ac4fe92e
--- /dev/null
+++ b/src/runtime/testdata/testprogcgo/pprof.go
@@ -0,0 +1,96 @@
+// Copyright 2016 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 main
+
+// Run a slow C function saving a CPU profile.
+
+/*
+#include <stdint.h>
+
+int salt1;
+int salt2;
+
+void cpuHog() {
+	int foo = salt1;
+	int i;
+
+	for (i = 0; i < 100000; i++) {
+		if (foo > 0) {
+			foo *= foo;
+		} else {
+			foo *= foo + 1;
+		}
+	}
+	salt2 = foo;
+}
+
+static int cpuHogCount;
+
+struct cgoTracebackArg {
+	uintptr_t  context;
+	uintptr_t* buf;
+	uintptr_t  max;
+};
+
+// pprofCgoTraceback is passed to runtime.SetCgoTraceback.
+// For testing purposes it pretends that all CPU hits in C code are in cpuHog.
+void pprofCgoTraceback(void* parg) {
+	struct cgoTracebackArg* arg = (struct cgoTracebackArg*)(parg);
+	arg->buf[0] = (uintptr_t)(cpuHog) + 0x10;
+	arg->buf[1] = 0;
+	++cpuHogCount;
+}
+
+// getCpuHogCount fetches the number of times we've seen cpuHog in the
+// traceback.
+int getCpuHogCount() {
+	return cpuHogCount;
+}
+*/
+import "C"
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"runtime"
+	"runtime/pprof"
+	"time"
+	"unsafe"
+)
+
+func init() {
+	register("CgoPprof", CgoPprof)
+}
+
+func CgoPprof() {
+	runtime.SetCgoTraceback(0, unsafe.Pointer(C.pprofCgoTraceback), nil, nil)
+
+	f, err := ioutil.TempFile("", "prof")
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(2)
+	}
+
+	if err := pprof.StartCPUProfile(f); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(2)
+	}
+
+	t0 := time.Now()
+	for C.getCpuHogCount() < 2 && time.Since(t0) < time.Second {
+		C.cpuHog()
+	}
+
+	pprof.StopCPUProfile()
+
+	name := f.Name()
+	if err := f.Close(); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(2)
+	}
+
+	fmt.Println(name)
+}