testing/synctest: SEGV when running test in race mode #76691
Description
Go version
go1.25.3 linux/arm64
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=''
GOARCH='arm64'
GOARM64='v8.0'
GOAUTH='netrc'
GOBIN=''
GOCACHE='/home/ubuntu/.cache/go-build'
GOCACHEPROG=''
GODEBUG=''
GOENV='/home/ubuntu/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFIPS140='off'
GOFLAGS=''
GOGCCFLAGS='-fPIC -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build2656902165=/tmp/go-build -gno-record-gcc-switches'
GOHOSTARCH='arm64'
GOHOSTOS='linux'
GOINSECURE=''
GOMOD='/opt/actions-runner/_work/warpstream/warpstream/go.mod'
GOMODCACHE='/home/ubuntu/go/pkg/mod'
GONOPROXY='github.com/warpstreamlabs [REDACTED]'
GONOSUMDB='github.com/warpstreamlabs [REDACTED]'
GOOS='linux'
GOPATH='/home/ubuntu/go'
GOPRIVATE='github.com/warpstreamlabs [REDACTED]'
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/opt/actions-runner/_work/_tool/go/1.25.3/arm64'
GOSUMDB='sum.golang.org'
GOTELEMETRY='local'
GOTELEMETRYDIR='/home/ubuntu/.config/go/telemetry'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/opt/actions-runner/_work/_tool/go/1.25.3/arm64/pkg/tool/linux_arm64'
GOVCS=''
GOVERSION='go1.25.3'
GOWORK=''
PKG_CONFIG='pkg-config'What did you do?
We have a complex integration test that uses synctest that would occasionally crash with SIGSEGV: segmentation violation when run using go test -vet off -race -count 1 -p 1 -timeout 5m0s. Unfortunately the test cannot be shared and we have yet to come up with a minimal reproducer.
This has not happen when the test is run without synctest in race mode or with synctest but not in race mode.
What did you see happen?
Stacktraces from two instances of the crash can be found here https://gist.github.com/ella-chao/f487923e491329d17fe26112ca5cd57c
What did you expect to see?
No crashes