From 9a963abfc8b27c6fdfb5b6b4b38e5905d6a360a7 Mon Sep 17 00:00:00 2001
From: Xudong Zheng <7pkvm5aw@slicealias.com>
Date: Mon, 17 Jul 2023 17:16:04 -0400
Subject: [PATCH] refactor: use low priority workqueue for underglow and
 battery reporting

Blocking operations on the high priority system workqueue may result in
deadlocks, particularly when Bluetooth is in use.
---
 app/CMakeLists.txt          |  1 +
 app/Kconfig                 |  8 ++++++++
 app/include/zmk/workqueue.h |  1 +
 app/src/battery.c           | 14 +++++---------
 app/src/rgb_underglow.c     |  3 ++-
 app/src/workqueue.c         | 27 +++++++++++++++++++++++++++
 6 files changed, 44 insertions(+), 10 deletions(-)
 create mode 100644 app/include/zmk/workqueue.h
 create mode 100644 app/src/workqueue.c

diff --git a/app/CMakeLists.txt b/app/CMakeLists.txt
index 4c1c63c2..efa34905 100644
--- a/app/CMakeLists.txt
+++ b/app/CMakeLists.txt
@@ -87,6 +87,7 @@ target_sources_ifdef(CONFIG_USB_DEVICE_STACK app PRIVATE src/usb.c)
 target_sources_ifdef(CONFIG_ZMK_USB app PRIVATE src/usb_hid.c)
 target_sources_ifdef(CONFIG_ZMK_RGB_UNDERGLOW app PRIVATE src/rgb_underglow.c)
 target_sources_ifdef(CONFIG_ZMK_BACKLIGHT app PRIVATE src/backlight.c)
+target_sources(app PRIVATE src/workqueue.c)
 target_sources(app PRIVATE src/main.c)
 
 add_subdirectory(src/display/)
diff --git a/app/Kconfig b/app/Kconfig
index fe019918..89a128b5 100644
--- a/app/Kconfig
+++ b/app/Kconfig
@@ -504,6 +504,14 @@ config ZMK_BATTERY_REPORT_INTERVAL
     int "Battery level report interval in seconds"
     default 60
 
+config ZMK_LOW_PRIORITY_THREAD_STACK_SIZE
+    int "Low priority thread stack size"
+    default 768
+
+config ZMK_LOW_PRIORITY_THREAD_PRIORITY
+    int "Low priority thread priority"
+    default 10
+
 #Advanced
 endmenu
 
diff --git a/app/include/zmk/workqueue.h b/app/include/zmk/workqueue.h
new file mode 100644
index 00000000..41e94580
--- /dev/null
+++ b/app/include/zmk/workqueue.h
@@ -0,0 +1 @@
+struct k_work_q *zmk_workqueue_lowprio_work_q();
diff --git a/app/src/battery.c b/app/src/battery.c
index 540f7c3e..87a25e08 100644
--- a/app/src/battery.c
+++ b/app/src/battery.c
@@ -18,6 +18,7 @@ LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
 #include <zmk/event_manager.h>
 #include <zmk/battery.h>
 #include <zmk/events/battery_state_changed.h>
+#include <zmk/workqueue.h>
 
 static uint8_t last_state_of_charge = 0;
 
@@ -77,7 +78,9 @@ static void zmk_battery_work(struct k_work *work) {
 
 K_WORK_DEFINE(battery_work, zmk_battery_work);
 
-static void zmk_battery_timer(struct k_timer *timer) { k_work_submit(&battery_work); }
+static void zmk_battery_timer(struct k_timer *timer) {
+    k_work_submit_to_queue(zmk_workqueue_lowprio_work_q(), &battery_work);
+}
 
 K_TIMER_DEFINE(battery_timer, zmk_battery_timer, NULL);
 
@@ -97,14 +100,7 @@ static int zmk_battery_init(const struct device *_arg) {
         return -ENODEV;
     }
 
-    int rc = zmk_battery_update(battery);
-
-    if (rc != 0) {
-        LOG_DBG("Failed to update battery value: %d.", rc);
-        return rc;
-    }
-
-    k_timer_start(&battery_timer, K_MINUTES(1), K_SECONDS(CONFIG_ZMK_BATTERY_REPORT_INTERVAL));
+    k_timer_start(&battery_timer, K_NO_WAIT, K_SECONDS(CONFIG_ZMK_BATTERY_REPORT_INTERVAL));
 
     return 0;
 }
diff --git a/app/src/rgb_underglow.c b/app/src/rgb_underglow.c
index 7b649174..08ba2fb2 100644
--- a/app/src/rgb_underglow.c
+++ b/app/src/rgb_underglow.c
@@ -24,6 +24,7 @@
 #include <zmk/event_manager.h>
 #include <zmk/events/activity_state_changed.h>
 #include <zmk/events/usb_conn_state_changed.h>
+#include <zmk/workqueue.h>
 
 LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
 
@@ -203,7 +204,7 @@ static void zmk_rgb_underglow_tick_handler(struct k_timer *timer) {
         return;
     }
 
-    k_work_submit(&underglow_work);
+    k_work_submit_to_queue(zmk_workqueue_lowprio_work_q(), &underglow_work);
 }
 
 K_TIMER_DEFINE(underglow_tick, zmk_rgb_underglow_tick_handler, NULL);
diff --git a/app/src/workqueue.c b/app/src/workqueue.c
new file mode 100644
index 00000000..a9a8bce5
--- /dev/null
+++ b/app/src/workqueue.c
@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) 2023 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <zephyr/kernel.h>
+#include <zephyr/device.h>
+
+#include <zmk/workqueue.h>
+
+K_THREAD_STACK_DEFINE(lowprio_q_stack, CONFIG_ZMK_LOW_PRIORITY_THREAD_STACK_SIZE);
+
+static struct k_work_q lowprio_work_q;
+
+struct k_work_q *zmk_workqueue_lowprio_work_q() {
+    return &lowprio_work_q;
+}
+
+static int workqueue_init() {
+    static const struct k_work_queue_config queue_config = {.name = "Low Priority Work Queue"};
+    k_work_queue_start(&lowprio_work_q, lowprio_q_stack, K_THREAD_STACK_SIZEOF(lowprio_q_stack),
+                       CONFIG_ZMK_LOW_PRIORITY_THREAD_PRIORITY, &queue_config);
+    return 0;
+}
+
+SYS_INIT(workqueue_init, POST_KERNEL, CONFIG_KERNEL_INIT_PRIORITY_DEFAULT);