platform_system_core/init/action_manager.h
Tom Cherry 802864c782 init: handle property messages asynchronously #2
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.

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

A previous version of this change was reverted and added locks around
all service operations and allowed the property thread to spawn
services directly.  This was complex due to the fact that this code
was not designed to be multi-threaded.  It was reverted due to
apparent issues during reboot.  This change keeps a queue of processes
pending control messages, which it will then handle in the future.  It
is less flexible but safer.

Bug: 146877356
Bug: 148236233
Bug: 150863651
Bug: 151251827
Test: multiple reboot tests, safely restarting hwservicemanager
Change-Id: Ice773436e85d3bf636bb0a892f3f6002bdf996b6
2020-03-12 17:15:07 -07:00

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/*
* Copyright (C) 2018 The Android Open Source Project
*
* 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.
*/
#pragma once
#include <mutex>
#include <string>
#include <vector>
#include <android-base/thread_annotations.h>
#include "action.h"
#include "builtins.h"
namespace android {
namespace init {
class ActionManager {
public:
static ActionManager& GetInstance();
// Exposed for testing
ActionManager();
size_t CheckAllCommands();
void AddAction(std::unique_ptr<Action> action);
void QueueEventTrigger(const std::string& trigger);
void QueuePropertyChange(const std::string& name, const std::string& value);
void QueueAllPropertyActions();
void QueueBuiltinAction(BuiltinFunction func, const std::string& name);
void ExecuteOneCommand();
bool HasMoreCommands() const;
void DumpState() const;
void ClearQueue();
private:
ActionManager(ActionManager const&) = delete;
void operator=(ActionManager const&) = delete;
std::vector<std::unique_ptr<Action>> actions_;
std::queue<std::variant<EventTrigger, PropertyChange, BuiltinAction>> event_queue_
GUARDED_BY(event_queue_lock_);
mutable std::mutex event_queue_lock_;
std::queue<const Action*> current_executing_actions_;
std::size_t current_command_;
};
} // namespace init
} // namespace android