runtime/pprof: support OS X CPU profiling

Work around profiling kernel bug with signal masks.
Still broken on 64-bit Snow Leopard kernel,
but I think we can ignore that one and let people
upgrade to Lion.

Add new trivial tools addr2line and objdump to take
the place of the GNU tools of the same name, since
those are not installed on OS X.

Adapt pprof to invoke 'go tool addr2line' and
'go tool objdump' if the system tools do not exist.

Clean up disassembly of base register on amd64.

Fixes #2008.

R=golang-dev, bradfitz, mikioh.mikioh, r, iant
CC=golang-dev
https://golang.org/cl/5697066

misc/pprof

@@ -1,7 +1,7 @@
 #! /usr/bin/env perl
 
 # This is a copy of http://google-perftools.googlecode.com/svn/trunk/src/pprof
-# with local modifications to handle generation of SVG images and 
+# with local modifications to handle generation of SVG images and
 # the Go-style pprof paths.  These modifications will probably filter
 # back into the official source before long.
 # It's convenient to have a copy here because we need just the one
@@ -9,11 +9,11 @@
 
 # Copyright (c) 1998-2007, Google Inc.
 # All rights reserved.
-# 
+#
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
-# 
+#
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
@@ -23,7 +23,7 @@
 #     * Neither the name of Google Inc. nor the names of its
 # contributors may be used to endorse or promote products derived from
 # this software without specific prior written permission.
-# 
+#
 # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
@@ -1234,6 +1234,13 @@ sub Disassemble {
   my $cmd = sprintf("$objdump -C -d -l --no-show-raw-insn " .
                     "--start-address=0x$start_addr " .
                     "--stop-address=0x$end_addr $prog");
+
+  if (system("$objdump --help >/dev/null 2>&1") != 0) {
+    # objdump must not exist.  Fall back to go tool objdump.
+    $objdump = "go tool objdump";
+    $cmd = "$objdump $prog 0x$start_addr 0x$end_addr";
+  }
+
   open(OBJDUMP, "$cmd |") || error("$objdump: $!\n");
   my @result = ();
   my $filename = "";
@@ -1305,10 +1312,10 @@ sub PrintListing {
   my $cumulative = shift;
   my $list_opts = shift;
   my $html = shift;
-  
+
   my $output = \*STDOUT;
   my $fname = "";
-  
+
 
   if ($html) {
     # Arrange to write the output to a temporary file
@@ -1323,7 +1330,7 @@ sub PrintListing {
     printf $output ("<div class=\"legend\">%s<br>Total: %s %s</div>\n",
                     $main::prog, Unparse($total), Units());
   }
- 
+
   my $listed = 0;
   foreach my $lib (@{$libs}) {
     my $symbol_table = GetProcedureBoundaries($lib->[0], $list_opts);
@@ -2221,7 +2228,7 @@ function handleMouseWheel(evt) {
 		z = 0.1;
 	if(z > 10.0)
 		z = 10.0;
-		
+
 	var g = svgDoc.getElementById("viewport");
 
 	var p = getEventPoint(evt);
@@ -4391,6 +4398,12 @@ sub MapToSymbols {
     $cmd = "$addr2line --demangle -f -C -e $image";
   }
 
+  if (system("$addr2line --help >/dev/null 2>&1") != 0) {
+    # addr2line must not exist.  Fall back to go tool addr2line.
+    $addr2line = "go tool addr2line";
+    $cmd = "$addr2line $image";
+  }
+
   # If "addr2line" isn't installed on the system at all, just use
   # nm to get what info we can (function names, but not line numbers).
   if (system("$addr2line --help >/dev/null 2>&1") != 0) {
@@ -4434,7 +4447,7 @@ sub MapToSymbols {
   if ($debug) {
     print("----\n");
     system("cat $main::tmpfile_sym");
-    print("----\n");
+    print("---- $cmd\n");
     system("$cmd <$main::tmpfile_sym");
     print("----\n");
   }
@@ -4544,7 +4557,7 @@ sub ShortFunctionName {
 # Trim overly long symbols found in disassembler output
 sub CleanDisassembly {
   my $d = shift;
-  while ($d =~ s/(?<!\.)\([^()%]*\)(\s*const)?//g) { } # Argument types, not (%rax)
+  while ($d =~ s/(?<!\.)\([^()%A-Z]*\)(\s*const)?//g) { } # Argument types, not (%rax)
   while ($d =~ s/(\w+)<[^<>]*>/$1/g)  { }       # Remove template arguments
   return $d;
 }
@@ -4625,7 +4638,7 @@ sub ConfigureTool {
     my $dirname = $`;    # this is everything up to and including the last slash
     if (-x "$dirname$tool") {
       $path = "$dirname$tool";
-    } else { 
+    } else {
       $path = $tool;
     }
   }

src/cmd/addr2line/main.c

@@ -0,0 +1,68 @@
+// Copyright 2012 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.
+
+/*
+ * addr2line simulation - only enough to make pprof work on Macs
+ */
+
+#include <u.h>
+#include <libc.h>
+#include <bio.h>
+#include <mach.h>
+
+void
+usage(void)
+{
+	fprint(2, "usage: addr2line binary\n");
+	fprint(2, "reads addresses from standard input and writes two lines for each:\n");
+	fprint(2, "\tfunction name\n");
+	fprint(2, "\tfile:line\n");
+	exits("usage");
+}
+
+void
+main(int argc, char **argv)
+{
+	int fd;
+	char *p;
+	uvlong pc;
+	Symbol s;
+	Fhdr fhdr;
+	Biobuf bin, bout;
+	char file[1024];
+
+	ARGBEGIN{
+	default:
+		usage();
+	}ARGEND
+
+	if(argc != 1)
+		usage();
+
+	fd = open(argv[0], OREAD);
+	if(fd < 0)
+		sysfatal("open %s: %r", argv[0]);
+	if(crackhdr(fd, &fhdr) <= 0)
+		sysfatal("crackhdr: %r");
+	machbytype(fhdr.type);
+	if(syminit(fd, &fhdr) <= 0)
+		sysfatal("syminit: %r");
+
+	Binit(&bin, 0, OREAD);
+	Binit(&bout, 1, OWRITE);
+	for(;;) {
+		p = Brdline(&bin, '\n');
+		if(p == nil)
+			break;
+		p[Blinelen(&bin)-1] = '\0';
+		pc = strtoull(p, 0, 16);
+		if(!findsym(pc, CTEXT, &s))
+			s.name = "??";
+		if(!fileline(file, sizeof file, pc))
+			strcpy(file, "??:0");
+		Bprint(&bout, "%s\n%s\n", s.name, file);
+	}
+	Bflush(&bout);
+	exits(0);
+}

src/cmd/dist/build.c

@@ -59,7 +59,7 @@ int
 find(char *p, char **l, int n)
 {
 	int i;
-	
+
 	for(i=0; i<n; i++)
 		if(streq(p, l[i]))
 			return i;
@@ -73,7 +73,7 @@ init(void)
 	char *p;
 	int i;
 	Buf b;
-	
+
 	binit(&b);
 
 	xgetenv(&b, "GOROOT");
@@ -126,7 +126,7 @@ init(void)
 	xsetenv("GOROOT", goroot);
 	xsetenv("GOARCH", goarch);
 	xsetenv("GOOS", goos);
-	
+
 	// Make the environment more predictable.
 	xsetenv("LANG", "C");
 	xsetenv("LANGUAGE", "en_US.UTF8");
@@ -170,13 +170,13 @@ findgoversion(void)
 	int i, nrev;
 	Buf b, path, bmore, branch;
 	Vec tags;
-	
+
 	binit(&b);
 	binit(&path);
 	binit(&bmore);
 	binit(&branch);
 	vinit(&tags);
-	
+
 	// The $GOROOT/VERSION file takes priority, for distributions
 	// without the Mercurial repo.
 	bpathf(&path, "%s/VERSION", goroot);
@@ -232,14 +232,14 @@ findgoversion(void)
 		bprintf(&b, "branch.%s", bstr(&branch));
 		tag = btake(&b);
 	}
-	
+
 	if(rev[0]) {
 		// Tag is before the revision we're building.
 		// Add extra information.
 		run(&bmore, goroot, CheckExit, "hg", "log", "--template", " +{node|short}", "-r", rev, nil);
 		chomp(&bmore);
 	}
-	
+
 	bprintf(&b, "%s", tag);
 	if(bmore.len > 0)
 		bwriteb(&b, &bmore);
@@ -249,14 +249,14 @@ findgoversion(void)
 
 done:
 	p = btake(&b);
-	
+
-	
+
 	bfree(&b);
 	bfree(&path);
 	bfree(&bmore);
 	bfree(&branch);
 	vfree(&tags);
-	
+
 	return p;
 }
 
@@ -325,7 +325,7 @@ setup(void)
 			xremoveall(p);
 		xmkdirall(p);
 	}
-	
+
 	// Create object directory.
 	// We keep it in pkg/ so that all the generated binaries
 	// are in one tree.  If pkg/obj/libgc.a exists, it is a dreg from
@@ -393,7 +393,7 @@ static char *proto_gccargs[] = {
 static Vec gccargs;
 
 // deptab lists changes to the default dependencies for a given prefix.
-// deps ending in /* read the whole directory; deps beginning with - 
+// deps ending in /* read the whole directory; deps beginning with -
 // exclude files with that prefix.
 static struct {
 	char *prefix;  // prefix of target
@@ -559,7 +559,7 @@ install(char *dir)
 	vinit(&clean);
 	vinit(&lib);
 	vinit(&extra);
-	
+
 	// path = full path to dir.
 	bpathf(&path, "%s/src/%s", goroot, dir);
 	name = lastelem(dir);
@@ -599,7 +599,7 @@ install(char *dir)
 	exe = "";
 	if(streq(gohostos, "windows"))
 		exe = ".exe";
-	
+
 	// Start final link command line.
 	// Note: code below knows that link.p[targ] is the target.
 	if(islib) {
@@ -696,13 +696,13 @@ install(char *dir)
 					}
 					files.len = n;
 					continue;
-				}				
+				}
 				vadd(&files, p);
 			}
 		}
 	}
 	vuniq(&files);
-	
+
 	// Convert to absolute paths.
 	for(i=0; i<files.len; i++) {
 		if(!isabs(files.p[i])) {
@@ -740,11 +740,11 @@ install(char *dir)
 		files.p[n++] = files.p[i];
 	}
 	files.len = n;
-	
+
 	for(i=0; i<lib.len && !stale; i++)
 		if(mtime(lib.p[i]) > ttarg)
 			stale = 1;
-		
+
 	if(!stale)
 		goto out;
 
@@ -792,9 +792,9 @@ install(char *dir)
 		copy(bpathf(&b, "%s/zasm_GOOS_GOARCH.h", workdir),
 			bpathf(&b1, "%s/zasm_%s_%s.h", bstr(&path), goos, goarch), 0);
 	}
-	
+
 	// Generate .c files from .goc files.
-	if(streq(dir, "pkg/runtime")) {		
+	if(streq(dir, "pkg/runtime")) {
 		for(i=0; i<files.len; i++) {
 			p = files.p[i];
 			if(!hassuffix(p, ".goc"))
@@ -808,7 +808,7 @@ install(char *dir)
 		}
 		vuniq(&files);
 	}
-	
+
 	if((!streq(goos, gohostos) || !streq(goarch, gohostarch)) && isgo) {
 		// We've generated the right files; the go command can do the build.
 		if(vflag > 1)
@@ -833,13 +833,13 @@ install(char *dir)
 				vadd(&compile, "-m32");
 			if(streq(dir, "lib9"))
 				vadd(&compile, "-DPLAN9PORT");
-	
+
 			vadd(&compile, "-I");
 			vadd(&compile, bpathf(&b, "%s/include", goroot));
-			
+
 			vadd(&compile, "-I");
 			vadd(&compile, bstr(&path));
-	
+
 			// lib9/goos.c gets the default constants hard-coded.
 			if(streq(name, "goos.c")) {
 				vadd(&compile, bprintf(&b, "-DGOOS=\"%s\"", goos));
@@ -849,7 +849,7 @@ install(char *dir)
 				vadd(&compile, bprintf(&b, "-DGOROOT=\"%s\"", bstr(&b1)));
 				vadd(&compile, bprintf(&b, "-DGOVERSION=\"%s\"", goversion));
 			}
-	
+
 			// gc/lex.c records the GOEXPERIMENT setting used during the build.
 			if(streq(name, "lex.c")) {
 				xgetenv(&b, "GOEXPERIMENT");
@@ -867,7 +867,7 @@ install(char *dir)
 			vadd(&compile, workdir);
 			vadd(&compile, bprintf(&b, "-DGOOS_%s", goos));
 			vadd(&compile, bprintf(&b, "-DGOARCH_%s", goarch));
-		}	
+		}
 
 		bpathf(&b, "%s/%s", workdir, lastelem(files.p[i]));
 		doclean = 1;
@@ -893,7 +893,7 @@ install(char *dir)
 			vadd(&clean, bstr(&b));
 	}
 	bgwait();
-	
+
 	if(isgo) {
 		// The last loop was compiling individual files.
 		// Hand the Go files to the compiler en masse.
@@ -905,16 +905,16 @@ install(char *dir)
 		vadd(&compile, bstr(&b));
 		vadd(&clean, bstr(&b));
 		vadd(&link, bstr(&b));
-		
+
 		vadd(&compile, "-p");
 		if(hasprefix(dir, "pkg/"))
 			vadd(&compile, dir+4);
 		else
 			vadd(&compile, "main");
-		
+
 		if(streq(dir, "pkg/runtime"))
 			vadd(&compile, "-+");
-		
+
 		vcopy(&compile, go.p, go.len);
 
 		runv(nil, bstr(&path), CheckExit, &compile);
@@ -980,7 +980,7 @@ shouldbuild(char *file, char *dir)
 	int i, j, ret;
 	Buf b;
 	Vec lines, fields;
-	
+
 	// Check file name for GOOS or GOARCH.
 	name = lastelem(file);
 	for(i=0; i<nelem(okgoos); i++)
@@ -989,11 +989,11 @@ shouldbuild(char *file, char *dir)
 	for(i=0; i<nelem(okgoarch); i++)
 		if(contains(name, okgoarch[i]) && !streq(okgoarch[i], goarch))
 			return 0;
-	
+
 	// Omit test files.
 	if(contains(name, "_test"))
 		return 0;
-	
+
 	// cmd/go/doc.go has a giant /* */ comment before
 	// it gets to the important detail that it is not part of
 	// package main.  We don't parse those comments,
@@ -1046,7 +1046,7 @@ out:
 	bfree(&b);
 	vfree(&lines);
 	vfree(&fields);
-	
+
 	return ret;
 }
 
@@ -1055,7 +1055,7 @@ static void
 copy(char *dst, char *src, int exec)
 {
 	Buf b;
-	
+
 	if(vflag > 1)
 		xprintf("cp %s %s\n", src, dst);
 
@@ -1070,11 +1070,13 @@ static char *buildorder[] = {
 	"lib9",
 	"libbio",
 	"libmach",
-	
+
 	"misc/pprof",
 
+	"cmd/addr2line",
 	"cmd/cov",
 	"cmd/nm",
+	"cmd/objdump",
 	"cmd/pack",
 	"cmd/prof",
 
@@ -1122,12 +1124,12 @@ static char *buildorder[] = {
 	"pkg/go/scanner",
 	"pkg/go/ast",
 	"pkg/go/parser",
-	"pkg/go/build",
 	"pkg/os/exec",
 	"pkg/net/url",
 	"pkg/text/template/parse",
 	"pkg/text/template",
 	"pkg/go/doc",
+	"pkg/go/build",
 	"cmd/go",
 };
 
@@ -1147,11 +1149,13 @@ static char *cleantab[] = {
 	"cmd/8c",
 	"cmd/8g",
 	"cmd/8l",
+	"cmd/addr2line",
 	"cmd/cc",
 	"cmd/cov",
 	"cmd/gc",
 	"cmd/go",
 	"cmd/nm",
+	"cmd/objdump",
 	"cmd/pack",
 	"cmd/prof",
 	"lib9",
@@ -1204,11 +1208,11 @@ clean(void)
 	int i, j, k;
 	Buf b, path;
 	Vec dir;
-	
+
 	binit(&b);
 	binit(&path);
 	vinit(&dir);
-	
+
 	for(i=0; i<nelem(cleantab); i++) {
 		bpathf(&path, "%s/src/%s", goroot, cleantab[i]);
 		xreaddir(&dir, bstr(&path));
@@ -1227,7 +1231,7 @@ clean(void)
 	if(rebuildall) {
 		// Remove object tree.
 		xremoveall(bpathf(&b, "%s/pkg/obj/%s_%s", goroot, gohostos, gohostarch));
-	
+
 		// Remove installed packages and tools.
 		xremoveall(bpathf(&b, "%s/pkg/%s_%s", goroot, gohostos, gohostarch));
 		xremoveall(bpathf(&b, "%s/pkg/%s_%s", goroot, goos, goarch));
@@ -1294,7 +1298,7 @@ cmdenv(int argc, char **argv)
 
 	if(argc > 0)
 		usage();
-	
+
 	xprintf(format, "GOROOT", goroot);
 	xprintf(format, "GOBIN", gobin);
 	xprintf(format, "GOARCH", goarch);
@@ -1346,7 +1350,7 @@ cmdbootstrap(int argc, char **argv)
 		clean();
 	goversion = findgoversion();
 	setup();
-	
+
 	// For the main bootstrap, building for host os/arch.
 	oldgoos = goos;
 	oldgoarch = goarch;
@@ -1356,7 +1360,7 @@ cmdbootstrap(int argc, char **argv)
 	gochar = gohostchar;
 	xsetenv("GOARCH", goarch);
 	xsetenv("GOOS", goos);
-	
+
 	for(i=0; i<nelem(buildorder); i++) {
 		install(bprintf(&b, buildorder[i], gohostchar));
 		if(!streq(oldgochar, gohostchar) && xstrstr(buildorder[i], "%s"))
@@ -1381,7 +1385,7 @@ defaulttarg(void)
 {
 	char *p;
 	Buf pwd, src, real_src;
-	
+
 	binit(&pwd);
 	binit(&src);
 	binit(&real_src);
@@ -1404,7 +1408,7 @@ defaulttarg(void)
 	bfree(&pwd);
 	bfree(&src);
 	bfree(&real_src);
-	
+
 	return p;
 }
 
@@ -1421,7 +1425,7 @@ cmdinstall(int argc, char **argv)
 	default:
 		usage();
 	}ARGEND
-	
+
 	if(argc == 0)
 		install(defaulttarg());
 
@@ -1469,7 +1473,7 @@ cmdbanner(int argc, char **argv)
 	binit(&b);
 	binit(&b1);
 	binit(&search);
-	
+
 	xprintf("\n");
 	xprintf("---\n");
 	xprintf("Installed Go for %s/%s in %s\n", goos, goarch, goroot);
@@ -1490,7 +1494,7 @@ cmdbanner(int argc, char **argv)
 			"On OS X the debuggers must be installed setgrp procmod.\n"
 			"Read and run ./sudo.bash to install the debuggers.\n");
 	}
-	
+
 	if(!streq(goroot_final, goroot)) {
 		xprintf("\n"
 			"The binaries expect %s to be copied or moved to %s\n",

src/cmd/objdump/main.c

@@ -0,0 +1,68 @@
+// Copyright 2012 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.
+
+/*
+ * objdump simulation - only enough to make pprof work on Macs
+ */
+
+#include <u.h>
+#include <libc.h>
+#include <bio.h>
+#include <mach.h>
+
+void
+usage(void)
+{
+	fprint(2, "usage: objdump binary start stop\n");
+	fprint(2, "Disassembles binary from PC start up to stop.\n");
+	exits("usage");
+}
+
+void
+main(int argc, char **argv)
+{
+	int fd, n;
+	uvlong pc, start, stop;
+	Fhdr fhdr;
+	Biobuf bout;
+	char buf[1024];
+	Map *text;
+
+	ARGBEGIN{
+	default:
+		usage();
+	}ARGEND
+
+	if(argc != 3)
+		usage();
+	start = strtoull(argv[1], 0, 16);
+	stop = strtoull(argv[2], 0, 16);
+
+	fd = open(argv[0], OREAD);
+	if(fd < 0)
+		sysfatal("open %s: %r", argv[0]);
+	if(crackhdr(fd, &fhdr) <= 0)
+		sysfatal("crackhdr: %r");
+	machbytype(fhdr.type);
+	if(syminit(fd, &fhdr) <= 0)
+		sysfatal("syminit: %r");
+	text = loadmap(nil, fd, &fhdr);
+	if(text == nil)
+		sysfatal("loadmap: %r");
+
+	Binit(&bout, 1, OWRITE);
+	for(pc=start; pc<stop; ) {
+		if(fileline(buf, sizeof buf, pc))
+			Bprint(&bout, "%s\n", buf);
+		buf[0] = '\0';
+		machdata->das(text, pc, 0, buf, sizeof buf);
+		Bprint(&bout, " %llx: %s\n", pc, buf);
+		n = machdata->instsize(text, pc);
+		if(n <= 0)
+			break;
+		pc += n;
+	}
+	Bflush(&bout);
+	exits(0);
+}

src/libmach/8db.c

@@ -1,11 +1,11 @@
 // Inferno libmach/8db.c
 // http://code.google.com/p/inferno-os/source/browse/utils/libmach/8db.c
 //
-// 	Copyright © 1994-1999 Lucent Technologies Inc.
+//	Copyright © 1994-1999 Lucent Technologies Inc.
-// 	Power PC support Copyright © 1995-2004 C H Forsyth (forsyth@terzarima.net).
+//	Power PC support Copyright © 1995-2004 C H Forsyth (forsyth@terzarima.net).
-// 	Portions Copyright © 1997-1999 Vita Nuova Limited.
+//	Portions Copyright © 1997-1999 Vita Nuova Limited.
-// 	Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com).
+//	Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com).
-// 	Revisions Copyright © 2000-2004 Lucent Technologies Inc. and others.
+//	Revisions Copyright © 2000-2004 Lucent Technologies Inc. and others.
 //	Portions Copyright © 2009 The Go Authors.  All rights reserved.
 //
 // Permission is hereby granted, free of charge, to any person obtaining a copy
@@ -2088,18 +2088,23 @@ immediate(Instr *ip, vlong val)
 static void
 pea(Instr *ip)
 {
+	int base;
+
+	base = ip->base;
+	if(base >= 0 && (ip->rex & REXB))
+		base += 8;
+
 	if (ip->mod == 3) {
 		if (ip->osize == 'B')
 			bprint(ip, (ip->rex & REXB? breg64: breg)[(uchar)ip->base]);
-		else if(ip->rex & REXB)
-			bprint(ip, "%s%s", ANAME(ip), reg[ip->base+8]);
 		else
-			bprint(ip, "%s%s", ANAME(ip), reg[(uchar)ip->base]);
+			bprint(ip, "%s%s", ANAME(ip), reg[base]);
 		return;
 	}
+
 	if (ip->segment)
 		bprint(ip, ip->segment);
-	if (ip->asize == 'E' && ip->base == SP)
+	if (ip->asize == 'E' && base == SP)
 		plocal(ip);
 	else {
 		if (ip->base < 0)

src/pkg/runtime/lock_futex.c

@@ -118,8 +118,12 @@ runtime·notewakeup(Note *n)
 void
 runtime·notesleep(Note *n)
 {
+	if(m->profilehz > 0)
+		runtime·setprof(false);
 	while(runtime·atomicload(&n->key) == 0)
 		runtime·futexsleep(&n->key, 0, -1);
+	if(m->profilehz > 0)
+		runtime·setprof(true);
 }
 
 void
@@ -135,14 +139,18 @@ runtime·notetsleep(Note *n, int64 ns)
 	if(runtime·atomicload(&n->key) != 0)
 		return;
 
+	if(m->profilehz > 0)
+		runtime·setprof(false);
 	deadline = runtime·nanotime() + ns;
 	for(;;) {
 		runtime·futexsleep(&n->key, 0, ns);
 		if(runtime·atomicload(&n->key) != 0)
-			return;
+			break;
 		now = runtime·nanotime();
 		if(now >= deadline)
-			return;
+			break;
 		ns = deadline - now;
 	}
+	if(m->profilehz > 0)
+		runtime·setprof(true);
 }

src/pkg/runtime/lock_sema.c

@@ -154,7 +154,11 @@ runtime·notesleep(Note *n)
 		return;
 	}
 	// Queued.  Sleep.
+	if(m->profilehz > 0)
+		runtime·setprof(false);
 	runtime·semasleep(-1);
+	if(m->profilehz > 0)
+		runtime·setprof(true);
 }
 
 void
@@ -178,12 +182,16 @@ runtime·notetsleep(Note *n, int64 ns)
 		return;
 	}
 
+	if(m->profilehz > 0)
+		runtime·setprof(false);
 	deadline = runtime·nanotime() + ns;
 	for(;;) {
 		// Registered.  Sleep.
 		if(runtime·semasleep(ns) >= 0) {
 			// Acquired semaphore, semawakeup unregistered us.
 			// Done.
+			if(m->profilehz > 0)
+				runtime·setprof(true);
 			return;
 		}
 
@@ -196,6 +204,9 @@ runtime·notetsleep(Note *n, int64 ns)
 		ns = deadline - now;
 	}
 
+	if(m->profilehz > 0)
+		runtime·setprof(true);
+
 	// Deadline arrived.  Still registered.  Semaphore not acquired.
 	// Want to give up and return, but have to unregister first,
 	// so that any notewakeup racing with the return does not

src/pkg/runtime/os_darwin.h

@@ -38,4 +38,7 @@ void	runtime·raisesigpipe(void);
 
 #define	NSIG 32
 #define	SI_USER	0  /* empirically true, but not what headers say */
+#define	SIG_BLOCK 1
+#define	SIG_UNBLOCK 2
 #define	SIG_SETMASK 3
+

src/pkg/runtime/os_freebsd.h

@@ -9,7 +9,6 @@ struct	sigaction;
 void	runtime·sigaction(int32, struct sigaction*, struct sigaction*);
 void	runtime·sigprocmask(Sigset *, Sigset *);
 void	runtime·setsig(int32, void(*)(int32, Siginfo*, void*, G*), bool);
-void	runtiem·setitimerval(int32, Itimerval*, Itimerval*);
 void	runtime·setitimer(int32, Itimerval*, Itimerval*);
 int32	runtime·sysctl(uint32*, uint32, byte*, uintptr*, byte*, uintptr);
 

src/pkg/runtime/os_netbsd.h

@@ -12,7 +12,6 @@ void	runtime·sigaltstack(Sigaltstack*, Sigaltstack*);
 void	runtime·sigaction(int32, struct sigaction*, struct sigaction*);
 void	runtime·setsig(int32, void(*)(int32, Siginfo*, void*, G*), bool);
 void	runtime·sighandler(int32 sig, Siginfo *info, void *context, G *gp);
-void	runtime·setitimerval(int32, Itimerval*, Itimerval*);
 void	runtime·setitimer(int32, Itimerval*, Itimerval*);
 int32	runtime·sysctl(uint32*, uint32, byte*, uintptr*, byte*, uintptr);
 

src/pkg/runtime/os_openbsd.h

@@ -12,7 +12,6 @@ void	runtime·sigaltstack(Sigaltstack*, Sigaltstack*);
 void	runtime·sigaction(int32, struct sigaction*, struct sigaction*);
 void	runtime·setsig(int32, void(*)(int32, Siginfo*, void*, G*), bool);
 void	runtime·sighandler(int32 sig, Siginfo *info, void *context, G *gp);
-void	runtime·setitimerval(int32, Itimerval*, Itimerval*);
 void	runtime·setitimer(int32, Itimerval*, Itimerval*);
 int32	runtime·sysctl(uint32*, uint32, byte*, uintptr*, byte*, uintptr);
 

src/pkg/runtime/pprof/pprof.go

@@ -20,8 +20,8 @@ import (
 	"text/tabwriter"
 )
 
-// BUG(rsc): CPU profiling is broken on OS X, due to an Apple kernel bug.
+// BUG(rsc): A bug in the OS X Snow Leopard 64-bit kernel prevents
-// For details, see http://code.google.com/p/go/source/detail?r=35b716c94225.
+// CPU profiling from giving accurate results on that system.
 
 // A Profile is a collection of stack traces showing the call sequences
 // that led to instances of a particular event, such as allocation.
@@ -156,7 +156,7 @@ func (p *Profile) Count() int {
 }
 
 // Add adds the current execution stack to the profile, associated with value.
-// Add stores value in an internal map, so value must be suitable for use as 
+// Add stores value in an internal map, so value must be suitable for use as
 // a map key and will not be garbage collected until the corresponding
 // call to Remove.  Add panics if the profile already contains a stack for value.
 //

src/pkg/runtime/pprof/pprof_test.go

@@ -7,6 +7,7 @@ package pprof_test
 import (
 	"bytes"
 	"hash/crc32"
+	"os/exec"
 	"runtime"
 	. "runtime/pprof"
 	"strings"
@@ -17,8 +18,15 @@ import (
 func TestCPUProfile(t *testing.T) {
 	switch runtime.GOOS {
 	case "darwin":
-		// see Apple Bug Report #9177434 (copied into change description)
+		out, err := exec.Command("uname", "-a").CombinedOutput()
-		return
+		if err != nil {
+			t.Fatal(err)
+		}
+		vers := string(out)
+		t.Logf("uname -a: %v", vers)
+		if strings.Contains(vers, "Darwin Kernel Version 10.8.0") && strings.Contains(vers, "root:xnu-1504.15.3~1/RELEASE_X86_64") {
+			t.Logf("skipping test on known-broken kernel (64-bit Snow Leopard)")
+		}
 	case "plan9":
 		// unimplemented
 		return

src/pkg/runtime/proc.c

@@ -338,7 +338,7 @@ mcommoninit(M *m)
 		m->mcache = runtime·allocmcache();
 
 	runtime·callers(1, m->createstack, nelem(m->createstack));
-	
+
 	// Add to runtime·allm so garbage collector doesn't free m
 	// when it is just in a register or thread-local storage.
 	m->alllink = runtime·allm;
@@ -728,7 +728,6 @@ runtime·mstart(void)
 	// so other calls can reuse this stack space.
 	runtime·gosave(&m->g0->sched);
 	m->g0->sched.pc = (void*)-1;  // make sure it is never used
-
 	runtime·asminit();
 	runtime·minit();
 	schedule(nil);
@@ -916,6 +915,9 @@ runtime·entersyscall(void)
 {
 	uint32 v;
 
+	if(m->profilehz > 0)
+		runtime·setprof(false);
+
 	// Leave SP around for gc and traceback.
 	runtime·gosave(&g->sched);
 	g->gcsp = g->sched.sp;
@@ -979,6 +981,9 @@ runtime·exitsyscall(void)
 		// Garbage collector isn't running (since we are),
 		// so okay to clear gcstack.
 		g->gcstack = nil;
+
+		if(m->profilehz > 0)
+			runtime·setprof(true);
 		return;
 	}
 

src/pkg/runtime/runtime.h

@@ -730,3 +730,13 @@ bool	runtime·showframe(Func*);
 void	runtime·ifaceE2I(struct InterfaceType*, Eface, Iface*);
 
 uintptr	runtime·memlimit(void);
+
+// If appropriate, ask the operating system to control whether this
+// thread should receive profiling signals.  This is only necessary on OS X.
+// An operating system should not deliver a profiling signal to a
+// thread that is not actually executing (what good is that?), but that's
+// what OS X prefers to do.  When profiling is turned on, we mask
+// away the profiling signal when threads go to sleep, so that OS X
+// is forced to deliver the signal to a thread that's actually running.
+// This is a no-op on other systems.
+void	runtime·setprof(bool);

src/pkg/runtime/signal_darwin_386.c

@@ -40,7 +40,8 @@ runtime·sighandler(int32 sig, Siginfo *info, void *context, G *gp)
 	r = &mc->ss;
 
 	if(sig == SIGPROF) {
-		runtime·sigprof((uint8*)r->eip, (uint8*)r->esp, nil, gp);
+		if(gp != m->g0 && gp != m->gsignal)
+			runtime·sigprof((uint8*)r->eip, (uint8*)r->esp, nil, gp);
 		return;
 	}
 
@@ -58,7 +59,7 @@ runtime·sighandler(int32 sig, Siginfo *info, void *context, G *gp)
 			if(pc[0] == 0xF6 || pc[0] == 0xF7)
 				info->si_code = FPE_INTDIV;
 		}
-		
+
 		// Make it look like a call to the signal func.
 		// Have to pass arguments out of band since
 		// augmenting the stack frame would break

src/pkg/runtime/signal_darwin_amd64.c

@@ -48,7 +48,8 @@ runtime·sighandler(int32 sig, Siginfo *info, void *context, G *gp)
 	r = &mc->ss;
 
 	if(sig == SIGPROF) {
-		runtime·sigprof((uint8*)r->rip, (uint8*)r->rsp, nil, gp);
+		if(gp != m->g0 && gp != m->gsignal)
+			runtime·sigprof((uint8*)r->rip, (uint8*)r->rsp, nil, gp);
 		return;
 	}
 
@@ -68,7 +69,7 @@ runtime·sighandler(int32 sig, Siginfo *info, void *context, G *gp)
 			if(pc[0] == 0xF6 || pc[0] == 0xF7)
 				info->si_code = FPE_INTDIV;
 		}
-		
+
 		// Make it look like a call to the signal func.
 		// Have to pass arguments out of band since
 		// augmenting the stack frame would break
@@ -77,7 +78,7 @@ runtime·sighandler(int32 sig, Siginfo *info, void *context, G *gp)
 		gp->sigcode0 = info->si_code;
 		gp->sigcode1 = (uintptr)info->si_addr;
 		gp->sigpc = r->rip;
-		
+
 		// Only push runtime·sigpanic if r->rip != 0.
 		// If r->rip == 0, probably panicked because of a
 		// call to a nil func.  Not pushing that onto sp will
@@ -92,7 +93,7 @@ runtime·sighandler(int32 sig, Siginfo *info, void *context, G *gp)
 		r->rip = (uintptr)runtime·sigpanic;
 		return;
 	}
-	
+
 	if(info->si_code == SI_USER || (t->flags & SigNotify))
 		if(runtime·sigsend(sig))
 			return;

src/pkg/runtime/signal_unix.c

@@ -55,17 +55,17 @@ void
 runtime·resetcpuprofiler(int32 hz)
 {
 	Itimerval it;
-	
+
 	runtime·memclr((byte*)&it, sizeof it);
 	if(hz == 0) {
 		runtime·setitimer(ITIMER_PROF, &it, nil);
-		runtime·setsig(SIGPROF, SIG_IGN, true);
+		runtime·setprof(false);
 	} else {
-		runtime·setsig(SIGPROF, runtime·sighandler, true);
 		it.it_interval.tv_sec = 0;
 		it.it_interval.tv_usec = 1000000 / hz;
 		it.it_value = it.it_interval;
 		runtime·setitimer(ITIMER_PROF, &it, nil);
+		runtime·setprof(true);
 	}
 	m->profilehz = hz;
 }

src/pkg/runtime/sys_darwin_386.s

@@ -100,14 +100,14 @@ TEXT runtime·nanotime(SB), 7, $32
 	IMULL	$1000, BX
 	ADDL	BX, AX
 	ADCL	$0, DX
-	
+
 	MOVL	ret+0(FP), DI
 	MOVL	AX, 0(DI)
 	MOVL	DX, 4(DI)
 	RET
 
 TEXT runtime·sigprocmask(SB),7,$0
-	MOVL	$48, AX
+	MOVL	$329, AX  // pthread_sigmask (on OS X, sigprocmask==entire process)
 	INT	$0x80
 	JAE	2(PC)
 	CALL	runtime·notok(SB)

src/pkg/runtime/sys_darwin_amd64.s

@@ -96,7 +96,7 @@ TEXT runtime·sigprocmask(SB),7,$0
 	MOVL	8(SP), DI
 	MOVQ	16(SP), SI
 	MOVQ	24(SP), DX
-	MOVL	$(0x2000000+48), AX	// syscall entry
+	MOVL	$(0x2000000+329), AX  // pthread_sigmask (on OS X, sigprocmask==entire process)
 	SYSCALL
 	JCC	2(PC)
 	CALL	runtime·notok(SB)

src/pkg/runtime/thread_darwin.c

@@ -11,6 +11,7 @@ extern SigTab runtime·sigtab[];
 
 static Sigset sigset_all = ~(Sigset)0;
 static Sigset sigset_none;
+static Sigset sigset_prof = 1<<(SIGPROF-1);
 
 static void
 unimplemented(int8 *name)
@@ -23,7 +24,14 @@ unimplemented(int8 *name)
 int32
 runtime·semasleep(int64 ns)
 {
-	return runtime·mach_semacquire(m->waitsema, ns);
+	int32 v;
+
+	if(m->profilehz > 0)
+		runtime·setprof(false);
+	v = runtime·mach_semacquire(m->waitsema, ns);
+	if(m->profilehz > 0)
+		runtime·setprof(true);
+	return v;
 }
 
 void
@@ -84,7 +92,7 @@ runtime·newosproc(M *m, G *g, void *stk, void (*fn)(void))
 	runtime·sigprocmask(SIG_SETMASK, &sigset_all, &oset);
 	errno = runtime·bsdthread_create(stk, m, g, fn);
 	runtime·sigprocmask(SIG_SETMASK, &oset, nil);
-	
+
 	if(errno < 0) {
 		runtime·printf("runtime: failed to create new OS thread (have %d already; errno=%d)\n", runtime·mcount(), -errno);
 		runtime·throw("runtime.newosproc");
@@ -98,7 +106,11 @@ runtime·minit(void)
 	// Initialize signal handling.
 	m->gsignal = runtime·malg(32*1024);	// OS X wants >=8K, Linux >=2K
 	runtime·signalstack(m->gsignal->stackguard - StackGuard, 32*1024);
-	runtime·sigprocmask(SIG_SETMASK, &sigset_none, nil);
+
+	if(m->profilehz > 0)
+		runtime·sigprocmask(SIG_SETMASK, &sigset_none, nil);
+	else
+		runtime·sigprocmask(SIG_SETMASK, &sigset_prof, nil);
 }
 
 // Mach IPC, to get at semaphores
@@ -434,3 +446,34 @@ runtime·memlimit(void)
 	// the limit.
 	return 0;
 }
+
+// NOTE(rsc): On OS X, when the CPU profiling timer expires, the SIGPROF
+// signal is not guaranteed to be sent to the thread that was executing to
+// cause it to expire.  It can and often does go to a sleeping thread, which is
+// not interesting for our profile.  This is filed Apple Bug Report #9177434,
+// copied to http://code.google.com/p/go/source/detail?r=35b716c94225.
+// To work around this bug, we disable receipt of the profiling signal on
+// a thread while in blocking system calls.  This forces the kernel to deliver
+// the profiling signal to an executing thread.
+//
+// The workaround fails on OS X machines using a 64-bit Snow Leopard kernel.
+// In that configuration, the kernel appears to want to deliver SIGPROF to the
+// sleeping threads regardless of signal mask and, worse, does not deliver
+// the signal until the thread wakes up on its own.
+//
+// If necessary, we can switch to using ITIMER_REAL for OS X and handle
+// the kernel-generated SIGALRM by generating our own SIGALRMs to deliver
+// to all the running threads.  SIGALRM does not appear to be affected by
+// the 64-bit Snow Leopard bug.  However, as of this writing Mountain Lion
+// is in preview, making Snow Leopard two versions old, so it is unclear how
+// much effort we need to spend on one buggy kernel.
+
+// Control whether profiling signal can be delivered to this thread.
+void
+runtime·setprof(bool on)
+{
+	if(on)
+		runtime·sigprocmask(SIG_UNBLOCK, &sigset_prof, nil);
+	else
+		runtime·sigprocmask(SIG_BLOCK, &sigset_prof, nil);
+}

src/pkg/runtime/thread_freebsd.c

@@ -189,3 +189,9 @@ runtime·memlimit(void)
 
 	return rl.rlim_cur - used;
 }
+
+void
+runtime·setprof(bool on)
+{
+	USED(on);
+}

src/pkg/runtime/thread_linux.c

@@ -228,7 +228,7 @@ runtime·memlimit(void)
 	Rlimit rl;
 	extern byte text[], end[];
 	uintptr used;
-	
+
 	if(runtime·getrlimit(RLIMIT_AS, &rl) != 0)
 		return 0;
 	if(rl.rlim_cur >= 0x7fffffff)
@@ -249,3 +249,9 @@ runtime·memlimit(void)
 
 	return rl.rlim_cur - used;
 }
+
+void
+runtime·setprof(bool on)
+{
+	USED(on);
+}

src/pkg/runtime/thread_netbsd.c

@@ -207,3 +207,9 @@ runtime·memlimit(void)
 {
 	return 0;
 }
+
+void
+runtime·setprof(bool on)
+{
+	USED(on);
+}

src/pkg/runtime/thread_openbsd.c

@@ -207,3 +207,9 @@ runtime·memlimit(void)
 {
 	return 0;
 }
+
+void
+runtime·setprof(bool on)
+{
+	USED(on);
+}

src/pkg/runtime/thread_plan9.c

@@ -87,7 +87,7 @@ runtime·nanotime(void)
 	// The naïve implementation (without the cached
 	// file descriptor) is roughly four times slower
 	// in 9vx on a 2.16 GHz Intel Core 2 Duo.
-	
+
 	if(fd < 0 && (fd = runtime·open((byte*)"/dev/bintime", OREAD|OCEXEC)) < 0)
 		return 0;
 	if(runtime·pread(fd, b, sizeof b, 0) != sizeof b)
@@ -241,3 +241,9 @@ runtime·memlimit(void)
 {
 	return 0;
 }
+
+void
+runtime·setprof(bool on)
+{
+	USED(on);
+}

src/pkg/runtime/thread_windows.c

@@ -226,7 +226,7 @@ void
 time·now(int64 sec, int32 usec)
 {
 	int64 ns;
-	
+
 	ns = runtime·nanotime();
 	sec = ns / 1000000000LL;
 	usec = ns - sec * 1000000000LL;
@@ -431,3 +431,9 @@ runtime·memlimit(void)
 {
 	return 0;
 }
+
+void
+runtime·setprof(bool on)
+{
+	USED(on);
+}