4 files changed, 178 insertions, 6 deletions
diff --git a/pkg/sync/checklocks_off_unsafe.go b/pkg/sync/checklocks_off_unsafe.go
new file mode 100644
index 000000000..62c81b149
--- /dev/null
+++ b/pkg/sync/checklocks_off_unsafe.go
@@ -0,0 +1,18 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !checklocks
+
+package sync
+
+import (
+	"unsafe"
+)
+
+func noteLock(l unsafe.Pointer) {
+}
+
+func noteUnlock(l unsafe.Pointer) {
+}
diff --git a/pkg/sync/checklocks_on_unsafe.go b/pkg/sync/checklocks_on_unsafe.go
new file mode 100644
index 000000000..24f933ed1
--- /dev/null
+++ b/pkg/sync/checklocks_on_unsafe.go
@@ -0,0 +1,108 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build checklocks
+
+package sync
+
+import (
+	"fmt"
+	"strings"
+	"sync"
+	"unsafe"
+
+	"gvisor.dev/gvisor/pkg/goid"
+)
+
+// gLocks contains metadata about the locks held by a goroutine.
+type gLocks struct {
+	locksHeld []unsafe.Pointer
+}
+
+// map[goid int]*gLocks
+//
+// Each key may only be written by the G with the goid it refers to.
+//
+// Note that entries are not evicted when a G exit, causing unbounded growth
+// with new G creation / destruction. If this proves problematic, entries could
+// be evicted when no locks are held at the expense of more allocations when
+// taking top-level locks.
+var locksHeld sync.Map
+
+func getGLocks() *gLocks {
+	id := goid.Get()
+
+	var locks *gLocks
+	if l, ok := locksHeld.Load(id); ok {
+		locks = l.(*gLocks)
+	} else {
+		locks = &gLocks{
+			// Initialize space for a few locks.
+			locksHeld: make([]unsafe.Pointer, 0, 8),
+		}
+		locksHeld.Store(id, locks)
+	}
+
+	return locks
+}
+
+func noteLock(l unsafe.Pointer) {
+	locks := getGLocks()
+
+	for _, lock := range locks.locksHeld {
+		if lock == l {
+			panic(fmt.Sprintf("Deadlock on goroutine %d! Double lock of %p: %+v", goid.Get(), l, locks))
+		}
+	}
+
+	// Commit only after checking for panic conditions so that this lock
+	// isn't on the list if the above panic is recovered.
+	locks.locksHeld = append(locks.locksHeld, l)
+}
+
+func noteUnlock(l unsafe.Pointer) {
+	locks := getGLocks()
+
+	if len(locks.locksHeld) == 0 {
+		panic(fmt.Sprintf("Unlock of %p on goroutine %d without any locks held! All locks:\n%s", l, goid.Get(), dumpLocks()))
+	}
+
+	// Search backwards since callers are most likely to unlock in LIFO order.
+	length := len(locks.locksHeld)
+	for i := length - 1; i >= 0; i-- {
+		if l == locks.locksHeld[i] {
+			copy(locks.locksHeld[i:length-1], locks.locksHeld[i+1:length])
+			// Clear last entry to ensure addr can be GC'd.
+			locks.locksHeld[length-1] = nil
+			locks.locksHeld = locks.locksHeld[:length-1]
+			return
+		}
+	}
+
+	panic(fmt.Sprintf("Unlock of %p on goroutine %d without matching lock! All locks:\n%s", l, goid.Get(), dumpLocks()))
+}
+
+func dumpLocks() string {
+	var s strings.Builder
+	locksHeld.Range(func(key, value interface{}) bool {
+		goid := key.(int64)
+		locks := value.(*gLocks)
+
+		// N.B. accessing gLocks of another G is fundamentally racy.
+
+		fmt.Fprintf(&s, "goroutine %d:\n", goid)
+		if len(locks.locksHeld) == 0 {
+			fmt.Fprintf(&s, "\t<none>\n")
+		}
+		for _, lock := range locks.locksHeld {
+			fmt.Fprintf(&s, "\t%p\n", lock)
+		}
+		fmt.Fprintf(&s, "\n")
+
+		return true
+	})
+
+	return s.String()
+}
diff --git a/pkg/sync/mutex_unsafe.go b/pkg/sync/mutex_unsafe.go
index f4c2e9642..21084b857 100644
--- a/pkg/sync/mutex_unsafe.go
+++ b/pkg/sync/mutex_unsafe.go
@@ -17,8 +17,9 @@ import (
 	"unsafe"
 )
 
-// Mutex is a try lock.
-type Mutex struct {
+// CrossGoroutineMutex is equivalent to Mutex, but it need not be unlocked by a
+// the same goroutine that locked the mutex.
+type CrossGoroutineMutex struct {
 	sync.Mutex
 }
 
@@ -27,7 +28,7 @@ type syncMutex struct {
 	sema  uint32
 }
 
-func (m *Mutex) state() *int32 {
+func (m *CrossGoroutineMutex) state() *int32 {
 	return &(*syncMutex)(unsafe.Pointer(&m.Mutex)).state
 }
 
@@ -36,9 +37,9 @@ const (
 	mutexLocked   = 1
 )
 
-// TryLock tries to aquire the mutex. It returns true if it succeeds and false
+// TryLock tries to acquire the mutex. It returns true if it succeeds and false
 // otherwise. TryLock does not block.
-func (m *Mutex) TryLock() bool {
+func (m *CrossGoroutineMutex) TryLock() bool {
 	if atomic.CompareAndSwapInt32(m.state(), mutexUnlocked, mutexLocked) {
 		if RaceEnabled {
 			RaceAcquire(unsafe.Pointer(&m.Mutex))
@@ -47,3 +48,43 @@ func (m *Mutex) TryLock() bool {
 	}
 	return false
 }
+
+// Mutex is a mutual exclusion lock. The zero value for a Mutex is an unlocked
+// mutex.
+//
+// A Mutex must not be copied after first use.
+//
+// A Mutex must be unlocked by the same goroutine that locked it. This
+// invariant is enforced with the 'checklocks' build tag.
+type Mutex struct {
+	m CrossGoroutineMutex
+}
+
+// Lock locks m. If the lock is already in use, the calling goroutine blocks
+// until the mutex is available.
+func (m *Mutex) Lock() {
+	noteLock(unsafe.Pointer(m))
+	m.m.Lock()
+}
+
+// Unlock unlocks m.
+//
+// Preconditions:
+// * m is locked.
+// * m was locked by this goroutine.
+func (m *Mutex) Unlock() {
+	noteUnlock(unsafe.Pointer(m))
+	m.m.Unlock()
+}
+
+// TryLock tries to acquire the mutex. It returns true if it succeeds and false
+// otherwise. TryLock does not block.
+func (m *Mutex) TryLock() bool {
+	// Note lock first to enforce proper locking even if unsuccessful.
+	noteLock(unsafe.Pointer(m))
+	locked := m.m.TryLock()
+	if !locked {
+		noteUnlock(unsafe.Pointer(m))
+	}
+	return locked
+}
diff --git a/pkg/sync/rwmutex_unsafe.go b/pkg/sync/rwmutex_unsafe.go
index b3b4dee78..fa023f5bb 100644
--- a/pkg/sync/rwmutex_unsafe.go
+++ b/pkg/sync/rwmutex_unsafe.go
@@ -32,7 +32,12 @@ func runtimeSemrelease(s *uint32, handoff bool, skipframes int)
 // RWMutex is identical to sync.RWMutex, but adds the DowngradeLock,
 // TryLock and TryRLock methods.
 type RWMutex struct {
-	w           Mutex  // held if there are pending writers
+	// w is held if there are pending writers
+	//
+	// We use CrossGoroutineMutex rather than Mutex because the lock
+	// annotation instrumentation in Mutex will trigger false positives in
+	// the race detector when called inside of RaceDisable.
+	w           CrossGoroutineMutex
 	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