~sircmpwn/aerc

9ef2a57b51601cc0e18824bbfe8026891da1a38d — Simon Ser 2 years ago 2159eb8
worker/types: fix Worker.Callbacks race condition

Worker.Process* functions were called in different goroutines than
Worker.Post*. Protect the map with a mutex. Also make the map unexported to
prevent external unprotected accesses.

Worker.Process* functions used to delete items from the map. However they
didn't delete the element they retrieved: callbacks[msg.InResponseTo()] was
read while callbacks[msg] was deleted. I'm not sure I understand why. I tried
to delete the element that was accessed - but this broke everything (UI froze
at "Connecting..."). I don't believe any elements were actually removed from
the map, so the new code just doesn't remove anything.
2 files changed, 42 insertions(+), 21 deletions(-)

M worker/types/worker.go
M worker/worker.go
M worker/types/worker.go => worker/types/worker.go +41 -15
@@ 2,6 2,7 @@ package types

import (
	"log"
	"sync"
)

type Backend interface {


@@ 9,11 10,42 @@ type Backend interface {
}

type Worker struct {
	Actions   chan WorkerMessage
	Backend   Backend
	Callbacks map[WorkerMessage]func(msg WorkerMessage)
	Messages  chan WorkerMessage
	Logger    *log.Logger
	Backend  Backend
	Actions  chan WorkerMessage
	Messages chan WorkerMessage
	Logger   *log.Logger

	callbacks map[WorkerMessage]func(msg WorkerMessage) // protected by mutex
	mutex     sync.Mutex
}

func NewWorker(logger *log.Logger) *Worker {
	return &Worker{
		Actions:   make(chan WorkerMessage, 50),
		Messages:  make(chan WorkerMessage, 50),
		Logger:    logger,
		callbacks: make(map[WorkerMessage]func(msg WorkerMessage)),
	}
}

func (worker *Worker) setCallback(msg WorkerMessage,
	cb func(msg WorkerMessage)) {

	if cb != nil {
		worker.mutex.Lock()
		worker.callbacks[msg] = cb
		worker.mutex.Unlock()
	}
}

func (worker *Worker) getCallback(msg WorkerMessage) (func(msg WorkerMessage),
	bool) {

	worker.mutex.Lock()
	cb, ok := worker.callbacks[msg]
	worker.mutex.Unlock()

	return cb, ok
}

func (worker *Worker) PostAction(msg WorkerMessage,


@@ 26,9 58,7 @@ func (worker *Worker) PostAction(msg WorkerMessage,
	}
	worker.Actions <- msg

	if cb != nil {
		worker.Callbacks[msg] = cb
	}
	worker.setCallback(msg, cb)
}

func (worker *Worker) PostMessage(msg WorkerMessage,


@@ 41,9 71,7 @@ func (worker *Worker) PostMessage(msg WorkerMessage,
	}
	worker.Messages <- msg

	if cb != nil {
		worker.Callbacks[msg] = cb
	}
	worker.setCallback(msg, cb)
}

func (worker *Worker) ProcessMessage(msg WorkerMessage) WorkerMessage {


@@ 52,9 80,8 @@ func (worker *Worker) ProcessMessage(msg WorkerMessage) WorkerMessage {
	} else {
		worker.Logger.Printf("(ui)<= %T\n", msg)
	}
	if cb, ok := worker.Callbacks[msg.InResponseTo()]; ok {
	if cb, ok := worker.getCallback(msg.InResponseTo()); ok {
		cb(msg)
		delete(worker.Callbacks, msg)
	}
	return msg
}


@@ 65,9 92,8 @@ func (worker *Worker) ProcessAction(msg WorkerMessage) WorkerMessage {
	} else {
		worker.Logger.Printf("<-(ui) %T\n", msg)
	}
	if cb, ok := worker.Callbacks[msg.InResponseTo()]; ok {
	if cb, ok := worker.getCallback(msg.InResponseTo()); ok {
		cb(msg)
		delete(worker.Callbacks, msg)
	}
	return msg
}

M worker/worker.go => worker/worker.go +1 -6
@@ 15,12 15,7 @@ func NewWorker(source string, logger *log.Logger) (*types.Worker, error) {
	if err != nil {
		return nil, err
	}
	worker := &types.Worker{
		Actions:   make(chan types.WorkerMessage, 50),
		Callbacks: make(map[types.WorkerMessage]func(msg types.WorkerMessage)),
		Messages:  make(chan types.WorkerMessage, 50),
		Logger:    logger,
	}
	worker := types.NewWorker(logger)
	switch u.Scheme {
	case "imap":
		fallthrough