runtime/pprof: non-self-recursive function (runtime.pcvalue) shows self-calls #52764
Description
What version of Go are you using (go version)?
This is broken in tip, working in go1.18.1
Does this issue reproduce with the latest release?
No, working in go1.18.1
What operating system and processor architecture are you using (go env)?
go env Output
$ go env GO111MODULE="" GOARCH="arm64" GOBIN="" GOCACHE="/Users/rhys/Library/Caches/go-build" GOENV="/Users/rhys/Library/Application Support/go/env" GOEXE="" GOEXPERIMENT="" GOFLAGS="" GOHOSTARCH="arm64" GOHOSTOS="darwin" GOINSECURE="" GOMODCACHE="/Users/rhys/go/pkg/mod" GONOPROXY="*" GONOSUMDB="*" GOOS="darwin" GOPATH="/Users/rhys/go" GOPRIVATE="*" GOPROXY="direct" GOROOT="/usr/local/go" GOSUMDB="sum.golang.org" GOTMPDIR="" GOTOOLDIR="/usr/local/go/pkg/tool/darwin_arm64" GOVCS="" GOVERSION="go1.18.1" GCCGO="gccgo" AR="ar" CC="clang" CXX="clang++" CGO_ENABLED="1" GOMOD="/dev/null" GOWORK="" CGO_CFLAGS="-g -O2" CGO_CPPFLAGS="" CGO_CXXFLAGS="-g -O2" CGO_FFLAGS="-g -O2" CGO_LDFLAGS="-g -O2" PKG_CONFIG="pkg-config" GOGCCFLAGS="-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/lf/n4ry0qv5639_3z0nhyhy3z7c0000gs/T/go-build4034971770=/tmp/go-build -gno-record-gcc-switches -fno-common"
What did you do?
I added a test to src/runtime/pprof/pprof_test.go for the duplicate runtime.pcvalue entries I saw in #52693.
func TestCPUProfileDupFrameInlining(t *testing.T) {
var stk [32]uintptr
matches := matchAndAvoidStacks(stackContains, []string{"runtime.pcvalue"}, avoidFunctions())
p := testCPUProfile(t, matches, func(dur time.Duration) {
cpuHogger(func(i int) int {
_ = runtime.Callers(0, stk[:])
return i
}, &salt1, dur)
})
for _, sam := range p.Sample {
var stack []string
var bad string
for _, loc := range sam.Location {
for _, line := range loc.Line {
name := fmt.Sprintf("%s:%d", line.Function.Name, line.Line)
if len(stack) != 0 && name == stack[len(stack)-1] {
bad = name
}
stack = append(stack, name)
}
}
if bad != "" {
t.Logf("found repeated function entry %q in stack %q", bad, stack)
if strings.HasPrefix(bad, "runtime.pcvalue:") {
// The profile may show legitimate recursive functions, but we
// know that runtime.pcvalue does not call itself and so should
// not appear to in the profile.
t.Fail()
}
}
}
}
What did you expect to see?
Because runtime.pcvalue does not call itself, the CPU profiler should never indicate that it does.
What did you see instead?
The test fails on the development branch / tip about 25% of the time on my darwin/arm64 machine. (The failures are much less likely in -short mode.) It does not fail with go1.18.1 (passes 60+ times).
found repeated function entry "runtime.pcvalue:932" in stack ["runtime.fastrand:135" "runtime.fastrandn:157" "runtime.pcvalue:932" "runtime.pcvalue:932" "runtime.pcdatavalue:1076" "runtime.gentraceback:364" "runtime.callers.func1:914" "runtime.systemstack:233" "runtime.callers:913" "runtime.Callers:237" "runtime/pprof.TestCPUProfileDupFrameInlining.func1.1:343" "runtime/pprof.cpuHogger:41" "runtime/pprof.TestCPUProfileDupFrameInlining.func1:342" "runtime/pprof.testCPUProfile:497" "runtime/pprof.TestCPUProfileDupFrameInlining:341" "testing.tRunner:1449"]
Maybe this is a recurrence of #50996, or maybe the fix for that broke this behavior? I plan to bisect. CC @prattmic