1/*
2 Simple DirectMedia Layer
3 Copyright (C) 1997-2024 Sam Lantinga <slouken@libsdl.org>
4
5 This software is provided 'as-is', without any express or implied
6 warranty. In no event will the authors be held liable for any damages
7 arising from the use of this software.
8
9 Permission is granted to anyone to use this software for any purpose,
10 including commercial applications, and to alter it and redistribute it
11 freely, subject to the following restrictions:
12
13 1. The origin of this software must not be misrepresented; you must not
14 claim that you wrote the original software. If you use this software
15 in a product, an acknowledgment in the product documentation would be
16 appreciated but is not required.
17 2. Altered source versions must be plainly marked as such, and must not be
18 misrepresented as being the original software.
19 3. This notice may not be removed or altered from any source distribution.
20*/
21
22#ifndef SDL_mutex_h_
23#define SDL_mutex_h_
24
25/**
26 * \file SDL_mutex.h
27 *
28 * Functions to provide thread synchronization primitives.
29 */
30
31#include "SDL_stdinc.h"
32#include "SDL_error.h"
33
34/******************************************************************************/
35/* Enable thread safety attributes only with clang.
36 * The attributes can be safely erased when compiling with other compilers.
37 */
38#if defined(SDL_THREAD_SAFETY_ANALYSIS) && \
39 defined(__clang__) && (!defined(SWIG))
40#define SDL_THREAD_ANNOTATION_ATTRIBUTE__(x) __attribute__((x))
41#else
42#define SDL_THREAD_ANNOTATION_ATTRIBUTE__(x) /* no-op */
43#endif
44
45#define SDL_CAPABILITY(x) \
46 SDL_THREAD_ANNOTATION_ATTRIBUTE__(capability(x))
47
48#define SDL_SCOPED_CAPABILITY \
49 SDL_THREAD_ANNOTATION_ATTRIBUTE__(scoped_lockable)
50
51#define SDL_GUARDED_BY(x) \
52 SDL_THREAD_ANNOTATION_ATTRIBUTE__(guarded_by(x))
53
54#define SDL_PT_GUARDED_BY(x) \
55 SDL_THREAD_ANNOTATION_ATTRIBUTE__(pt_guarded_by(x))
56
57#define SDL_ACQUIRED_BEFORE(x) \
58 SDL_THREAD_ANNOTATION_ATTRIBUTE__(acquired_before(x))
59
60#define SDL_ACQUIRED_AFTER(x) \
61 SDL_THREAD_ANNOTATION_ATTRIBUTE__(acquired_after(x))
62
63#define SDL_REQUIRES(x) \
64 SDL_THREAD_ANNOTATION_ATTRIBUTE__(requires_capability(x))
65
66#define SDL_REQUIRES_SHARED(x) \
67 SDL_THREAD_ANNOTATION_ATTRIBUTE__(requires_shared_capability(x))
68
69#define SDL_ACQUIRE(x) \
70 SDL_THREAD_ANNOTATION_ATTRIBUTE__(acquire_capability(x))
71
72#define SDL_ACQUIRE_SHARED(x) \
73 SDL_THREAD_ANNOTATION_ATTRIBUTE__(acquire_shared_capability(x))
74
75#define SDL_RELEASE(x) \
76 SDL_THREAD_ANNOTATION_ATTRIBUTE__(release_capability(x))
77
78#define SDL_RELEASE_SHARED(x) \
79 SDL_THREAD_ANNOTATION_ATTRIBUTE__(release_shared_capability(x))
80
81#define SDL_RELEASE_GENERIC(x) \
82 SDL_THREAD_ANNOTATION_ATTRIBUTE__(release_generic_capability(x))
83
84#define SDL_TRY_ACQUIRE(x, y) \
85 SDL_THREAD_ANNOTATION_ATTRIBUTE__(try_acquire_capability(x, y))
86
87#define SDL_TRY_ACQUIRE_SHARED(x, y) \
88 SDL_THREAD_ANNOTATION_ATTRIBUTE__(try_acquire_shared_capability(x, y))
89
90#define SDL_EXCLUDES(x) \
91 SDL_THREAD_ANNOTATION_ATTRIBUTE__(locks_excluded(x))
92
93#define SDL_ASSERT_CAPABILITY(x) \
94 SDL_THREAD_ANNOTATION_ATTRIBUTE__(assert_capability(x))
95
96#define SDL_ASSERT_SHARED_CAPABILITY(x) \
97 SDL_THREAD_ANNOTATION_ATTRIBUTE__(assert_shared_capability(x))
98
99#define SDL_RETURN_CAPABILITY(x) \
100 SDL_THREAD_ANNOTATION_ATTRIBUTE__(lock_returned(x))
101
102#define SDL_NO_THREAD_SAFETY_ANALYSIS \
103 SDL_THREAD_ANNOTATION_ATTRIBUTE__(no_thread_safety_analysis)
104
105/******************************************************************************/
106
107
108#include "begin_code.h"
109/* Set up for C function definitions, even when using C++ */
110#ifdef __cplusplus
111extern "C" {
112#endif
113
114/**
115 * Synchronization functions which can time out return this value
116 * if they time out.
117 */
118#define SDL_MUTEX_TIMEDOUT 1
119
120/**
121 * This is the timeout value which corresponds to never time out.
122 */
123#define SDL_MUTEX_MAXWAIT (~(Uint32)0)
124
125
126/**
127 * \name Mutex functions
128 */
129/* @{ */
130
131/* The SDL mutex structure, defined in SDL_sysmutex.c */
132struct SDL_mutex;
133typedef struct SDL_mutex SDL_mutex;
134
135/**
136 * Create a new mutex.
137 *
138 * All newly-created mutexes begin in the _unlocked_ state.
139 *
140 * Calls to SDL_LockMutex() will not return while the mutex is locked by
141 * another thread. See SDL_TryLockMutex() to attempt to lock without blocking.
142 *
143 * SDL mutexes are reentrant.
144 *
145 * \returns the initialized and unlocked mutex or NULL on failure; call
146 * SDL_GetError() for more information.
147 *
148 * \since This function is available since SDL 2.0.0.
149 *
150 * \sa SDL_DestroyMutex
151 * \sa SDL_LockMutex
152 * \sa SDL_TryLockMutex
153 * \sa SDL_UnlockMutex
154 */
155extern DECLSPEC SDL_mutex *SDLCALL SDL_CreateMutex(void);
156
157/**
158 * Lock the mutex.
159 *
160 * This will block until the mutex is available, which is to say it is in the
161 * unlocked state and the OS has chosen the caller as the next thread to lock
162 * it. Of all threads waiting to lock the mutex, only one may do so at a time.
163 *
164 * It is legal for the owning thread to lock an already-locked mutex. It must
165 * unlock it the same number of times before it is actually made available for
166 * other threads in the system (this is known as a "recursive mutex").
167 *
168 * \param mutex the mutex to lock
169 * \return 0, or -1 on error.
170 *
171 * \since This function is available since SDL 2.0.0.
172 */
173extern DECLSPEC int SDLCALL SDL_LockMutex(SDL_mutex * mutex) SDL_ACQUIRE(mutex);
174#define SDL_mutexP(m) SDL_LockMutex(m)
175
176/**
177 * Try to lock a mutex without blocking.
178 *
179 * This works just like SDL_LockMutex(), but if the mutex is not available,
180 * this function returns `SDL_MUTEX_TIMEOUT` immediately.
181 *
182 * This technique is useful if you need exclusive access to a resource but
183 * don't want to wait for it, and will return to it to try again later.
184 *
185 * \param mutex the mutex to try to lock
186 * \returns 0, `SDL_MUTEX_TIMEDOUT`, or -1 on error; call SDL_GetError() for
187 * more information.
188 *
189 * \since This function is available since SDL 2.0.0.
190 *
191 * \sa SDL_CreateMutex
192 * \sa SDL_DestroyMutex
193 * \sa SDL_LockMutex
194 * \sa SDL_UnlockMutex
195 */
196extern DECLSPEC int SDLCALL SDL_TryLockMutex(SDL_mutex * mutex) SDL_TRY_ACQUIRE(0, mutex);
197
198/**
199 * Unlock the mutex.
200 *
201 * It is legal for the owning thread to lock an already-locked mutex. It must
202 * unlock it the same number of times before it is actually made available for
203 * other threads in the system (this is known as a "recursive mutex").
204 *
205 * It is an error to unlock a mutex that has not been locked by the current
206 * thread, and doing so results in undefined behavior.
207 *
208 * It is also an error to unlock a mutex that isn't locked at all.
209 *
210 * \param mutex the mutex to unlock.
211 * \returns 0, or -1 on error.
212 *
213 * \since This function is available since SDL 2.0.0.
214 */
215extern DECLSPEC int SDLCALL SDL_UnlockMutex(SDL_mutex * mutex) SDL_RELEASE(mutex);
216#define SDL_mutexV(m) SDL_UnlockMutex(m)
217
218/**
219 * Destroy a mutex created with SDL_CreateMutex().
220 *
221 * This function must be called on any mutex that is no longer needed. Failure
222 * to destroy a mutex will result in a system memory or resource leak. While
223 * it is safe to destroy a mutex that is _unlocked_, it is not safe to attempt
224 * to destroy a locked mutex, and may result in undefined behavior depending
225 * on the platform.
226 *
227 * \param mutex the mutex to destroy
228 *
229 * \since This function is available since SDL 2.0.0.
230 *
231 * \sa SDL_CreateMutex
232 * \sa SDL_LockMutex
233 * \sa SDL_TryLockMutex
234 * \sa SDL_UnlockMutex
235 */
236extern DECLSPEC void SDLCALL SDL_DestroyMutex(SDL_mutex * mutex);
237
238/* @} *//* Mutex functions */
239
240
241/**
242 * \name Semaphore functions
243 */
244/* @{ */
245
246/* The SDL semaphore structure, defined in SDL_syssem.c */
247struct SDL_semaphore;
248typedef struct SDL_semaphore SDL_sem;
249
250/**
251 * Create a semaphore.
252 *
253 * This function creates a new semaphore and initializes it with the value
254 * `initial_value`. Each wait operation on the semaphore will atomically
255 * decrement the semaphore value and potentially block if the semaphore value
256 * is 0. Each post operation will atomically increment the semaphore value and
257 * wake waiting threads and allow them to retry the wait operation.
258 *
259 * \param initial_value the starting value of the semaphore
260 * \returns a new semaphore or NULL on failure; call SDL_GetError() for more
261 * information.
262 *
263 * \since This function is available since SDL 2.0.0.
264 *
265 * \sa SDL_DestroySemaphore
266 * \sa SDL_SemPost
267 * \sa SDL_SemTryWait
268 * \sa SDL_SemValue
269 * \sa SDL_SemWait
270 * \sa SDL_SemWaitTimeout
271 */
272extern DECLSPEC SDL_sem *SDLCALL SDL_CreateSemaphore(Uint32 initial_value);
273
274/**
275 * Destroy a semaphore.
276 *
277 * It is not safe to destroy a semaphore if there are threads currently
278 * waiting on it.
279 *
280 * \param sem the semaphore to destroy
281 *
282 * \since This function is available since SDL 2.0.0.
283 *
284 * \sa SDL_CreateSemaphore
285 * \sa SDL_SemPost
286 * \sa SDL_SemTryWait
287 * \sa SDL_SemValue
288 * \sa SDL_SemWait
289 * \sa SDL_SemWaitTimeout
290 */
291extern DECLSPEC void SDLCALL SDL_DestroySemaphore(SDL_sem * sem);
292
293/**
294 * Wait until a semaphore has a positive value and then decrements it.
295 *
296 * This function suspends the calling thread until either the semaphore
297 * pointed to by `sem` has a positive value or the call is interrupted by a
298 * signal or error. If the call is successful it will atomically decrement the
299 * semaphore value.
300 *
301 * This function is the equivalent of calling SDL_SemWaitTimeout() with a time
302 * length of `SDL_MUTEX_MAXWAIT`.
303 *
304 * \param sem the semaphore wait on
305 * \returns 0 on success or a negative error code on failure; call
306 * SDL_GetError() for more information.
307 *
308 * \since This function is available since SDL 2.0.0.
309 *
310 * \sa SDL_CreateSemaphore
311 * \sa SDL_DestroySemaphore
312 * \sa SDL_SemPost
313 * \sa SDL_SemTryWait
314 * \sa SDL_SemValue
315 * \sa SDL_SemWait
316 * \sa SDL_SemWaitTimeout
317 */
318extern DECLSPEC int SDLCALL SDL_SemWait(SDL_sem * sem);
319
320/**
321 * See if a semaphore has a positive value and decrement it if it does.
322 *
323 * This function checks to see if the semaphore pointed to by `sem` has a
324 * positive value and atomically decrements the semaphore value if it does. If
325 * the semaphore doesn't have a positive value, the function immediately
326 * returns SDL_MUTEX_TIMEDOUT.
327 *
328 * \param sem the semaphore to wait on
329 * \returns 0 if the wait succeeds, `SDL_MUTEX_TIMEDOUT` if the wait would
330 * block, or a negative error code on failure; call SDL_GetError()
331 * for more information.
332 *
333 * \since This function is available since SDL 2.0.0.
334 *
335 * \sa SDL_CreateSemaphore
336 * \sa SDL_DestroySemaphore
337 * \sa SDL_SemPost
338 * \sa SDL_SemValue
339 * \sa SDL_SemWait
340 * \sa SDL_SemWaitTimeout
341 */
342extern DECLSPEC int SDLCALL SDL_SemTryWait(SDL_sem * sem);
343
344/**
345 * Wait until a semaphore has a positive value and then decrements it.
346 *
347 * This function suspends the calling thread until either the semaphore
348 * pointed to by `sem` has a positive value, the call is interrupted by a
349 * signal or error, or the specified time has elapsed. If the call is
350 * successful it will atomically decrement the semaphore value.
351 *
352 * \param sem the semaphore to wait on
353 * \param timeout the length of the timeout, in milliseconds
354 * \returns 0 if the wait succeeds, `SDL_MUTEX_TIMEDOUT` if the wait does not
355 * succeed in the allotted time, or a negative error code on failure;
356 * call SDL_GetError() for more information.
357 *
358 * \since This function is available since SDL 2.0.0.
359 *
360 * \sa SDL_CreateSemaphore
361 * \sa SDL_DestroySemaphore
362 * \sa SDL_SemPost
363 * \sa SDL_SemTryWait
364 * \sa SDL_SemValue
365 * \sa SDL_SemWait
366 */
367extern DECLSPEC int SDLCALL SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout);
368
369/**
370 * Atomically increment a semaphore's value and wake waiting threads.
371 *
372 * \param sem the semaphore to increment
373 * \returns 0 on success or a negative error code on failure; call
374 * SDL_GetError() for more information.
375 *
376 * \since This function is available since SDL 2.0.0.
377 *
378 * \sa SDL_CreateSemaphore
379 * \sa SDL_DestroySemaphore
380 * \sa SDL_SemTryWait
381 * \sa SDL_SemValue
382 * \sa SDL_SemWait
383 * \sa SDL_SemWaitTimeout
384 */
385extern DECLSPEC int SDLCALL SDL_SemPost(SDL_sem * sem);
386
387/**
388 * Get the current value of a semaphore.
389 *
390 * \param sem the semaphore to query
391 * \returns the current value of the semaphore.
392 *
393 * \since This function is available since SDL 2.0.0.
394 *
395 * \sa SDL_CreateSemaphore
396 */
397extern DECLSPEC Uint32 SDLCALL SDL_SemValue(SDL_sem * sem);
398
399/* @} *//* Semaphore functions */
400
401
402/**
403 * \name Condition variable functions
404 */
405/* @{ */
406
407/* The SDL condition variable structure, defined in SDL_syscond.c */
408struct SDL_cond;
409typedef struct SDL_cond SDL_cond;
410
411/**
412 * Create a condition variable.
413 *
414 * \returns a new condition variable or NULL on failure; call SDL_GetError()
415 * for more information.
416 *
417 * \since This function is available since SDL 2.0.0.
418 *
419 * \sa SDL_CondBroadcast
420 * \sa SDL_CondSignal
421 * \sa SDL_CondWait
422 * \sa SDL_CondWaitTimeout
423 * \sa SDL_DestroyCond
424 */
425extern DECLSPEC SDL_cond *SDLCALL SDL_CreateCond(void);
426
427/**
428 * Destroy a condition variable.
429 *
430 * \param cond the condition variable to destroy
431 *
432 * \since This function is available since SDL 2.0.0.
433 *
434 * \sa SDL_CondBroadcast
435 * \sa SDL_CondSignal
436 * \sa SDL_CondWait
437 * \sa SDL_CondWaitTimeout
438 * \sa SDL_CreateCond
439 */
440extern DECLSPEC void SDLCALL SDL_DestroyCond(SDL_cond * cond);
441
442/**
443 * Restart one of the threads that are waiting on the condition variable.
444 *
445 * \param cond the condition variable to signal
446 * \returns 0 on success or a negative error code on failure; call
447 * SDL_GetError() for more information.
448 *
449 * \since This function is available since SDL 2.0.0.
450 *
451 * \sa SDL_CondBroadcast
452 * \sa SDL_CondWait
453 * \sa SDL_CondWaitTimeout
454 * \sa SDL_CreateCond
455 * \sa SDL_DestroyCond
456 */
457extern DECLSPEC int SDLCALL SDL_CondSignal(SDL_cond * cond);
458
459/**
460 * Restart all threads that are waiting on the condition variable.
461 *
462 * \param cond the condition variable to signal
463 * \returns 0 on success or a negative error code on failure; call
464 * SDL_GetError() for more information.
465 *
466 * \since This function is available since SDL 2.0.0.
467 *
468 * \sa SDL_CondSignal
469 * \sa SDL_CondWait
470 * \sa SDL_CondWaitTimeout
471 * \sa SDL_CreateCond
472 * \sa SDL_DestroyCond
473 */
474extern DECLSPEC int SDLCALL SDL_CondBroadcast(SDL_cond * cond);
475
476/**
477 * Wait until a condition variable is signaled.
478 *
479 * This function unlocks the specified `mutex` and waits for another thread to
480 * call SDL_CondSignal() or SDL_CondBroadcast() on the condition variable
481 * `cond`. Once the condition variable is signaled, the mutex is re-locked and
482 * the function returns.
483 *
484 * The mutex must be locked before calling this function.
485 *
486 * This function is the equivalent of calling SDL_CondWaitTimeout() with a
487 * time length of `SDL_MUTEX_MAXWAIT`.
488 *
489 * \param cond the condition variable to wait on
490 * \param mutex the mutex used to coordinate thread access
491 * \returns 0 when it is signaled or a negative error code on failure; call
492 * SDL_GetError() for more information.
493 *
494 * \since This function is available since SDL 2.0.0.
495 *
496 * \sa SDL_CondBroadcast
497 * \sa SDL_CondSignal
498 * \sa SDL_CondWaitTimeout
499 * \sa SDL_CreateCond
500 * \sa SDL_DestroyCond
501 */
502extern DECLSPEC int SDLCALL SDL_CondWait(SDL_cond * cond, SDL_mutex * mutex);
503
504/**
505 * Wait until a condition variable is signaled or a certain time has passed.
506 *
507 * This function unlocks the specified `mutex` and waits for another thread to
508 * call SDL_CondSignal() or SDL_CondBroadcast() on the condition variable
509 * `cond`, or for the specified time to elapse. Once the condition variable is
510 * signaled or the time elapsed, the mutex is re-locked and the function
511 * returns.
512 *
513 * The mutex must be locked before calling this function.
514 *
515 * \param cond the condition variable to wait on
516 * \param mutex the mutex used to coordinate thread access
517 * \param ms the maximum time to wait, in milliseconds, or `SDL_MUTEX_MAXWAIT`
518 * to wait indefinitely
519 * \returns 0 if the condition variable is signaled, `SDL_MUTEX_TIMEDOUT` if
520 * the condition is not signaled in the allotted time, or a negative
521 * error code on failure; call SDL_GetError() for more information.
522 *
523 * \since This function is available since SDL 2.0.0.
524 *
525 * \sa SDL_CondBroadcast
526 * \sa SDL_CondSignal
527 * \sa SDL_CondWait
528 * \sa SDL_CreateCond
529 * \sa SDL_DestroyCond
530 */
531extern DECLSPEC int SDLCALL SDL_CondWaitTimeout(SDL_cond * cond,
532 SDL_mutex * mutex, Uint32 ms);
533
534/* @} *//* Condition variable functions */
535
536
537/* Ends C function definitions when using C++ */
538#ifdef __cplusplus
539}
540#endif
541#include "close_code.h"
542
543#endif /* SDL_mutex_h_ */
544
545/* vi: set ts=4 sw=4 expandtab: */
546