cmd/trace: wrong number of GCWaiting goroutines

[mneverov]

Go version

go version go1.25.0 linux/amd64

Output of go env in your module/workspace:

AR='ar'
CC='gcc'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_ENABLED='1'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
CXX='g++'
GCCGO='gccgo'
GO111MODULE=''
GOAMD64='v1'
GOARCH='amd64'
GOAUTH='netrc'
GOBIN=''
GOCACHE='/home/mneverov/.cache/go-build'
GOCACHEPROG=''
GODEBUG=''
GOENV='/home/mneverov/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFIPS140='off'
GOFLAGS=''
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/home/mneverov/tmp/go-build2142671078=/tmp/go-build -gno-record-gcc-switches'
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMOD='/home/mneverov/go/src/github.com/mneverov/memtest/go.mod'
GOMODCACHE='/home/mneverov/go/pkg/mod'
GOOS='linux'
GOPATH='/home/mneverov/go'
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/home/mneverov/go/pkg/mod/golang.org/toolchain@v0.0.1-go1.25.0.linux-amd64'
GOSUMDB='sum.golang.org'
GOTELEMETRY='on'
GOTELEMETRYDIR='/home/mneverov/.config/go/telemetry'
GOTMPDIR='/home/mneverov/tmp'
GOTOOLCHAIN='auto'
GOTOOLDIR='/home/mneverov/go/pkg/mod/golang.org/toolchain@v0.0.1-go1.25.0.linux-amd64/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.25.0'
GOWORK=''
PKG_CONFIG='pkg-config'

What did you do?

Capture a program snapshot with flight recorder.
Open the snapshot with go tool trace <snapshot>

What did you see happen?

What did you expect to see?

Correct number of GCWaiting goroutines

[gabyhelp]

Related Issues

• cmd/trace: goroutine in unexpected state #17719 (closed)
• runtime/trace: Bad HeapGoal/NextGC Metric #63864 (closed)
• runtime/trace: NextGC is 0 if no GC was triggered during the trace #52517 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[prattmic]

cc @golang/runtime @mknyszek @cagedmantis

[mknyszek]

Oops! That's no good. I'll take a look.

[mneverov]

Seems related.
On the receiving side I can see multiple transitions from gc waiting mark assist to other states but only few transitions from some state to gc waiting mark assist (anecdotal ratio 30:1).
Negative counter then converted to uint64 GCWaiting that results in the number 18446744073709552000.