sync, sync/atomic: do not corrupt race detector after a nil dereference.

The race detector uses a global lock to analyze atomic
operations. A panic in the middle of the code leaves the
lock acquired.

Similarly, the sync package may leave the race detectro
inconsistent when methods are called on nil pointers.

R=golang-dev, r, minux.ma, dvyukov, rsc, adg
CC=golang-dev
https://golang.org/cl/7981043

src/pkg/runtime/race/testdata/atomic_test.go

@@ -6,6 +6,7 @@ package race_test
 
 import (
 	"runtime"
+	"sync"
 	"sync/atomic"
 	"testing"
 	"unsafe"
@@ -269,3 +270,21 @@ func TestRaceAtomicAddStore(t *testing.T) {
 	a = 42
 	<-c
 }
+
+// A nil pointer in an atomic operation should not deadlock
+// the rest of the program. Used to hang indefinitely.
+func TestNoRaceAtomicCrash(t *testing.T) {
+	var mutex sync.Mutex
+	var nilptr *int32
+	panics := 0
+	defer func() {
+		if x := recover(); x != nil {
+			mutex.Lock()
+			panics++
+			mutex.Unlock()
+		} else {
+			panic("no panic")
+		}
+	}()
+	atomic.AddInt32(nilptr, 1)
+}

src/pkg/runtime/race/testdata/sync_test.go

@@ -195,3 +195,22 @@ func TestRaceGoroutineCreationStack(t *testing.T) {
 	x = 2
 	<-ch
 }
+
+// A nil pointer in a mutex method call should not
+// corrupt the race detector state.
+// Used to hang indefinitely.
+func TestNoRaceNilMutexCrash(t *testing.T) {
+	var mutex sync.Mutex
+	panics := 0
+	defer func() {
+		if x := recover(); x != nil {
+			mutex.Lock()
+			panics++
+			mutex.Unlock()
+		} else {
+			panic("no panic")
+		}
+	}()
+	var othermutex *sync.RWMutex
+	othermutex.RLock()
+}

src/pkg/sync/atomic/race.go

@@ -25,6 +25,7 @@ func CompareAndSwapInt32(val *int32, old, new int32) bool {
 }
 
 func CompareAndSwapUint32(val *uint32, old, new uint32) (swapped bool) {
+	_ = *val
 	swapped = false
 	runtime.RaceSemacquire(&mtx)
 	runtime.RaceRead(unsafe.Pointer(val))
@@ -43,6 +44,7 @@ func CompareAndSwapInt64(val *int64, old, new int64) bool {
 }
 
 func CompareAndSwapUint64(val *uint64, old, new uint64) (swapped bool) {
+	_ = *val
 	swapped = false
 	runtime.RaceSemacquire(&mtx)
 	runtime.RaceRead(unsafe.Pointer(val))
@@ -57,6 +59,7 @@ func CompareAndSwapUint64(val *uint64, old, new uint64) (swapped bool) {
 }
 
 func CompareAndSwapPointer(val *unsafe.Pointer, old, new unsafe.Pointer) (swapped bool) {
+	_ = *val
 	swapped = false
 	runtime.RaceSemacquire(&mtx)
 	runtime.RaceRead(unsafe.Pointer(val))
@@ -71,6 +74,7 @@ func CompareAndSwapPointer(val *unsafe.Pointer, old, new unsafe.Pointer) (swappe
 }
 
 func CompareAndSwapUintptr(val *uintptr, old, new uintptr) (swapped bool) {
+	_ = *val
 	swapped = false
 	runtime.RaceSemacquire(&mtx)
 	runtime.RaceRead(unsafe.Pointer(val))
@@ -89,6 +93,7 @@ func AddInt32(val *int32, delta int32) int32 {
 }
 
 func AddUint32(val *uint32, delta uint32) (new uint32) {
+	_ = *val
 	runtime.RaceSemacquire(&mtx)
 	runtime.RaceRead(unsafe.Pointer(val))
 	runtime.RaceAcquire(unsafe.Pointer(val))
@@ -105,6 +110,7 @@ func AddInt64(val *int64, delta int64) int64 {
 }
 
 func AddUint64(val *uint64, delta uint64) (new uint64) {
+	_ = *val
 	runtime.RaceSemacquire(&mtx)
 	runtime.RaceRead(unsafe.Pointer(val))
 	runtime.RaceAcquire(unsafe.Pointer(val))
@@ -117,6 +123,7 @@ func AddUint64(val *uint64, delta uint64) (new uint64) {
 }
 
 func AddUintptr(val *uintptr, delta uintptr) (new uintptr) {
+	_ = *val
 	runtime.RaceSemacquire(&mtx)
 	runtime.RaceRead(unsafe.Pointer(val))
 	runtime.RaceAcquire(unsafe.Pointer(val))
@@ -133,6 +140,7 @@ func LoadInt32(addr *int32) int32 {
 }
 
 func LoadUint32(addr *uint32) (val uint32) {
+	_ = *addr
 	runtime.RaceSemacquire(&mtx)
 	runtime.RaceRead(unsafe.Pointer(addr))
 	runtime.RaceAcquire(unsafe.Pointer(addr))
@@ -146,6 +154,7 @@ func LoadInt64(addr *int64) int64 {
 }
 
 func LoadUint64(addr *uint64) (val uint64) {
+	_ = *addr
 	runtime.RaceSemacquire(&mtx)
 	runtime.RaceRead(unsafe.Pointer(addr))
 	runtime.RaceAcquire(unsafe.Pointer(addr))
@@ -155,6 +164,7 @@ func LoadUint64(addr *uint64) (val uint64) {
 }
 
 func LoadPointer(addr *unsafe.Pointer) (val unsafe.Pointer) {
+	_ = *addr
 	runtime.RaceSemacquire(&mtx)
 	runtime.RaceRead(unsafe.Pointer(addr))
 	runtime.RaceAcquire(unsafe.Pointer(addr))
@@ -164,6 +174,7 @@ func LoadPointer(addr *unsafe.Pointer) (val unsafe.Pointer) {
 }
 
 func LoadUintptr(addr *uintptr) (val uintptr) {
+	_ = *addr
 	runtime.RaceSemacquire(&mtx)
 	runtime.RaceRead(unsafe.Pointer(addr))
 	runtime.RaceAcquire(unsafe.Pointer(addr))
@@ -177,6 +188,7 @@ func StoreInt32(addr *int32, val int32) {
 }
 
 func StoreUint32(addr *uint32, val uint32) {
+	_ = *addr
 	runtime.RaceSemacquire(&mtx)
 	runtime.RaceRead(unsafe.Pointer(addr))
 	*addr = val
@@ -189,6 +201,7 @@ func StoreInt64(addr *int64, val int64) {
 }
 
 func StoreUint64(addr *uint64, val uint64) {
+	_ = *addr
 	runtime.RaceSemacquire(&mtx)
 	runtime.RaceRead(unsafe.Pointer(addr))
 	*addr = val
@@ -197,6 +210,7 @@ func StoreUint64(addr *uint64, val uint64) {
 }
 
 func StorePointer(addr *unsafe.Pointer, val unsafe.Pointer) {
+	_ = *addr
 	runtime.RaceSemacquire(&mtx)
 	runtime.RaceRead(unsafe.Pointer(addr))
 	*addr = val
@@ -205,6 +219,7 @@ func StorePointer(addr *unsafe.Pointer, val unsafe.Pointer) {
 }
 
 func StoreUintptr(addr *uintptr, val uintptr) {
+	_ = *addr
 	runtime.RaceSemacquire(&mtx)
 	runtime.RaceRead(unsafe.Pointer(addr))
 	*addr = val

src/pkg/sync/cond.go

@@ -57,6 +57,7 @@ func NewCond(l Locker) *Cond {
 //
 func (c *Cond) Wait() {
 	if raceenabled {
+		_ = c.m.state
 		raceDisable()
 	}
 	c.m.Lock()
@@ -80,6 +81,7 @@ func (c *Cond) Wait() {
 // during the call.
 func (c *Cond) Signal() {
 	if raceenabled {
+		_ = c.m.state
 		raceDisable()
 	}
 	c.m.Lock()
@@ -106,6 +108,7 @@ func (c *Cond) Signal() {
 // during the call.
 func (c *Cond) Broadcast() {
 	if raceenabled {
+		_ = c.m.state
 		raceDisable()
 	}
 	c.m.Lock()

src/pkg/sync/mutex.go

@@ -81,6 +81,7 @@ func (m *Mutex) Lock() {
 // arrange for another goroutine to unlock it.
 func (m *Mutex) Unlock() {
 	if raceenabled {
+		_ = m.state
 		raceRelease(unsafe.Pointer(m))
 	}
 

src/pkg/sync/rwmutex.go

@@ -28,6 +28,7 @@ const rwmutexMaxReaders = 1 << 30
 // RLock locks rw for reading.
 func (rw *RWMutex) RLock() {
 	if raceenabled {
+		_ = rw.w.state
 		raceDisable()
 	}
 	if atomic.AddInt32(&rw.readerCount, 1) < 0 {
@@ -46,6 +47,7 @@ func (rw *RWMutex) RLock() {
 // on entry to RUnlock.
 func (rw *RWMutex) RUnlock() {
 	if raceenabled {
+		_ = rw.w.state
 		raceReleaseMerge(unsafe.Pointer(&rw.writerSem))
 		raceDisable()
 	}
@@ -69,6 +71,7 @@ func (rw *RWMutex) RUnlock() {
 // the lock.
 func (rw *RWMutex) Lock() {
 	if raceenabled {
+		_ = rw.w.state
 		raceDisable()
 	}
 	// First, resolve competition with other writers.
@@ -94,6 +97,7 @@ func (rw *RWMutex) Lock() {
 // arrange for another goroutine to RUnlock (Unlock) it.
 func (rw *RWMutex) Unlock() {
 	if raceenabled {
+		_ = rw.w.state
 		raceRelease(unsafe.Pointer(&rw.readerSem))
 		raceRelease(unsafe.Pointer(&rw.writerSem))
 		raceDisable()

src/pkg/sync/waitgroup.go

@@ -43,6 +43,7 @@ type WaitGroup struct {
 // other event to be waited for. See the WaitGroup example.
 func (wg *WaitGroup) Add(delta int) {
 	if raceenabled {
+		_ = wg.m.state
 		raceReleaseMerge(unsafe.Pointer(wg))
 		raceDisable()
 		defer raceEnable()
@@ -71,6 +72,7 @@ func (wg *WaitGroup) Done() {
 // Wait blocks until the WaitGroup counter is zero.
 func (wg *WaitGroup) Wait() {
 	if raceenabled {
+		_ = wg.m.state
 		raceDisable()
 	}
 	if atomic.LoadInt32(&wg.counter) == 0 {