Fix scheduler race conditions and add comprehensive test suite (#9348)

tests/integration/fixtures/external_components/scheduler_simultaneous_callbacks_component/__init__.py

@@ -0,0 +1,23 @@
+import esphome.codegen as cg
+import esphome.config_validation as cv
+from esphome.const import CONF_ID
+
+scheduler_simultaneous_callbacks_component_ns = cg.esphome_ns.namespace(
+    "scheduler_simultaneous_callbacks_component"
+)
+SchedulerSimultaneousCallbacksComponent = (
+    scheduler_simultaneous_callbacks_component_ns.class_(
+        "SchedulerSimultaneousCallbacksComponent", cg.Component
+    )
+)
+
+CONFIG_SCHEMA = cv.Schema(
+    {
+        cv.GenerateID(): cv.declare_id(SchedulerSimultaneousCallbacksComponent),
+    }
+).extend(cv.COMPONENT_SCHEMA)
+
+
+async def to_code(config):
+    var = cg.new_Pvariable(config[CONF_ID])
+    await cg.register_component(var, config)

tests/integration/fixtures/external_components/scheduler_simultaneous_callbacks_component/simultaneous_callbacks_component.cpp

@@ -0,0 +1,109 @@
+#include "simultaneous_callbacks_component.h"
+#include "esphome/core/log.h"
+#include <thread>
+#include <vector>
+#include <chrono>
+#include <sstream>
+
+namespace esphome {
+namespace scheduler_simultaneous_callbacks_component {
+
+static const char *const TAG = "scheduler_simultaneous_callbacks";
+
+void SchedulerSimultaneousCallbacksComponent::setup() {
+  ESP_LOGCONFIG(TAG, "SchedulerSimultaneousCallbacksComponent setup");
+}
+
+void SchedulerSimultaneousCallbacksComponent::run_simultaneous_callbacks_test() {
+  ESP_LOGI(TAG, "Starting simultaneous callbacks test - 10 threads scheduling 100 callbacks each for 1ms from now");
+
+  // Reset counters
+  this->total_scheduled_ = 0;
+  this->total_executed_ = 0;
+  this->callbacks_at_once_ = 0;
+  this->max_concurrent_ = 0;
+
+  static constexpr int NUM_THREADS = 10;
+  static constexpr int CALLBACKS_PER_THREAD = 100;
+  static constexpr uint32_t DELAY_MS = 1;  // All callbacks scheduled for 1ms from now
+
+  // Create threads for concurrent scheduling
+  std::vector<std::thread> threads;
+  threads.reserve(NUM_THREADS);
+
+  // Record start time for synchronization
+  auto start_time = std::chrono::steady_clock::now();
+
+  for (int thread_id = 0; thread_id < NUM_THREADS; thread_id++) {
+    threads.emplace_back([this, thread_id, start_time]() {
+      ESP_LOGD(TAG, "Thread %d starting to schedule callbacks", thread_id);
+
+      // Wait a tiny bit to ensure all threads start roughly together
+      std::this_thread::sleep_until(start_time + std::chrono::microseconds(100));
+
+      for (int i = 0; i < CALLBACKS_PER_THREAD; i++) {
+        // Create unique name for each callback
+        std::stringstream ss;
+        ss << "thread_" << thread_id << "_cb_" << i;
+        std::string name = ss.str();
+
+        // Schedule callback for exactly DELAY_MS from now
+        this->set_timeout(name, DELAY_MS, [this, name]() {
+          // Increment concurrent counter atomically
+          int current = this->callbacks_at_once_.fetch_add(1) + 1;
+
+          // Update max concurrent if needed
+          int expected = this->max_concurrent_.load();
+          while (current > expected && !this->max_concurrent_.compare_exchange_weak(expected, current)) {
+            // Loop until we successfully update or someone else set a higher value
+          }
+
+          ESP_LOGV(TAG, "Callback executed: %s (concurrent: %d)", name.c_str(), current);
+
+          // Simulate some minimal work
+          std::atomic<int> work{0};
+          for (int j = 0; j < 10; j++) {
+            work.fetch_add(j);
+          }
+
+          // Increment executed counter
+          this->total_executed_.fetch_add(1);
+
+          // Decrement concurrent counter
+          this->callbacks_at_once_.fetch_sub(1);
+        });
+
+        this->total_scheduled_.fetch_add(1);
+        ESP_LOGV(TAG, "Scheduled callback %s", name.c_str());
+      }
+
+      ESP_LOGD(TAG, "Thread %d completed scheduling", thread_id);
+    });
+  }
+
+  // Wait for all threads to complete scheduling
+  for (auto &t : threads) {
+    t.join();
+  }
+
+  ESP_LOGI(TAG, "All threads completed scheduling. Total scheduled: %d", this->total_scheduled_.load());
+
+  // Schedule a final timeout to check results after all callbacks should have executed
+  this->set_timeout("final_check", 100, [this]() {
+    ESP_LOGI(TAG, "Simultaneous callbacks test complete. Final executed count: %d", this->total_executed_.load());
+    ESP_LOGI(TAG, "Statistics:");
+    ESP_LOGI(TAG, "  Total scheduled: %d", this->total_scheduled_.load());
+    ESP_LOGI(TAG, "  Total executed: %d", this->total_executed_.load());
+    ESP_LOGI(TAG, "  Max concurrent callbacks: %d", this->max_concurrent_.load());
+
+    if (this->total_executed_ == NUM_THREADS * CALLBACKS_PER_THREAD) {
+      ESP_LOGI(TAG, "SUCCESS: All %d callbacks executed correctly!", this->total_executed_.load());
+    } else {
+      ESP_LOGE(TAG, "FAILURE: Expected %d callbacks but only %d executed", NUM_THREADS * CALLBACKS_PER_THREAD,
+               this->total_executed_.load());
+    }
+  });
+}
+
+}  // namespace scheduler_simultaneous_callbacks_component
+}  // namespace esphome

tests/integration/fixtures/external_components/scheduler_simultaneous_callbacks_component/simultaneous_callbacks_component.h

@@ -0,0 +1,24 @@
+#pragma once
+
+#include "esphome/core/component.h"
+#include <atomic>
+
+namespace esphome {
+namespace scheduler_simultaneous_callbacks_component {
+
+class SchedulerSimultaneousCallbacksComponent : public Component {
+ public:
+  void setup() override;
+  float get_setup_priority() const override { return setup_priority::LATE; }
+
+  void run_simultaneous_callbacks_test();
+
+ private:
+  std::atomic<int> total_scheduled_{0};
+  std::atomic<int> total_executed_{0};
+  std::atomic<int> callbacks_at_once_{0};
+  std::atomic<int> max_concurrent_{0};
+};
+
+}  // namespace scheduler_simultaneous_callbacks_component
+}  // namespace esphome