init: handle property service callbacks asynchronously
A previous change moved property_service into its own thread, since
there was otherwise a deadlock whenever a process called by init would
try to set a property. This new thread, however, would send a message
via a blocking socket to init for each property that it received,
since init may need to take action depending on which property it is.
Unfortunately, this means that the deadlock is still possible, the
only difference is the socket's buffer must be filled before init deadlocks.
There are possible partial solutions here: the socket's buffer may be
increased or property_service may only send messages for the
properties that init will take action on, however all of these
solutions still lead to eventual deadlock. The only complete solution
is to handle these messages asynchronously.
This change, therefore, adds the following:
1) A lock for instructing init to reboot
2) A lock for waiting on properties
3) A lock for queueing new properties
4) A lock for any actions with ServiceList or any Services, enforced
through thread annotations, particularly since this code was not
designed with the intention of being multi-threaded.
Bug: 146877356
Bug: 148236233
Test: boot
Test: kill hwservicemanager without deadlock
Change-Id: I84108e54217866205a48c45e8b59355012c32ea8
diff --git a/init/action_manager.cpp b/init/action_manager.cpp
index ebca762..b45f5cd 100644
--- a/init/action_manager.cpp
+++ b/init/action_manager.cpp
@@ -41,10 +41,12 @@
}
void ActionManager::QueueEventTrigger(const std::string& trigger) {
+ auto lock = std::lock_guard{event_queue_lock_};
event_queue_.emplace(trigger);
}
void ActionManager::QueuePropertyChange(const std::string& name, const std::string& value) {
+ auto lock = std::lock_guard{event_queue_lock_};
event_queue_.emplace(std::make_pair(name, value));
}
@@ -53,6 +55,7 @@
}
void ActionManager::QueueBuiltinAction(BuiltinFunction func, const std::string& name) {
+ auto lock = std::lock_guard{event_queue_lock_};
auto action = std::make_unique<Action>(true, nullptr, "<Builtin Action>", 0, name,
std::map<std::string, std::string>{});
action->AddCommand(std::move(func), {name}, 0);
@@ -62,15 +65,18 @@
}
void ActionManager::ExecuteOneCommand() {
- // Loop through the event queue until we have an action to execute
- while (current_executing_actions_.empty() && !event_queue_.empty()) {
- for (const auto& action : actions_) {
- if (std::visit([&action](const auto& event) { return action->CheckEvent(event); },
- event_queue_.front())) {
- current_executing_actions_.emplace(action.get());
+ {
+ auto lock = std::lock_guard{event_queue_lock_};
+ // Loop through the event queue until we have an action to execute
+ while (current_executing_actions_.empty() && !event_queue_.empty()) {
+ for (const auto& action : actions_) {
+ if (std::visit([&action](const auto& event) { return action->CheckEvent(event); },
+ event_queue_.front())) {
+ current_executing_actions_.emplace(action.get());
+ }
}
+ event_queue_.pop();
}
- event_queue_.pop();
}
if (current_executing_actions_.empty()) {
@@ -103,6 +109,7 @@
}
bool ActionManager::HasMoreCommands() const {
+ auto lock = std::lock_guard{event_queue_lock_};
return !current_executing_actions_.empty() || !event_queue_.empty();
}
@@ -113,6 +120,7 @@
}
void ActionManager::ClearQueue() {
+ auto lock = std::lock_guard{event_queue_lock_};
// We are shutting down so don't claim the oneshot builtin actions back
current_executing_actions_ = {};
event_queue_ = {};