Update dependencies

vendor/gvisor.dev/gvisor/pkg/refs/refcounter.go

@@ -0,0 +1,196 @@
+// Copyright 2018 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package refs defines an interface for reference counted objects.
+package refs
+
+import (
+	"bytes"
+	"fmt"
+	"runtime"
+
+	"gvisor.dev/gvisor/pkg/atomicbitops"
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/sync"
+)
+
+// RefCounter is the interface to be implemented by objects that are reference
+// counted.
+type RefCounter interface {
+	// IncRef increments the reference counter on the object.
+	IncRef()
+
+	// DecRef decrements the object's reference count. Users of refs_template.Refs
+	// may specify a destructor to be called once the reference count reaches zero.
+	DecRef(ctx context.Context)
+}
+
+// TryRefCounter is like RefCounter but allow the ref increment to be tried.
+type TryRefCounter interface {
+	RefCounter
+
+	// TryIncRef attempts to increment the reference count, but may fail if all
+	// references have already been dropped, in which case it returns false. If
+	// true is returned, then a valid reference is now held on the object.
+	TryIncRef() bool
+}
+
+// LeakMode configures the leak checker.
+type LeakMode uint32
+
+const (
+	// NoLeakChecking indicates that no effort should be made to check for
+	// leaks.
+	NoLeakChecking LeakMode = iota
+
+	// LeaksLogWarning indicates that a warning should be logged when leaks
+	// are found.
+	LeaksLogWarning
+
+	// LeaksPanic indidcates that a panic should be issued when leaks are found.
+	LeaksPanic
+)
+
+// Set implements flag.Value.
+func (l *LeakMode) Set(v string) error {
+	switch v {
+	case "disabled":
+		*l = NoLeakChecking
+	case "log-names":
+		*l = LeaksLogWarning
+	case "panic":
+		*l = LeaksPanic
+	default:
+		return fmt.Errorf("invalid ref leak mode %q", v)
+	}
+	return nil
+}
+
+// Get implements flag.Value.
+func (l *LeakMode) Get() any {
+	return *l
+}
+
+// String implements flag.Value.
+func (l LeakMode) String() string {
+	switch l {
+	case NoLeakChecking:
+		return "disabled"
+	case LeaksLogWarning:
+		return "log-names"
+	case LeaksPanic:
+		return "panic"
+	default:
+		panic(fmt.Sprintf("invalid ref leak mode %d", l))
+	}
+}
+
+// leakMode stores the current mode for the reference leak checker.
+//
+// Values must be one of the LeakMode values.
+//
+// leakMode must be accessed atomically.
+var leakMode atomicbitops.Uint32
+
+// SetLeakMode configures the reference leak checker.
+func SetLeakMode(mode LeakMode) {
+	leakMode.Store(uint32(mode))
+}
+
+// GetLeakMode returns the current leak mode.
+func GetLeakMode() LeakMode {
+	return LeakMode(leakMode.Load())
+}
+
+const maxStackFrames = 40
+
+type fileLine struct {
+	file string
+	line int
+}
+
+// A stackKey is a representation of a stack frame for use as a map key.
+//
+// The fileLine type is used as PC values seem to vary across collections, even
+// for the same call stack.
+type stackKey [maxStackFrames]fileLine
+
+var stackCache = struct {
+	sync.Mutex
+	entries map[stackKey][]uintptr
+}{entries: map[stackKey][]uintptr{}}
+
+func makeStackKey(pcs []uintptr) stackKey {
+	frames := runtime.CallersFrames(pcs)
+	var key stackKey
+	keySlice := key[:0]
+	for {
+		frame, more := frames.Next()
+		keySlice = append(keySlice, fileLine{frame.File, frame.Line})
+
+		if !more || len(keySlice) == len(key) {
+			break
+		}
+	}
+	return key
+}
+
+// RecordStack constructs and returns the PCs on the current stack.
+func RecordStack() []uintptr {
+	pcs := make([]uintptr, maxStackFrames)
+	n := runtime.Callers(1, pcs)
+	if n == 0 {
+		// No pcs available. Stop now.
+		//
+		// This can happen if the first argument to runtime.Callers
+		// is large.
+		return nil
+	}
+	pcs = pcs[:n]
+	key := makeStackKey(pcs)
+	stackCache.Lock()
+	v, ok := stackCache.entries[key]
+	if !ok {
+		// Reallocate to prevent pcs from escaping.
+		v = append([]uintptr(nil), pcs...)
+		stackCache.entries[key] = v
+	}
+	stackCache.Unlock()
+	return v
+}
+
+// FormatStack converts the given stack into a readable format.
+func FormatStack(pcs []uintptr) string {
+	frames := runtime.CallersFrames(pcs)
+	var trace bytes.Buffer
+	for {
+		frame, more := frames.Next()
+		fmt.Fprintf(&trace, "%s:%d: %s\n", frame.File, frame.Line, frame.Function)
+
+		if !more {
+			break
+		}
+	}
+	return trace.String()
+}
+
+// OnExit is called on sandbox exit. It runs GC to enqueue refcount finalizers,
+// which check for reference leaks. There is no way to guarantee that every
+// finalizer will run before exiting, but this at least ensures that they will
+// be discovered/enqueued by GC.
+func OnExit() {
+	if LeakMode(leakMode.Load()) != NoLeakChecking {
+		runtime.GC()
+	}
+}