event/Loop: add compile-time option to disable multithreading
Not for MPD, but for other applications which might want to copy its event loop, but do not need multi-threading.
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e9f6af61f9
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38dab040b3
@ -37,18 +37,27 @@ EventLoop::TimerCompare::operator()(const TimerEvent &a,
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return a.due < b.due;
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}
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EventLoop::EventLoop(ThreadId _thread)
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:SocketMonitor(*this),
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EventLoop::EventLoop(
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#ifdef HAVE_THREADED_EVENT_LOOP
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ThreadId _thread
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#endif
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)
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:
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#ifdef HAVE_THREADED_EVENT_LOOP
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SocketMonitor(*this),
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thread(_thread),
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/* if this instance is hosted by an EventThread (no ThreadId
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known yet) then we're not yet alive until the thread is
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started; for the main EventLoop instance, we assume it's
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already alive, because nobody but EventThread will call
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SetAlive() */
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alive(!_thread.IsNull()),
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quit(false),
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thread(_thread)
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#endif
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quit(false)
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{
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#ifdef HAVE_THREADED_EVENT_LOOP
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SocketMonitor::Open(SocketDescriptor(wake_fd.Get()));
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#endif
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}
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EventLoop::~EventLoop() noexcept
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@ -83,13 +92,17 @@ EventLoop::Break() noexcept
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if (quit.exchange(true))
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return;
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#ifdef HAVE_THREADED_EVENT_LOOP
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wake_fd.Write();
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#endif
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}
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bool
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EventLoop::Abandon(int _fd) noexcept
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{
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#ifdef HAVE_THREADED_EVENT_LOOP
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assert(!IsAlive() || IsInside());
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#endif
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return poll_group.Abandon(_fd);
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}
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@ -97,7 +110,9 @@ EventLoop::Abandon(int _fd) noexcept
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bool
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EventLoop::RemoveFD(int _fd) noexcept
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{
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#ifdef HAVE_THREADED_EVENT_LOOP
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assert(!IsAlive() || IsInside());
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#endif
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return poll_group.Remove(_fd);
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}
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@ -169,15 +184,19 @@ ExportTimeoutMS(Event::Duration timeout)
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void
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EventLoop::Run() noexcept
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{
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#ifdef HAVE_THREADED_EVENT_LOOP
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if (thread.IsNull())
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thread = ThreadId::GetCurrent();
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#endif
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assert(IsInside());
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assert(!quit);
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#ifdef HAVE_THREADED_EVENT_LOOP
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assert(alive);
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assert(busy);
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SocketMonitor::Schedule(SocketMonitor::READ);
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#endif
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AtScopeExit(this) {
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#ifdef HAVE_URING
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/* make sure that the Uring::Manager gets destructed
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@ -188,7 +207,9 @@ EventLoop::Run() noexcept
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uring_initialized = false;
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#endif
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#ifdef HAVE_THREADED_EVENT_LOOP
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SocketMonitor::Cancel();
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#endif
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};
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do {
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@ -212,6 +233,7 @@ EventLoop::Run() noexcept
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return;
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}
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#ifdef HAVE_THREADED_EVENT_LOOP
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/* try to handle DeferEvents without WakeFD
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overhead */
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{
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@ -225,6 +247,7 @@ EventLoop::Run() noexcept
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new timeout */
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continue;
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}
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#endif
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/* wait for new event */
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@ -240,10 +263,12 @@ EventLoop::Run() noexcept
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now = std::chrono::steady_clock::now();
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#ifdef HAVE_THREADED_EVENT_LOOP
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{
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const std::lock_guard<Mutex> lock(mutex);
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busy = true;
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}
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#endif
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/* invoke sockets */
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while (!ready_sockets.empty() && !quit) {
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@ -254,11 +279,15 @@ EventLoop::Run() noexcept
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}
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} while (!quit);
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#ifdef HAVE_THREADED_EVENT_LOOP
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#ifndef NDEBUG
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assert(thread.IsInside());
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#endif
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#endif
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}
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#ifdef HAVE_THREADED_EVENT_LOOP
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void
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EventLoop::AddDeferred(DeferEvent &d) noexcept
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{
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@ -316,3 +345,5 @@ EventLoop::OnSocketReady([[maybe_unused]] unsigned flags) noexcept
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return true;
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}
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#endif
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@ -22,11 +22,15 @@
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#include "Chrono.hxx"
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#include "PollGroup.hxx"
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#include "WakeFD.hxx"
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#include "SocketMonitor.hxx"
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#include "event/Features.h"
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#include "util/Compiler.h"
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#ifdef HAVE_THREADED_EVENT_LOOP
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#include "WakeFD.hxx"
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#include "thread/Id.hxx"
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#include "thread/Mutex.hxx"
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#include "util/Compiler.h"
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#endif
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#include <boost/intrusive/set.hpp>
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#include <boost/intrusive/list.hpp>
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@ -54,9 +58,14 @@ class DeferEvent;
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*
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* @see SocketMonitor, MultiSocketMonitor, TimerEvent, IdleEvent
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*/
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class EventLoop final : SocketMonitor
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class EventLoop final
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#ifdef HAVE_THREADED_EVENT_LOOP
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: SocketMonitor
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#endif
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{
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#ifdef HAVE_THREADED_EVENT_LOOP
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WakeFD wake_fd;
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#endif
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struct TimerCompare {
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constexpr bool operator()(const TimerEvent &a,
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@ -76,6 +85,7 @@ class EventLoop final : SocketMonitor
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boost::intrusive::constant_time_size<false>>;
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IdleList idle;
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#ifdef HAVE_THREADED_EVENT_LOOP
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Mutex mutex;
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using DeferredList =
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@ -83,6 +93,7 @@ class EventLoop final : SocketMonitor
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boost::intrusive::base_hook<boost::intrusive::list_base_hook<>>,
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boost::intrusive::constant_time_size<false>>;
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DeferredList deferred;
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#endif
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using ReadySocketList =
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boost::intrusive::list<SocketMonitor,
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@ -103,6 +114,12 @@ class EventLoop final : SocketMonitor
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Event::Clock::time_point now = Event::Clock::now();
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#ifdef HAVE_THREADED_EVENT_LOOP
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/**
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* A reference to the thread that is currently inside Run().
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*/
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ThreadId thread = ThreadId::Null();
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/**
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* Is this #EventLoop alive, i.e. can events be scheduled?
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* This is used by BlockingCall() to determine whether
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@ -110,6 +127,7 @@ class EventLoop final : SocketMonitor
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* there's no #EventThread yet/anymore).
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*/
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bool alive;
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#endif
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std::atomic_bool quit;
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@ -119,6 +137,7 @@ class EventLoop final : SocketMonitor
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*/
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bool again;
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#ifdef HAVE_THREADED_EVENT_LOOP
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/**
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* True when handling callbacks, false when waiting for I/O or
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* timeout.
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@ -126,6 +145,7 @@ class EventLoop final : SocketMonitor
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* Protected with #mutex.
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*/
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bool busy = true;
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#endif
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#ifdef HAVE_URING
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bool uring_initialized = false;
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@ -133,18 +153,17 @@ class EventLoop final : SocketMonitor
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PollGroup poll_group;
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/**
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* A reference to the thread that is currently inside Run().
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*/
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ThreadId thread = ThreadId::Null();
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public:
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/**
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* Throws on error.
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*/
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#ifdef HAVE_THREADED_EVENT_LOOP
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explicit EventLoop(ThreadId _thread);
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EventLoop():EventLoop(ThreadId::GetCurrent()) {}
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#else
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EventLoop();
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#endif
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~EventLoop() noexcept;
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@ -152,7 +171,9 @@ public:
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* A caching wrapper for Event::Clock::now().
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*/
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auto GetTime() const {
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#ifdef HAVE_THREADED_EVENT_LOOP
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assert(IsInside());
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#endif
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return now;
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}
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@ -170,13 +191,17 @@ public:
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void Break() noexcept;
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bool AddFD(int _fd, unsigned flags, SocketMonitor &m) noexcept {
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#ifdef HAVE_THREADED_EVENT_LOOP
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assert(!IsAlive() || IsInside());
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#endif
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return poll_group.Add(_fd, flags, &m);
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}
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bool ModifyFD(int _fd, unsigned flags, SocketMonitor &m) noexcept {
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#ifdef HAVE_THREADED_EVENT_LOOP
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assert(!IsAlive() || IsInside());
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#endif
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return poll_group.Modify(_fd, flags, &m);
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}
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@ -195,6 +220,7 @@ public:
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void AddTimer(TimerEvent &t, Event::Duration d) noexcept;
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#ifdef HAVE_THREADED_EVENT_LOOP
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/**
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* Schedule a call to DeferEvent::RunDeferred().
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*
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@ -209,6 +235,7 @@ public:
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* This method is thread-safe.
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*/
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void RemoveDeferred(DeferEvent &d) noexcept;
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#endif
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/**
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* The main function of this class. It will loop until
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@ -217,12 +244,14 @@ public:
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void Run() noexcept;
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private:
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#ifdef HAVE_THREADED_EVENT_LOOP
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/**
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* Invoke all pending DeferEvents.
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*
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* Caller must lock the mutex.
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*/
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void HandleDeferred() noexcept;
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#endif
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/**
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* Invoke all expired #TimerEvent instances and return the
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@ -231,9 +260,12 @@ private:
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*/
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Event::Duration HandleTimers() noexcept;
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#ifdef HAVE_THREADED_EVENT_LOOP
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bool OnSocketReady(unsigned flags) noexcept override;
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#endif
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public:
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#ifdef HAVE_THREADED_EVENT_LOOP
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void SetAlive(bool _alive) noexcept {
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alive = _alive;
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}
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@ -241,13 +273,18 @@ public:
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bool IsAlive() const noexcept {
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return alive;
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}
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#endif
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/**
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* Are we currently running inside this EventLoop's thread?
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*/
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gcc_pure
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bool IsInside() const noexcept {
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#ifdef HAVE_THREADED_EVENT_LOOP
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return thread.IsInside();
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#else
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return true;
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#endif
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}
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};
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@ -2,6 +2,7 @@ event_features = configuration_data()
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event_features.set('USE_EVENTFD', is_linux and get_option('eventfd'))
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event_features.set('USE_SIGNALFD', is_linux and get_option('signalfd'))
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event_features.set('USE_EPOLL', is_linux and get_option('epoll'))
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event_features.set('HAVE_THREADED_EVENT_LOOP', true)
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configure_file(output: 'Features.h', configuration: event_features)
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event_sources = []
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