From 5b60b689c14bcb84ee034bdf400a75c0b63ef999 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Niklas=20S=C3=B6derlund?= Date: Sat, 30 Jan 2021 00:52:54 +0100 Subject: cam: event_loop: Execute events in the libevent loop MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Cam uses libevent to deal with threads and idle loop while still implementing its own event queue. This creates issues when the event loop is terminated as it might get stuck in the idle loop if exit() is called while the thread is busy with dispatchCalls(). Solve this by removing the custom event execution and instead injecting the calls as events to the base event loop. Reported-by: Sebastian Fricke Signed-off-by: Niklas Söderlund Reviewed-by: Jacopo Mondi Reviewed-by: Laurent Pinchart --- src/cam/event_loop.cpp | 40 ++++++++++++++++++---------------------- src/cam/event_loop.h | 9 +++++---- 2 files changed, 23 insertions(+), 26 deletions(-) (limited to 'src') diff --git a/src/cam/event_loop.cpp b/src/cam/event_loop.cpp index 3a2b665a..6a4c47f2 100644 --- a/src/cam/event_loop.cpp +++ b/src/cam/event_loop.cpp @@ -38,25 +38,13 @@ EventLoop *EventLoop::instance() int EventLoop::exec() { exitCode_ = -1; - exit_.store(false, std::memory_order_release); - - while (!exit_.load(std::memory_order_acquire)) { - dispatchCalls(); - event_base_loop(base_, EVLOOP_NO_EXIT_ON_EMPTY); - } - + event_base_loop(base_, EVLOOP_NO_EXIT_ON_EMPTY); return exitCode_; } void EventLoop::exit(int code) { exitCode_ = code; - exit_.store(true, std::memory_order_release); - interrupt(); -} - -void EventLoop::interrupt() -{ event_base_loopbreak(base_); } @@ -67,20 +55,28 @@ void EventLoop::callLater(const std::function &func) calls_.push_back(func); } - interrupt(); + event_base_once(base_, -1, EV_TIMEOUT, dispatchCallback, this, nullptr); } -void EventLoop::dispatchCalls() +void EventLoop::dispatchCallback([[maybe_unused]] evutil_socket_t fd, + [[maybe_unused]] short flags, void *param) { - std::unique_lock locker(lock_); + EventLoop *loop = static_cast(param); + loop->dispatchCall(); +} - for (auto iter = calls_.begin(); iter != calls_.end(); ) { - std::function call = std::move(*iter); +void EventLoop::dispatchCall() +{ + std::function call; - iter = calls_.erase(iter); + { + std::unique_lock locker(lock_); + if (calls_.empty()) + return; - locker.unlock(); - call(); - locker.lock(); + call = calls_.front(); + calls_.pop_front(); } + + call(); } diff --git a/src/cam/event_loop.h b/src/cam/event_loop.h index d0d5b5a5..ba3ba3a4 100644 --- a/src/cam/event_loop.h +++ b/src/cam/event_loop.h @@ -7,11 +7,12 @@ #ifndef __CAM_EVENT_LOOP_H__ #define __CAM_EVENT_LOOP_H__ -#include #include #include #include +#include + struct event_base; class EventLoop @@ -31,14 +32,14 @@ private: static EventLoop *instance_; struct event_base *base_; - std::atomic exit_; int exitCode_; std::list> calls_; std::mutex lock_; - void interrupt(); - void dispatchCalls(); + static void dispatchCallback(evutil_socket_t fd, short flags, + void *param); + void dispatchCall(); }; #endif /* __CAM_EVENT_LOOP_H__ */ -- cgit v1.2.1