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, 10 insertions, 7 deletions

diff --git a/src/runtime/netpoll.go b/src/runtime/netpoll.go
index 7c6e3fa93e..19adeff787 100644
--- a/src/runtime/netpoll.go
+++ b/src/runtime/netpoll.go
@@ -6,7 +6,10 @@
 
 package runtime
 
-import "unsafe"
+import (
+	"runtime/internal/atomic"
+	"unsafe"
+)
 
 // Integrated network poller (platform-independent part).
 // A particular implementation (epoll/kqueue) must define the following functions:
@@ -77,11 +80,11 @@ var (
 //go:linkname net_runtime_pollServerInit net.runtime_pollServerInit
 func net_runtime_pollServerInit() {
 	netpollinit()
-	atomicstore(&netpollInited, 1)
+	atomic.Store(&netpollInited, 1)
 }
 
 func netpollinited() bool {
-	return atomicload(&netpollInited) != 0
+	return atomic.Load(&netpollInited) != 0
 }
 
 //go:linkname net_runtime_pollOpen net.runtime_pollOpen
@@ -305,7 +308,7 @@ func netpollcheckerr(pd *pollDesc, mode int32) int {
 }
 
 func netpollblockcommit(gp *g, gpp unsafe.Pointer) bool {
-	return casuintptr((*uintptr)(gpp), pdWait, uintptr(unsafe.Pointer(gp)))
+	return atomic.Casuintptr((*uintptr)(gpp), pdWait, uintptr(unsafe.Pointer(gp)))
 }
 
 // returns true if IO is ready, or false if timedout or closed
@@ -326,7 +329,7 @@ func netpollblock(pd *pollDesc, mode int32, waitio bool) bool {
 		if old != 0 {
 			throw("netpollblock: double wait")
 		}
-		if casuintptr(gpp, 0, pdWait) {
+		if atomic.Casuintptr(gpp, 0, pdWait) {
 			break
 		}
 	}
@@ -338,7 +341,7 @@ func netpollblock(pd *pollDesc, mode int32, waitio bool) bool {
 		gopark(netpollblockcommit, unsafe.Pointer(gpp), "IO wait", traceEvGoBlockNet, 5)
 	}
 	// be careful to not lose concurrent READY notification
-	old := xchguintptr(gpp, 0)
+	old := atomic.Xchguintptr(gpp, 0)
 	if old > pdWait {
 		throw("netpollblock: corrupted state")
 	}
@@ -365,7 +368,7 @@ func netpollunblock(pd *pollDesc, mode int32, ioready bool) *g {
 		if ioready {
 			new = pdReady
 		}
-		if casuintptr(gpp, old, new) {
+		if atomic.Casuintptr(gpp, old, new) {
 			if old == pdReady || old == pdWait {
 				old = 0
 			}