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, 15 insertions, 12 deletions

diff --git a/src/runtime/lock_futex.go b/src/runtime/lock_futex.go
index 768fd5769f..fc480290cf 100644
--- a/src/runtime/lock_futex.go
+++ b/src/runtime/lock_futex.go
@@ -6,7 +6,10 @@
 
 package runtime
 
-import "unsafe"
+import (
+	"runtime/internal/atomic"
+	"unsafe"
+)
 
 // This implementation depends on OS-specific implementations of
 //
@@ -48,7 +51,7 @@ func lock(l *mutex) {
 	gp.m.locks++
 
 	// Speculative grab for lock.
-	v := xchg(key32(&l.key), mutex_locked)
+	v := atomic.Xchg(key32(&l.key), mutex_locked)
 	if v == mutex_unlocked {
 		return
 	}
@@ -72,7 +75,7 @@ func lock(l *mutex) {
 		// Try for lock, spinning.
 		for i := 0; i < spin; i++ {
 			for l.key == mutex_unlocked {
-				if cas(key32(&l.key), mutex_unlocked, wait) {
+				if atomic.Cas(key32(&l.key), mutex_unlocked, wait) {
 					return
 				}
 			}
@@ -82,7 +85,7 @@ func lock(l *mutex) {
 		// Try for lock, rescheduling.
 		for i := 0; i < passive_spin; i++ {
 			for l.key == mutex_unlocked {
-				if cas(key32(&l.key), mutex_unlocked, wait) {
+				if atomic.Cas(key32(&l.key), mutex_unlocked, wait) {
 					return
 				}
 			}
@@ -90,7 +93,7 @@ func lock(l *mutex) {
 		}
 
 		// Sleep.
-		v = xchg(key32(&l.key), mutex_sleeping)
+		v = atomic.Xchg(key32(&l.key), mutex_sleeping)
 		if v == mutex_unlocked {
 			return
 		}
@@ -100,7 +103,7 @@ func lock(l *mutex) {
 }
 
 func unlock(l *mutex) {
-	v := xchg(key32(&l.key), mutex_unlocked)
+	v := atomic.Xchg(key32(&l.key), mutex_unlocked)
 	if v == mutex_unlocked {
 		throw("unlock of unlocked lock")
 	}
@@ -124,7 +127,7 @@ func noteclear(n *note) {
 }
 
 func notewakeup(n *note) {
-	old := xchg(key32(&n.key), 1)
+	old := atomic.Xchg(key32(&n.key), 1)
 	if old != 0 {
 		print("notewakeup - double wakeup (", old, ")\n")
 		throw("notewakeup - double wakeup")
@@ -137,7 +140,7 @@ func notesleep(n *note) {
 	if gp != gp.m.g0 {
 		throw("notesleep not on g0")
 	}
-	for atomicload(key32(&n.key)) == 0 {
+	for atomic.Load(key32(&n.key)) == 0 {
 		gp.m.blocked = true
 		futexsleep(key32(&n.key), 0, -1)
 		gp.m.blocked = false
@@ -153,7 +156,7 @@ func notetsleep_internal(n *note, ns int64) bool {
 	gp := getg()
 
 	if ns < 0 {
-		for atomicload(key32(&n.key)) == 0 {
+		for atomic.Load(key32(&n.key)) == 0 {
 			gp.m.blocked = true
 			futexsleep(key32(&n.key), 0, -1)
 			gp.m.blocked = false
@@ -161,7 +164,7 @@ func notetsleep_internal(n *note, ns int64) bool {
 		return true
 	}
 
-	if atomicload(key32(&n.key)) != 0 {
+	if atomic.Load(key32(&n.key)) != 0 {
 		return true
 	}
 
@@ -170,7 +173,7 @@ func notetsleep_internal(n *note, ns int64) bool {
 		gp.m.blocked = true
 		futexsleep(key32(&n.key), 0, ns)
 		gp.m.blocked = false
-		if atomicload(key32(&n.key)) != 0 {
+		if atomic.Load(key32(&n.key)) != 0 {
 			break
 		}
 		now := nanotime()
@@ -179,7 +182,7 @@ func notetsleep_internal(n *note, ns int64) bool {
 		}
 		ns = deadline - now
 	}
-	return atomicload(key32(&n.key)) != 0
+	return atomic.Load(key32(&n.key)) != 0
 }
 
 func notetsleep(n *note, ns int64) bool {