Rename DowngradableRWMutex to RWmutex.

Also renames TMutex to Mutex.

These custom mutexes aren't any worse than the standard library versions (same
code), so having both seems redundant.

PiperOrigin-RevId: 290873587

pkg/sentry/fs/overlay.go

@@ -198,7 +198,7 @@ type overlayEntry struct {
 	upper *Inode
 
 	// dirCacheMu protects dirCache.
-	dirCacheMu sync.DowngradableRWMutex `state:"nosave"`
+	dirCacheMu sync.RWMutex `state:"nosave"`
 
 	// dirCache is cache of DentAttrs from upper and lower Inodes.
 	dirCache *SortedDentryMap

pkg/sentry/mm/mm.go

@@ -80,7 +80,7 @@ type MemoryManager struct {
 	users int32
 
 	// mappingMu is analogous to Linux's struct mm_struct::mmap_sem.
-	mappingMu sync.DowngradableRWMutex `state:"nosave"`
+	mappingMu sync.RWMutex `state:"nosave"`
 
 	// vmas stores virtual memory areas. Since vmas are stored by value,
 	// clients should usually use vmaIterator.ValuePtr() instead of
@@ -123,7 +123,7 @@ type MemoryManager struct {
 
 	// activeMu is loosely analogous to Linux's struct
 	// mm_struct::page_table_lock.
-	activeMu sync.DowngradableRWMutex `state:"nosave"`
+	activeMu sync.RWMutex `state:"nosave"`
 
 	// pmas stores platform mapping areas used to implement vmas. Since pmas
 	// are stored by value, clients should usually use pmaIterator.ValuePtr()

pkg/sync/aliases.go

@@ -11,12 +11,6 @@ import (
 
 // Aliases of standard library types.
 type (
-	// Mutex is an alias of sync.Mutex.
-	Mutex = sync.Mutex
-
-	// RWMutex is an alias of sync.RWMutex.
-	RWMutex = sync.RWMutex
-
 	// Cond is an alias of sync.Cond.
 	Cond = sync.Cond
 

pkg/sync/downgradable_rwmutex_test.go

@@ -18,7 +18,7 @@ import (
 	"testing"
 )
 
-func parallelReader(m *DowngradableRWMutex, clocked, cunlock, cdone chan bool) {
+func parallelReader(m *RWMutex, clocked, cunlock, cdone chan bool) {
 	m.RLock()
 	clocked <- true
 	<-cunlock
@@ -28,7 +28,7 @@ func parallelReader(m *DowngradableRWMutex, clocked, cunlock, cdone chan bool) {
 
 func doTestParallelReaders(numReaders, gomaxprocs int) {
 	runtime.GOMAXPROCS(gomaxprocs)
-	var m DowngradableRWMutex
+	var m RWMutex
 	clocked := make(chan bool)
 	cunlock := make(chan bool)
 	cdone := make(chan bool)
@@ -55,7 +55,7 @@ func TestParallelReaders(t *testing.T) {
 	doTestParallelReaders(4, 2)
 }
 
-func reader(rwm *DowngradableRWMutex, numIterations int, activity *int32, cdone chan bool) {
+func reader(rwm *RWMutex, numIterations int, activity *int32, cdone chan bool) {
 	for i := 0; i < numIterations; i++ {
 		rwm.RLock()
 		n := atomic.AddInt32(activity, 1)
@@ -70,7 +70,7 @@ func reader(rwm *DowngradableRWMutex, numIterations int, activity *int32, cdone
 	cdone <- true
 }
 
-func writer(rwm *DowngradableRWMutex, numIterations int, activity *int32, cdone chan bool) {
+func writer(rwm *RWMutex, numIterations int, activity *int32, cdone chan bool) {
 	for i := 0; i < numIterations; i++ {
 		rwm.Lock()
 		n := atomic.AddInt32(activity, 10000)
@@ -85,7 +85,7 @@ func writer(rwm *DowngradableRWMutex, numIterations int, activity *int32, cdone
 	cdone <- true
 }
 
-func downgradingWriter(rwm *DowngradableRWMutex, numIterations int, activity *int32, cdone chan bool) {
+func downgradingWriter(rwm *RWMutex, numIterations int, activity *int32, cdone chan bool) {
 	for i := 0; i < numIterations; i++ {
 		rwm.Lock()
 		n := atomic.AddInt32(activity, 10000)
@@ -112,7 +112,7 @@ func HammerDowngradableRWMutex(gomaxprocs, numReaders, numIterations int) {
 	runtime.GOMAXPROCS(gomaxprocs)
 	// Number of active readers + 10000 * number of active writers.
 	var activity int32
-	var rwm DowngradableRWMutex
+	var rwm RWMutex
 	cdone := make(chan bool)
 	go writer(&rwm, numIterations, &activity, cdone)
 	go downgradingWriter(&rwm, numIterations, &activity, cdone)
@@ -150,56 +150,56 @@ func TestDowngradableRWMutex(t *testing.T) {
 }
 
 func TestRWDoubleTryLock(t *testing.T) {
-	var m DowngradableRWMutex
-	if !m.TryLock() {
+	var rwm RWMutex
+	if !rwm.TryLock() {
 		t.Fatal("failed to aquire lock")
 	}
-	if m.TryLock() {
+	if rwm.TryLock() {
 		t.Fatal("unexpectedly succeeded in aquiring locked mutex")
 	}
 }
 
 func TestRWTryLockAfterLock(t *testing.T) {
-	var m DowngradableRWMutex
-	m.Lock()
-	if m.TryLock() {
+	var rwm RWMutex
+	rwm.Lock()
+	if rwm.TryLock() {
 		t.Fatal("unexpectedly succeeded in aquiring locked mutex")
 	}
 }
 
 func TestRWTryLockUnlock(t *testing.T) {
-	var m DowngradableRWMutex
-	if !m.TryLock() {
+	var rwm RWMutex
+	if !rwm.TryLock() {
 		t.Fatal("failed to aquire lock")
 	}
-	m.Unlock()
-	if !m.TryLock() {
+	rwm.Unlock()
+	if !rwm.TryLock() {
 		t.Fatal("failed to aquire lock after unlock")
 	}
 }
 
 func TestTryRLockAfterLock(t *testing.T) {
-	var m DowngradableRWMutex
-	m.Lock()
-	if m.TryRLock() {
+	var rwm RWMutex
+	rwm.Lock()
+	if rwm.TryRLock() {
 		t.Fatal("unexpectedly succeeded in aquiring locked mutex")
 	}
 }
 
 func TestTryLockAfterRLock(t *testing.T) {
-	var m DowngradableRWMutex
-	m.RLock()
-	if m.TryLock() {
+	var rwm RWMutex
+	rwm.RLock()
+	if rwm.TryLock() {
 		t.Fatal("unexpectedly succeeded in aquiring locked mutex")
 	}
 }
 
 func TestDoubleTryRLock(t *testing.T) {
-	var m DowngradableRWMutex
-	if !m.TryRLock() {
+	var rwm RWMutex
+	if !rwm.TryRLock() {
 		t.Fatal("failed to aquire lock")
 	}
-	if !m.TryRLock() {
+	if !rwm.TryRLock() {
 		t.Fatal("failed to read aquire read locked lock")
 	}
 }

pkg/sync/downgradable_rwmutex_unsafe.go

@@ -29,10 +29,10 @@ func runtimeSemacquire(s *uint32)
 //go:linkname runtimeSemrelease sync.runtime_Semrelease
 func runtimeSemrelease(s *uint32, handoff bool, skipframes int)
 
-// DowngradableRWMutex is identical to sync.RWMutex, but adds the DowngradeLock,
+// RWMutex is identical to sync.RWMutex, but adds the DowngradeLock,
 // TryLock and TryRLock methods.
-type DowngradableRWMutex struct {
-	w           TMutex // held if there are pending writers
+type RWMutex struct {
+	w           Mutex  // held if there are pending writers
 	writerSem   uint32 // semaphore for writers to wait for completing readers
 	readerSem   uint32 // semaphore for readers to wait for completing writers
 	readerCount int32  // number of pending readers
@@ -43,7 +43,7 @@ const rwmutexMaxReaders = 1 << 30
 
 // TryRLock locks rw for reading. It returns true if it succeeds and false
 // otherwise. It does not block.
-func (rw *DowngradableRWMutex) TryRLock() bool {
+func (rw *RWMutex) TryRLock() bool {
 	if RaceEnabled {
 		RaceDisable()
 	}
@@ -67,7 +67,7 @@ func (rw *DowngradableRWMutex) TryRLock() bool {
 }
 
 // RLock locks rw for reading.
-func (rw *DowngradableRWMutex) RLock() {
+func (rw *RWMutex) RLock() {
 	if RaceEnabled {
 		RaceDisable()
 	}
@@ -82,14 +82,14 @@ func (rw *DowngradableRWMutex) RLock() {
 }
 
 // RUnlock undoes a single RLock call.
-func (rw *DowngradableRWMutex) RUnlock() {
+func (rw *RWMutex) RUnlock() {
 	if RaceEnabled {
 		RaceReleaseMerge(unsafe.Pointer(&rw.writerSem))
 		RaceDisable()
 	}
 	if r := atomic.AddInt32(&rw.readerCount, -1); r < 0 {
 		if r+1 == 0 || r+1 == -rwmutexMaxReaders {
-			panic("RUnlock of unlocked DowngradableRWMutex")
+			panic("RUnlock of unlocked RWMutex")
 		}
 		// A writer is pending.
 		if atomic.AddInt32(&rw.readerWait, -1) == 0 {
@@ -104,7 +104,7 @@ func (rw *DowngradableRWMutex) RUnlock() {
 
 // TryLock locks rw for writing. It returns true if it succeeds and false
 // otherwise. It does not block.
-func (rw *DowngradableRWMutex) TryLock() bool {
+func (rw *RWMutex) TryLock() bool {
 	if RaceEnabled {
 		RaceDisable()
 	}
@@ -131,7 +131,7 @@ func (rw *DowngradableRWMutex) TryLock() bool {
 }
 
 // Lock locks rw for writing.
-func (rw *DowngradableRWMutex) Lock() {
+func (rw *RWMutex) Lock() {
 	if RaceEnabled {
 		RaceDisable()
 	}
@@ -150,7 +150,7 @@ func (rw *DowngradableRWMutex) Lock() {
 }
 
 // Unlock unlocks rw for writing.
-func (rw *DowngradableRWMutex) Unlock() {
+func (rw *RWMutex) Unlock() {
 	if RaceEnabled {
 		RaceRelease(unsafe.Pointer(&rw.writerSem))
 		RaceRelease(unsafe.Pointer(&rw.readerSem))
@@ -159,7 +159,7 @@ func (rw *DowngradableRWMutex) Unlock() {
 	// Announce to readers there is no active writer.
 	r := atomic.AddInt32(&rw.readerCount, rwmutexMaxReaders)
 	if r >= rwmutexMaxReaders {
-		panic("Unlock of unlocked DowngradableRWMutex")
+		panic("Unlock of unlocked RWMutex")
 	}
 	// Unblock blocked readers, if any.
 	for i := 0; i < int(r); i++ {
@@ -173,7 +173,7 @@ func (rw *DowngradableRWMutex) Unlock() {
 }
 
 // DowngradeLock atomically unlocks rw for writing and locks it for reading.
-func (rw *DowngradableRWMutex) DowngradeLock() {
+func (rw *RWMutex) DowngradeLock() {
 	if RaceEnabled {
 		RaceRelease(unsafe.Pointer(&rw.readerSem))
 		RaceDisable()
@@ -181,7 +181,7 @@ func (rw *DowngradableRWMutex) DowngradeLock() {
 	// Announce to readers there is no active writer and one additional reader.
 	r := atomic.AddInt32(&rw.readerCount, rwmutexMaxReaders+1)
 	if r >= rwmutexMaxReaders+1 {
-		panic("DowngradeLock of unlocked DowngradableRWMutex")
+		panic("DowngradeLock of unlocked RWMutex")
 	}
 	// Unblock blocked readers, if any. Note that this loop starts as 1 since r
 	// includes this goroutine.

pkg/sync/tmutex_test.go

@@ -30,7 +30,7 @@ func TestStructSize(t *testing.T) {
 //
 // The correctness of this package relies on these remaining in sync.
 func TestFieldValues(t *testing.T) {
-	var m TMutex
+	var m Mutex
 	m.Lock()
 	if got := *m.state(); got != mutexLocked {
 		t.Errorf("got locked sync.Mutex.state = %d, want = %d", got, mutexLocked)
@@ -42,7 +42,7 @@ func TestFieldValues(t *testing.T) {
 }
 
 func TestDoubleTryLock(t *testing.T) {
-	var m TMutex
+	var m Mutex
 	if !m.TryLock() {
 		t.Fatal("failed to aquire lock")
 	}
@@ -52,7 +52,7 @@ func TestDoubleTryLock(t *testing.T) {
 }
 
 func TestTryLockAfterLock(t *testing.T) {
-	var m TMutex
+	var m Mutex
 	m.Lock()
 	if m.TryLock() {
 		t.Fatal("unexpectedly succeeded in aquiring locked mutex")
@@ -60,7 +60,7 @@ func TestTryLockAfterLock(t *testing.T) {
 }
 
 func TestTryLockUnlock(t *testing.T) {
-	var m TMutex
+	var m Mutex
 	if !m.TryLock() {
 		t.Fatal("failed to aquire lock")
 	}

pkg/sync/tmutex_unsafe.go

@@ -17,8 +17,8 @@ import (
 	"unsafe"
 )
 
-// TMutex is a try lock.
-type TMutex struct {
+// Mutex is a try lock.
+type Mutex struct {
 	sync.Mutex
 }
 
@@ -27,7 +27,7 @@ type syncMutex struct {
 	sema  uint32
 }
 
-func (m *TMutex) state() *int32 {
+func (m *Mutex) state() *int32 {
 	return &(*syncMutex)(unsafe.Pointer(&m.Mutex)).state
 }
 
@@ -38,7 +38,7 @@ const (
 
 // TryLock tries to aquire the mutex. It returns true if it succeeds and false
 // otherwise. TryLock does not block.
-func (m *TMutex) TryLock() bool {
+func (m *Mutex) TryLock() bool {
 	if atomic.CompareAndSwapInt32(m.state(), mutexUnlocked, mutexLocked) {
 		if RaceEnabled {
 			RaceAcquire(unsafe.Pointer(&m.Mutex))