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

2 files changed, 165 insertions, 0 deletions

diff --git a/pkg/sync/seqatomictest/BUILD b/pkg/sync/seqatomictest/BUILD
new file mode 100644
index 000000000..eba21518d
--- /dev/null
+++ b/pkg/sync/seqatomictest/BUILD
@@ -0,0 +1,33 @@
+load("//tools/go_stateify:defs.bzl", "go_library")
+load("@io_bazel_rules_go//go:def.bzl", "go_test")
+load("//tools/go_generics:defs.bzl", "go_template_instance")
+
+package(licenses = ["notice"])
+
+go_template_instance(
+    name = "seqatomic_int",
+    out = "seqatomic_int_unsafe.go",
+    package = "seqatomic",
+    suffix = "Int",
+    template = "//pkg/sync:generic_seqatomic",
+    types = {
+        "Value": "int",
+    },
+)
+
+go_library(
+    name = "seqatomic",
+    srcs = ["seqatomic_int_unsafe.go"],
+    importpath = "gvisor.dev/gvisor/pkg/sync/seqatomic",
+    deps = [
+        "//pkg/sync",
+    ],
+)
+
+go_test(
+    name = "seqatomic_test",
+    size = "small",
+    srcs = ["seqatomic_test.go"],
+    embed = [":seqatomic"],
+    deps = ["//pkg/sync"],
+)
diff --git a/pkg/sync/seqatomictest/seqatomic_test.go b/pkg/sync/seqatomictest/seqatomic_test.go
new file mode 100644
index 000000000..2c4568b07
--- /dev/null
+++ b/pkg/sync/seqatomictest/seqatomic_test.go
@@ -0,0 +1,132 @@
+// Copyright 2018 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 seqatomic
+
+import (
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"gvisor.dev/gvisor/pkg/sync"
+)
+
+func TestSeqAtomicLoadUncontended(t *testing.T) {
+	var seq sync.SeqCount
+	const want = 1
+	data := want
+	if got := SeqAtomicLoadInt(&seq, &data); got != want {
+		t.Errorf("SeqAtomicLoadInt: got %v, wanted %v", got, want)
+	}
+}
+
+func TestSeqAtomicLoadAfterWrite(t *testing.T) {
+	var seq sync.SeqCount
+	var data int
+	const want = 1
+	seq.BeginWrite()
+	data = want
+	seq.EndWrite()
+	if got := SeqAtomicLoadInt(&seq, &data); got != want {
+		t.Errorf("SeqAtomicLoadInt: got %v, wanted %v", got, want)
+	}
+}
+
+func TestSeqAtomicLoadDuringWrite(t *testing.T) {
+	var seq sync.SeqCount
+	var data int
+	const want = 1
+	seq.BeginWrite()
+	go func() {
+		time.Sleep(time.Second)
+		data = want
+		seq.EndWrite()
+	}()
+	if got := SeqAtomicLoadInt(&seq, &data); got != want {
+		t.Errorf("SeqAtomicLoadInt: got %v, wanted %v", got, want)
+	}
+}
+
+func TestSeqAtomicTryLoadUncontended(t *testing.T) {
+	var seq sync.SeqCount
+	const want = 1
+	data := want
+	epoch := seq.BeginRead()
+	if got, ok := SeqAtomicTryLoadInt(&seq, epoch, &data); !ok || got != want {
+		t.Errorf("SeqAtomicTryLoadInt: got (%v, %v), wanted (%v, true)", got, ok, want)
+	}
+}
+
+func TestSeqAtomicTryLoadDuringWrite(t *testing.T) {
+	var seq sync.SeqCount
+	var data int
+	epoch := seq.BeginRead()
+	seq.BeginWrite()
+	if got, ok := SeqAtomicTryLoadInt(&seq, epoch, &data); ok {
+		t.Errorf("SeqAtomicTryLoadInt: got (%v, true), wanted (_, false)", got)
+	}
+	seq.EndWrite()
+}
+
+func TestSeqAtomicTryLoadAfterWrite(t *testing.T) {
+	var seq sync.SeqCount
+	var data int
+	epoch := seq.BeginRead()
+	seq.BeginWrite()
+	seq.EndWrite()
+	if got, ok := SeqAtomicTryLoadInt(&seq, epoch, &data); ok {
+		t.Errorf("SeqAtomicTryLoadInt: got (%v, true), wanted (_, false)", got)
+	}
+}
+
+func BenchmarkSeqAtomicLoadIntUncontended(b *testing.B) {
+	var seq sync.SeqCount
+	const want = 42
+	data := want
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			if got := SeqAtomicLoadInt(&seq, &data); got != want {
+				b.Fatalf("SeqAtomicLoadInt: got %v, wanted %v", got, want)
+			}
+		}
+	})
+}
+
+func BenchmarkSeqAtomicTryLoadIntUncontended(b *testing.B) {
+	var seq sync.SeqCount
+	const want = 42
+	data := want
+	b.RunParallel(func(pb *testing.PB) {
+		epoch := seq.BeginRead()
+		for pb.Next() {
+			if got, ok := SeqAtomicTryLoadInt(&seq, epoch, &data); !ok || got != want {
+				b.Fatalf("SeqAtomicTryLoadInt: got (%v, %v), wanted (%v, true)", got, ok, want)
+			}
+		}
+	})
+}
+
+// For comparison:
+func BenchmarkAtomicValueLoadIntUncontended(b *testing.B) {
+	var a atomic.Value
+	const want = 42
+	a.Store(int(want))
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			if got := a.Load().(int); got != want {
+				b.Fatalf("atomic.Value.Load: got %v, wanted %v", got, want)
+			}
+		}
+	})
+}