runtime: fix build on non-Linux platforms

CL 78538 was updated after running TryBots to depend on
syscall.NanoSleep which isn't available on all non-Linux platforms.

Change-Id: I1fa615232b3920453431861310c108b208628441
Reviewed-on: https://go-review.googlesource.com/79175
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

src/runtime/proc_test.go

@@ -750,16 +750,18 @@ func BenchmarkWakeupParallelSpinning(b *testing.B) {
 	})
 }
 
+// sysNanosleep is defined by OS-specific files (such as runtime_linux_test.go)
+// to sleep for the given duration. If nil, dependent tests are skipped.
+// The implementation should invoke a blocking system call and not
+// call time.Sleep, which would deschedule the goroutine.
+var sysNanosleep func(d time.Duration)
+
 func BenchmarkWakeupParallelSyscall(b *testing.B) {
-	benchmarkWakeupParallel(b, func(d time.Duration) {
-		// Invoke a blocking syscall directly; calling time.Sleep()
-		// would deschedule the goroutine instead.
-		ts := syscall.NsecToTimespec(d.Nanoseconds())
-		for {
-			if err := syscall.Nanosleep(&ts, &ts); err != syscall.EINTR {
-				return
-			}
+	if sysNanosleep == nil {
+		b.Skipf("skipping on %v; sysNanosleep not defined", runtime.GOOS)
 	}
+	benchmarkWakeupParallel(b, func(d time.Duration) {
+		sysNanosleep(d)
 	})
 }
 

src/runtime/runtime_linux_test.go

@@ -8,6 +8,7 @@ import (
 	. "runtime"
 	"syscall"
 	"testing"
+	"time"
 	"unsafe"
 )
 
@@ -21,6 +22,17 @@ func init() {
 	// for how it is used in init (must be on main thread).
 	pid, tid = syscall.Getpid(), syscall.Gettid()
 	LockOSThread()
+
+	sysNanosleep = func(d time.Duration) {
+		// Invoke a blocking syscall directly; calling time.Sleep()
+		// would deschedule the goroutine instead.
+		ts := syscall.NsecToTimespec(d.Nanoseconds())
+		for {
+			if err := syscall.Nanosleep(&ts, &ts); err != syscall.EINTR {
+				return
+			}
+		}
+	}
 }
 
 func TestLockOSThread(t *testing.T) {