1 files changed, 108 insertions, 0 deletions
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()
+}