修复webserver死锁

web_server/app/Gallery_Plot_Session.cpp

@@ -10,15 +10,21 @@
 #include <algorithm>
 #include <atomic>
 #include <chrono>
+#include <condition_variable>
 #include <cmath>
+#include <cstddef>
 #include <cstdint>
+#include <deque>
 #include <exception>
+#include <functional>
 #include <mutex>
 #include <optional>
 #include <string>
 #include <string_view>
+#include <thread>
 #include <type_traits>
 #include <utility>
+#include <vector>
 namespace renderive::web {
 namespace {
 Gallery_View_Input gallery_input(const Event& event) {
@@ -133,6 +139,56 @@ trantor::EventLoop* automatic_render_loop() {
     return thread.getLoop();
 }
 }
+namespace detail {
+class Automatic_Render_Executor final {
+public:
+    Automatic_Render_Executor() {
+        const std::size_t worker_count = renderive::scheduling::scheduler_concurrency();
+        workers_.reserve(worker_count);
+        for (std::size_t index = 0; index < worker_count; ++index) {
+            workers_.emplace_back([this](std::stop_token stop) {
+                run(stop);
+            });
+        }
+    }
+    ~Automatic_Render_Executor() {
+        for (auto& worker : workers_)
+            worker.request_stop();
+        condition_.notify_all();
+    }
+    void enqueue(std::function<void()> task) {
+        {
+            std::lock_guard lock(mutex_);
+            tasks_.push_back(std::move(task));
+        }
+        condition_.notify_one();
+    }
+private:
+    void run(std::stop_token stop) {
+        for (;;) {
+            std::function<void()> task;
+            {
+                std::unique_lock lock(mutex_);
+                if (!condition_.wait(lock, stop, [this] {
+                    return !tasks_.empty();
+                }))
+                    return;
+                task = std::move(tasks_.front());
+                tasks_.pop_front();
+            }
+            task();
+        }
+    }
+    std::mutex mutex_;
+    std::condition_variable_any condition_;
+    std::deque<std::function<void()>> tasks_;
+    std::vector<std::jthread> workers_;
+};
+Automatic_Render_Executor& automatic_render_executor() {
+    static Automatic_Render_Executor executor;
+    return executor;
+}
+}
 struct Gallery_Plot_Session::Impl : std::enable_shared_from_this<Gallery_Plot_Session::Impl> {
     using Clock = std::chrono::steady_clock;
     explicit Impl(bool enable_automatic_low_latency)
@@ -247,7 +303,7 @@ struct Gallery_Plot_Session::Impl : std::enable_shared_from_this<Gallery_Plot_Se
         }
         auto self = shared_from_this();
         try {
-            renderive::scheduling::enqueue_task([self = std::move(self), generation] {
+            detail::automatic_render_executor().enqueue([self = std::move(self), generation] {
                 self->run_automatic_render(generation);
             });
         } catch (...) {