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// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef CONTENT_CHILD_CHILD_PROCESS_H_
#define CONTENT_CHILD_CHILD_PROCESS_H_
#include <memory>
#include <vector>
#include "base/auto_reset.h"
#include "base/synchronization/waitable_event.h"
#include "base/task/single_thread_task_runner.h"
#include "base/task/thread_pool/thread_pool_instance.h"
#include "base/threading/platform_thread.h"
#include "base/threading/thread.h"
#include "content/common/content_export.h"
namespace content {
class ChildThreadImpl;
// Base class for child processes of the browser process (i.e. renderer and
// plugin host). This is a singleton object for each child process.
//
// The constructor will call ThreadPoolInstance::Start() unless a ThreadPool is
// already running, which can happen when the ChildProcess object is
// instantiated in the browser process or in tests.
//
// During process shutdown the following sequence of actions happens in
// order.
//
// 1. ChildProcess::~ChildProcess() is called.
// 2. Shutdown event is fired. Background threads should stop.
// 3. ChildThreadImpl::Shutdown() is called. ChildThread is also deleted.
// 4. IO thread is stopped.
// 5. ThreadPoolInstance::Shutdown() is called if the constructor called
// ThreadPoolInstance::Start().
// 6. Main message loop exits.
// 7. Child process is now fully stopped.
//
// Note: IO thread outlives the ChildThreadImpl object.
class CONTENT_EXPORT ChildProcess {
public:
// Child processes should have an object that derives from this class.
// Normally you would immediately call set_main_thread after construction.
// |io_thread_type| is the type of the IO thread.
// |thread_pool_init_params| is used to start the ThreadPool. Default params
// are used if |thread_pool_init_params| is nullptr. It is ignored if a
// ThreadPool is already running.
explicit ChildProcess(
base::ThreadType io_thread_type = base::ThreadType::kDefault,
std::unique_ptr<base::ThreadPoolInstance::InitParams>
thread_pool_init_params = nullptr);
// This constructor can be used to create a ChildProcess within the browser
// process which shares the IO thread. `io_thread_runner` passes an existing
// task runner to use for the child IO thread instead of creating a new
// thread.
explicit ChildProcess(
scoped_refptr<base::SingleThreadTaskRunner> io_thread_runner);
ChildProcess(const ChildProcess&) = delete;
ChildProcess& operator=(const ChildProcess&) = delete;
virtual ~ChildProcess();
// May be NULL if the main thread hasn't been set explicitly.
ChildThreadImpl* main_thread();
// Sets the object associated with the main thread of this process.
// Takes ownership of the pointer.
void set_main_thread(ChildThreadImpl* thread);
// We need to stop the IO thread here instead of just flushing it, so that it
// can no longer post tasks back to the main thread.
void StopIOThreadForTesting() { io_thread_->Stop(); }
base::SingleThreadTaskRunner* io_task_runner() {
return io_thread_runner_.get();
}
#if BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS)
// Changes the thread type of the child process IO thread.
void SetIOThreadType(base::ThreadType thread_type);
#endif
// A global event object that is signalled when the main thread's message
// loop exits. This gives background threads a way to observe the main
// thread shutting down. This can be useful when a background thread is
// waiting for some information from the browser process. If the browser
// process goes away prematurely, the background thread can at least notice
// the child processes's main thread exiting to determine that it should give
// up waiting.
// For example, see the renderer code used to implement GetCookies().
base::WaitableEvent* GetShutDownEvent();
// These are used for ref-counting the child process. The process shuts
// itself down when the ref count reaches 0.
//
// This is not used for renderer processes. The browser process is the only
// one responsible for shutting them down. See mojo::KeepAliveHandle and more
// generally the RenderProcessHostImpl class if you want to keep the renderer
// process alive longer.
virtual void AddRefProcess();
virtual void ReleaseProcess();
// Getter for the one ChildProcess object for this process. Can only be called
// on the main thread.
static ChildProcess* current();
private:
const base::AutoReset<ChildProcess*> resetter_;
int ref_count_ = 0;
// An event that will be signalled when we shutdown.
base::WaitableEvent shutdown_event_{
base::WaitableEvent::ResetPolicy::MANUAL,
base::WaitableEvent::InitialState::NOT_SIGNALED};
// The thread that handles IO events. May be null if `io_thread_runner` was
// passed to the constructor.
std::unique_ptr<base::Thread> io_thread_;
// The task runner to use for IO thread tasks.
scoped_refptr<base::SingleThreadTaskRunner> io_thread_runner_;
// NOTE: make sure that main_thread_ is listed after shutdown_event_, since
// it depends on it (indirectly through IPC::SyncChannel). Same for
// io_thread_.
std::unique_ptr<ChildThreadImpl> main_thread_;
// Whether this ChildProcess initialized ThreadPoolInstance.
bool initialized_thread_pool_ = false;
};
} // namespace content
#endif // CONTENT_CHILD_CHILD_PROCESS_H_