New sync package.

* Rename syncutil to sync.
* Add aliases to sync types.
* Replace existing usage of standard library sync package.

This will make it easier to swap out synchronization primitives. For example,
this will allow us to use primitives from github.com/sasha-s/go-deadlock to
check for lock ordering violations.

Updates #1472

PiperOrigin-RevId: 289033387

1 files changed, 47 insertions, 0 deletions

diff --git a/pkg/sync/atomicptr_unsafe.go b/pkg/sync/atomicptr_unsafe.go
new file mode 100644
index 000000000..525c4beed
--- /dev/null
+++ b/pkg/sync/atomicptr_unsafe.go
@@ -0,0 +1,47 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package template doesn't exist. This file must be instantiated using the
+// go_template_instance rule in tools/go_generics/defs.bzl.
+package template
+
+import (
+	"sync/atomic"
+	"unsafe"
+)
+
+// Value is a required type parameter.
+type Value struct{}
+
+// An AtomicPtr is a pointer to a value of type Value that can be atomically
+// loaded and stored. The zero value of an AtomicPtr represents nil.
+//
+// Note that copying AtomicPtr by value performs a non-atomic read of the
+// stored pointer, which is unsafe if Store() can be called concurrently; in
+// this case, do `dst.Store(src.Load())` instead.
+//
+// +stateify savable
+type AtomicPtr struct {
+	ptr unsafe.Pointer `state:".(*Value)"`
+}
+
+func (p *AtomicPtr) savePtr() *Value {
+	return p.Load()
+}
+
+func (p *AtomicPtr) loadPtr(v *Value) {
+	p.Store(v)
+}
+
+// Load returns the value set by the most recent Store. It returns nil if there
+// has been no previous call to Store.
+func (p *AtomicPtr) Load() *Value {
+	return (*Value)(atomic.LoadPointer(&p.ptr))
+}
+
+// Store sets the value returned by Load to x.
+func (p *AtomicPtr) Store(x *Value) {
+	atomic.StorePointer(&p.ptr, (unsafe.Pointer)(x))
+}