From c64ca8c6ef13723b9f25f4b5e1c7b6986b958d2e Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Felix=20Geisend=C3=B6rfer?= Date: Sat, 7 Sep 2024 13:44:09 +0200 Subject: [PATCH] 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 #69335 Change-Id: I1600fe62548ea84981df0916d25072c3ddf1ea1a Reviewed-on: https://go-review.googlesource.com/c/go/+/611615 Reviewed-by: David Chase Reviewed-by: Nick Ripley Reviewed-by: Michael Pratt LUCI-TryBot-Result: Go LUCI --- 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 d84f8d26ea7b0d..59267f5eaf74af 100644 --- a/src/runtime/mprof.go +++ b/src/runtime/mprof.go @@ -1142,11 +1142,12 @@ 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 391588d4acd0ec..ef373b36848437 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 6d03c6464b4176..3492d7211d7e70 100644 --- a/src/runtime/pprof/pprof_test.go +++ b/src/runtime/pprof/pprof_test.go @@ -973,7 +973,7 @@ 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) @@ -983,7 +983,7 @@ 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 { @@ -996,6 +996,22 @@ 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) { @@ -1280,7 +1296,7 @@ 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"}, } { @@ -1320,6 +1336,28 @@ 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) { @@ -2470,7 +2508,7 @@ 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) {