src/runtime/signal_unix.go:202 Normal gameplay and subsequent code execution

[tracySun2]

Go version

go version go1.22.3 linux/amd64

Output of go env in your module/workspace:

GO111MODULE=''
GOARCH='amd64'
GOBIN=''
GOCACHE='/root/.cache/go-build'
GOENV='/root/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/root/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/root/go'
GOPRIVATE=''
GOPROXY='https://goproxy.io,direct'
GOROOT='/data/build/go'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/data/build/go/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.22.3'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='gcc'
CXX='g++'
CGO_ENABLED='1'
GOMOD='/data/tracy/go_server/go.mod'
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 -Wl,--no-gc-sections -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build2645800351=/tmp/go-build -gno-record-gcc-switches'

What did you do?

package main

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

func main() {

pid, _, err := syscall.RawSyscall(syscall.SYS_FORK, 0, 0, 0)
if err != 0 {
	return
}

if pid > 0 {
	syscall.Exit(0)
}

syscall.Setsid()

pid, _, err = syscall.RawSyscall(syscall.SYS_FORK, 0, 0, 0)
if err != 0 {
	return
}

if pid > 0 {
	syscall.Exit(0)
}

if err := syscall.Chdir("/"); err != nil {
	return
}

fd, err2 := os.OpenFile("/dev/null", os.O_RDWR, 0)
if err2 != nil {
	return
}
defer fd.Close()
syscall.Umask(0)

println("111111111111111111111")
sigChan := make(chan os.Signal, 1)
signal.Notify(sigChan, syscall.SIGSEGV)     //problem occur
println("222222222222222222222")
for sig := range sigChan {
	switch sig {
	case syscall.SIGSEGV:
		println("333333333333333333")
	}
	break

}
select {}

}

What did you see happen?

[[email protected] access]# ps -ef | grep access
root 13804 1 0 13:37 ? 00:00:00 ./access
root 13826 9359 0 13:37 pts/1 00:00:00 grep --color=auto access
[[email protected] access]# dlv attach 13804
Type 'help' for list of commands.
(dlv) bt
0 0x00000000004636c3 in runtime.futex
at /data/build/go/src/runtime/sys_linux_amd64.s:558
1 0x000000000042e8b0 in runtime.futexsleep
at /data/build/go/src/runtime/os_linux.go:69
2 0x000000000040a607 in runtime.notesleep
at /data/build/go/src/runtime/lock_futex.go:170
3 0x00000000004397f3 in runtime.mPark
at /data/build/go/src/runtime/proc.go:1761
4 0x00000000004397f3 in runtime.stoplockedm
at /data/build/go/src/runtime/proc.go:3026
5 0x000000000043bb1a in runtime.schedule
at /data/build/go/src/runtime/proc.go:3847
6 0x000000000043c16c in runtime.park_m
at /data/build/go/src/runtime/proc.go:4036
7 0x000000000045fa4e in runtime.mcall
at /data/build/go/src/runtime/asm_amd64.s:458
(dlv)

What did you expect to see?

The process is executing normally
Deadlock occurs
not print "222222222222222222222"

create a daemon and custom sign handle

[ianlancetaylor]

Unfortunately you simply can't call fork in a Go program. In general you can't safely call fork in any multi-threaded program, and all Go programs are multi-threaded. You'll need to exec the program setting SysProcAttr.Setsid.