all: update go directive to 1.18
Done with:
go get go@1.18
go mod tidy
go fix ./...
Using go1.21.3.
While here, simplify package syncmap by taking advantage of knowing
that all supported Go versions will have the go1.9 build constraint
satisfied.
For golang/go#60268.
Change-Id: Ic0f24ab13ada6839573e55beee5516c1a6c7f3cc
Reviewed-on: https://go-review.googlesource.com/c/sync/+/534220
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
diff --git a/errgroup/go120.go b/errgroup/go120.go
index 7d419d3..f93c740 100644
--- a/errgroup/go120.go
+++ b/errgroup/go120.go
@@ -3,7 +3,6 @@
// license that can be found in the LICENSE file.
//go:build go1.20
-// +build go1.20
package errgroup
diff --git a/errgroup/go120_test.go b/errgroup/go120_test.go
index 0c354a1..068f104 100644
--- a/errgroup/go120_test.go
+++ b/errgroup/go120_test.go
@@ -3,7 +3,6 @@
// license that can be found in the LICENSE file.
//go:build go1.20
-// +build go1.20
package errgroup_test
diff --git a/errgroup/pre_go120.go b/errgroup/pre_go120.go
index 1795c18..88ce334 100644
--- a/errgroup/pre_go120.go
+++ b/errgroup/pre_go120.go
@@ -3,7 +3,6 @@
// license that can be found in the LICENSE file.
//go:build !go1.20
-// +build !go1.20
package errgroup
diff --git a/go.mod b/go.mod
index 782b734..74bd0ac 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,3 @@
module golang.org/x/sync
-go 1.17
+go 1.18
diff --git a/semaphore/semaphore_bench_test.go b/semaphore/semaphore_bench_test.go
index 3b60ca8..aa64258 100644
--- a/semaphore/semaphore_bench_test.go
+++ b/semaphore/semaphore_bench_test.go
@@ -2,9 +2,6 @@
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
-//go:build go1.7
-// +build go1.7
-
package semaphore_test
import (
diff --git a/syncmap/go19.go b/syncmap/go19.go
deleted file mode 100644
index fa04dba..0000000
--- a/syncmap/go19.go
+++ /dev/null
@@ -1,18 +0,0 @@
-// Copyright 2019 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build go1.9
-// +build go1.9
-
-package syncmap
-
-import "sync" // home to the standard library's sync.map implementation as of Go 1.9
-
-// Map is a concurrent map with amortized-constant-time loads, stores, and deletes.
-// It is safe for multiple goroutines to call a Map's methods concurrently.
-//
-// The zero Map is valid and empty.
-//
-// A Map must not be copied after first use.
-type Map = sync.Map
diff --git a/syncmap/map.go b/syncmap/map.go
index 4b638cb..c9a07f3 100644
--- a/syncmap/map.go
+++ b/syncmap/map.go
@@ -6,3 +6,13 @@
// This was the prototype for sync.Map which was added to the standard library's
// sync package in Go 1.9. https://golang.org/pkg/sync/#Map.
package syncmap
+
+import "sync" // home to the standard library's sync.map implementation as of Go 1.9
+
+// Map is a concurrent map with amortized-constant-time loads, stores, and deletes.
+// It is safe for multiple goroutines to call a Map's methods concurrently.
+//
+// The zero Map is valid and empty.
+//
+// A Map must not be copied after first use.
+type Map = sync.Map
diff --git a/syncmap/pre_go19.go b/syncmap/pre_go19.go
deleted file mode 100644
index 5bba413..0000000
--- a/syncmap/pre_go19.go
+++ /dev/null
@@ -1,371 +0,0 @@
-// Copyright 2016 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build !go1.9
-// +build !go1.9
-
-package syncmap
-
-import (
- "sync"
- "sync/atomic"
- "unsafe"
-)
-
-// Map is a concurrent map with amortized-constant-time loads, stores, and deletes.
-// It is safe for multiple goroutines to call a Map's methods concurrently.
-//
-// The zero Map is valid and empty.
-//
-// A Map must not be copied after first use.
-type Map struct {
- mu sync.Mutex
-
- // read contains the portion of the map's contents that are safe for
- // concurrent access (with or without mu held).
- //
- // The read field itself is always safe to load, but must only be stored with
- // mu held.
- //
- // Entries stored in read may be updated concurrently without mu, but updating
- // a previously-expunged entry requires that the entry be copied to the dirty
- // map and unexpunged with mu held.
- read atomic.Value // readOnly
-
- // dirty contains the portion of the map's contents that require mu to be
- // held. To ensure that the dirty map can be promoted to the read map quickly,
- // it also includes all of the non-expunged entries in the read map.
- //
- // Expunged entries are not stored in the dirty map. An expunged entry in the
- // clean map must be unexpunged and added to the dirty map before a new value
- // can be stored to it.
- //
- // If the dirty map is nil, the next write to the map will initialize it by
- // making a shallow copy of the clean map, omitting stale entries.
- dirty map[interface{}]*entry
-
- // misses counts the number of loads since the read map was last updated that
- // needed to lock mu to determine whether the key was present.
- //
- // Once enough misses have occurred to cover the cost of copying the dirty
- // map, the dirty map will be promoted to the read map (in the unamended
- // state) and the next store to the map will make a new dirty copy.
- misses int
-}
-
-// readOnly is an immutable struct stored atomically in the Map.read field.
-type readOnly struct {
- m map[interface{}]*entry
- amended bool // true if the dirty map contains some key not in m.
-}
-
-// expunged is an arbitrary pointer that marks entries which have been deleted
-// from the dirty map.
-var expunged = unsafe.Pointer(new(interface{}))
-
-// An entry is a slot in the map corresponding to a particular key.
-type entry struct {
- // p points to the interface{} value stored for the entry.
- //
- // If p == nil, the entry has been deleted and m.dirty == nil.
- //
- // If p == expunged, the entry has been deleted, m.dirty != nil, and the entry
- // is missing from m.dirty.
- //
- // Otherwise, the entry is valid and recorded in m.read.m[key] and, if m.dirty
- // != nil, in m.dirty[key].
- //
- // An entry can be deleted by atomic replacement with nil: when m.dirty is
- // next created, it will atomically replace nil with expunged and leave
- // m.dirty[key] unset.
- //
- // An entry's associated value can be updated by atomic replacement, provided
- // p != expunged. If p == expunged, an entry's associated value can be updated
- // only after first setting m.dirty[key] = e so that lookups using the dirty
- // map find the entry.
- p unsafe.Pointer // *interface{}
-}
-
-func newEntry(i interface{}) *entry {
- return &entry{p: unsafe.Pointer(&i)}
-}
-
-// Load returns the value stored in the map for a key, or nil if no
-// value is present.
-// The ok result indicates whether value was found in the map.
-func (m *Map) Load(key interface{}) (value interface{}, ok bool) {
- read, _ := m.read.Load().(readOnly)
- e, ok := read.m[key]
- if !ok && read.amended {
- m.mu.Lock()
- // Avoid reporting a spurious miss if m.dirty got promoted while we were
- // blocked on m.mu. (If further loads of the same key will not miss, it's
- // not worth copying the dirty map for this key.)
- read, _ = m.read.Load().(readOnly)
- e, ok = read.m[key]
- if !ok && read.amended {
- e, ok = m.dirty[key]
- // Regardless of whether the entry was present, record a miss: this key
- // will take the slow path until the dirty map is promoted to the read
- // map.
- m.missLocked()
- }
- m.mu.Unlock()
- }
- if !ok {
- return nil, false
- }
- return e.load()
-}
-
-func (e *entry) load() (value interface{}, ok bool) {
- p := atomic.LoadPointer(&e.p)
- if p == nil || p == expunged {
- return nil, false
- }
- return *(*interface{})(p), true
-}
-
-// Store sets the value for a key.
-func (m *Map) Store(key, value interface{}) {
- read, _ := m.read.Load().(readOnly)
- if e, ok := read.m[key]; ok && e.tryStore(&value) {
- return
- }
-
- m.mu.Lock()
- read, _ = m.read.Load().(readOnly)
- if e, ok := read.m[key]; ok {
- if e.unexpungeLocked() {
- // The entry was previously expunged, which implies that there is a
- // non-nil dirty map and this entry is not in it.
- m.dirty[key] = e
- }
- e.storeLocked(&value)
- } else if e, ok := m.dirty[key]; ok {
- e.storeLocked(&value)
- } else {
- if !read.amended {
- // We're adding the first new key to the dirty map.
- // Make sure it is allocated and mark the read-only map as incomplete.
- m.dirtyLocked()
- m.read.Store(readOnly{m: read.m, amended: true})
- }
- m.dirty[key] = newEntry(value)
- }
- m.mu.Unlock()
-}
-
-// tryStore stores a value if the entry has not been expunged.
-//
-// If the entry is expunged, tryStore returns false and leaves the entry
-// unchanged.
-func (e *entry) tryStore(i *interface{}) bool {
- p := atomic.LoadPointer(&e.p)
- if p == expunged {
- return false
- }
- for {
- if atomic.CompareAndSwapPointer(&e.p, p, unsafe.Pointer(i)) {
- return true
- }
- p = atomic.LoadPointer(&e.p)
- if p == expunged {
- return false
- }
- }
-}
-
-// unexpungeLocked ensures that the entry is not marked as expunged.
-//
-// If the entry was previously expunged, it must be added to the dirty map
-// before m.mu is unlocked.
-func (e *entry) unexpungeLocked() (wasExpunged bool) {
- return atomic.CompareAndSwapPointer(&e.p, expunged, nil)
-}
-
-// storeLocked unconditionally stores a value to the entry.
-//
-// The entry must be known not to be expunged.
-func (e *entry) storeLocked(i *interface{}) {
- atomic.StorePointer(&e.p, unsafe.Pointer(i))
-}
-
-// LoadOrStore returns the existing value for the key if present.
-// Otherwise, it stores and returns the given value.
-// The loaded result is true if the value was loaded, false if stored.
-func (m *Map) LoadOrStore(key, value interface{}) (actual interface{}, loaded bool) {
- // Avoid locking if it's a clean hit.
- read, _ := m.read.Load().(readOnly)
- if e, ok := read.m[key]; ok {
- actual, loaded, ok := e.tryLoadOrStore(value)
- if ok {
- return actual, loaded
- }
- }
-
- m.mu.Lock()
- read, _ = m.read.Load().(readOnly)
- if e, ok := read.m[key]; ok {
- if e.unexpungeLocked() {
- m.dirty[key] = e
- }
- actual, loaded, _ = e.tryLoadOrStore(value)
- } else if e, ok := m.dirty[key]; ok {
- actual, loaded, _ = e.tryLoadOrStore(value)
- m.missLocked()
- } else {
- if !read.amended {
- // We're adding the first new key to the dirty map.
- // Make sure it is allocated and mark the read-only map as incomplete.
- m.dirtyLocked()
- m.read.Store(readOnly{m: read.m, amended: true})
- }
- m.dirty[key] = newEntry(value)
- actual, loaded = value, false
- }
- m.mu.Unlock()
-
- return actual, loaded
-}
-
-// tryLoadOrStore atomically loads or stores a value if the entry is not
-// expunged.
-//
-// If the entry is expunged, tryLoadOrStore leaves the entry unchanged and
-// returns with ok==false.
-func (e *entry) tryLoadOrStore(i interface{}) (actual interface{}, loaded, ok bool) {
- p := atomic.LoadPointer(&e.p)
- if p == expunged {
- return nil, false, false
- }
- if p != nil {
- return *(*interface{})(p), true, true
- }
-
- // Copy the interface after the first load to make this method more amenable
- // to escape analysis: if we hit the "load" path or the entry is expunged, we
- // shouldn't bother heap-allocating.
- ic := i
- for {
- if atomic.CompareAndSwapPointer(&e.p, nil, unsafe.Pointer(&ic)) {
- return i, false, true
- }
- p = atomic.LoadPointer(&e.p)
- if p == expunged {
- return nil, false, false
- }
- if p != nil {
- return *(*interface{})(p), true, true
- }
- }
-}
-
-// Delete deletes the value for a key.
-func (m *Map) Delete(key interface{}) {
- read, _ := m.read.Load().(readOnly)
- e, ok := read.m[key]
- if !ok && read.amended {
- m.mu.Lock()
- read, _ = m.read.Load().(readOnly)
- e, ok = read.m[key]
- if !ok && read.amended {
- delete(m.dirty, key)
- }
- m.mu.Unlock()
- }
- if ok {
- e.delete()
- }
-}
-
-func (e *entry) delete() (hadValue bool) {
- for {
- p := atomic.LoadPointer(&e.p)
- if p == nil || p == expunged {
- return false
- }
- if atomic.CompareAndSwapPointer(&e.p, p, nil) {
- return true
- }
- }
-}
-
-// Range calls f sequentially for each key and value present in the map.
-// If f returns false, range stops the iteration.
-//
-// Range does not necessarily correspond to any consistent snapshot of the Map's
-// contents: no key will be visited more than once, but if the value for any key
-// is stored or deleted concurrently, Range may reflect any mapping for that key
-// from any point during the Range call.
-//
-// Range may be O(N) with the number of elements in the map even if f returns
-// false after a constant number of calls.
-func (m *Map) Range(f func(key, value interface{}) bool) {
- // We need to be able to iterate over all of the keys that were already
- // present at the start of the call to Range.
- // If read.amended is false, then read.m satisfies that property without
- // requiring us to hold m.mu for a long time.
- read, _ := m.read.Load().(readOnly)
- if read.amended {
- // m.dirty contains keys not in read.m. Fortunately, Range is already O(N)
- // (assuming the caller does not break out early), so a call to Range
- // amortizes an entire copy of the map: we can promote the dirty copy
- // immediately!
- m.mu.Lock()
- read, _ = m.read.Load().(readOnly)
- if read.amended {
- read = readOnly{m: m.dirty}
- m.read.Store(read)
- m.dirty = nil
- m.misses = 0
- }
- m.mu.Unlock()
- }
-
- for k, e := range read.m {
- v, ok := e.load()
- if !ok {
- continue
- }
- if !f(k, v) {
- break
- }
- }
-}
-
-func (m *Map) missLocked() {
- m.misses++
- if m.misses < len(m.dirty) {
- return
- }
- m.read.Store(readOnly{m: m.dirty})
- m.dirty = nil
- m.misses = 0
-}
-
-func (m *Map) dirtyLocked() {
- if m.dirty != nil {
- return
- }
-
- read, _ := m.read.Load().(readOnly)
- m.dirty = make(map[interface{}]*entry, len(read.m))
- for k, e := range read.m {
- if !e.tryExpungeLocked() {
- m.dirty[k] = e
- }
- }
-}
-
-func (e *entry) tryExpungeLocked() (isExpunged bool) {
- p := atomic.LoadPointer(&e.p)
- for p == nil {
- if atomic.CompareAndSwapPointer(&e.p, nil, expunged) {
- return true
- }
- p = atomic.LoadPointer(&e.p)
- }
- return p == expunged
-}
