[src][scheduler] Split scheduler.c (#7103)

3 files changed, 509 insertions, 321 deletions

diff --git a/src/SConscript b/src/SConscript
index c2d849670f..499747de84 100644
--- a/src/SConscript
+++ b/src/SConscript
@@ -25,7 +25,10 @@ if GetDepend('RT_USING_DEVICE') == False:
     SrcRemove(src, ['device.c'])
 
 if GetDepend('RT_USING_SMP') == False:
-    SrcRemove(src, ['cpu.c'])
+    SrcRemove(src, ['cpu.c','scheduler_mp.c'])
+
+if GetDepend('RT_USING_SMP') == True:
+    SrcRemove(src, ['scheduler_up.c'])
 
 if GetDepend('RT_USING_DM') == False:
     SrcRemove(src, ['driver.c'])
diff --git a/src/scheduler.c b/src/scheduler_mp.c
index c760fa8ed9..a4d07e6233 100644
--- a/src/scheduler.c
+++ b/src/scheduler_mp.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2006-2022, RT-Thread Development Team
+ * Copyright (c) 2006-2023, RT-Thread Development Team
  *
  * SPDX-License-Identifier: Apache-2.0
  *
@@ -28,15 +28,12 @@
  *                             in smp version, rt_hw_context_switch_interrupt maybe switch to
  *                             new task directly
  * 2022-01-07     Gabriel      Moving __on_rt_xxxxx_hook to scheduler.c
+ * 2023-03-27     rose_man     Split into scheduler upc and scheduler_mp.c
  */
 
 #include <rtthread.h>
 #include <rthw.h>
 
-#ifdef RT_USING_SMART
-#include <lwp.h>
-#endif /* RT_USING_SMART */
-
 rt_list_t rt_thread_priority_table[RT_THREAD_PRIORITY_MAX];
 rt_uint32_t rt_thread_ready_priority_group;
 #if RT_THREAD_PRIORITY_MAX > 32
@@ -44,13 +41,6 @@ rt_uint32_t rt_thread_ready_priority_group;
 rt_uint8_t rt_thread_ready_table[32];
 #endif /* RT_THREAD_PRIORITY_MAX > 32 */
 
-#ifndef RT_USING_SMP
-extern volatile rt_uint8_t rt_interrupt_nest;
-static rt_int16_t rt_scheduler_lock_nest;
-struct rt_thread *rt_current_thread = RT_NULL;
-rt_uint8_t rt_current_priority;
-#endif /* RT_USING_SMP */
-
 #ifndef __on_rt_scheduler_hook
     #define __on_rt_scheduler_hook(from, to)        __ON_HOOK_ARGS(rt_scheduler_hook, (from, to))
 #endif
@@ -146,7 +136,6 @@ static void _scheduler_stack_check(struct rt_thread *thread)
 /*
  * get the highest priority thread in ready queue
  */
-#ifdef RT_USING_SMP
 static struct rt_thread* _scheduler_get_highest_priority_thread(rt_ubase_t *highest_prio)
 {
     struct rt_thread *highest_priority_thread;
@@ -182,46 +171,15 @@ static struct rt_thread* _scheduler_get_highest_priority_thread(rt_ubase_t *high
 
     return highest_priority_thread;
 }
-#else
-static struct rt_thread* _scheduler_get_highest_priority_thread(rt_ubase_t *highest_prio)
-{
-    struct rt_thread *highest_priority_thread;
-    rt_ubase_t highest_ready_priority;
-
-#if RT_THREAD_PRIORITY_MAX > 32
-    rt_ubase_t number;
-
-    number = __rt_ffs(rt_thread_ready_priority_group) - 1;
-    highest_ready_priority = (number << 3) + __rt_ffs(rt_thread_ready_table[number]) - 1;
-#else
-    highest_ready_priority = __rt_ffs(rt_thread_ready_priority_group) - 1;
-#endif /* RT_THREAD_PRIORITY_MAX > 32 */
-
-    /* get highest ready priority thread */
-    highest_priority_thread = rt_list_entry(rt_thread_priority_table[highest_ready_priority].next,
-                              struct rt_thread,
-                              tlist);
-
-    *highest_prio = highest_ready_priority;
-
-    return highest_priority_thread;
-}
-#endif /* RT_USING_SMP */
 
 /**
  * @brief This function will initialize the system scheduler.
  */
 void rt_system_scheduler_init(void)
 {
-#ifdef RT_USING_SMP
     int cpu;
-#endif /* RT_USING_SMP */
     rt_base_t offset;
 
-#ifndef RT_USING_SMP
-    rt_scheduler_lock_nest = 0;
-#endif /* RT_USING_SMP */
-
     RT_DEBUG_LOG(RT_DEBUG_SCHEDULER, ("start scheduler: max priority 0x%02x\n",
                                       RT_THREAD_PRIORITY_MAX));
 
@@ -229,7 +187,7 @@ void rt_system_scheduler_init(void)
     {
         rt_list_init(&rt_thread_priority_table[offset]);
     }
-#ifdef RT_USING_SMP
+
     for (cpu = 0; cpu < RT_CPUS_NR; cpu++)
     {
         struct rt_cpu *pcpu =  rt_cpu_index(cpu);
@@ -247,7 +205,6 @@ void rt_system_scheduler_init(void)
         rt_memset(pcpu->ready_table, 0, sizeof(pcpu->ready_table));
 #endif /* RT_THREAD_PRIORITY_MAX > 32 */
     }
-#endif /* RT_USING_SMP */
 
     /* initialize ready priority group */
     rt_thread_ready_priority_group = 0;
@@ -269,21 +226,13 @@ void rt_system_scheduler_start(void)
 
     to_thread = _scheduler_get_highest_priority_thread(&highest_ready_priority);
 
-#ifdef RT_USING_SMP
     to_thread->oncpu = rt_hw_cpu_id();
-#else
-    rt_current_thread = to_thread;
-#endif /* RT_USING_SMP */
 
     rt_schedule_remove_thread(to_thread);
     to_thread->stat = RT_THREAD_RUNNING;
 
     /* switch to new thread */
-#ifdef RT_USING_SMP
     rt_hw_context_switch_to((rt_ubase_t)&to_thread->sp, to_thread);
-#else
-    rt_hw_context_switch_to((rt_ubase_t)&to_thread->sp);
-#endif /* RT_USING_SMP */
 
     /* never come back */
 }
@@ -294,8 +243,6 @@ void rt_system_scheduler_start(void)
 
 /**@{*/
 
-
-#ifdef RT_USING_SMP
 /**
  * @brief This function will handle IPI interrupt and do a scheduling in system.
  *
@@ -443,142 +390,12 @@ void rt_schedule(void)
 __exit:
     return ;
 }
-#else
-/**
- * @brief This function will perform scheduling once. It will select one thread
- *        with the highest priority, and switch to it immediately.
- */
-void rt_schedule(void)
-{
-    rt_base_t level;
-    struct rt_thread *to_thread;
-    struct rt_thread *from_thread;
-
-    /* disable interrupt */
-    level = rt_hw_interrupt_disable();
-
-    /* check the scheduler is enabled or not */
-    if (rt_scheduler_lock_nest == 0)
-    {
-        rt_ubase_t highest_ready_priority;
-
-        if (rt_thread_ready_priority_group != 0)
-        {
-            /* need_insert_from_thread: need to insert from_thread to ready queue */
-            int need_insert_from_thread = 0;
-
-            to_thread = _scheduler_get_highest_priority_thread(&highest_ready_priority);
-
-            if ((rt_current_thread->stat & RT_THREAD_STAT_MASK) == RT_THREAD_RUNNING)
-            {
-                if (rt_current_thread->current_priority < highest_ready_priority)
-                {
-                    to_thread = rt_current_thread;
-                }
-                else if (rt_current_thread->current_priority == highest_ready_priority && (rt_current_thread->stat & RT_THREAD_STAT_YIELD_MASK) == 0)
-                {
-                    to_thread = rt_current_thread;
-                }
-                else
-                {
-                    need_insert_from_thread = 1;
-                }
-                rt_current_thread->stat &= ~RT_THREAD_STAT_YIELD_MASK;
-            }
-
-            if (to_thread != rt_current_thread)
-            {
-                /* if the destination thread is not the same as current thread */
-                rt_current_priority = (rt_uint8_t)highest_ready_priority;
-                from_thread         = rt_current_thread;
-                rt_current_thread   = to_thread;
-
-                RT_OBJECT_HOOK_CALL(rt_scheduler_hook, (from_thread, to_thread));
-
-                if (need_insert_from_thread)
-                {
-                    rt_schedule_insert_thread(from_thread);
-                }
-
-                rt_schedule_remove_thread(to_thread);
-                to_thread->stat = RT_THREAD_RUNNING | (to_thread->stat & ~RT_THREAD_STAT_MASK);
-
-                /* switch to new thread */
-                RT_DEBUG_LOG(RT_DEBUG_SCHEDULER,
-                        ("[%d]switch to priority#%d "
-                         "thread:%.*s(sp:0x%08x), "
-                         "from thread:%.*s(sp: 0x%08x)\n",
-                         rt_interrupt_nest, highest_ready_priority,
-                         RT_NAME_MAX, to_thread->name, to_thread->sp,
-                         RT_NAME_MAX, from_thread->name, from_thread->sp));
-
-#ifdef RT_USING_OVERFLOW_CHECK
-                _scheduler_stack_check(to_thread);
-#endif /* RT_USING_OVERFLOW_CHECK */
-
-                if (rt_interrupt_nest == 0)
-                {
-                    extern void rt_thread_handle_sig(rt_bool_t clean_state);
-
-                    RT_OBJECT_HOOK_CALL(rt_scheduler_switch_hook, (from_thread));
-
-                    rt_hw_context_switch((rt_ubase_t)&from_thread->sp,
-                            (rt_ubase_t)&to_thread->sp);
-
-                    /* enable interrupt */
-                    rt_hw_interrupt_enable(level);
-
-#ifdef RT_USING_SIGNALS
-                    /* check stat of thread for signal */
-                    level = rt_hw_interrupt_disable();
-                    if (rt_current_thread->stat & RT_THREAD_STAT_SIGNAL_PENDING)
-                    {
-                        extern void rt_thread_handle_sig(rt_bool_t clean_state);
-
-                        rt_current_thread->stat &= ~RT_THREAD_STAT_SIGNAL_PENDING;
-
-                        rt_hw_interrupt_enable(level);
-
-                        /* check signal status */
-                        rt_thread_handle_sig(RT_TRUE);
-                    }
-                    else
-                    {
-                        rt_hw_interrupt_enable(level);
-                    }
-#endif /* RT_USING_SIGNALS */
-                    goto __exit;
-                }
-                else
-                {
-                    RT_DEBUG_LOG(RT_DEBUG_SCHEDULER, ("switch in interrupt\n"));
-
-                    rt_hw_context_switch_interrupt((rt_ubase_t)&from_thread->sp,
-                            (rt_ubase_t)&to_thread->sp, from_thread, to_thread);
-                }
-            }
-            else
-            {
-                rt_schedule_remove_thread(rt_current_thread);
-                rt_current_thread->stat = RT_THREAD_RUNNING | (rt_current_thread->stat & ~RT_THREAD_STAT_MASK);
-            }
-        }
-    }
-
-    /* enable interrupt */
-    rt_hw_interrupt_enable(level);
-
-__exit:
-    return;
-}
-#endif /* RT_USING_SMP */
 
 /**
  * @brief This function checks whether a scheduling is needed after an IRQ context switching. If yes,
  *        it will select one thread with the highest priority level, and then switch
  *        to it.
  */
-#ifdef RT_USING_SMP
 void rt_scheduler_do_irq_switch(void *context)
 {
     int cpu_id;
@@ -679,7 +496,6 @@ void rt_scheduler_do_irq_switch(void *context)
     }
     rt_hw_interrupt_enable(level);
 }
-#endif /* RT_USING_SMP */
 
 /**
  * @brief This function will insert a thread to the system ready queue. The state of
@@ -689,7 +505,6 @@ void rt_scheduler_do_irq_switch(void *context)
  *
  * @note  Please do not invoke this function in user application.
  */
-#ifdef RT_USING_SMP
 void rt_schedule_insert_thread(struct rt_thread *thread)
 {
     int cpu_id;
@@ -775,52 +590,6 @@ __exit:
     /* enable interrupt */
     rt_hw_interrupt_enable(level);
 }
-#else
-void rt_schedule_insert_thread(struct rt_thread *thread)
-{
-    rt_base_t level;
-
-    RT_ASSERT(thread != RT_NULL);
-
-    /* disable interrupt */
-    level = rt_hw_interrupt_disable();
-
-    /* it's current thread, it should be RUNNING thread */
-    if (thread == rt_current_thread)
-    {
-        thread->stat = RT_THREAD_RUNNING | (thread->stat & ~RT_THREAD_STAT_MASK);
-        goto __exit;
-    }
-
-    /* READY thread, insert to ready queue */
-    thread->stat = RT_THREAD_READY | (thread->stat & ~RT_THREAD_STAT_MASK);
-    /* there is no time slices left(YIELD), inserting thread before ready list*/
-    if((thread->stat & RT_THREAD_STAT_YIELD_MASK) != 0)
-    {
-        rt_list_insert_before(&(rt_thread_priority_table[thread->current_priority]),
-                              &(thread->tlist));
-    }
-    /* there are some time slices left, inserting thread after ready list to schedule it firstly at next time*/
-    else
-    {
-        rt_list_insert_after(&(rt_thread_priority_table[thread->current_priority]),
-                              &(thread->tlist));
-    }
-
-    RT_DEBUG_LOG(RT_DEBUG_SCHEDULER, ("insert thread[%.*s], the priority: %d\n",
-                                      RT_NAME_MAX, thread->name, thread->current_priority));
-
-    /* set priority mask */
-#if RT_THREAD_PRIORITY_MAX > 32
-    rt_thread_ready_table[thread->number] |= thread->high_mask;
-#endif /* RT_THREAD_PRIORITY_MAX > 32 */
-    rt_thread_ready_priority_group |= thread->number_mask;
-
-__exit:
-    /* enable interrupt */
-    rt_hw_interrupt_enable(level);
-}
-#endif /* RT_USING_SMP */
 
 /**
  * @brief This function will remove a thread from system ready queue.
@@ -829,7 +598,6 @@ __exit:
  *
  * @note  Please do not invoke this function in user application.
  */
-#ifdef RT_USING_SMP
 void rt_schedule_remove_thread(struct rt_thread *thread)
 {
     rt_base_t level;
@@ -881,44 +649,10 @@ void rt_schedule_remove_thread(struct rt_thread *thread)
     /* enable interrupt */
     rt_hw_interrupt_enable(level);
 }
-#else
-void rt_schedule_remove_thread(struct rt_thread *thread)
-{
-    rt_base_t level;
-
-    RT_ASSERT(thread != RT_NULL);
-
-    /* disable interrupt */
-    level = rt_hw_interrupt_disable();
-
-    RT_DEBUG_LOG(RT_DEBUG_SCHEDULER, ("remove thread[%.*s], the priority: %d\n",
-                                      RT_NAME_MAX, thread->name,
-                                      thread->current_priority));
-
-    /* remove thread from ready list */
-    rt_list_remove(&(thread->tlist));
-    if (rt_list_isempty(&(rt_thread_priority_table[thread->current_priority])))
-    {
-#if RT_THREAD_PRIORITY_MAX > 32
-        rt_thread_ready_table[thread->number] &= ~thread->high_mask;
-        if (rt_thread_ready_table[thread->number] == 0)
-        {
-            rt_thread_ready_priority_group &= ~thread->number_mask;
-        }
-#else
-        rt_thread_ready_priority_group &= ~thread->number_mask;
-#endif /* RT_THREAD_PRIORITY_MAX > 32 */
-    }
-
-    /* enable interrupt */
-    rt_hw_interrupt_enable(level);
-}
-#endif /* RT_USING_SMP */
 
 /**
  * @brief This function will lock the thread scheduler.
  */
-#ifdef RT_USING_SMP
 void rt_enter_critical(void)
 {
     rt_base_t level;
@@ -958,30 +692,11 @@ void rt_enter_critical(void)
     /* enable interrupt */
     rt_hw_local_irq_enable(level);
 }
-#else
-void rt_enter_critical(void)
-{
-    rt_base_t level;
-
-    /* disable interrupt */
-    level = rt_hw_interrupt_disable();
-
-    /*
-     * the maximal number of nest is RT_UINT16_MAX, which is big
-     * enough and does not check here
-     */
-    rt_scheduler_lock_nest ++;
-
-    /* enable interrupt */
-    rt_hw_interrupt_enable(level);
-}
-#endif /* RT_USING_SMP */
 RTM_EXPORT(rt_enter_critical);
 
 /**
  * @brief This function will unlock the thread scheduler.
  */
-#ifdef RT_USING_SMP
 void rt_exit_critical(void)
 {
     rt_base_t level;
@@ -1023,34 +738,6 @@ void rt_exit_critical(void)
         rt_hw_local_irq_enable(level);
     }
 }
-#else
-void rt_exit_critical(void)
-{
-    rt_base_t level;
-
-    /* disable interrupt */
-    level = rt_hw_interrupt_disable();
-
-    rt_scheduler_lock_nest --;
-    if (rt_scheduler_lock_nest <= 0)
-    {
-        rt_scheduler_lock_nest = 0;
-        /* enable interrupt */
-        rt_hw_interrupt_enable(level);
-
-        if (rt_current_thread)
-        {
-            /* if scheduler is started, do a schedule */
-            rt_schedule();
-        }
-    }
-    else
-    {
-        /* enable interrupt */
-        rt_hw_interrupt_enable(level);
-    }
-}
-#endif /* RT_USING_SMP */
 RTM_EXPORT(rt_exit_critical);
 
 /**
@@ -1060,13 +747,9 @@ RTM_EXPORT(rt_exit_critical);
  */
 rt_uint16_t rt_critical_level(void)
 {
-#ifdef RT_USING_SMP
     struct rt_thread *current_thread = rt_cpu_self()->current_thread;
 
     return current_thread->critical_lock_nest;
-#else
-    return rt_scheduler_lock_nest;
-#endif /* RT_USING_SMP */
 }
 RTM_EXPORT(rt_critical_level);
 
diff --git a/src/scheduler_up.c b/src/scheduler_up.c
new file mode 100644
index 0000000000..a5cfecc6f2
--- /dev/null
+++ b/src/scheduler_up.c
@@ -0,0 +1,502 @@
+/*
+ * Copyright (c) 2006-2023, RT-Thread Development Team
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Change Logs:
+ * Date           Author       Notes
+ * 2006-03-17     Bernard      the first version
+ * 2006-04-28     Bernard      fix the scheduler algorthm
+ * 2006-04-30     Bernard      add SCHEDULER_DEBUG
+ * 2006-05-27     Bernard      fix the scheduler algorthm for same priority
+ *                             thread schedule
+ * 2006-06-04     Bernard      rewrite the scheduler algorithm
+ * 2006-08-03     Bernard      add hook support
+ * 2006-09-05     Bernard      add 32 priority level support
+ * 2006-09-24     Bernard      add rt_system_scheduler_start function
+ * 2009-09-16     Bernard      fix _rt_scheduler_stack_check
+ * 2010-04-11     yi.qiu       add module feature
+ * 2010-07-13     Bernard      fix the maximal number of rt_scheduler_lock_nest
+ *                             issue found by kuronca
+ * 2010-12-13     Bernard      add defunct list initialization even if not use heap.
+ * 2011-05-10     Bernard      clean scheduler debug log.
+ * 2013-12-21     Grissiom     add rt_critical_level
+ * 2018-11-22     Jesven       remove the current task from ready queue
+ *                             add per cpu ready queue
+ *                             add _scheduler_get_highest_priority_thread to find highest priority task
+ *                             rt_schedule_insert_thread won't insert current task to ready queue
+ *                             in smp version, rt_hw_context_switch_interrupt maybe switch to
+ *                             new task directly
+ * 2022-01-07     Gabriel      Moving __on_rt_xxxxx_hook to scheduler.c
+ * 2023-03-27     rose_man     Split into scheduler upc and scheduler_mp.c
+ */
+
+#include <rtthread.h>
+#include <rthw.h>
+
+rt_list_t rt_thread_priority_table[RT_THREAD_PRIORITY_MAX];
+rt_uint32_t rt_thread_ready_priority_group;
+#if RT_THREAD_PRIORITY_MAX > 32
+/* Maximum priority level, 256 */
+rt_uint8_t rt_thread_ready_table[32];
+#endif /* RT_THREAD_PRIORITY_MAX > 32 */
+
+extern volatile rt_uint8_t rt_interrupt_nest;
+static rt_int16_t rt_scheduler_lock_nest;
+struct rt_thread *rt_current_thread = RT_NULL;
+rt_uint8_t rt_current_priority;
+
+#ifndef __on_rt_scheduler_hook
+    #define __on_rt_scheduler_hook(from, to)        __ON_HOOK_ARGS(rt_scheduler_hook, (from, to))
+#endif
+#ifndef __on_rt_scheduler_switch_hook
+    #define __on_rt_scheduler_switch_hook(tid)      __ON_HOOK_ARGS(rt_scheduler_switch_hook, (tid))
+#endif
+
+#if defined(RT_USING_HOOK) && defined(RT_HOOK_USING_FUNC_PTR)
+static void (*rt_scheduler_hook)(struct rt_thread *from, struct rt_thread *to);
+static void (*rt_scheduler_switch_hook)(struct rt_thread *tid);
+
+/**
+ * @addtogroup Hook
+ */
+
+/**@{*/
+
+/**
+ * @brief This function will set a hook function, which will be invoked when thread
+ *        switch happens.
+ *
+ * @param hook is the hook function.
+ */
+void rt_scheduler_sethook(void (*hook)(struct rt_thread *from, struct rt_thread *to))
+{
+    rt_scheduler_hook = hook;
+}
+
+/**
+ * @brief This function will set a hook function, which will be invoked when context
+ *        switch happens.
+ *
+ * @param hook is the hook function.
+ */
+void rt_scheduler_switch_sethook(void (*hook)(struct rt_thread *tid))
+{
+    rt_scheduler_switch_hook = hook;
+}
+
+/**@}*/
+#endif /* RT_USING_HOOK */
+
+#ifdef RT_USING_OVERFLOW_CHECK
+static void _scheduler_stack_check(struct rt_thread *thread)
+{
+    RT_ASSERT(thread != RT_NULL);
+
+#ifdef RT_USING_SMART
+#ifndef ARCH_MM_MMU
+    struct rt_lwp *lwp = thread ? (struct rt_lwp *)thread->lwp : 0;
+
+    /* if stack pointer locate in user data section skip stack check. */
+    if (lwp && ((rt_uint32_t)thread->sp > (rt_uint32_t)lwp->data_entry &&
+    (rt_uint32_t)thread->sp <= (rt_uint32_t)lwp->data_entry + (rt_uint32_t)lwp->data_size))
+    {
+        return;
+    }
+#endif /* not defined ARCH_MM_MMU */
+#endif /* RT_USING_SMART */
+
+#ifdef ARCH_CPU_STACK_GROWS_UPWARD
+    if (*((rt_uint8_t *)((rt_ubase_t)thread->stack_addr + thread->stack_size - 1)) != '#' ||
+#else
+    if (*((rt_uint8_t *)thread->stack_addr) != '#' ||
+#endif /* ARCH_CPU_STACK_GROWS_UPWARD */
+        (rt_ubase_t)thread->sp <= (rt_ubase_t)thread->stack_addr ||
+        (rt_ubase_t)thread->sp >
+        (rt_ubase_t)thread->stack_addr + (rt_ubase_t)thread->stack_size)
+    {
+        rt_base_t level;
+
+        rt_kprintf("thread:%s stack overflow\n", thread->name);
+
+        level = rt_hw_interrupt_disable();
+        while (level);
+    }
+#ifdef ARCH_CPU_STACK_GROWS_UPWARD
+    else if ((rt_ubase_t)thread->sp > ((rt_ubase_t)thread->stack_addr + thread->stack_size))
+    {
+        rt_kprintf("warning: %s stack is close to the top of stack address.\n",
+                   thread->name);
+    }
+#else
+    else if ((rt_ubase_t)thread->sp <= ((rt_ubase_t)thread->stack_addr + 32))
+    {
+        rt_kprintf("warning: %s stack is close to end of stack address.\n",
+                   thread->name);
+    }
+#endif /* ARCH_CPU_STACK_GROWS_UPWARD */
+}
+#endif /* RT_USING_OVERFLOW_CHECK */
+
+static struct rt_thread* _scheduler_get_highest_priority_thread(rt_ubase_t *highest_prio)
+{
+    struct rt_thread *highest_priority_thread;
+    rt_ubase_t highest_ready_priority;
+
+#if RT_THREAD_PRIORITY_MAX > 32
+    rt_ubase_t number;
+
+    number = __rt_ffs(rt_thread_ready_priority_group) - 1;
+    highest_ready_priority = (number << 3) + __rt_ffs(rt_thread_ready_table[number]) - 1;
+#else
+    highest_ready_priority = __rt_ffs(rt_thread_ready_priority_group) - 1;
+#endif /* RT_THREAD_PRIORITY_MAX > 32 */
+
+    /* get highest ready priority thread */
+    highest_priority_thread = rt_list_entry(rt_thread_priority_table[highest_ready_priority].next,
+                              struct rt_thread,
+                              tlist);
+
+    *highest_prio = highest_ready_priority;
+
+    return highest_priority_thread;
+}
+
+/**
+ * @brief This function will initialize the system scheduler.
+ */
+void rt_system_scheduler_init(void)
+{
+    rt_base_t offset;
+    rt_scheduler_lock_nest = 0;
+
+    RT_DEBUG_LOG(RT_DEBUG_SCHEDULER, ("start scheduler: max priority 0x%02x\n",
+                                      RT_THREAD_PRIORITY_MAX));
+
+    for (offset = 0; offset < RT_THREAD_PRIORITY_MAX; offset ++)
+    {
+        rt_list_init(&rt_thread_priority_table[offset]);
+    }
+
+    /* initialize ready priority group */
+    rt_thread_ready_priority_group = 0;
+
+#if RT_THREAD_PRIORITY_MAX > 32
+    /* initialize ready table */
+    rt_memset(rt_thread_ready_table, 0, sizeof(rt_thread_ready_table));
+#endif /* RT_THREAD_PRIORITY_MAX > 32 */
+}
+
+/**
+ * @brief This function will startup the scheduler. It will select one thread
+ *        with the highest priority level, then switch to it.
+ */
+void rt_system_scheduler_start(void)
+{
+    struct rt_thread *to_thread;
+    rt_ubase_t highest_ready_priority;
+
+    to_thread = _scheduler_get_highest_priority_thread(&highest_ready_priority);
+
+    rt_current_thread = to_thread;
+
+    rt_schedule_remove_thread(to_thread);
+    to_thread->stat = RT_THREAD_RUNNING;
+
+    /* switch to new thread */
+
+    rt_hw_context_switch_to((rt_ubase_t)&to_thread->sp);
+
+    /* never come back */
+}
+
+/**
+ * @addtogroup Thread
+ */
+
+/**@{*/
+
+/**
+ * @brief This function will perform scheduling once. It will select one thread
+ *        with the highest priority, and switch to it immediately.
+ */
+void rt_schedule(void)
+{
+    rt_base_t level;
+    struct rt_thread *to_thread;
+    struct rt_thread *from_thread;
+
+    /* disable interrupt */
+    level = rt_hw_interrupt_disable();
+
+    /* check the scheduler is enabled or not */
+    if (rt_scheduler_lock_nest == 0)
+    {
+        rt_ubase_t highest_ready_priority;
+
+        if (rt_thread_ready_priority_group != 0)
+        {
+            /* need_insert_from_thread: need to insert from_thread to ready queue */
+            int need_insert_from_thread = 0;
+
+            to_thread = _scheduler_get_highest_priority_thread(&highest_ready_priority);
+
+            if ((rt_current_thread->stat & RT_THREAD_STAT_MASK) == RT_THREAD_RUNNING)
+            {
+                if (rt_current_thread->current_priority < highest_ready_priority)
+                {
+                    to_thread = rt_current_thread;
+                }
+                else if (rt_current_thread->current_priority == highest_ready_priority && (rt_current_thread->stat & RT_THREAD_STAT_YIELD_MASK) == 0)
+                {
+                    to_thread = rt_current_thread;
+                }
+                else
+                {
+                    need_insert_from_thread = 1;
+                }
+                rt_current_thread->stat &= ~RT_THREAD_STAT_YIELD_MASK;
+            }
+
+            if (to_thread != rt_current_thread)
+            {
+                /* if the destination thread is not the same as current thread */
+                rt_current_priority = (rt_uint8_t)highest_ready_priority;
+                from_thread         = rt_current_thread;
+                rt_current_thread   = to_thread;
+
+                RT_OBJECT_HOOK_CALL(rt_scheduler_hook, (from_thread, to_thread));
+
+                if (need_insert_from_thread)
+                {
+                    rt_schedule_insert_thread(from_thread);
+                }
+
+                rt_schedule_remove_thread(to_thread);
+                to_thread->stat = RT_THREAD_RUNNING | (to_thread->stat & ~RT_THREAD_STAT_MASK);
+
+                /* switch to new thread */
+                RT_DEBUG_LOG(RT_DEBUG_SCHEDULER,
+                        ("[%d]switch to priority#%d "
+                         "thread:%.*s(sp:0x%08x), "
+                         "from thread:%.*s(sp: 0x%08x)\n",
+                         rt_interrupt_nest, highest_ready_priority,
+                         RT_NAME_MAX, to_thread->name, to_thread->sp,
+                         RT_NAME_MAX, from_thread->name, from_thread->sp));
+
+#ifdef RT_USING_OVERFLOW_CHECK
+                _scheduler_stack_check(to_thread);
+#endif /* RT_USING_OVERFLOW_CHECK */
+
+                if (rt_interrupt_nest == 0)
+                {
+                    extern void rt_thread_handle_sig(rt_bool_t clean_state);
+
+                    RT_OBJECT_HOOK_CALL(rt_scheduler_switch_hook, (from_thread));
+
+                    rt_hw_context_switch((rt_ubase_t)&from_thread->sp,
+                            (rt_ubase_t)&to_thread->sp);
+
+                    /* enable interrupt */
+                    rt_hw_interrupt_enable(level);
+
+#ifdef RT_USING_SIGNALS
+                    /* check stat of thread for signal */
+                    level = rt_hw_interrupt_disable();
+                    if (rt_current_thread->stat & RT_THREAD_STAT_SIGNAL_PENDING)
+                    {
+                        extern void rt_thread_handle_sig(rt_bool_t clean_state);
+
+                        rt_current_thread->stat &= ~RT_THREAD_STAT_SIGNAL_PENDING;
+
+                        rt_hw_interrupt_enable(level);
+
+                        /* check signal status */
+                        rt_thread_handle_sig(RT_TRUE);
+                    }
+                    else
+                    {
+                        rt_hw_interrupt_enable(level);
+                    }
+#endif /* RT_USING_SIGNALS */
+                    goto __exit;
+                }
+                else
+                {
+                    RT_DEBUG_LOG(RT_DEBUG_SCHEDULER, ("switch in interrupt\n"));
+
+                    rt_hw_context_switch_interrupt((rt_ubase_t)&from_thread->sp,
+                            (rt_ubase_t)&to_thread->sp, from_thread, to_thread);
+                }
+            }
+            else
+            {
+                rt_schedule_remove_thread(rt_current_thread);
+                rt_current_thread->stat = RT_THREAD_RUNNING | (rt_current_thread->stat & ~RT_THREAD_STAT_MASK);
+            }
+        }
+    }
+
+    /* enable interrupt */
+    rt_hw_interrupt_enable(level);
+
+__exit:
+    return;
+}
+
+/**
+ * @brief This function will insert a thread to the system ready queue. The state of
+ *        thread will be set as READY and the thread will be removed from suspend queue.
+ *
+ * @param thread is the thread to be inserted.
+ *
+ * @note  Please do not invoke this function in user application.
+ */
+void rt_schedule_insert_thread(struct rt_thread *thread)
+{
+    rt_base_t level;
+
+    RT_ASSERT(thread != RT_NULL);
+
+    /* disable interrupt */
+    level = rt_hw_interrupt_disable();
+
+    /* it's current thread, it should be RUNNING thread */
+    if (thread == rt_current_thread)
+    {
+        thread->stat = RT_THREAD_RUNNING | (thread->stat & ~RT_THREAD_STAT_MASK);
+        goto __exit;
+    }
+
+    /* READY thread, insert to ready queue */
+    thread->stat = RT_THREAD_READY | (thread->stat & ~RT_THREAD_STAT_MASK);
+    /* there is no time slices left(YIELD), inserting thread before ready list*/
+    if((thread->stat & RT_THREAD_STAT_YIELD_MASK) != 0)
+    {
+        rt_list_insert_before(&(rt_thread_priority_table[thread->current_priority]),
+                              &(thread->tlist));
+    }
+    /* there are some time slices left, inserting thread after ready list to schedule it firstly at next time*/
+    else
+    {
+        rt_list_insert_after(&(rt_thread_priority_table[thread->current_priority]),
+                              &(thread->tlist));
+    }
+
+    RT_DEBUG_LOG(RT_DEBUG_SCHEDULER, ("insert thread[%.*s], the priority: %d\n",
+                                      RT_NAME_MAX, thread->name, thread->current_priority));
+
+    /* set priority mask */
+#if RT_THREAD_PRIORITY_MAX > 32
+    rt_thread_ready_table[thread->number] |= thread->high_mask;
+#endif /* RT_THREAD_PRIORITY_MAX > 32 */
+    rt_thread_ready_priority_group |= thread->number_mask;
+
+__exit:
+    /* enable interrupt */
+    rt_hw_interrupt_enable(level);
+}
+
+/**
+ * @brief This function will remove a thread from system ready queue.
+ *
+ * @param thread is the thread to be removed.
+ *
+ * @note  Please do not invoke this function in user application.
+ */
+void rt_schedule_remove_thread(struct rt_thread *thread)
+{
+    rt_base_t level;
+
+    RT_ASSERT(thread != RT_NULL);
+
+    /* disable interrupt */
+    level = rt_hw_interrupt_disable();
+
+    RT_DEBUG_LOG(RT_DEBUG_SCHEDULER, ("remove thread[%.*s], the priority: %d\n",
+                                      RT_NAME_MAX, thread->name,
+                                      thread->current_priority));
+
+    /* remove thread from ready list */
+    rt_list_remove(&(thread->tlist));
+    if (rt_list_isempty(&(rt_thread_priority_table[thread->current_priority])))
+    {
+#if RT_THREAD_PRIORITY_MAX > 32
+        rt_thread_ready_table[thread->number] &= ~thread->high_mask;
+        if (rt_thread_ready_table[thread->number] == 0)
+        {
+            rt_thread_ready_priority_group &= ~thread->number_mask;
+        }
+#else
+        rt_thread_ready_priority_group &= ~thread->number_mask;
+#endif /* RT_THREAD_PRIORITY_MAX > 32 */
+    }
+
+    /* enable interrupt */
+    rt_hw_interrupt_enable(level);
+}
+
+/**
+ * @brief This function will lock the thread scheduler.
+ */
+void rt_enter_critical(void)
+{
+    rt_base_t level;
+
+    /* disable interrupt */
+    level = rt_hw_interrupt_disable();
+
+    /*
+     * the maximal number of nest is RT_UINT16_MAX, which is big
+     * enough and does not check here
+     */
+    rt_scheduler_lock_nest ++;
+
+    /* enable interrupt */
+    rt_hw_interrupt_enable(level);
+}
+RTM_EXPORT(rt_enter_critical);
+
+/**
+ * @brief This function will unlock the thread scheduler.
+ */
+void rt_exit_critical(void)
+{
+    rt_base_t level;
+
+    /* disable interrupt */
+    level = rt_hw_interrupt_disable();
+
+    rt_scheduler_lock_nest --;
+    if (rt_scheduler_lock_nest <= 0)
+    {
+        rt_scheduler_lock_nest = 0;
+        /* enable interrupt */
+        rt_hw_interrupt_enable(level);
+
+        if (rt_current_thread)
+        {
+            /* if scheduler is started, do a schedule */
+            rt_schedule();
+        }
+    }
+    else
+    {
+        /* enable interrupt */
+        rt_hw_interrupt_enable(level);
+    }
+}
+RTM_EXPORT(rt_exit_critical);
+
+/**
+ * @brief Get the scheduler lock level.
+ *
+ * @return the level of the scheduler lock. 0 means unlocked.
+ */
+rt_uint16_t rt_critical_level(void)
+{
+    return rt_scheduler_lock_nest;
+}
+RTM_EXPORT(rt_critical_level);
+
+/**@}*/