os/signal: sending SIGTSTP doesn't return to shell when non-SIGTSTP handler exists (OpenBSD)

[pafoster]

Go version

go version go1.20.1 openbsd/amd64

Output of go env in your module/workspace:

GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/peter/.cache/go-build"
GOENV="/home/peter/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="openbsd"
GOINSECURE=""
GOMODCACHE="/home/peter/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="openbsd"
GOPATH="/home/peter/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/openbsd_amd64"
GOVCS=""
GOVERSION="go1.20.1"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="cc"
CXX="c++"
CGO_ENABLED="1"
GOMOD="/dev/null"
GOWORK=""
CGO_CFLAGS="-O2 -g"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-O2 -g"
CGO_FFLAGS="-O2 -g"
CGO_LDFLAGS="-O2 -g"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -Wl,--no-gc-sections -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build1289460440=/tmp/go-build -gno-record-gcc-switches"

What did you do?

package main

import (
        "os"
        "os/signal"
        "syscall"
        "time"
)

func main() {
        c := make(chan os.Signal, 1)
        signal.Notify(c, syscall.SIGINT, syscall.SIGTERM)
        go func() {
                <-c
                os.Exit(1)
        }()

        for {
                time.Sleep(time.Second)
        }
}

go build test.go
./test
Hit Ctrl-Z

What did you see happen?

<Doesn't return to shell as expected>

What did you expect to see?

^Z[1] + Suspended            ./test 
me@mymachine:~$ 

[gabyhelp]

Related Issues

• os/signal: SIGTSTP can't be handled #41996 (closed)
• os/signal: Reset doesn't reset ignored signals #46321
• os/signal: sometimes SIGINT is not delivered #21905 (closed)
• os/signal: SIGINT cannot be catched with cgo system("ls") call #26245 (closed)
• x/crypto/ssh: cannot send a Signal to remote process without Pty #48715
• Go programs don't respond to SIGTSTP (ctl+Z) #776 (closed)
• runtime: signal handling changed by signal.Notify #36420 (closed)
• os: process already finished, when sending syscall.SIGCONT #19314 (closed)
• runtime: sigaction problem when using cgo on FreeBSD #25745 (closed)

Related Discussions

• Trap signal of terminal stop

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

[seankhliao]

is that a problem with your shell?
also, 1.20 is no longer a supported version.

[pafoster]

Using the above code, I get the same issue with ksh, bash, and csh.

By comparison, the issue doesn't occur if I run the following and hit Ctrl-Z:

package main

import (
    "time"
)

func main() {
    for {
        time.Sleep(time.Second)
    }
}

[pafoster]

I will try to reproduce also using a more recent version of Go.

[ianlancetaylor]

CC @golang/openbsd

[pafoster]

I can confirm that I observe the same issue with Go 1.23:

Go version

go version go1.23.1 openbsd/amd64

Output of go env in your module/workspace:

GO111MODULE=''
GOARCH='amd64'
GOBIN=''
GOCACHE='/home/peter/.cache/go-build'
GOENV='/home/peter/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='openbsd'
GOINSECURE=''
GOMODCACHE='/home/peter/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='openbsd'
GOPATH='/home/peter/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/local/go'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/local/go/pkg/tool/openbsd_amd64'
GOVCS=''
GOVERSION='go1.23.1'
GODEBUG=''
GOTELEMETRY='local'
GOTELEMETRYDIR='/home/peter/.config/go/telemetry'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='cc'
CXX='c++'
CGO_ENABLED='1'
GOMOD='/dev/null'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build3532196186=/tmp/go-build -gno-record-gcc-switches'

[4a6f656c]

What version of OpenBSD are you running this on?

I suspect it is kernel bug that has been fixed in recent snapshots - I'm able to successfully suspend and resume the test program on a current snapshot, while it failed as described on a snapshot from a few months back.

[pafoster]

I'm running the most recent release - OpenBSD 7.6. I don't run snapshots, but I'll re-run when the next release is made available.