Blocking SIGURG to avoid preempt in critical path

block_sigurg.go

package main

import (
	"runtime"
	"unsafe"

	"golang.org/x/sys/unix"
)

func backgroundGoroutine() {
	// Ensure running on separate thread
	runtime.LockOSThread()
	defer runtime.UnlockOSThread()

	// Block SIGURG signal
	var oldSigset, newSigset [8 / unsafe.Sizeof(uintptr(0))]uintptr
	newSigset[0] = 1 << (unix.SIGURG - 1)
	unix.RawSyscall6(
		unix.SYS_RT_SIGPROCMASK,
		unix.SIG_BLOCK,
		uintptr(unsafe.Pointer(&newSigset)),
		uintptr(unsafe.Pointer(&oldSigset)),
		uintptr(unsafe.Sizeof(newSigset)),
		0, 0,
	)
	defer unix.RawSyscall6(
		unix.SYS_RT_SIGPROCMASK,
		unix.SIG_SETMASK,
		uintptr(unsafe.Pointer(&oldSigset)),
		0,
		uintptr(unsafe.Sizeof(oldSigset)),
		0, 0,
	)

	// Do critical work here. Note that doing any of the following operations
	// could potentially cause preemption:
	//
	// - Memory allocation
	// - Any operation that sleeps or parks the goroutine
	// - Calling any function that is not //go:nosplit
	println("critical work")
}

func main() {
	go backgroundGoroutine()
	select {}
}

This is taken as a sample from issue:
golang/go#65874