[kernel]add doxygen comments for scheduler. (#10366)

* [kernel]add doxygen comments for scheduler.

* [kernel]fix spell error in comments.

3 files changed, 557 insertions, 31 deletions

diff --git a/src/scheduler_comm.c b/src/scheduler_comm.c
index c4e3e7a166..3a9332ddec 100644
--- a/src/scheduler_comm.c
+++ b/src/scheduler_comm.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2006-2024 RT-Thread Development Team
+ * Copyright (c) 2006-2025 RT-Thread Development Team
  *
  * SPDX-License-Identifier: Apache-2.0
  *
@@ -16,6 +16,20 @@
 
 #include <rtthread.h>
 
+/**
+ * @brief Initialize thread scheduling context
+ *
+ * @param thread The thread to be initialized
+ * @param tick Initial time slice value for the thread
+ * @param priority Initial priority of the thread
+ *
+ * @details This function performs the following initialization:
+ *   - Sets thread status to INIT
+ *   - For SMP systems:
+ *     * Sets bind CPU to none (RT_CPUS_NR)
+ *     * Marks CPU as detached (RT_CPU_DETACHED)
+ *   - Calls rt_sched_thread_init_priv() for private scheduling data initialization
+ */
 void rt_sched_thread_init_ctx(struct rt_thread *thread, rt_uint32_t tick, rt_uint8_t priority)
 {
     /* setup thread status */
@@ -30,6 +44,17 @@ void rt_sched_thread_init_ctx(struct rt_thread *thread, rt_uint32_t tick, rt_uin
     rt_sched_thread_init_priv(thread, tick, priority);
 }
 
+/**
+ * @brief Start the thread timer for scheduling
+ *
+ * @param thread The thread whose timer needs to be started
+ *
+ * @return rt_err_t Always returns RT_EOK on success
+ *
+ * @details This function:
+ *   - Requires scheduler lock to be held.
+ *   - Sets the thread's timer flag (sched_flag_ttmr_set) to indicate timer is active
+ */
 rt_err_t rt_sched_thread_timer_start(struct rt_thread *thread)
 {
     RT_SCHED_DEBUG_IS_LOCKED;
@@ -37,6 +62,15 @@ rt_err_t rt_sched_thread_timer_start(struct rt_thread *thread)
     return RT_EOK;
 }
 
+/**
+ * @brief Stop the thread timer for scheduling
+ *
+ * @param thread The thread whose timer needs to be stopped
+ *
+ * @return rt_err_t
+ *   - RT_EOK if timer was successfully stopped or not active
+ *   - Other error codes from rt_timer_stop() if stop operation failed
+ */
 rt_err_t rt_sched_thread_timer_stop(struct rt_thread *thread)
 {
     rt_err_t error;
@@ -56,26 +90,71 @@ rt_err_t rt_sched_thread_timer_stop(struct rt_thread *thread)
     return error;
 }
 
+/**
+ * @brief Get the current status of a thread
+ *
+ * @param thread The thread to get status from
+ *
+ * @return rt_uint8_t The thread status masked with RT_THREAD_STAT_MASK
+ *
+ * @details This function:
+ *   - Requires scheduler lock to be held (RT_SCHED_DEBUG_IS_LOCKED)
+ *   - Returns the thread's status field masked with RT_THREAD_STAT_MASK
+ */
 rt_uint8_t rt_sched_thread_get_stat(struct rt_thread *thread)
 {
     RT_SCHED_DEBUG_IS_LOCKED;
     return RT_SCHED_CTX(thread).stat & RT_THREAD_STAT_MASK;
 }
 
+/**
+ * @brief Get the current priority of a thread
+ *
+ * @param thread The thread to get priority from
+ *
+ * @return rt_uint8_t The current priority value of the thread
+ *
+ * @details This function:
+ *   - Requires scheduler lock to be held (RT_SCHED_DEBUG_IS_LOCKED)
+ *   - Returns the thread's current priority field from its private scheduling data
+ */
 rt_uint8_t rt_sched_thread_get_curr_prio(struct rt_thread *thread)
 {
     RT_SCHED_DEBUG_IS_LOCKED;
     return RT_SCHED_PRIV(thread).current_priority;
 }
 
+/**
+ * @brief Get the initial priority of a thread
+ *
+ * @param thread The thread to get priority from
+ *
+ * @return rt_uint8_t The initial priority value of the thread
+ *
+ * @details This function:
+ *   - Returns the thread's initial priority field from its private scheduling data
+ *   - Does not require scheduler lock as it accesses read-only fields
+ */
 rt_uint8_t rt_sched_thread_get_init_prio(struct rt_thread *thread)
 {
-    /* read only fields, so lock is unecessary */
+    /* read only fields, so lock is unnecessary */
     return RT_SCHED_PRIV(thread).init_priority;
 }
 
 /**
- * @note Caller must hold the scheduler lock
+ * @brief Check if a thread is in suspended state
+ *
+ * @param thread The thread to check
+ *
+ * @return rt_uint8_t
+ *   - 1 if thread is suspended (matches RT_THREAD_SUSPEND_MASK)
+ *   - 0 otherwise
+ *
+ * @details This function:
+ *   - Requires scheduler lock to be held (RT_SCHED_DEBUG_IS_LOCKED)
+ *   - Checks thread's status field against RT_THREAD_SUSPEND_MASK
+ *
+ * @note Caller must hold the scheduler lock before calling this function
  */
 rt_uint8_t rt_sched_thread_is_suspended(struct rt_thread *thread)
 {
@@ -83,6 +162,18 @@ rt_uint8_t rt_sched_thread_is_suspended(struct rt_thread *thread)
     return (RT_SCHED_CTX(thread).stat & RT_THREAD_SUSPEND_MASK) == RT_THREAD_SUSPEND_MASK;
 }
 
+/**
+ * @brief Close a thread by setting its status to CLOSED
+ *
+ * @param thread The thread to be closed
+ * @return rt_err_t Always returns RT_EOK on success
+ *
+ * @details This function:
+ *   - Requires scheduler lock to be held (RT_SCHED_DEBUG_IS_LOCKED)
+ *   - Sets the thread's status to RT_THREAD_CLOSE
+ *
+ * @note Must be called with scheduler lock held
+ */
 rt_err_t rt_sched_thread_close(struct rt_thread *thread)
 {
     RT_SCHED_DEBUG_IS_LOCKED;
@@ -90,6 +181,19 @@ rt_err_t rt_sched_thread_close(struct rt_thread *thread)
     return RT_EOK;
 }
 
+/**
+ * @brief Yield the current thread's remaining time slice
+ *
+ * @param thread The thread to yield
+ * @return rt_err_t Always returns RT_EOK on success
+ *
+ * @details This function:
+ *   - Requires scheduler lock to be held (RT_SCHED_DEBUG_IS_LOCKED)
+ *   - Resets the thread's remaining tick count to its initial value
+ *   - Sets the thread's status to YIELD state
+ *
+ * @note Must be called with scheduler lock held
+ */
 rt_err_t rt_sched_thread_yield(struct rt_thread *thread)
 {
     RT_SCHED_DEBUG_IS_LOCKED;
@@ -100,6 +204,27 @@ rt_err_t rt_sched_thread_yield(struct rt_thread *thread)
     return RT_EOK;
 }
 
+/**
+ * @brief Make a suspended thread ready for scheduling
+ *
+ * @param thread The thread to be made ready
+ *
+ * @return rt_err_t
+ *   - RT_EOK if operation succeeded
+ *   - -RT_EINVAL if thread is not suspended
+ *   - Other error codes from rt_sched_thread_timer_stop() if timer stop failed
+ *
+ * @details This function:
+ *   - Requires scheduler lock to be held (RT_SCHED_DEBUG_IS_LOCKED)
+ *   - Checks if thread is suspended (returns -RT_EINVAL if not)
+ *   - Stops thread timer if active
+ *   - Removes thread from suspend list
+ *   - Clears wakeup handler (if RT_USING_SMART is defined)
+ *   - Inserts thread into ready queue
+ *
+ * @note Must be called with scheduler lock held
+ *       May fail due to racing conditions with timeout ISR
+ */
 rt_err_t rt_sched_thread_ready(struct rt_thread *thread)
 {
     rt_err_t error;
@@ -144,6 +269,24 @@ rt_err_t rt_sched_thread_ready(struct rt_thread *thread)
     return error;
 }
 
+/**
+ * @brief Increase the system tick and update thread's remaining time slice
+ *
+ * @param tick The number of ticks to increase
+ * @return rt_err_t Always returns RT_EOK
+ *
+ * @details This function:
+ *   - Gets the current thread
+ *   - Locks the scheduler
+ *   - Decreases the thread's remaining tick count by the specified amount
+ *   - If remaining ticks reach zero:
+ *     * Calls rt_sched_thread_yield() to yield the thread
+ *     * Requests a reschedule with rt_sched_unlock_n_resched()
+ *   - Otherwise simply unlocks the scheduler
+ *
+ * @note This function is typically called from timer interrupt context
+ *       It handles both SMP and non-SMP cases
+ */
 rt_err_t rt_sched_tick_increase(rt_tick_t tick)
 {
     struct rt_thread *thread;
@@ -178,7 +321,26 @@ rt_err_t rt_sched_tick_increase(rt_tick_t tick)
 }
 
 /**
- * @brief Update priority of the target thread
+ * @brief Update thread priority and adjust scheduling attributes
+ *
+ * @param thread The thread to update priority for
+ * @param priority New priority value to set
+ * @param update_init_prio Flag to determine if initial priority should also be updated
+ * @return rt_err_t Always returns RT_EOK on success
+ *
+ * @details This function:
+ *   - Requires scheduler lock to be held (RT_SCHED_DEBUG_IS_LOCKED)
+ *   - For ready threads:
+ *     * Removes from ready queue
+ *     * Updates priority values
+ *     * Recalculates priority attributes (number, mask, etc.)
+ *     * Reinserts into ready queue with new priority
+ *   - For non-ready threads:
+ *     * Only updates priority values and attributes
+ *   - Handles both 32-bit and >32-bit priority systems
+ *
+ * @note Must be called with scheduler lock held
+ *       Thread status must be valid before calling
  */
 static rt_err_t _rt_sched_update_priority(struct rt_thread *thread, rt_uint8_t priority, rt_bool_t update_init_prio)
 {
@@ -249,6 +411,19 @@ rt_err_t rt_sched_thread_reset_priority(struct rt_thread *thread, rt_uint8_t pri
 }
 
 #ifdef RT_USING_OVERFLOW_CHECK
+/**
+ * @brief Check thread stack for overflow or near-overflow conditions
+ *
+ * @param thread The thread to check stack for
+ *
+ * @details This function performs the following checks:
+ *   - For SMART mode without MMU: skips check if SP is in user data section
+ *   - Without hardware stack guard:
+ *     * For upward-growing stacks: checks magic number at top and SP range
+ *     * For downward-growing stacks: checks magic number at bottom and SP range
+ *     * Triggers error and infinite loop on overflow
+ *   - Additional warnings when stack pointer is near boundaries
+ */
 void rt_scheduler_stack_check(struct rt_thread *thread)
 {
     RT_ASSERT(thread != RT_NULL);
@@ -306,4 +481,4 @@ void rt_scheduler_stack_check(struct rt_thread *thread)
 #endif /* ARCH_CPU_STACK_GROWS_UPWARD */
 }
 
-#endif /* RT_USING_OVERFLOW_CHECK */
+#endif /* RT_USING_OVERFLOW_CHECK */
\ No newline at end of file
diff --git a/src/scheduler_mp.c b/src/scheduler_mp.c
index eab1a7310d..bd9d57ea52 100644
--- a/src/scheduler_mp.c
+++ b/src/scheduler_mp.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2006-2023, RT-Thread Development Team
+ * Copyright (c) 2006-2025 RT-Thread Development Team
  *
  * SPDX-License-Identifier: Apache-2.0
  *
@@ -398,7 +398,20 @@ static void _sched_remove_thread_locked(struct rt_thread *thread)
 }
 
 /**
- * @brief This function will initialize the system scheduler.
+ * @brief Initialize the system scheduler.
+ *
+ * @details This function performs the following initialization tasks:
+ *          - Initializes the global scheduler spinlock for multi-core synchronization.
+ *          - Initializes the global priority table for saving ready threads of all priority levels.
+ *          - For each CPU core:
+ *            * Initializes per-CPU priority tables
+ *            * Sets initial CPU state (irq_switch_flag, current_priority, etc.)
+ *            * Initializes per-CPU ready tables (if priority > 32)
+ *            * Initializes per-CPU spinlock (if RT_USING_SMART is defined)
+ *          - Initializes the global ready priority group and tables (if priority > 32) as bitmaps for all priorities.
+ *
+ * @note This function must be called before any thread scheduling can occur.
+ *       It prepares the scheduler data structures for multi-core operation.
  */
 void rt_system_scheduler_init(void)
 {
@@ -447,8 +460,20 @@ void rt_system_scheduler_init(void)
 }
 
 /**
- * @brief This function will startup the scheduler. It will select one thread
- *        with the highest priority level, then switch to it.
+ * @brief Start the system scheduler and switch to the highest priority thread.
+ *
+ * @details This function performs the following operations:
+ *          - Releases legacy CPU lock (if any)
+ *          - Disables interrupts to ensure atomic operation
+ *          - Acquires scheduler lock for thread safety
+ *          - Selects the highest priority thread from ready queue
+ *          - Removes the selected thread from ready queue
+ *          - Assigns current CPU core to the selected thread
+ *          - Performs context switch to the selected thread
+ *
+ * @note This function will not return after successful execution.
+ *       It performs the initial thread switch during system startup.
+ *       The scheduler must be initialized before calling this function.
  */
 void rt_system_scheduler_start(void)
 {
@@ -549,6 +574,14 @@ rt_err_t rt_sched_unlock(rt_sched_lock_level_t level)
     return RT_EOK;
 }
 
+/**
+ * @brief Check if the scheduler is currently locked
+ *
+ * @return rt_bool_t Returns RT_TRUE if scheduler is locked, RT_FALSE otherwise
+ *
+ * @note This function checks the scheduler lock status in a thread-safe manner
+ *       by temporarily disabling interrupts to get consistent state.
+ */
 rt_bool_t rt_sched_is_locked(void)
 {
     rt_bool_t rc;
@@ -662,6 +695,14 @@ static rt_thread_t _prepare_context_switch_locked(int cpu_id,
 }
 
 #ifdef RT_USING_SIGNALS
+/**
+ * @brief Preprocess pending signals for a suspended thread
+ *
+ * @param current_thread The thread to check for pending signals
+ *
+ * @details This function checks if the specified thread is suspended and has pending signals.
+ *          If both conditions are met, it will wake up/resume the thread to process the signals.
+ */
 static void _sched_thread_preprocess_signal(struct rt_thread *current_thread)
 {
     /* should process signal? */
@@ -679,6 +720,20 @@ static void _sched_thread_preprocess_signal(struct rt_thread *current_thread)
     }
 }
 
+/**
+ * @brief Process pending signals for the current thread
+ *
+ * @param current_thread The thread to process signals for
+ *
+ * @details This function:
+ *          - Locks the scheduler to ensure thread safety
+ *          - Checks if the thread has pending signals
+ *          - If signals are pending:
+ *            * Clears the pending flag
+ *            * Unlocks the scheduler
+ *            * Calls signal handler to process the signals
+ *          - If no signals pending, simply unlocks the scheduler
+ */
 static void _sched_thread_process_signal(struct rt_thread *current_thread)
 {
     rt_base_t level;
@@ -722,6 +777,27 @@ static void _sched_thread_process_signal(struct rt_thread *current_thread)
 #define SCHED_THREAD_PROCESS_SIGNAL(curthr)
 #endif /* RT_USING_SIGNALS */
 
+/**
+ * @brief Unlock scheduler and perform rescheduling if needed
+ *
+ * @param level The scheduler lock level obtained from rt_sched_lock()
+ *
+ * @return rt_err_t
+ *   - RT_EOK: Success
+ *   - -RT_EBUSY: Scheduler not available
+ *   - -RT_ESCHEDISR: Called in interrupt context
+ *   - -RT_ESCHEDLOCKED: Scheduler still locked by others
+ *
+ * @details This function:
+ *   - Releases scheduler lock at specified level
+ *   - Checks if rescheduling is needed
+ *   - If needed, finds highest priority thread and switches to it
+ *   - Processes pending signals for current thread
+ *   - Handles various error conditions
+ *
+ * @note Must be called in pair with rt_sched_lock()
+ *       May trigger context switch if conditions met
+ */
 rt_err_t rt_sched_unlock_n_resched(rt_sched_lock_level_t level)
 {
     struct rt_thread *to_thread;
@@ -807,6 +883,15 @@ rt_err_t rt_sched_unlock_n_resched(rt_sched_lock_level_t level)
  * @brief This function will perform one scheduling. It will select one thread
  *        with the highest priority level in global ready queue or local ready queue,
  *        then switch to it.
+ *
+ * @details This function performs the following operations:
+ *   - Disables interrupts to enter critical section
+ *   - Gets current CPU and thread context
+ *   - Checks if called from interrupt context
+ *   - Finds highest priority ready thread
+ *   - Performs context switch if needed
+ *   - Processes pending signals
+ *   - Restores interrupt state
  */
 void rt_schedule(void)
 {
@@ -890,9 +975,16 @@ void rt_schedule(void)
 }
 
 /**
- * @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.
+ * @brief Perform thread scheduling after an interrupt context switch
+ *
+ * @param context The interrupt context pointer
+ *
+ * @details This function handles scheduling when returning from interrupt context:
+ *   - Checks if scheduling is needed (irq_switch_flag set)
+ *   - If needed, finds highest priority ready thread
+ *   - Performs context switch to new thread if available
+ *   - Handles cases where scheduler is locked or still in interrupt context
+ *   - Processes pending signals before scheduling
  */
 void rt_scheduler_do_irq_switch(void *context)
 {
@@ -1002,8 +1094,20 @@ void rt_sched_remove_thread(struct rt_thread *thread)
     RT_SCHED_CTX(thread).stat = RT_THREAD_SUSPEND_UNINTERRUPTIBLE;
 }
 
-/* thread status initialization and setting up on startup */
-
+/**
+ * @brief Initialize thread's scheduling private data
+ *
+ * @param thread The thread to be initialized
+ * @param tick Initial time slice value for the thread
+ * @param priority Initial priority of the thread
+ *
+ * @details This function performs the following initialization:
+ *   - Initializes thread's ready list node
+ *   - Sets initial and current priority (must be < RT_THREAD_PRIORITY_MAX)
+ *   - Initializes priority bitmasks (handles >32 priorities if needed)
+ *   - Sets initial time slice values
+ *   - For SMP systems, initializes critical section nesting counter
+ */
 void rt_sched_thread_init_priv(struct rt_thread *thread, rt_uint32_t tick, rt_uint8_t priority)
 {
     rt_list_init(&RT_THREAD_LIST_NODE(thread));
@@ -1032,7 +1136,22 @@ void rt_sched_thread_init_priv(struct rt_thread *thread, rt_uint32_t tick, rt_ui
 
 }
 
-/* Normally, there isn't anyone racing with us so this operation is lockless */
+/**
+ * @brief Initialize thread scheduling attributes for startup
+ *
+ * @param thread The thread to be initialized
+ *
+ * @details This function:
+ *   - For systems with >32 priorities:
+ *     * Sets priority number (5 bits)
+ *     * Initializes number_mask and high_mask (3 bits)
+ *   - For systems with <=32 priorities:
+ *     * Initializes number_mask
+ *   - Sets thread state to SUSPEND
+ *
+ * @note This is a lockless operation as it's called during thread creation
+ *       when no concurrent access is possible
+ */
 void rt_sched_thread_startup(struct rt_thread *thread)
 {
 #if RT_THREAD_PRIORITY_MAX > 32
@@ -1048,9 +1167,19 @@ void rt_sched_thread_startup(struct rt_thread *thread)
 }
 
 /**
- * @brief Update scheduling status of thread. this operation is taken as an
- *        atomic operation of the update of SP. Since the local irq is disabled,
- *        it's okay to assume that the stack will not be modified meanwhile.
+ * @brief Update thread scheduling status after context switch
+ *
+ * @param thread The thread that will be running after the context switch
+ *
+ * @details This function performs critical post-context-switch operations:
+ *   - Verifies interrupts are disabled (RT_ASSERT)
+ *   - Releases scheduler lock from previous thread if exists
+ *   - Updates current thread pointer for the CPU
+ *   - Must be called with interrupts disabled
+ *
+ * @note this operation is taken as an atomic operation of the update of SP.
+ *       Since the local irq is disabled, it's okay to assume that the stack
+ *       will not be modified meanwhile.
  */
 void rt_sched_post_ctx_switch(struct rt_thread *thread)
 {
@@ -1075,6 +1204,21 @@ void rt_sched_post_ctx_switch(struct rt_thread *thread)
 
 static volatile int _critical_error_occurred = 0;
 
+/**
+ * @brief Safely exit critical section with level checking
+ *
+ * @param critical_level The expected critical level to match
+ *
+ * @details This function provides a safe way to exit critical sections by:
+ *   - Verifying the current critical level matches the expected level
+ *   - If mismatch detected (debug build only):
+ *     * Prints error message with current and expected levels
+ *     * Triggers backtrace for debugging
+ *     * Enters infinite loop to halt execution
+ *   - Always calls rt_exit_critical() to ensure critical section is exited
+ *
+ * @note This is primarily used for debugging critical section mismatches.
+ */
 void rt_exit_critical_safe(rt_base_t critical_level)
 {
     struct rt_cpu *pcpu = rt_cpu_self();
@@ -1100,6 +1244,14 @@ void rt_exit_critical_safe(rt_base_t critical_level)
 
 #else /* !RT_DEBUGING_CRITICAL */
 
+/**
+ * @brief Safely exit critical section (non-debug version)
+ *
+ * @param critical_level The expected critical level (unused in non-debug build)
+ *
+ * @details This is the non-debug version that simply calls rt_exit_critical().
+ *          The critical_level parameter is ignored in this implementation.
+ */
 void rt_exit_critical_safe(rt_base_t critical_level)
 {
     RT_UNUSED(critical_level);
@@ -1122,7 +1274,20 @@ RTM_EXPORT(rt_exit_critical_safe);
 #endif /* ARCH_USING_HW_THREAD_SELF */
 
 /**
- * @brief This function will lock the thread scheduler.
+ * @brief Enter a critical section and lock the scheduler
+ *
+ * @return The critical level after entering (nesting count)
+ *         Returns -RT_EINVAL if scheduler is unavailable
+ *
+ * @details This function:
+ *   - Disables interrupts to ensure atomic operation
+ *   - Gets current thread context
+ *   - Increments critical section nesting counter
+ *   - Returns the new nesting level
+ *   - Handles both hardware-assisted and software thread context cases
+ *
+ * @note Must be paired with rt_exit_critical()
+ *       Can be nested, each call must have matching exit call
  */
 rt_base_t rt_enter_critical(void)
 {
@@ -1162,7 +1327,21 @@ rt_base_t rt_enter_critical(void)
 RTM_EXPORT(rt_enter_critical);
 
 /**
- * @brief This function will unlock the thread scheduler.
+ * @brief Exit a critical section and unlock the scheduler
+ *
+ * @details This function performs the following operations:
+ *   - Gets current thread context (using hardware-assisted or software method)
+ *   - Decrements critical section nesting counter
+ *   - If nesting level reaches 0:
+ *     * Checks if rescheduling is needed
+ *     * Clears critical switch flag
+ *     * Performs rescheduling if needed
+ *   - Verifies critical section nesting is valid (debug assertion)
+ *   - Restores interrupt state
+ *
+ * @note Must be called in pair with rt_enter_critical()
+ *       Handles both hardware-assisted and software thread context cases
+ *       May trigger rescheduling if conditions met
  */
 void rt_exit_critical(void)
 {
@@ -1245,6 +1424,30 @@ rt_uint16_t rt_critical_level(void)
 }
 RTM_EXPORT(rt_critical_level);
 
+/**
+ * @brief Bind a thread to a specific CPU core
+ *
+ * @param thread The thread to be bound
+ * @param cpu The target CPU core index (RT_CPUS_NR for no binding)
+ *
+ * @return rt_err_t
+ *   - RT_EOK: Operation successful
+ *
+ * @details This function handles thread-CPU binding with the following logic:
+ *   - If thread is READY:
+ *     * Removes from current ready queue
+ *     * Updates bind CPU information
+ *     * Inserts to new ready queue
+ *     * Triggers rescheduling if needed
+ *   - If thread is RUNNING:
+ *     * Updates bind CPU information
+ *     * Sends IPI to target CPU if binding changed
+ *     * Triggers rescheduling if needed
+ *   - For other states, just updates bind CPU info
+ *
+ * @note Caller must ensure scheduler is not locked before calling
+ *       This function will acquire scheduler lock internally
+ */
 rt_err_t rt_sched_thread_bind_cpu(struct rt_thread *thread, int cpu)
 {
     rt_sched_lock_level_t slvl;
@@ -1329,4 +1532,4 @@ rt_err_t rt_sched_thread_bind_cpu(struct rt_thread *thread, int cpu)
 }
 
 /**@}*/
-/**@endcond*/
+/**@endcond*/
\ No newline at end of file
diff --git a/src/scheduler_up.c b/src/scheduler_up.c
index 95e3cc7fb6..9e7b6f67f0 100644
--- a/src/scheduler_up.c
+++ b/src/scheduler_up.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2006-2023, RT-Thread Development Team
+ * Copyright (c) 2006-2025 RT-Thread Development Team
  *
  * SPDX-License-Identifier: Apache-2.0
  *
@@ -108,6 +108,23 @@ static struct rt_thread* _scheduler_get_highest_priority_thread(rt_ubase_t *high
     return highest_priority_thread;
 }
 
+/**
+ * @brief Lock the scheduler and save the interrupt level
+ *
+ * @param plvl Pointer to store the interrupt level before locking
+ *
+ * @return rt_err_t
+ *   - RT_EOK on success
+ *   - -RT_EINVAL if plvl is NULL
+ *
+ * @details This function:
+ *   - Disables interrupts to prevent preemption
+ *   - Saves the previous interrupt level in plvl
+ *   - Must be paired with rt_sched_unlock() to restore interrupts
+ *
+ * @note The lock is implemented by disabling interrupts
+ *       Caller must ensure plvl is valid
+ */
 rt_err_t rt_sched_lock(rt_sched_lock_level_t *plvl)
 {
     rt_base_t level;
@@ -120,6 +137,19 @@ rt_err_t rt_sched_lock(rt_sched_lock_level_t *plvl)
     return RT_EOK;
 }
 
+/**
+ * @brief Unlock the scheduler and restore the interrupt level
+ *
+ * @param level The interrupt level to restore (previously saved by rt_sched_lock)
+ * @return rt_err_t Always returns RT_EOK
+ *
+ * @details This function:
+ *   - Restores the interrupt level that was saved when locking the scheduler
+ *   - Must be called to match each rt_sched_lock() call
+ *
+ * @note Must be called with the same interrupt level that was saved by rt_sched_lock()
+ *       Should not be called without a corresponding rt_sched_lock() first
+ */
 rt_err_t rt_sched_unlock(rt_sched_lock_level_t level)
 {
     rt_hw_interrupt_enable(level);
@@ -127,6 +157,17 @@ rt_err_t rt_sched_unlock(rt_sched_lock_level_t level)
     return RT_EOK;
 }
 
+/**
+ * @brief Unlock scheduler and trigger a reschedule if needed
+ *
+ * @param level The interrupt level to restore (previously saved by rt_sched_lock)
+ * @return rt_err_t Always returns RT_EOK
+ *
+ * @details This function:
+ *   - Restores the interrupt level that was saved when locking the scheduler
+ *   - Triggers a reschedule if the scheduler is available (rt_thread_self() != NULL)
+ *   - Combines the functionality of rt_sched_unlock() and rt_schedule()
+ */
 rt_err_t rt_sched_unlock_n_resched(rt_sched_lock_level_t level)
 {
     if (rt_thread_self())
@@ -140,7 +181,16 @@ rt_err_t rt_sched_unlock_n_resched(rt_sched_lock_level_t level)
 }
 
 /**
- * @brief This function will initialize the system scheduler.
+ * @brief Initialize the system scheduler for single-core systems
+ *
+ * @details This function performs the following initialization tasks:
+ *   - Resets the scheduler lock nest counter to 0
+ *   - Initializes the priority table for all priority levels
+ *   - Clears the ready priority group bitmap
+ *   - For systems with >32 priority levels, initializes the ready table
+ *
+ * @note This function must be called before any thread scheduling can occur.
+ *       It prepares the scheduler data structures for single-core operation
  */
 void rt_system_scheduler_init(void)
 {
@@ -165,8 +215,17 @@ void rt_system_scheduler_init(void)
 }
 
 /**
- * @brief This function will startup the scheduler. It will select one thread
- *        with the highest priority level, then switch to it.
+ * @brief Start the system scheduler and switch to the highest priority thread
+ *
+ * @details This function:
+ *   - Gets the highest priority ready thread using _scheduler_get_highest_priority_thread()
+ *   - Sets it as the current thread for the CPU
+ *   - Removes the thread from ready queue and sets its status to RUNNING
+ *   - Performs a context switch to the selected thread using rt_hw_context_switch_to()
+ *
+ * @note This function does not return as it switches to the first thread to run.
+ *       Must be called after rt_system_scheduler_init().
+ *       The selected thread will begin execution immediately
  */
 void rt_system_scheduler_start(void)
 {
@@ -195,8 +254,18 @@ void rt_system_scheduler_start(void)
 /**@{*/
 
 /**
- * @brief This function will perform scheduling once. It will select one thread
- *        with the highest priority, and switch to it immediately.
+ * @brief Perform thread scheduling once. Select the highest priority thread and switch to it.
+ *
+ * @details This function:
+ *   - Disables interrupts to prevent preemption during scheduling
+ *   - Checks if scheduler is enabled (lock_nest == 0)
+ *   - Gets the highest priority ready thread
+ *   - Determines if current thread should continue running or be preempted
+ *   - Performs context switch if needed:
+ *     * From current thread to new thread (normal case)
+ *     * Handles special cases like interrupt context switches
+ *   - Manages thread states (READY/RUNNING) and priority queues
+ *   - Handles thread yield flags and signal processing
  */
 void rt_schedule(void)
 {
@@ -326,7 +395,24 @@ __exit:
     return;
 }
 
-/* Normally, there isn't anyone racing with us so this operation is lockless */
+/**
+ * @brief Initialize thread scheduling attributes for startup
+ *
+ * @param thread The thread to be initialized
+ *
+ * @details This function:
+ *   - For systems with >32 priority levels:
+ *     * Sets the thread's priority group number (5 bits)
+ *     * Creates number mask for the priority group
+ *     * Creates high mask for the specific priority (3 bits)
+ *   - For systems with <=32 priority levels:
+ *     * Creates a simple number mask for the priority
+ *   - Sets thread state to SUSPEND to prepare for later activation
+ *
+ * @note This function must be called before a thread can be scheduled.
+ *       It prepares the thread's priority-related data structures.
+ *       Normally, there isn't anyone racing with us so this operation is lockless
+ */
 void rt_sched_thread_startup(struct rt_thread *thread)
 {
 #if RT_THREAD_PRIORITY_MAX > 32
@@ -341,6 +427,19 @@ void rt_sched_thread_startup(struct rt_thread *thread)
     RT_SCHED_CTX(thread).stat = RT_THREAD_SUSPEND;
 }
 
+/**
+ * @brief Initialize thread's scheduling private data
+ *
+ * @param thread Pointer to the thread control block
+ * @param tick Initial time slice value for the thread
+ * @param priority Initial priority of the thread
+ *
+ * @details This function:
+ *   - Initializes the thread's list node
+ *   - Sets initial and current priority (must be < RT_THREAD_PRIORITY_MAX)
+ *   - Initializes priority masks (number_mask, number, high_mask for >32 priorities)
+ *   - Sets initial and remaining time slice ticks
+ */
 void rt_sched_thread_init_priv(struct rt_thread *thread, rt_uint32_t tick, rt_uint8_t priority)
 {
     rt_list_init(&RT_THREAD_LIST_NODE(thread));
@@ -458,6 +557,22 @@ void rt_sched_remove_thread(struct rt_thread *thread)
 
 static volatile int _critical_error_occurred = 0;
 
+/**
+ * @brief Safely exit critical section with level checking
+ *
+ * @param critical_level The expected critical level to match current lock nest
+ *
+ * @details This function:
+ *   - Disables interrupts to prevent preemption during check
+ *   - Verifies the provided critical_level matches current rt_scheduler_lock_nest
+ *   - If mismatch detected (debug mode only):
+ *     * Sets error flag
+ *     * Prints debug information including backtrace
+ *     * Enters infinite loop to halt system
+ *   - Always calls rt_exit_critical() to perform actual exit
+ *
+ * @note This is a debug version that adds safety checks for critical section exit.
+ */
 void rt_exit_critical_safe(rt_base_t critical_level)
 {
     rt_base_t level;
@@ -487,6 +602,14 @@ void rt_exit_critical_safe(rt_base_t critical_level)
 
 #else /* !RT_DEBUGING_CRITICAL */
 
+/**
+ * @brief Safely exit critical section (non-debug version)
+ *
+ * @param critical_level The expected critical level (unused in non-debug build)
+ *
+ * @details This is the non-debug version that simply calls rt_exit_critical().
+ *          The critical_level parameter is ignored in this implementation.
+ */
 void rt_exit_critical_safe(rt_base_t critical_level)
 {
     rt_exit_critical();
@@ -496,7 +619,19 @@ void rt_exit_critical_safe(rt_base_t critical_level)
 RTM_EXPORT(rt_exit_critical_safe);
 
 /**
- * @brief This function will lock the thread scheduler.
+ * @brief Enter critical section and lock the scheduler
+ *
+ * @return rt_base_t The current critical level (nesting count)
+ *
+ * @details This function:
+ *   - Disables interrupts to prevent preemption
+ *   - Increments the scheduler lock nesting count
+ *   - Returns the new nesting count as critical level
+ *   - Re-enables interrupts while maintaining the lock
+ *
+ * @note The nesting count can go up to RT_UINT16_MAX.
+ *       Must be paired with rt_exit_critical().
+ *       Interrupts are only disabled during the lock operation.
  */
 rt_base_t rt_enter_critical(void)
 {
@@ -521,7 +656,20 @@ rt_base_t rt_enter_critical(void)
 RTM_EXPORT(rt_enter_critical);
 
 /**
- * @brief This function will unlock the thread scheduler.
+ * @brief Exit critical section and unlock scheduler
+ *
+ * @details This function:
+ *   - Decrements the scheduler lock nesting count
+ *   - If nesting count reaches zero:
+ *     * Resets the nesting count
+ *     * Re-enables interrupts
+ *     * Triggers a scheduler run if current thread exists
+ *   - If nesting count still positive:
+ *     * Just re-enables interrupts while maintaining lock
+ *
+ * @note Must be paired with rt_enter_critical().
+ *       Interrupts are only disabled during the lock operation.
+ *       Scheduling only occurs when fully unlocked (nest=0)
  */
 void rt_exit_critical(void)
 {
@@ -568,4 +716,4 @@ rt_err_t rt_sched_thread_bind_cpu(struct rt_thread *thread, int cpu)
 }
 
 /**@}*/
-/**@endcond*/
+/**@endcond*/
\ No newline at end of file