From 5e8602c6e07bf66ab82402140577eb37c98bc560 Mon Sep 17 00:00:00 2001 From: ligr Date: Sat, 16 Nov 2024 13:20:53 +0800 Subject: [PATCH] [components/libc/posix][pthreads]add comments for thread APIs of pthread. --- components/libc/posix/pthreads/pthread.c | 539 ++++++++++++++++++++++- 1 file changed, 537 insertions(+), 2 deletions(-) diff --git a/components/libc/posix/pthreads/pthread.c b/components/libc/posix/pthreads/pthread.c index 0d7ed8f3d3..0ad8f9fecd 100644 --- a/components/libc/posix/pthreads/pthread.c +++ b/components/libc/posix/pthreads/pthread.c @@ -1,5 +1,5 @@ /* - * Copyright (c) 2006-2021, RT-Thread Development Team + * Copyright (c) 2006-2024 RT-Thread Development Team * * SPDX-License-Identifier: Apache-2.0 * @@ -213,6 +213,42 @@ static void pthread_entry_stub(void *parameter) } } +/** + * @brief Creates a new thread in a POSIX-compliant system. + * + * The `pthread_create` function initializes a new thread in the calling process. The new thread starts execution + * by invoking the function specified by the `start` parameter. The thread runs concurrently with the calling thread. + * + * @param[out] pid + * A pointer to a `pthread_t` object where the ID of the newly created thread will be stored. + * This ID can be used to refer to the thread in subsequent function calls. + * + * @param[in] attr + * A pointer to a `pthread_attr_t` object that specifies attributes for the new thread, or `NULL` for default attributes. + * Default attributes include: + * - Detached state: joinable. + * - Stack size: implementation-defined default. + * + * @param[in] start + * A pointer to the function that the new thread will execute. This function must have the following signature: + * `void *start(void *parameter)`. + * + * @param[in] parameter + * A pointer to data passed as an argument to the `start` function. The meaning and handling of this data is determined + * by the `start` function. + * + * @return + * Returns 0 on success. On failure, a non-zero error code is returned, indicating the error condition: + * - `EAGAIN`: Insufficient resources to create another thread. + * - `EINVAL`: Invalid attributes specified in `attr`. + * - `EPERM`: Insufficient permissions to set the requested attributes. + * + * @note + * It is the caller's responsibility to manage the lifetime of any resources associated with the new thread. + * If the thread is not detached, it must be joined using `pthread_join` to avoid resource leaks. + * + * @see pthread_join, pthread_exit, pthread_attr_init + */ int pthread_create(pthread_t *pid, const pthread_attr_t *attr, void *(*start)(void *), void *parameter) @@ -334,6 +370,28 @@ __exit: } RTM_EXPORT(pthread_create); +/** + * @brief Marks a thread as detached, allowing its resources to be automatically released upon termination. + * + * The `pthread_detach` function separates the specified thread from the calling thread. Once a thread is detached, + * its resources will be automatically reclaimed by the system upon the thread's termination. A detached thread cannot + * be joined using `pthread_join`. + * + * @param[in] thread + * The thread ID of the thread to be detached. This must be a valid thread ID returned by `pthread_create`. + * + * @return + * Returns 0 on success. On failure, an error code is returned: + * - `EINVAL`: The specified thread is not joinable or is already detached. + * - `ESRCH`: No thread with the specified ID could be found. + * + * @note + * - Detaching a thread allows it to run independently. Once detached, the thread's termination status cannot + * be retrieved, and it cannot be joined. + * - Threads can be created in a detached state using attributes set with `pthread_attr_setdetachstate`. + * + * @see pthread_create, pthread_join, pthread_attr_setdetachstate + */ int pthread_detach(pthread_t thread) { int ret = 0; @@ -378,6 +436,33 @@ __exit: } RTM_EXPORT(pthread_detach); +/** + * @brief Waits for the specified thread to terminate and retrieves its exit status. + * + * The `pthread_join` function blocks the calling thread until the specified thread terminates. + * If the specified thread has already terminated, it returns immediately. The exit status of + * the terminated thread can optionally be retrieved via the `value_ptr` parameter. + * + * @param[in] thread + * The thread ID of the thread to wait for. This must be a joinable thread created with `pthread_create`. + * + * @param[out] value_ptr + * A pointer to a location where the exit status of the terminated thread will be stored. + * If the thread terminated by calling `pthread_exit`, the value passed to `pthread_exit` + * will be stored at this location. If this parameter is `NULL`, the exit status is ignored. + * + * @return + * Returns 0 on success. On failure, an error code is returned: + * - `ESRCH`: The specified thread does not exist. + * - `EINVAL`: The specified thread is not joinable. + * - `EDEADLK`: A deadlock was detected (e.g., a thread tries to join itself). + * + * @note + * - Threads must not be detached to use `pthread_join`. + * - If `pthread_join` is not called for joinable threads, their resources are not released, leading to resource leaks. + * + * @see pthread_create, pthread_exit, pthread_detach + */ int pthread_join(pthread_t thread, void **value_ptr) { _pthread_data_t *ptd; @@ -390,7 +475,7 @@ int pthread_join(pthread_t thread, void **value_ptr) return EINVAL; /* invalid pthread id */ } - if (ptd && ptd->tid == rt_thread_self()) + if (ptd->tid == rt_thread_self()) { /* join self */ return EDEADLK; @@ -420,6 +505,25 @@ int pthread_join(pthread_t thread, void **value_ptr) } RTM_EXPORT(pthread_join); +/** + * @brief Returns the thread ID of the calling thread. + * + * The `pthread_self` function returns the thread ID of the calling thread. The thread ID is unique to the + * thread within a process and can be used to identify the calling thread in the context of multithreading. + * + * The value returned by `pthread_self` can be compared with the thread IDs of other threads to determine + * if two threads are the same. + * + * @return + * The thread ID of the calling thread. + * + * @note + * - The thread ID returned by `pthread_self` is not the same as the operating system's thread ID. + * - This function does not affect the calling thread's state or execution. + * - The thread ID returned by `pthread_self` is only meaningful in the context of the current process. + * + * @see pthread_create, pthread_equal, pthread_join + */ pthread_t pthread_self (void) { rt_thread_t tid; @@ -436,6 +540,32 @@ pthread_t pthread_self (void) } RTM_EXPORT(pthread_self); +/** + * @brief Retrieves the clock ID for the specified thread. + * + * The `pthread_getcpuclockid` function retrieves the clock ID associated with the CPU time used + * by the specified thread. + * + * @param[in] thread + * The thread whose CPU clock ID is to be retrieved. If the thread is the calling thread, + * the current thread's ID is used. + * + * @param[out] clock_id + * A pointer to a `clockid_t` variable that will be filled with the clock ID associated + * with the specified thread. + * + * @return + * - `0` on success. + * - `EINVAL` if the `thread` is not a valid thread identifier. + * - `ESRCH` if the specified thread does not exist. + * + * @note + * The clock returned by this function is specific to the thread and is different from the + * system-wide clock. It measures the CPU time consumed by the specified thread, not wall-clock + * time. The thread's CPU time can be obtained using `clock_gettime` with the returned `clock_id`. + * + * @see clock_gettime, pthread_create, pthread_self + */ int pthread_getcpuclockid(pthread_t thread, clockid_t *clock_id) { if(_pthread_get_data(thread) == NULL) @@ -449,12 +579,62 @@ int pthread_getcpuclockid(pthread_t thread, clockid_t *clock_id) } RTM_EXPORT(pthread_getcpuclockid); +/** + * @brief Retrieves the current concurrency level of the program. + * + * The `pthread_getconcurrency` function returns the current concurrency level of the program. + * This value represents the number of threads that can run concurrently in the program, + * based on the current settings of the pthreads library. It is used to help tune the behavior + * of thread scheduling in some systems. + * + * @return + * The current concurrency level of the program. + * - The value is an integer representing the number of threads that are permitted to run + * concurrently in the system, based on the library's current configuration. + * - A return value of `0` typically means that the system is using the default concurrency + * level, which may be determined automatically by the system or by thread creation behavior. + * + * @note + * - The behavior and meaning of concurrency levels can be implementation-dependent, + * and it may vary across different systems or environments. + * - The function is typically used for diagnostic purposes, and its behavior may not + * affect thread execution directly. + * + * @see pthread_setconcurrency + */ int pthread_getconcurrency(void) { return concurrency_level; } RTM_EXPORT(pthread_getconcurrency); +/** + * @brief Sets the concurrency level of the program. + * + * The `pthread_setconcurrency` function sets the number of threads that are allowed to run concurrently. + * The concurrency level defines the maximum number of threads that can be executed in parallel by the system. + * This is useful for tuning thread behavior and controlling system resource usage, especially in environments + * with limited resources (e.g., CPU cores). + * + * @param[in] new_level + * The new concurrency level to be set. This value represents the number of threads that can execute concurrently. + * - A value of `0` typically means that the system will automatically determine the concurrency level based on + * the system's configuration and available resources. + * - A non-zero value explicitly sets the maximum number of threads that can run concurrently. + * + * @return + * - `0` on success. + * - `EINVAL` if the `new_level` is invalid or if the system does not support this functionality. + * + * @note + * - The behavior of this function is system-dependent. Some systems may ignore the concurrency setting + * and automatically manage the concurrency based on available resources (e.g., CPU cores). + * - This function may not have any effect on systems that do not support concurrency settings at the library level. + * - The concurrency level controls thread scheduling policies and is intended to influence how the thread library + * manages threads, not how the operating system schedules them at the kernel level. + * + * @see pthread_getconcurrency + */ int pthread_setconcurrency(int new_level) { concurrency_level = new_level; @@ -463,6 +643,44 @@ int pthread_setconcurrency(int new_level) } RTM_EXPORT(pthread_setconcurrency); +/** + * @brief Retrieves the scheduling policy and parameters of a thread. + * + * The `pthread_getschedparam` function retrieves the scheduling policy and the scheduling parameters + * (such as priority) for the specified thread. This allows you to check the scheduling settings of a thread + * and can be useful for thread management and performance tuning in a multithreaded application. + * + * @param[in] thread + * The thread whose scheduling policy and parameters are to be retrieved. This is typically a valid + * `pthread_t` identifier of a thread that has already been created. + * + * @param[out] policy + * A pointer to an integer where the scheduling policy of the specified thread will be stored. The + * value will be one of the following constants defined in ``: + * - `SCHED_FIFO`: First-in, first-out scheduling policy. + * - `SCHED_RR`: Round-robin scheduling policy. + * - `SCHED_OTHER`: Default policy, which is typically used by non-realtime threads. + * - `SCHED_IDLE`: For idle threads (system-level threads that do minimal work). + * - `SCHED_BATCH`: For threads that should be scheduled with lower priority than interactive threads. + * - `SCHED_DEADLINE`: A policy that allows specifying real-time deadlines (on systems that support it). + * + * @param[out] param + * A pointer to a `struct sched_param` where the scheduling parameters (e.g., priority) for the thread + * will be stored. The `sched_param` structure typically contains: + * - `sched_priority`: The priority value associated with the thread's scheduling policy. + * + * @return + * - `0` on success. + * - `ESRCH` if the specified thread does not exist. + * - `EINVAL` if an invalid argument is provided, such as an invalid thread ID or null pointers for the policy or parameters. + * + * @note + * - This function retrieves the current scheduling settings for a thread. These settings can be used + * to monitor or adjust thread behavior. + * - The scheduling policies and priorities may be platform-dependent and subject to system configuration. + * + * @see pthread_setschedparam, sched_getparam + */ int pthread_getschedparam(pthread_t thread, int *policy, struct sched_param *param) { _pthread_data_t *ptd; @@ -475,6 +693,47 @@ int pthread_getschedparam(pthread_t thread, int *policy, struct sched_param *par } RTM_EXPORT(pthread_getschedparam); +/** + * @brief Sets the scheduling policy and parameters for a thread. + * + * The `pthread_setschedparam` function sets the scheduling policy and scheduling parameters (such as priority) + * for the specified thread. This allows you to control how the thread is scheduled by the operating system. + * It is useful for adjusting thread behavior, especially for real-time or performance-sensitive applications. + * + * @param[in] thread + * The thread whose scheduling policy and parameters are to be set. This is a valid `pthread_t` identifier. + * + * @param[in] policy + * The scheduling policy to be set for the thread. This can be one of the following values: + * - `SCHED_FIFO`: First-in, first-out scheduling policy, where threads are scheduled based on their arrival time. + * - `SCHED_RR`: Round-robin scheduling policy, where each thread is allocated a fixed time slice and scheduled cyclically. + * - `SCHED_OTHER`: Default policy for non-realtime threads. + * - `SCHED_IDLE`: For threads intended to run only when no other threads are runnable. + * - `SCHED_BATCH`: For threads that should run with lower priority than interactive threads. + * - `SCHED_DEADLINE`: For real-time threads that have a specified deadline (if supported). + * + * @param[in] param + * A pointer to a `struct sched_param`, which contains the scheduling parameters, typically the thread's priority. + * The `sched_priority` field is the most commonly used parameter, and it controls the thread's priority within + * the specified scheduling policy. + * + * @return + * - `0` on success. + * - `EINVAL` if an invalid policy or parameter is provided. + * - `ESRCH` if the specified thread does not exist. + * - `EPERM` if the caller does not have permission to modify the thread's scheduling attributes. + * + * @note + * - The `sched_param` structure's `sched_priority` field specifies the priority of the thread. The priority + * range depends on the policy used. For example, for `SCHED_FIFO` and `SCHED_RR`, higher priority values + * correspond to higher priority threads, while for `SCHED_OTHER`, priorities are not as strictly enforced. + * - Changing a thread's scheduling parameters may affect its execution behavior, including how it competes with + * other threads for CPU time. + * - The system may not allow you to modify scheduling parameters for all threads, depending on system configuration + * and privileges. + * + * @see pthread_getschedparam + */ int pthread_setschedparam(pthread_t thread, int policy, const struct sched_param *param) { _pthread_data_t *ptd; @@ -487,6 +746,35 @@ int pthread_setschedparam(pthread_t thread, int policy, const struct sched_param } RTM_EXPORT(pthread_setschedparam); +/** + * @brief Sets the scheduling priority for a thread. + * + * The `pthread_setschedprio` function adjusts the priority of the specified thread while leaving its + * scheduling policy unchanged. This is useful for fine-tuning thread behavior in multithreaded applications. + * + * @param[in] thread + * The thread whose scheduling priority is to be changed. This must be a valid `pthread_t` identifier. + * + * @param[in] prio + * The new scheduling priority for the thread. The priority must fall within the valid range for the + * thread's current scheduling policy, as defined by `sched_get_priority_min` and `sched_get_priority_max`. + * + * @return + * - `0` on success. + * - `EINVAL` if the specified priority is invalid for the thread's current scheduling policy. + * - `ESRCH` if the specified thread does not exist. + * - `EPERM` if the calling process lacks the necessary privileges to set the thread's priority. + * + * @note + * - Changing a thread's priority may require elevated privileges (e.g., root) on certain systems, especially + * for real-time priorities. + * - The priority range and behavior depend on the thread's current scheduling policy. For example: + * - `SCHED_FIFO` and `SCHED_RR`: Priorities are used for strict scheduling. + * - `SCHED_OTHER`: Priorities may have minimal or no effect. + * - The behavior of this function is platform-dependent and may vary between different operating systems. + * + * @see pthread_setschedparam, pthread_getschedparam + */ int pthread_setschedprio(pthread_t thread, int prio) { _pthread_data_t *ptd; @@ -500,6 +788,24 @@ int pthread_setschedprio(pthread_t thread, int prio) } RTM_EXPORT(pthread_setschedprio); +/** + * @brief Terminates the calling thread and optionally returns a value. + * + * The `pthread_exit` function terminates the calling thread. It can optionally provide an exit status that can be + * retrieved by other threads that join the calling thread using `pthread_join`. If the thread is detached, the + * exit status is ignored and the system automatically reclaims resources once the thread terminates. + * + * @param[in] value + * A pointer to a value that will be returned to any thread that calls `pthread_join` on this thread. + * If `NULL`, no value is returned. + * + * @note + * - This function does not terminate the process. It only terminates the calling thread. + * - If the calling thread is the main thread, `pthread_exit` allows other threads to continue execution. + * - If a thread terminates without calling `pthread_exit`, it returns control to the system when the thread's function ends. + * + * @see pthread_join, pthread_create + */ void pthread_exit(void *value) { _pthread_data_t *ptd; @@ -564,6 +870,33 @@ void pthread_exit(void *value) } RTM_EXPORT(pthread_exit); +/** + * @brief Executes a routine once in a multithreaded environment. + * + * The `pthread_once` function ensures that the specified initialization routine is executed exactly once, + * even if multiple threads attempt to execute it simultaneously. It is typically used for one-time + * initialization tasks in a multithreaded program. + * + * @param[in] once_control + * A pointer to a `pthread_once_t` control variable. The init_routine can only be excuted + * when (*once_control) is zero. + * + * @param[in] init_routine + * A pointer to the initialization routine to be executed. This routine takes no arguments and + * returns no value. It is guaranteed to be executed exactly once. + * + * @return + * - `0` on success. + * + * @note + * - The `pthread_once` function is thread-safe and guarantees that the `init_routine` is called only once. + * - The `once_control` variable must remain valid and should not be modified by the application after + * initialization. + * - If the initialization routine fails or encounters an error, it is the responsibility of the routine + * to handle it appropriately. + * + * @see pthread_mutex_lock, pthread_mutex_unlock + */ int pthread_once(pthread_once_t *once_control, void (*init_routine)(void)) { RT_ASSERT(once_control != RT_NULL); @@ -590,6 +923,35 @@ int pthread_atfork(void (*prepare)(void), void (*parent)(void), void (*child)(vo } RTM_EXPORT(pthread_atfork); +/** + * @brief Sends a signal to a specific thread. + * + * The `pthread_kill` function sends the specified signal to the target thread. This allows fine-grained + * control over signal handling in multithreaded applications. + * + * @param[in] thread + * The target thread to which the signal is sent. This is a valid `pthread_t` identifier. + * + * @param[in] sig + * The signal to be sent. This can be any valid signal, such as those defined in ``. For example: + * - `SIGTERM`: Request thread termination. + * - `SIGUSR1` or `SIGUSR2`: User-defined signals. + * - `0`: Used to check if the thread is still valid without sending a signal. + * + * @return + * - `0` on success. + * - `ESRCH` if the specified thread does not exist or is invalid. + * - `EINVAL` if the signal number `sig` is invalid. + * + * @note + * - The signal is delivered to the specified thread only if the thread has the appropriate signal handlers + * set up. Unhandled signals might result in the default action for that signal. + * - If `sig` is `0`, no signal is sent, but the function checks if the thread is valid and exists. + * - Signal handling behavior is shared across threads in a process. For example, blocking or ignoring a signal + * in one thread affects the entire process. + * + * @see pthread_sigmask, sigaction + */ int pthread_kill(pthread_t thread, int sig) { #ifdef RT_USING_SIGNALS @@ -616,12 +978,62 @@ int pthread_kill(pthread_t thread, int sig) RTM_EXPORT(pthread_kill); #ifdef RT_USING_SIGNALS +/** + * @brief Modifies or retrieves the signal mask of the calling thread. + * + * The `pthread_sigmask` function allows a thread to block, unblock, or examine the signals in its signal mask. + * Signals that are blocked are not delivered to the thread until they are unblocked. + * + * @param[in] how + * Specifies how the signal mask is modified. Possible values: + * - `SIG_BLOCK`: Add the signals in `set` to the current signal mask. + * - `SIG_UNBLOCK`: Remove the signals in `set` from the current signal mask. + * - `SIG_SETMASK`: Replace the current signal mask with the signals in `set`. + * + * @param[in] set + * A pointer to a `sigset_t` containing the signals to be modified in the mask. Can be `NULL` if no change is needed. + * + * @param[out] oset + * A pointer to a `sigset_t` where the previous signal mask will be stored. Can be `NULL` if the previous mask is not required. + * + * @return + * - `0` on success. + * + * @note + * - Signal masks are thread-specific in a multithreaded program. + * - The `pthread_sigmask` function is designed for multithreaded programs, whereas `sigprocmask` should not be used. + * - Blocking a signal prevents it from being delivered to the thread until unblocked. + * + * @see sigprocmask, sigaction, pthread_kill + */ int pthread_sigmask(int how, const sigset_t *set, sigset_t *oset) { return sigprocmask(how, set, oset); } #endif +/** + * @brief Unregisters a cleanup handler and optionally executes it. + * + * The `pthread_cleanup_pop` function unregisters a cleanup handler that was previously registered + * using `pthread_cleanup_push`. If the `execute` parameter is non-zero, the cleanup handler is executed + * at the point where the thread terminates or is canceled. + * + * If `execute` is zero, the handler is unregistered without being executed. This allows the handler + * to be removed from the cleanup stack without performing any actions. + * + * @param[in] execute + * If non-zero, the cleanup handler is executed when the thread terminates or is canceled. + * If zero, the handler is simply removed from the stack without executing it. + * + * @note + * - Cleanup handlers are executed in the reverse order of their registration (i.e., last-in, first-out). + * - It is important to use `pthread_cleanup_push` to register cleanup handlers and `pthread_cleanup_pop` + * to ensure they are properly unregistered and executed if needed. + * - This function should be paired with `pthread_cleanup_push` to manage cleanup handlers effectively. + * + * @see pthread_cleanup_push, pthread_exit, pthread_cancel + */ void pthread_cleanup_pop(int execute) { _pthread_data_t *ptd; @@ -651,6 +1063,33 @@ void pthread_cleanup_pop(int execute) } RTM_EXPORT(pthread_cleanup_pop); +/** + * @brief Registers a cleanup handler to be executed when the calling thread terminates. + * + * The `pthread_cleanup_push` function registers a cleanup handler that is executed when the calling thread + * is canceled or exits (either normally or via `pthread_exit`). The cleanup handler will be executed + * in the reverse order of their registration. + * + * The cleanup handler can be used to release resources such as memory or file descriptors when the thread + * is terminated, whether it terminates normally or is canceled. + * + * @param[in] routine + * A pointer to the cleanup handler function. The function must have the following signature: + * `void routine(void* arg);`. It is invoked when the thread terminates or is canceled. + * + * @param[in] arg + * A pointer to the argument that will be passed to the cleanup handler (`routine`). + * This allows the handler to perform actions with the passed argument. + * + * @note + * - The cleanup handler is automatically invoked when a thread terminates or is canceled. + * - The cleanup handlers are executed in the reverse order of their registration, similar to how + * destructors are executed in a stack-based fashion. + * - `pthread_cleanup_pop` must be called to unregister the cleanup handler. It ensures that the handler + * is only invoked during the thread's termination process. + * + * @see pthread_cleanup_pop, pthread_cancel, pthread_exit + */ void pthread_cleanup_push(void (*routine)(void *), void *arg) { _pthread_data_t *ptd; @@ -704,6 +1143,33 @@ RTM_EXPORT(pthread_cleanup_push); * functions are defined to be async-cancel safe. */ +/** + * @brief Sets the cancelability state of the calling thread. + * + * The `pthread_setcancelstate` function allows a thread to enable or disable its ability to be canceled + * by another thread. Cancelability determines if and when a thread responds to a cancellation request. + * + * @param[in] state + * The new cancelability state for the calling thread. Possible values: + * - `PTHREAD_CANCEL_ENABLE`: The thread can be canceled. + * - `PTHREAD_CANCEL_DISABLE`: The thread cannot be canceled. + * + * @param[out] oldstate + * A pointer to an integer where the previous cancelability state will be stored. Can be `NULL` if + * the previous state is not needed. + * + * @return + * - `0` on success. + * - `EINVAL` if the `state` is not a valid cancelability state. + * + * @note + * - The cancelability state affects how the thread responds to cancellation requests: + * - In the `PTHREAD_CANCEL_DISABLE` state, cancellation requests are held pending until the state is changed to `PTHREAD_CANCEL_ENABLE`. + * - Cancelability is distinct from the cancelability type, which controls the timing of cancellation (deferred or asynchronous). + * - By default, threads are created with `PTHREAD_CANCEL_ENABLE`. + * + * @see pthread_cancel, pthread_setcanceltype + */ int pthread_setcancelstate(int state, int *oldstate) { _pthread_data_t *ptd; @@ -727,6 +1193,34 @@ int pthread_setcancelstate(int state, int *oldstate) } RTM_EXPORT(pthread_setcancelstate); +/** + * @brief Sets the cancellation type of the calling thread. + * + * The `pthread_setcanceltype` function allows a thread to specify when it should respond to + * a cancellation request. The cancellation type can be set to deferred or asynchronous. + * + * @param[in] type + * The new cancellation type for the calling thread. Possible values: + * - `PTHREAD_CANCEL_DEFERRED`: Cancellation occurs at cancellation points (default behavior). + * - `PTHREAD_CANCEL_ASYNCHRONOUS`: Cancellation occurs immediately when a request is received. + * + * @param[out] oldtype + * A pointer to an integer where the previous cancellation type will be stored. Can be `NULL` + * if the previous type is not required. + * + * @return + * - `0` on success. + * - `EINVAL` if the `type` is not a valid cancellation type. + * + * @note + * - The cancellation type determines when a thread processes a cancellation request: + * - **Deferred**: The thread responds to cancellation only at well-defined cancellation points. + * - **Asynchronous**: The thread can be canceled immediately, which may lead to resource inconsistencies. + * - By default, threads use `PTHREAD_CANCEL_DEFERRED`. + * - Asynchronous cancellation should be used cautiously as it can interrupt a thread at any point. + * + * @see pthread_cancel, pthread_setcancelstate, pthread_testcancel + */ int pthread_setcanceltype(int type, int *oldtype) { _pthread_data_t *ptd; @@ -748,6 +1242,23 @@ int pthread_setcanceltype(int type, int *oldtype) } RTM_EXPORT(pthread_setcanceltype); +/** + * @brief Explicitly checks for pending cancellation requests in the calling thread. + * + * The `pthread_testcancel` function allows a thread to determine if it has a pending + * cancellation request. If a cancellation request is pending and the thread's cancelability + * state is set to `PTHREAD_CANCEL_ENABLE`, the thread will terminate immediately. + * + * @note + * - This function is a cancellation point, meaning it checks for cancellation and responds if applicable. + * - If the thread's cancelability state is `PTHREAD_CANCEL_DISABLE`, the function has no effect. + * - The thread will invoke any cleanup handlers registered with `pthread_cleanup_push` before termination. + * + * @return + * This function does not return if a cancellation is performed. Otherwise, it returns normally. + * + * @see pthread_setcancelstate, pthread_setcanceltype, pthread_cancel + */ void pthread_testcancel(void) { int cancel = 0; @@ -766,6 +1277,30 @@ void pthread_testcancel(void) } RTM_EXPORT(pthread_testcancel); +/** + * @brief Sends a cancellation request to a specified thread. + * + * The `pthread_cancel` function requests the cancellation of the thread identified by `thread`. + * The actual response to the request depends on the target thread's cancelability state and type. + * + * @param[in] thread + * The identifier of the thread to be canceled. + * + * @return + * - `0` on success. + * - `EINVAL` if the specified thread does not exist. + * + * @note + * - Cancellation is an asynchronous mechanism. The thread may not terminate immediately or at all + * if its cancelability state is set to `PTHREAD_CANCEL_DISABLE`. + * - If the thread is cancelable and terminates, it invokes cleanup handlers registered with + * `pthread_cleanup_push` before termination. + * - The thread's cancellation type determines when it processes the cancellation request: + * - `PTHREAD_CANCEL_DEFERRED` (default): At specific cancellation points. + * - `PTHREAD_CANCEL_ASYNCHRONOUS`: Immediately upon receipt of the request. + * + * @see pthread_setcancelstate, pthread_setcanceltype, pthread_testcancel + */ int pthread_cancel(pthread_t thread) { _pthread_data_t *ptd;