Do not copy sleep.Waker

sleep.Waker's fields are modified as values.

PiperOrigin-RevId: 320873451

pkg/sleep/BUILD

@@ -12,6 +12,7 @@ go_library(
         "sleep_unsafe.go",
     ],
     visibility = ["//:sandbox"],
+    deps = ["//pkg/sync"],
 )
 
 go_test(

pkg/sleep/sleep_test.go

@@ -379,10 +379,7 @@ func TestRace(t *testing.T) {
 // TestRaceInOrder tests that multiple wakers can continuously send wake requests to
 // the sleeper and that the wakers are retrieved in the order asserted.
 func TestRaceInOrder(t *testing.T) {
-	const wakers = 100
-	const wakeRequests = 10000
-
-	w := make([]Waker, wakers)
+	w := make([]Waker, 10000)
 	s := Sleeper{}
 
 	// Associate each waker and start goroutines that will assert them.
@@ -390,19 +387,16 @@ func TestRaceInOrder(t *testing.T) {
 		s.AddWaker(&w[i], i)
 	}
 	go func() {
-		n := 0
-		for n < wakeRequests {
-			wk := w[n%len(w)]
-			wk.Assert()
-			n++
+		for i := range w {
+			w[i].Assert()
 		}
 	}()
 
 	// Wait for all wake up notifications from all wakers.
-	for i := 0; i < wakeRequests; i++ {
-		v, _ := s.Fetch(true)
-		if got, want := v, i%wakers; got != want {
-			t.Fatalf("got  %d want %d", got, want)
+	for want := range w {
+		got, _ := s.Fetch(true)
+		if got != want {
+			t.Fatalf("got %d want %d", got, want)
 		}
 	}
 }

pkg/sleep/sleep_unsafe.go

@@ -75,6 +75,8 @@ package sleep
 import (
 	"sync/atomic"
 	"unsafe"
+
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 const (
@@ -323,7 +325,12 @@ func (s *Sleeper) enqueueAssertedWaker(w *Waker) {
 //
 // This struct is thread-safe, that is, its methods can be called concurrently
 // by multiple goroutines.
+//
+// Note, it is not safe to copy a Waker as its fields are modified by value
+// (the pointer fields are individually modified with atomic operations).
 type Waker struct {
+	_ sync.NoCopy
+
 	// s is the sleeper that this waker can wake up. Only one sleeper at a
 	// time is allowed. This field can have three classes of values:
 	// nil -- the waker is not asserted: it either is not associated with

pkg/sync/BUILD

@@ -33,6 +33,7 @@ go_library(
         "aliases.go",
         "memmove_unsafe.go",
         "mutex_unsafe.go",
+        "nocopy.go",
         "norace_unsafe.go",
         "race_unsafe.go",
         "rwmutex_unsafe.go",

pkg/sync/nocopy.go

@@ -0,0 +1,28 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package sync
+
+// NoCopy may be embedded into structs which must not be copied
+// after the first use.
+//
+// See https://golang.org/issues/8005#issuecomment-190753527
+// for details.
+type NoCopy struct{}
+
+// Lock is a no-op used by -copylocks checker from `go vet`.
+func (*NoCopy) Lock() {}
+
+// Unlock is a no-op used by -copylocks checker from `go vet`.
+func (*NoCopy) Unlock() {}

pkg/tcpip/stack/packet_buffer.go

@@ -14,6 +14,7 @@
 package stack
 
 import (
+	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 )
@@ -24,7 +25,7 @@ import (
 // multiple endpoints. Clone() should be called in such cases so that
 // modifications to the Data field do not affect other copies.
 type PacketBuffer struct {
-	_ noCopy
+	_ sync.NoCopy
 
 	// PacketBufferEntry is used to build an intrusive list of
 	// PacketBuffers.
@@ -102,14 +103,3 @@ func (pk *PacketBuffer) Clone() *PacketBuffer {
 		NatDone:               pk.NatDone,
 	}
 }
-
-// noCopy may be embedded into structs which must not be copied
-// after the first use.
-//
-// See https://golang.org/issues/8005#issuecomment-190753527
-// for details.
-type noCopy struct{}
-
-// Lock is a no-op used by -copylocks checker from `go vet`.
-func (*noCopy) Lock()   {}
-func (*noCopy) Unlock() {}

pkg/tcpip/timer.go

@@ -15,8 +15,9 @@
 package tcpip
 
 import (
-	"sync"
 	"time"
+
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // cancellableTimerInstance is a specific instance of CancellableTimer.
@@ -92,6 +93,8 @@ func (t *cancellableTimerInstance) stop() {
 // Note, it is not safe to copy a CancellableTimer as its timer instance creates
 // a closure over the address of the CancellableTimer.
 type CancellableTimer struct {
+	_ sync.NoCopy
+
 	// The active instance of a cancellable timer.
 	instance cancellableTimerInstance
 
@@ -157,22 +160,6 @@ func (t *CancellableTimer) Reset(d time.Duration) {
 	}
 }
 
-// Lock is a no-op used by the copylocks checker from go vet.
-//
-// See CancellableTimer for details about why it shouldn't be copied.
-//
-// See https://github.com/golang/go/issues/8005#issuecomment-190753527 for more
-// details about the copylocks checker.
-func (*CancellableTimer) Lock() {}
-
-// Unlock is a no-op used by the copylocks checker from go vet.
-//
-// See CancellableTimer for details about why it shouldn't be copied.
-//
-// See https://github.com/golang/go/issues/8005#issuecomment-190753527 for more
-// details about the copylocks checker.
-func (*CancellableTimer) Unlock() {}
-
 // NewCancellableTimer returns an unscheduled CancellableTimer with the given
 // locker and fn.
 //