From a0d15cb9c8f3c35c96129857984d25446041f29e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Felix=20Geisend=C3=B6rfer?=
<felix.geisendoerfer@datadoghq.com>
Date: Sat, 7 Sep 2024 13:44:09 +0200
Subject: [PATCH] [release-branch.go1.23] runtime: fix MutexProfile missing
root frames
Fix a regression introduced in CL 598515 causing runtime.MutexProfile
stack traces to omit their root frames.
In most cases this was merely causing the `runtime.goexit` frame to go
missing. But in the case of runtime._LostContendedRuntimeLock, an empty
stack trace was being produced.
Add a test that catches this regression by checking for a stack trace
with the `runtime.goexit` frame.
Also fix a separate problem in expandFrame that could cause
out-of-bounds panics when profstackdepth is set to a value below 32.
There is no test for this fix because profstackdepth can't be changed at
runtime right now.
Fixes #69865
Change-Id: I1600fe62548ea84981df0916d25072c3ddf1ea1a
Reviewed-on: https://go-review.googlesource.com/c/go/+/611615
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Nick Ripley <nick.ripley@datadoghq.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
(cherry picked from commit c64ca8c6ef13723b9f25f4b5e1c7b6986b958d2e)
Reviewed-on: https://go-review.googlesource.com/c/go/+/621276
Reviewed-by: Cherry Mui <cherryyz@google.com>
---
src/runtime/mprof.go | 3 ++-
src/runtime/pprof/mprof_test.go | 2 +-
src/runtime/pprof/pprof_test.go | 46 ++++++++++++++++++++++++++++++---
3 files changed, 45 insertions(+), 6 deletions(-)
diff --git a/src/runtime/mprof.go b/src/runtime/mprof.go
index 82b7fa68aec..ee3e59a9aa9 100644
--- a/src/runtime/mprof.go
+++ b/src/runtime/mprof.go
@@ -1136,11 +1136,12 @@ func expandFrames(p []BlockProfileRecord) {
for i := range p {
cf := CallersFrames(p[i].Stack())
j := 0
- for ; j < len(expandedStack); j++ {
+ for j < len(expandedStack) {
f, more := cf.Next()
// f.PC is a "call PC", but later consumers will expect
// "return PCs"
expandedStack[j] = f.PC + 1
+ j++
if !more {
break
}
diff --git a/src/runtime/pprof/mprof_test.go b/src/runtime/pprof/mprof_test.go
index 391588d4acd..ef373b36848 100644
--- a/src/runtime/pprof/mprof_test.go
+++ b/src/runtime/pprof/mprof_test.go
@@ -145,7 +145,7 @@ func TestMemoryProfiler(t *testing.T) {
}
t.Logf("Profile = %v", p)
- stks := stacks(p)
+ stks := profileStacks(p)
for _, test := range tests {
if !containsStack(stks, test.stk) {
t.Fatalf("No matching stack entry for %q\n\nProfile:\n%v\n", test.stk, p)
diff --git a/src/runtime/pprof/pprof_test.go b/src/runtime/pprof/pprof_test.go
index 41952ff147c..da4ad17d77e 100644
--- a/src/runtime/pprof/pprof_test.go
+++ b/src/runtime/pprof/pprof_test.go
@@ -982,7 +982,7 @@ func TestBlockProfile(t *testing.T) {
t.Fatalf("invalid profile: %v", err)
}
- stks := stacks(p)
+ stks := profileStacks(p)
for _, test := range tests {
if !containsStack(stks, test.stk) {
t.Errorf("No matching stack entry for %v, want %+v", test.name, test.stk)
@@ -992,7 +992,7 @@ func TestBlockProfile(t *testing.T) {
}
-func stacks(p *profile.Profile) (res [][]string) {
+func profileStacks(p *profile.Profile) (res [][]string) {
for _, s := range p.Sample {
var stk []string
for _, l := range s.Location {
@@ -1005,6 +1005,22 @@ func stacks(p *profile.Profile) (res [][]string) {
return res
}
+func blockRecordStacks(records []runtime.BlockProfileRecord) (res [][]string) {
+ for _, record := range records {
+ frames := runtime.CallersFrames(record.Stack())
+ var stk []string
+ for {
+ frame, more := frames.Next()
+ stk = append(stk, frame.Function)
+ if !more {
+ break
+ }
+ }
+ res = append(res, stk)
+ }
+ return res
+}
+
func containsStack(got [][]string, want []string) bool {
for _, stk := range got {
if len(stk) < len(want) {
@@ -1289,7 +1305,7 @@ func TestMutexProfile(t *testing.T) {
t.Fatalf("invalid profile: %v", err)
}
- stks := stacks(p)
+ stks := profileStacks(p)
for _, want := range [][]string{
{"sync.(*Mutex).Unlock", "runtime/pprof.blockMutexN.func1"},
} {
@@ -1329,6 +1345,28 @@ func TestMutexProfile(t *testing.T) {
t.Fatalf("profile samples total %v, want within range [%v, %v] (target: %v)", d, lo, hi, N*D)
}
})
+
+ t.Run("records", func(t *testing.T) {
+ // Record a mutex profile using the structured record API.
+ var records []runtime.BlockProfileRecord
+ for {
+ n, ok := runtime.MutexProfile(records)
+ if ok {
+ records = records[:n]
+ break
+ }
+ records = make([]runtime.BlockProfileRecord, n*2)
+ }
+
+ // Check that we see the same stack trace as the proto profile. For
+ // historical reason we expect a runtime.goexit root frame here that is
+ // omitted in the proto profile.
+ stks := blockRecordStacks(records)
+ want := []string{"sync.(*Mutex).Unlock", "runtime/pprof.blockMutexN.func1", "runtime.goexit"}
+ if !containsStack(stks, want) {
+ t.Errorf("No matching stack entry for %+v", want)
+ }
+ })
}
func TestMutexProfileRateAdjust(t *testing.T) {
@@ -2514,7 +2552,7 @@ func TestProfilerStackDepth(t *testing.T) {
}
t.Logf("Profile = %v", p)
- stks := stacks(p)
+ stks := profileStacks(p)
var stk []string
for _, s := range stks {
if hasPrefix(s, test.prefix) {
--
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