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[wifi] Replace FreeRTOS queue with LockFreeQueue on ESP-IDF

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Replace the FreeRTOS xQueue (xQueueCreate/xQueueSend/xQueueReceive)
used for WiFi event passing with a lock-free SPSC queue. This avoids
the FreeRTOS kernel spinlock overhead on every loop iteration when
checking for events — the common case is an empty queue.

The LockFreeQueue::pop() fast path is just two atomic loads and a
comparison, vs xQueueReceive which takes a spinlock, checks the
queue, and releases the spinlock even when empty.

WiFi events are rare (connect/disconnect/scan) so heap allocation
for event data is retained — no EventPool needed unlike the BLE
path which processes hundreds of events per second.

This matches the lock-free pattern already used by esp32_ble.
This commit is contained in:
J. Nick Koston
2026-03-29 19:22:09 -10:00
parent 18168ad7fd
commit 09fc3bb9f5
1 changed files with 10 additions and 20 deletions
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esphome/components/wifi/wifi_component_esp_idf.cpp
+10 -20
View File
@@ -39,6 +39,7 @@
#include "esphome/core/application.h"
#include "esphome/core/hal.h"
#include "esphome/core/helpers.h"
#include "esphome/core/lock_free_queue.h"
#include "esphome/core/log.h"
#include "esphome/core/util.h"
@@ -47,8 +48,11 @@ namespace esphome::wifi {
static const char *const TAG = "wifi_esp32";
static EventGroupHandle_t s_wifi_event_group; // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
static QueueHandle_t s_event_queue; // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
static esp_netif_t *s_sta_netif = nullptr; // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
// Lock-free SPSC queue replaces FreeRTOS xQueue to avoid kernel spinlock
// overhead on every loop iteration. WiFi events are rare so 64 slots is plenty.
// 65 slots = 64 usable (ring buffer reserves one slot to distinguish full from empty)
static LockFreeQueue<IDFWiFiEvent, 65> s_event_queue; // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
static esp_netif_t *s_sta_netif = nullptr; // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
#ifdef USE_WIFI_AP
static esp_netif_t *s_ap_netif = nullptr; // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
#endif // USE_WIFI_AP
@@ -132,11 +136,10 @@ void event_handler(void *arg, esp_event_base_t event_base, int32_t event_id, voi
return;
}
// copy to heap to keep queue object small
// copy to heap — WiFi events are rare so heap alloc is fine
auto *to_send = new IDFWiFiEvent; // NOLINT(cppcoreguidelines-owning-memory)
memcpy(to_send, &event, sizeof(IDFWiFiEvent));
// don't block, we may miss events but the core can handle that
if (xQueueSend(s_event_queue, &to_send, 0L) != pdPASS) {
if (!s_event_queue.push(to_send)) {
delete to_send; // NOLINT(cppcoreguidelines-owning-memory)
}
}
@@ -157,12 +160,6 @@ void WiFiComponent::wifi_pre_setup_() {
ESP_LOGE(TAG, "xEventGroupCreate failed");
return;
}
// NOLINTNEXTLINE(bugprone-sizeof-expression)
s_event_queue = xQueueCreate(64, sizeof(IDFWiFiEvent *));
if (s_event_queue == nullptr) {
ESP_LOGE(TAG, "xQueueCreate failed");
return;
}
err = esp_event_loop_create_default();
if (err != ERR_OK) {
ESP_LOGE(TAG, "esp_event_loop_create_default failed: %s", esp_err_to_name(err));
@@ -724,16 +721,9 @@ const char *get_disconnect_reason_str(uint8_t reason) {
}
void WiFiComponent::wifi_loop_() {
while (true) {
IDFWiFiEvent *data;
if (xQueueReceive(s_event_queue, &data, 0L) != pdTRUE) {
// no event ready
break;
}
// process event
IDFWiFiEvent *data;
while ((data = s_event_queue.pop()) != nullptr) {
wifi_process_event_(data);
delete data; // NOLINT(cppcoreguidelines-owning-memory)
}
}