runtime: break atomics out into package runtime/internal/atomic

This change breaks out most of the atomics functions in the runtime
into package runtime/internal/atomic. It adds some basic support
in the toolchain for runtime packages, and also modifies linux/arm
atomics to remove the dependency on the runtime's mutex. The mutexes
have been replaced with spinlocks.

all trybots are happy!
In addition to the trybots, I've tested on the darwin/arm64 builder,
on the darwin/arm builder, and on a ppc64le machine.

Change-Id: I6698c8e3cf3834f55ce5824059f44d00dc8e3c2f
Reviewed-on: https://go-review.googlesource.com/14204
Run-TryBot: Michael Matloob <matloob@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

1 files changed, 12 insertions, 9 deletions

diff --git a/src/runtime/sigqueue.go b/src/runtime/sigqueue.go
index f28067f3f9..8c9951ae1d 100644
--- a/src/runtime/sigqueue.go
+++ b/src/runtime/sigqueue.go
@@ -28,7 +28,10 @@
 
 package runtime
 
-import "unsafe"
+import (
+	"runtime/internal/atomic"
+	"unsafe"
+)
 
 var sig struct {
 	note   note
@@ -59,7 +62,7 @@ func sigsend(s uint32) bool {
 		if mask&bit != 0 {
 			return true // signal already in queue
 		}
-		if cas(&sig.mask[s/32], mask, mask|bit) {
+		if atomic.Cas(&sig.mask[s/32], mask, mask|bit) {
 			break
 		}
 	}
@@ -67,18 +70,18 @@ func sigsend(s uint32) bool {
 	// Notify receiver that queue has new bit.
 Send:
 	for {
-		switch atomicload(&sig.state) {
+		switch atomic.Load(&sig.state) {
 		default:
 			throw("sigsend: inconsistent state")
 		case sigIdle:
-			if cas(&sig.state, sigIdle, sigSending) {
+			if atomic.Cas(&sig.state, sigIdle, sigSending) {
 				break Send
 			}
 		case sigSending:
 			// notification already pending
 			break Send
 		case sigReceiving:
-			if cas(&sig.state, sigReceiving, sigIdle) {
+			if atomic.Cas(&sig.state, sigReceiving, sigIdle) {
 				notewakeup(&sig.note)
 				break Send
 			}
@@ -104,17 +107,17 @@ func signal_recv() uint32 {
 		// Wait for updates to be available from signal sender.
 	Receive:
 		for {
-			switch atomicload(&sig.state) {
+			switch atomic.Load(&sig.state) {
 			default:
 				throw("signal_recv: inconsistent state")
 			case sigIdle:
-				if cas(&sig.state, sigIdle, sigReceiving) {
+				if atomic.Cas(&sig.state, sigIdle, sigReceiving) {
 					notetsleepg(&sig.note, -1)
 					noteclear(&sig.note)
 					break Receive
 				}
 			case sigSending:
-				if cas(&sig.state, sigSending, sigIdle) {
+				if atomic.Cas(&sig.state, sigSending, sigIdle) {
 					break Receive
 				}
 			}
@@ -122,7 +125,7 @@ func signal_recv() uint32 {
 
 		// Incorporate updates from sender into local copy.
 		for i := range sig.mask {
-			sig.recv[i] = xchg(&sig.mask[i], 0)
+			sig.recv[i] = atomic.Xchg(&sig.mask[i], 0)
 		}
 	}
 }