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authorJohn Firebaugh <john.firebaugh@gmail.com>2017-05-22 16:05:58 -0700
committerJohn Firebaugh <john.firebaugh@gmail.com>2017-05-24 08:19:19 -0700
commit2c8343aa8233333dae0caf91f25bf1fe4689c88e (patch)
treec3b60896400a8b556f698553acccb5022cf02c4e /src/mbgl/actor
parent8b448786fed2251c345ff6ccbeb65afac8af8cf1 (diff)
downloadqtlocation-mapboxgl-2c8343aa8233333dae0caf91f25bf1fe4689c88e.tar.gz
[core] Block in Mailbox::close() until neither receive nor push are in progress
Otherwise, an ActorRef that's in the process of sending a message could attempt to access an invalid Scheduler reference: Thread 1 Thread 2 -------------------------------------------------- Scheduler::Scheduler Actor::Actor weakMailbox.lock() Actor::~Actor Scheduler::~Scheduler mailbox->push() scheduler.schedule() 💣
Diffstat (limited to 'src/mbgl/actor')
-rw-r--r--src/mbgl/actor/mailbox.cpp27
1 files changed, 18 insertions, 9 deletions
diff --git a/src/mbgl/actor/mailbox.cpp b/src/mbgl/actor/mailbox.cpp
index 5f60629833..947f6f9028 100644
--- a/src/mbgl/actor/mailbox.cpp
+++ b/src/mbgl/actor/mailbox.cpp
@@ -10,8 +10,23 @@ Mailbox::Mailbox(Scheduler& scheduler_)
: scheduler(scheduler_) {
}
+void Mailbox::close() {
+ // Block until neither receive() nor push() are in progress. Two mutexes are used because receive()
+ // must not block send(). Of the two, the receiving mutex must be acquired first, because that is
+ // the order that an actor will obtain them when it self-sends a message, and consistent lock
+ // acquisition order prevents deadlocks.
+ std::lock_guard<std::mutex> receivingLock(receivingMutex);
+ std::lock_guard<std::mutex> pushingLock(pushingMutex);
+
+ closed = true;
+}
+
void Mailbox::push(std::unique_ptr<Message> message) {
- assert(!closing);
+ std::lock_guard<std::mutex> pushingLock(pushingMutex);
+
+ if (closed) {
+ return;
+ }
std::lock_guard<std::mutex> queueLock(queueMutex);
bool wasEmpty = queue.empty();
@@ -21,16 +36,10 @@ void Mailbox::push(std::unique_ptr<Message> message) {
}
}
-void Mailbox::close() {
- // Block until the scheduler is guaranteed not to be executing receive().
- std::lock_guard<std::mutex> closingLock(closingMutex);
- closing = true;
-}
-
void Mailbox::receive() {
- std::lock_guard<std::mutex> closingLock(closingMutex);
+ std::lock_guard<std::mutex> receivingLock(receivingMutex);
- if (closing) {
+ if (closed) {
return;
}