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36 * https://github.com/halayli/lthread which carrys the following license.
38 * Copyright (C) 2012, Hasan Alayli <halayli@gmail.com>
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41 * modification, are permitted provided that the following conditions
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58 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
66 * @b EXPERIMENTAL: this API may change without prior notice
68 * This file contains the public API for the L-thread subsystem
70 * The L_thread subsystem provides a simple cooperative scheduler to
71 * enable arbitrary functions to run as cooperative threads within a
74 * The subsystem provides a P-thread like API that is intended to assist in
75 * reuse of legacy code written for POSIX p_threads.
77 * The L-thread subsystem relies on cooperative multitasking, as such
78 * an L-thread must possess frequent rescheduling points. Often these
79 * rescheduling points are provided transparently when the application
80 * invokes an L-thread API.
82 * In some applications it is possible that the program may enter a loop the
83 * exit condition for which depends on the action of another thread or a
84 * response from hardware. In such a case it is necessary to yield the thread
85 * periodically in the loop body, to allow other threads an opportunity to
86 * run. This can be done by inserting a call to lthread_yield() or
87 * lthread_sleep(n) in the body of the loop.
89 * If the application makes expensive / blocking system calls or does other
90 * work that would take an inordinate amount of time to complete, this will
91 * stall the cooperative scheduler resulting in very poor performance.
93 * In such cases an L-thread can be migrated temporarily to another scheduler
94 * running in a different P-thread on another core. When the expensive or
95 * blocking operation is completed it can be migrated back to the original
96 * scheduler. In this way other threads can continue to run on the original
97 * scheduler and will be completely unaffected by the blocking behaviour.
98 * To migrate an L-thread to another scheduler the API lthread_set_affinity()
101 * If L-threads that share data are running on the same core it is possible
102 * to design programs where mutual exclusion mechanisms to protect shared data
103 * can be avoided. This is due to the fact that the cooperative threads cannot
104 * preempt each other.
106 * There are two cases where mutual exclusion mechanisms are necessary.
108 * a) Where the L-threads sharing data are running on different cores.
109 * b) Where code must yield while updating data shared with another thread.
111 * The L-thread subsystem provides a set of mutex APIs to help with such
112 * scenarios, however excessive reliance on on these will impact performance
113 * and is best avoided if possible.
115 * L-threads can synchronise using a fast condition variable implementation
116 * that supports signal and broadcast. An L-thread running on any core can
117 * wait on a condition.
119 * L-threads can have L-thread local storage with an API modelled on either the
120 * P-thread get/set specific API or using PER_LTHREAD macros modelled on the
121 * RTE_PER_LCORE macros. Alternatively a simple user data pointer may be set
122 * and retrieved from a thread.
132 #include <sys/socket.h>
134 #include <netinet/in.h>
136 #include <rte_cycles.h>
141 struct lthread_mutex;
143 struct lthread_condattr;
144 struct lthread_mutexattr;
146 typedef void (*lthread_func_t) (void *);
149 * Define the size of stack for an lthread
150 * Then this is the size that will be allocated on lthread creation
151 * This is a fixed size and will not grow.
153 #define LTHREAD_MAX_STACK_SIZE (1024*64)
156 * Define the maximum number of TLS keys that can be created
159 #define LTHREAD_MAX_KEYS 1024
162 * Define the maximum number of attempts to destroy an lthread's
163 * TLS data on thread exit
165 #define LTHREAD_DESTRUCTOR_ITERATIONS 4
169 * Define the maximum number of lcores that will support lthreads
171 #define LTHREAD_MAX_LCORES RTE_MAX_LCORE
174 * How many lthread objects to pre-allocate as the system grows
175 * applies to lthreads + stacks, TLS, mutexs, cond vars.
177 * @see _lthread_alloc()
179 * @see _mutex_alloc()
182 #define LTHREAD_PREALLOC 100
185 * Set the number of schedulers in the system.
187 * This function may optionally be called before starting schedulers.
189 * If the number of schedulers is not set, or set to 0 then each scheduler
190 * will begin scheduling lthreads immediately it is started.
192 * If the number of schedulers is set to greater than 0, then each scheduler
193 * will wait until all schedulers have started before beginning to schedule
196 * If an application wishes to have threads migrate between cores using
197 * lthread_set_affinity(), or join threads running on other cores using
198 * lthread_join(), then it is prudent to set the number of schedulers to ensure
199 * that all schedulers are initialised beforehand.
202 * the number of schedulers in the system
204 * the number of schedulers in the system
206 int lthread_num_schedulers_set(int num);
209 * Return the number of schedulers currently running
211 * the number of schedulers in the system
213 int lthread_active_schedulers(void);
216 * Shutdown the specified scheduler
218 * This function tells the specified scheduler to
219 * exit if/when there is no more work to do.
221 * Note that although the scheduler will stop
222 * resources are not freed.
225 * The lcore of the scheduler to shutdown
230 void lthread_scheduler_shutdown(unsigned lcore);
233 * Shutdown all schedulers
235 * This function tells all schedulers including the current scheduler to
236 * exit if/when there is no more work to do.
238 * Note that although the schedulers will stop
239 * resources are not freed.
244 void lthread_scheduler_shutdown_all(void);
247 * Run the lthread scheduler
249 * Runs the lthread scheduler.
250 * This function returns only if/when all lthreads have exited.
251 * This function must be the main loop of an EAL thread.
257 void lthread_run(void);
262 * Creates an lthread and places it in the ready queue on a particular
265 * If no scheduler exists yet on the curret lcore then one is created.
268 * Pointer to an lthread pointer that will be initialized
270 * the lcore the thread should be started on or the current clore
271 * -1 the current lcore
272 * 0 - LTHREAD_MAX_LCORES any other lcore
273 * @param lthread_func
274 * Pointer to the function the for the thread to run
276 * Pointer to args that will be passed to the thread
280 * EAGAIN no resources available
281 * EINVAL NULL thread or function pointer, or lcore_id out of range
284 lthread_create(struct lthread **new_lt,
285 int lcore, lthread_func_t func, void *arg);
290 * Cancels an lthread and causes it to be terminated
291 * If the lthread is detached it will be freed immediately
292 * otherwise its resources will not be released until it is joined.
295 * Pointer to an lthread that will be cancelled
299 * EINVAL thread was NULL
301 int lthread_cancel(struct lthread *lt);
306 * Joins the current thread with the specified lthread, and waits for that
308 * Passes an optional pointer to collect returned data.
311 * Pointer to the lthread to be joined
313 * Pointer to pointer to collect returned data
317 * EINVAL lthread could not be joined.
319 int lthread_join(struct lthread *lt, void **ptr);
324 * Detaches the current thread
325 * On exit a detached lthread will be freed immediately and will not wait
326 * to be joined. The default state for a thread is not detached.
331 void lthread_detach(void);
336 * Terminate the current thread, optionally return data.
337 * The data may be collected by lthread_join()
339 * After calling this function the lthread will be suspended until it is
340 * joined. After it is joined then its resources will be freed.
343 * Pointer to pointer to data to be returned
348 void lthread_exit(void *val);
351 * Cause the current lthread to sleep for n nanoseconds
353 * The current thread will be suspended until the specified time has elapsed
354 * or has been exceeded.
356 * Execution will switch to the next lthread that is ready to run
359 * Number of nanoseconds to sleep
364 void lthread_sleep(uint64_t nsecs);
367 * Cause the current lthread to sleep for n cpu clock ticks
369 * The current thread will be suspended until the specified time has elapsed
370 * or has been exceeded.
372 * Execution will switch to the next lthread that is ready to run
375 * Number of clock ticks to sleep
380 void lthread_sleep_clks(uint64_t clks);
383 * Yield the current lthread
385 * The current thread will yield and execution will switch to the
386 * next lthread that is ready to run
391 void lthread_yield(void);
394 * Migrate the current thread to another scheduler
396 * This function migrates the current thread to another scheduler.
397 * Execution will switch to the next lthread that is ready to run on the
398 * current scheduler. The current thread will be resumed on the new scheduler.
401 * The lcore to migrate to
404 * 0 success we are now running on the specified core
405 * EINVAL the destination lcore was not valid
407 int lthread_set_affinity(unsigned lcore);
410 * Return the current lthread
412 * Returns the current lthread
415 * pointer to the current lthread
418 *lthread_current(void);
421 * Associate user data with an lthread
423 * This function sets a user data pointer in the current lthread
424 * The pointer can be retrieved with lthread_get_data()
425 * It is the users responsibility to allocate and free any data referenced
426 * by the user pointer.
429 * pointer to user data
434 void lthread_set_data(void *data);
437 * Get user data for the current lthread
439 * This function returns a user data pointer for the current lthread
440 * The pointer must first be set with lthread_set_data()
441 * It is the users responsibility to allocate and free any data referenced
442 * by the user pointer.
445 * pointer to user data
448 *lthread_get_data(void);
451 typedef void (*tls_destructor_func) (void *);
454 * Create a key for lthread TLS
456 * This function is modelled on pthread_key_create
457 * It creates a thread-specific data key visible to all lthreads on the
460 * Key values may be used to locate thread-specific data.
461 * The same key value may be used by different threads, the values bound
462 * to the key by lthread_setspecific() are maintained on a per-thread
463 * basis and persist for the life of the calling thread.
465 * An optional destructor function may be associated with each key value.
466 * At thread exit, if a key value has a non-NULL destructor pointer, and the
467 * thread has a non-NULL value associated with the key, the function pointed
468 * to is called with the current associated value as its sole argument.
471 * Pointer to the key to be created
473 * Pointer to destructor function
477 * EINVAL the key ptr was NULL
478 * EAGAIN no resources available
480 int lthread_key_create(unsigned int *key, tls_destructor_func destructor);
483 * Delete key for lthread TLS
485 * This function is modelled on pthread_key_delete().
486 * It deletes a thread-specific data key previously returned by
487 * lthread_key_create().
488 * The thread-specific data values associated with the key need not be NULL
489 * at the time that lthread_key_delete is called.
490 * It is the responsibility of the application to free any application
491 * storage or perform any cleanup actions for data structures related to the
492 * deleted key. This cleanup can be done either before or after
493 * lthread_key_delete is called.
496 * The key to be deleted
500 * EINVAL the key was invalid
502 int lthread_key_delete(unsigned int key);
507 * This function is modelled on pthread_get_specific().
508 * It returns the value currently bound to the specified key on behalf of the
509 * calling thread. Calling lthread_getspecific() with a key value not
510 * obtained from lthread_key_create() or after key has been deleted with
511 * lthread_key_delete() will result in undefined behaviour.
512 * lthread_getspecific() may be called from a thread-specific data destructor
516 * The key for which data is requested
519 * Pointer to the thread specific data associated with that key
520 * or NULL if no data has been set.
523 *lthread_getspecific(unsigned int key);
528 * This function is modelled on pthread_set_sepcific()
529 * It associates a thread-specific value with a key obtained via a previous
530 * call to lthread_key_create().
531 * Different threads may bind different values to the same key. These values
532 * are typically pointers to dynamically allocated memory that have been
533 * reserved by the calling thread. Calling lthread_setspecific with a key
534 * value not obtained from lthread_key_create or after the key has been
535 * deleted with lthread_key_delete will result in undefined behaviour.
538 * The key for which data is to be set
540 * Pointer to the user data
544 * EINVAL the key was invalid
547 int lthread_setspecific(unsigned int key, const void *value);
550 * The macros below provide an alternative mechanism to access lthread local
553 * The macros can be used to declare define and access per lthread local
554 * storage in a similar way to the RTE_PER_LCORE macros which control storage
557 * Memory for per lthread variables declared in this way is allocated when the
558 * lthread is created and a pointer to this memory is stored in the lthread.
559 * The per lthread variables are accessed via the pointer + the offset of the
560 * particular variable.
562 * The total size of per lthread storage, and the variable offsets are found by
563 * defining the variables in a unique global memory section, the start and end
564 * of which is known. This global memory section is used only in the
565 * computation of the addresses of the lthread variables, and is never actually
566 * used to store any data.
568 * Due to the fact that variables declared this way may be scattered across
569 * many files, the start and end of the section and variable offsets are only
570 * known after linking, thus the computation of section size and variable
571 * addresses is performed at run time.
573 * These macros are primarily provided to aid porting of code that makes use
574 * of the existing RTE_PER_LCORE macros. In principle it would be more efficient
575 * to gather all lthread local variables into a single structure and
576 * set/retrieve a pointer to that struct using the alternative
577 * lthread_data_set/get APIs.
579 * These macros are mutually exclusive with the lthread_data_set/get APIs.
580 * If you define storage using these macros then the lthread_data_set/get APIs
581 * will not perform as expected, the lthread_data_set API does nothing, and the
582 * lthread_data_get API returns the start of global section.
585 /* start and end of per lthread section */
586 extern char __start_per_lt;
587 extern char __stop_per_lt;
590 #define RTE_DEFINE_PER_LTHREAD(type, name) \
591 __typeof__(type)__attribute((section("per_lt"))) per_lt_##name
594 * Macro to declare an extern per lthread variable "var" of type "type"
596 #define RTE_DECLARE_PER_LTHREAD(type, name) \
597 extern __typeof__(type)__attribute((section("per_lt"))) per_lt_##name
600 * Read/write the per-lcore variable value
602 #define RTE_PER_LTHREAD(name) ((typeof(per_lt_##name) *)\
603 ((char *)lthread_get_data() +\
604 ((char *) &per_lt_##name - &__start_per_lt)))
609 * This function provides a mutual exclusion device, the need for which
610 * can normally be avoided in a cooperative multitasking environment.
611 * It is provided to aid porting of legacy code originally written for
612 * preemptive multitasking environments such as pthreads.
614 * A mutex may be unlocked (not owned by any thread), or locked (owned by
617 * A mutex can never be owned by more than one thread simultaneously.
618 * A thread attempting to lock a mutex that is already locked by another
619 * thread is suspended until the owning thread unlocks the mutex.
621 * lthread_mutex_init() initializes the mutex object pointed to by mutex
622 * Optional mutex attributes specified in mutexattr, are reserved for future
623 * use and are currently ignored.
625 * If a thread calls lthread_mutex_lock() on the mutex, then if the mutex
626 * is currently unlocked, it becomes locked and owned by the calling
627 * thread, and lthread_mutex_lock returns immediately. If the mutex is
628 * already locked by another thread, lthread_mutex_lock suspends the calling
629 * thread until the mutex is unlocked.
631 * lthread_mutex_trylock behaves identically to rte_thread_mutex_lock, except
632 * that it does not block the calling thread if the mutex is already locked
635 * lthread_mutex_unlock() unlocks the specified mutex. The mutex is assumed
636 * to be locked and owned by the calling thread.
638 * lthread_mutex_destroy() destroys a mutex object, freeing its resources.
639 * The mutex must be unlocked with nothing blocked on it before calling
640 * lthread_mutex_destroy.
643 * Optional pointer to string describing the mutex
645 * Pointer to pointer to the mutex to be initialized
647 * Pointer to attribute - unused reserved
651 * EINVAL mutex was not a valid pointer
652 * EAGAIN insufficient resources
656 lthread_mutex_init(char *name, struct lthread_mutex **mutex,
657 const struct lthread_mutexattr *attr);
662 * This function destroys the specified mutex freeing its resources.
663 * The mutex must be unlocked before calling lthread_mutex_destroy.
665 * @see lthread_mutex_init()
668 * Pointer to pointer to the mutex to be initialized
672 * EINVAL mutex was not an initialized mutex
673 * EBUSY mutex was still in use
675 int lthread_mutex_destroy(struct lthread_mutex *mutex);
680 * This function attempts to lock a mutex.
681 * If a thread calls lthread_mutex_lock() on the mutex, then if the mutex
682 * is currently unlocked, it becomes locked and owned by the calling
683 * thread, and lthread_mutex_lock returns immediately. If the mutex is
684 * already locked by another thread, lthread_mutex_lock suspends the calling
685 * thread until the mutex is unlocked.
687 * @see lthread_mutex_init()
690 * Pointer to pointer to the mutex to be initialized
694 * EINVAL mutex was not an initialized mutex
695 * EDEADLOCK the mutex was already owned by the calling thread
698 int lthread_mutex_lock(struct lthread_mutex *mutex);
701 * Try to lock a mutex
703 * This function attempts to lock a mutex.
704 * lthread_mutex_trylock behaves identically to rte_thread_mutex_lock, except
705 * that it does not block the calling thread if the mutex is already locked
709 * @see lthread_mutex_init()
712 * Pointer to pointer to the mutex to be initialized
716 * EINVAL mutex was not an initialized mutex
717 * EBUSY the mutex was already locked by another thread
719 int lthread_mutex_trylock(struct lthread_mutex *mutex);
724 * This function attempts to unlock the specified mutex. The mutex is assumed
725 * to be locked and owned by the calling thread.
727 * The oldest of any threads blocked on the mutex is made ready and may
728 * compete with any other running thread to gain the mutex, it fails it will
732 * Pointer to pointer to the mutex to be initialized
735 * 0 mutex was unlocked
736 * EINVAL mutex was not an initialized mutex
737 * EPERM the mutex was not owned by the calling thread
740 int lthread_mutex_unlock(struct lthread_mutex *mutex);
743 * Initialize a condition variable
745 * This function initializes a condition variable.
747 * Condition variables can be used to communicate changes in the state of data
748 * shared between threads.
750 * @see lthread_cond_wait()
753 * Pointer to optional string describing the condition variable
755 * Pointer to pointer to the condition variable to be initialized
757 * Pointer to optional attribute reserved for future use, currently ignored
761 * EINVAL cond was not a valid pointer
762 * EAGAIN insufficient resources
765 lthread_cond_init(char *name, struct lthread_cond **c,
766 const struct lthread_condattr *attr);
769 * Destroy a condition variable
771 * This function destroys a condition variable that was created with
772 * lthread_cond_init() and releases its resources.
775 * Pointer to pointer to the condition variable to be destroyed
779 * EBUSY condition variable was still in use
780 * EINVAL was not an initialised condition variable
782 int lthread_cond_destroy(struct lthread_cond *cond);
785 * Wait on a condition variable
787 * The function blocks the current thread waiting on the condition variable
788 * specified by cond. The waiting thread unblocks only after another thread
789 * calls lthread_cond_signal, or lthread_cond_broadcast, specifying the
790 * same condition variable.
793 * Pointer to pointer to the condition variable to be waited on
796 * reserved for future use
799 * 0 The condition was signalled ( Success )
800 * EINVAL was not a an initialised condition variable
802 int lthread_cond_wait(struct lthread_cond *c, uint64_t reserved);
805 * Signal a condition variable
807 * The function unblocks one thread waiting for the condition variable cond.
808 * If no threads are waiting on cond, the rte_lthead_cond_signal() function
812 * Pointer to pointer to the condition variable to be signalled
815 * 0 The condition was signalled ( Success )
816 * EINVAL was not a an initialised condition variable
818 int lthread_cond_signal(struct lthread_cond *c);
821 * Broadcast a condition variable
823 * The function unblocks all threads waiting for the condition variable cond.
824 * If no threads are waiting on cond, the rte_lthead_cond_broadcast()
825 * function has no effect.
828 * Pointer to pointer to the condition variable to be signalled
831 * 0 The condition was signalled ( Success )
832 * EINVAL was not a an initialised condition variable
834 int lthread_cond_broadcast(struct lthread_cond *c);
840 #endif /* LTHREAD_H */