102 lines
2.5 KiB
Go
102 lines
2.5 KiB
Go
// Copyright (C) 2014 The Syncthing Authors.
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//
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// This Source Code Form is subject to the terms of the Mozilla Public
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// License, v. 2.0. If a copy of the MPL was not distributed with this file,
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// You can obtain one at https://mozilla.org/MPL/2.0/.
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package model
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import (
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"fmt"
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"path/filepath"
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"sync"
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"time"
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"github.com/pkg/errors"
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"github.com/syncthing/syncthing/lib/fs"
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)
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type Holdable interface {
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Holders() string
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}
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func newDeadlockDetector(timeout time.Duration) *deadlockDetector {
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return &deadlockDetector{
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timeout: timeout,
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lockers: make(map[string]sync.Locker),
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}
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}
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type deadlockDetector struct {
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timeout time.Duration
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lockers map[string]sync.Locker
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}
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func (d *deadlockDetector) Watch(name string, mut sync.Locker) {
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d.lockers[name] = mut
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go func() {
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for {
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time.Sleep(d.timeout / 4)
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ok := make(chan bool, 2)
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go func() {
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mut.Lock()
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_ = 1 // empty critical section
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mut.Unlock()
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ok <- true
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}()
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go func() {
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time.Sleep(d.timeout)
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ok <- false
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}()
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if r := <-ok; !r {
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msg := fmt.Sprintf("deadlock detected at %s", name)
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for otherName, otherMut := range d.lockers {
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if otherHolder, ok := otherMut.(Holdable); ok {
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msg += "\n===" + otherName + "===\n" + otherHolder.Holders()
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}
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}
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panic(msg)
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}
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}
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}()
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}
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// inWritableDir calls fn(path), while making sure that the directory
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// containing `path` is writable for the duration of the call.
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func inWritableDir(fn func(string) error, targetFs fs.Filesystem, path string, ignorePerms bool) error {
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dir := filepath.Dir(path)
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info, err := targetFs.Stat(dir)
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if err != nil {
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return err
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}
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if !info.IsDir() {
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return errors.New("Not a directory: " + path)
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}
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if info.Mode()&0200 == 0 {
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// A non-writeable directory (for this user; we assume that's the
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// relevant part). Temporarily change the mode so we can delete the
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// file or directory inside it.
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if err := targetFs.Chmod(dir, 0755); err == nil {
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// Chmod succeeded, we should change the permissions back on the way
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// out. If we fail we log the error as we have irrevocably messed up
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// at this point. :( (The operation we were called to wrap has
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// succeeded or failed on its own so returning an error to the
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// caller is inappropriate.)
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defer func() {
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if err := targetFs.Chmod(dir, info.Mode()&fs.ModePerm); err != nil && !fs.IsNotExist(err) {
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logFn := l.Warnln
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if ignorePerms {
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logFn = l.Debugln
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}
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logFn("Failed to restore directory permissions after gaining write access:", err)
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}
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}()
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}
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}
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return fn(path)
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}
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