runtime: remove sigmask type, use sigset instead

The OS-independent sigmask type was not pulling its weight. Replace it
with the OS-dependent sigset type. This requires adding an OS-specific
sigaddset function, but permits removing the OS-specific sigmaskToSigset
function.

Change-Id: I43307b512b0264ec291baadaea902f05ce212305
Reviewed-on: https://go-review.googlesource.com/29950
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/runtime/os3_solaris.go

@@ -300,10 +300,8 @@ func setSignalstackSP(s *stackt, sp uintptr) {
 
 //go:nosplit
 //go:nowritebarrierrec
-func sigmaskToSigset(m sigmask) sigset {
-	var set sigset
-	copy(set.__sigbits[:], m[:])
-	return set
+func sigaddset(mask *sigset, i int) {
+	mask.__sigbits[(i-1)/32] |= 1 << ((uint32(i) - 1) & 31)
 }
 
 func sigdelset(mask *sigset, i int) {

src/runtime/os_darwin.go

@@ -544,8 +544,8 @@ func setSignalstackSP(s *stackt, sp uintptr) {
 
 //go:nosplit
 //go:nowritebarrierrec
-func sigmaskToSigset(m sigmask) sigset {
-	return sigset(m[0])
+func sigaddset(mask *sigset, i int) {
+	*mask |= 1 << (uint32(i) - 1)
 }
 
 func sigdelset(mask *sigset, i int) {

src/runtime/os_dragonfly.go

@@ -273,10 +273,8 @@ func setSignalstackSP(s *stackt, sp uintptr) {
 
 //go:nosplit
 //go:nowritebarrierrec
-func sigmaskToSigset(m sigmask) sigset {
-	var set sigset
-	copy(set.__bits[:], m[:])
-	return set
+func sigaddset(mask *sigset, i int) {
+	mask.__bits[(i-1)/32] |= 1 << ((uint32(i) - 1) & 31)
 }
 
 func sigdelset(mask *sigset, i int) {

src/runtime/os_freebsd.go

@@ -263,10 +263,8 @@ func setSignalstackSP(s *stackt, sp uintptr) {
 
 //go:nosplit
 //go:nowritebarrierrec
-func sigmaskToSigset(m sigmask) sigset {
-	var set sigset
-	copy(set.__bits[:], m[:])
-	return set
+func sigaddset(mask *sigset, i int) {
+	mask.__bits[(i-1)/32] |= 1 << ((uint32(i) - 1) & 31)
 }
 
 func sigdelset(mask *sigset, i int) {

src/runtime/os_linux_generic.go

@@ -31,6 +31,8 @@ type rlimit struct {
 
 var sigset_all = sigset{^uint32(0), ^uint32(0)}
 
+//go:nosplit
+//go:nowritebarrierrec
 func sigaddset(mask *sigset, i int) {
 	(*mask)[(i-1)/32] |= 1 << ((uint32(i) - 1) & 31)
 }
@@ -42,11 +44,3 @@ func sigdelset(mask *sigset, i int) {
 func sigfillset(mask *uint64) {
 	*mask = ^uint64(0)
 }
-
-//go:nosplit
-//go:nowritebarrierrec
-func sigmaskToSigset(m sigmask) sigset {
-	var set sigset
-	copy(set[:], m[:])
-	return set
-}

src/runtime/os_linux_mips64x.go

@@ -47,6 +47,8 @@ type rlimit struct {
 
 var sigset_all = sigset{^uint64(0), ^uint64(0)}
 
+//go:nosplit
+//go:nowritebarrierrec
 func sigaddset(mask *sigset, i int) {
 	(*mask)[(i-1)/64] |= 1 << ((uint32(i) - 1) & 63)
 }
@@ -58,11 +60,3 @@ func sigdelset(mask *sigset, i int) {
 func sigfillset(mask *[2]uint64) {
 	(*mask)[0], (*mask)[1] = ^uint64(0), ^uint64(0)
 }
-
-//go:nosplit
-//go:nowritebarrierrec
-func sigmaskToSigset(m sigmask) sigset {
-	var set sigset
-	set[0] = uint64(m[0]) | uint64(m[1])<<32
-	return set
-}

src/runtime/os_linux_s390x.go

@@ -23,6 +23,8 @@ type rlimit struct {
 
 var sigset_all = sigset(^uint64(0))
 
+//go:nosplit
+//go:nowritebarrierrec
 func sigaddset(mask *sigset, i int) {
 	if i > 64 {
 		throw("unexpected signal greater than 64")
@@ -40,9 +42,3 @@ func sigdelset(mask *sigset, i int) {
 func sigfillset(mask *uint64) {
 	*mask = ^uint64(0)
 }
-
-//go:nosplit
-//go:nowritebarrierrec
-func sigmaskToSigset(m sigmask) sigset {
-	return sigset(uint64(m[0]) | uint64(m[1])<<32)
-}

src/runtime/os_netbsd.go

@@ -301,10 +301,8 @@ func setSignalstackSP(s *stackt, sp uintptr) {
 
 //go:nosplit
 //go:nowritebarrierrec
-func sigmaskToSigset(m sigmask) sigset {
-	var set sigset
-	copy(set.__bits[:], m[:])
-	return set
+func sigaddset(mask *sigset, i int) {
+	mask.__bits[(i-1)/32] |= 1 << ((uint32(i) - 1) & 31)
 }
 
 func sigdelset(mask *sigset, i int) {

src/runtime/os_openbsd.go

@@ -279,8 +279,8 @@ func setSignalstackSP(s *stackt, sp uintptr) {
 
 //go:nosplit
 //go:nowritebarrierrec
-func sigmaskToSigset(m sigmask) sigset {
-	return sigset(m[0])
+func sigaddset(mask *sigset, i int) {
+	*mask |= 1 << (uint32(i) - 1)
 }
 
 func sigdelset(mask *sigset, i int) {

src/runtime/signal_unix.go

@@ -36,11 +36,6 @@ const (
 // Signal forwarding is currently available only on Darwin and Linux.
 var fwdSig [_NSIG]uintptr
 
-// sigmask represents a general signal mask compatible with the GOOS
-// specific sigset types: the signal numbered x is represented by bit x-1
-// to match the representation expected by sigprocmask.
-type sigmask [(_NSIG + 31) / 32]uint32
-
 // channels for synchronizing signal mask updates with the signal mask
 // thread
 var (
@@ -302,7 +297,7 @@ func sigpanic() {
 //go:nowritebarrierrec
 func dieFromSignal(sig int32) {
 	setsig(sig, _SIG_DFL, false)
-	updatesigmask(sigmask{})
+	unblocksig(sig)
 	raise(sig)
 
 	// That should have killed us. On some systems, though, raise
@@ -401,28 +396,25 @@ func ensureSigM() {
 		// initially all signals except the essential. When signal.Notify()/Stop is called,
 		// sigenable/sigdisable in turn notify this thread to update its signal
 		// mask accordingly.
-		var sigBlocked sigmask
-		for i := range sigBlocked {
-			sigBlocked[i] = ^uint32(0)
-		}
+		sigBlocked := sigset_all
 		for i := range sigtable {
 			if sigtable[i].flags&_SigUnblock != 0 {
-				sigBlocked[(i-1)/32] &^= 1 << ((uint32(i) - 1) & 31)
+				sigdelset(&sigBlocked, i)
 			}
 		}
-		updatesigmask(sigBlocked)
+		sigprocmask(_SIG_SETMASK, &sigBlocked, nil)
 		for {
 			select {
 			case sig := <-enableSigChan:
-				if b := sig - 1; sig > 0 {
-					sigBlocked[b/32] &^= (1 << (b & 31))
+				if sig > 0 {
+					sigdelset(&sigBlocked, int(sig))
 				}
 			case sig := <-disableSigChan:
-				if b := sig - 1; sig > 0 {
-					sigBlocked[b/32] |= (1 << (b & 31))
+				if sig > 0 {
+					sigaddset(&sigBlocked, int(sig))
 				}
 			}
-			updatesigmask(sigBlocked)
+			sigprocmask(_SIG_SETMASK, &sigBlocked, nil)
 			maskUpdatedChan <- struct{}{}
 		}
 	}()
@@ -554,22 +546,15 @@ func sigblock() {
 	sigprocmask(_SIG_SETMASK, &sigset_all, nil)
 }
 
-// updatesigmask sets the current thread's signal mask to m.
+// unblocksig removes sig from the current thread's signal mask.
 // This is nosplit and nowritebarrierrec because it is called from
 // dieFromSignal, which can be called by sigfwdgo while running in the
 // signal handler, on the signal stack, with no g available.
 //go:nosplit
 //go:nowritebarrierrec
-func updatesigmask(m sigmask) {
-	set := sigmaskToSigset(m)
-	sigprocmask(_SIG_SETMASK, &set, nil)
-}
-
-// unblocksig removes sig from the current thread's signal mask.
 func unblocksig(sig int32) {
-	var m sigmask
-	m[(sig-1)/32] |= 1 << ((uint32(sig) - 1) & 31)
-	set := sigmaskToSigset(m)
+	var set sigset
+	sigaddset(&set, int(sig))
 	sigprocmask(_SIG_UNBLOCK, &set, nil)
 }