SDL 3.0
SDL_mutex.h File Reference

Functions to provide thread synchronization primitives. More...

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Macros

#define SDL_THREAD_ANNOTATION_ATTRIBUTE__(x)   /* no-op */
 
#define SDL_CAPABILITY(x)    SDL_THREAD_ANNOTATION_ATTRIBUTE__(capability(x))
 
#define SDL_SCOPED_CAPABILITY    SDL_THREAD_ANNOTATION_ATTRIBUTE__(scoped_lockable)
 
#define SDL_GUARDED_BY(x)    SDL_THREAD_ANNOTATION_ATTRIBUTE__(guarded_by(x))
 
#define SDL_PT_GUARDED_BY(x)    SDL_THREAD_ANNOTATION_ATTRIBUTE__(pt_guarded_by(x))
 
#define SDL_ACQUIRED_BEFORE(x)    SDL_THREAD_ANNOTATION_ATTRIBUTE__(acquired_before(x))
 
#define SDL_ACQUIRED_AFTER(x)    SDL_THREAD_ANNOTATION_ATTRIBUTE__(acquired_after(x))
 
#define SDL_REQUIRES(x)    SDL_THREAD_ANNOTATION_ATTRIBUTE__(requires_capability(x))
 
#define SDL_REQUIRES_SHARED(x)    SDL_THREAD_ANNOTATION_ATTRIBUTE__(requires_shared_capability(x))
 
#define SDL_ACQUIRE(x)    SDL_THREAD_ANNOTATION_ATTRIBUTE__(acquire_capability(x))
 
#define SDL_ACQUIRE_SHARED(x)    SDL_THREAD_ANNOTATION_ATTRIBUTE__(acquire_shared_capability(x))
 
#define SDL_RELEASE(x)    SDL_THREAD_ANNOTATION_ATTRIBUTE__(release_capability(x))
 
#define SDL_RELEASE_SHARED(x)    SDL_THREAD_ANNOTATION_ATTRIBUTE__(release_shared_capability(x))
 
#define SDL_RELEASE_GENERIC(x)    SDL_THREAD_ANNOTATION_ATTRIBUTE__(release_generic_capability(x))
 
#define SDL_TRY_ACQUIRE(x, y)    SDL_THREAD_ANNOTATION_ATTRIBUTE__(try_acquire_capability(x, y))
 
#define SDL_TRY_ACQUIRE_SHARED(x, y)    SDL_THREAD_ANNOTATION_ATTRIBUTE__(try_acquire_shared_capability(x, y))
 
#define SDL_EXCLUDES(x)    SDL_THREAD_ANNOTATION_ATTRIBUTE__(locks_excluded(x))
 
#define SDL_ASSERT_CAPABILITY(x)    SDL_THREAD_ANNOTATION_ATTRIBUTE__(assert_capability(x))
 
#define SDL_ASSERT_SHARED_CAPABILITY(x)    SDL_THREAD_ANNOTATION_ATTRIBUTE__(assert_shared_capability(x))
 
#define SDL_RETURN_CAPABILITY(x)    SDL_THREAD_ANNOTATION_ATTRIBUTE__(lock_returned(x))
 
#define SDL_NO_THREAD_SAFETY_ANALYSIS    SDL_THREAD_ANNOTATION_ATTRIBUTE__(no_thread_safety_analysis)
 
#define SDL_MUTEX_TIMEDOUT   1
 
#define SDL_MUTEX_MAXWAIT   -1
 

Read/write lock functions

#define SDL_RWLOCK_TIMEDOUT   SDL_MUTEX_TIMEDOUT
 
typedef struct SDL_RWLock SDL_RWLock
 
int rwlock
 
SDL_RWLockSDL_CreateRWLock (void)
 
int SDL_LockRWLockForReading (SDL_RWLock *rwlock) SDL_ACQUIRE_SHARED(rwlock)
 
int SDL_LockRWLockForWriting (SDL_RWLock *rwlock) SDL_ACQUIRE(rwlock)
 
int SDL_TryLockRWLockForReading (SDL_RWLock *rwlock) SDL_TRY_ACQUIRE_SHARED(0
 
int SDL_TryLockRWLockForWriting (SDL_RWLock *rwlock) SDL_TRY_ACQUIRE(0
 
int SDL_UnlockRWLock (SDL_RWLock *rwlock) SDL_RELEASE_SHARED(rwlock)
 
void SDL_DestroyRWLock (SDL_RWLock *rwlock)
 

Mutex functions

typedef struct SDL_Mutex SDL_Mutex
 
int mutex
 
SDL_MutexSDL_CreateMutex (void)
 
int SDL_LockMutex (SDL_Mutex *mutex) SDL_ACQUIRE(mutex)
 
int SDL_TryLockMutex (SDL_Mutex *mutex) SDL_TRY_ACQUIRE(0
 
int SDL_UnlockMutex (SDL_Mutex *mutex) SDL_RELEASE(mutex)
 
void SDL_DestroyMutex (SDL_Mutex *mutex)
 

Semaphore functions

typedef struct SDL_Semaphore SDL_Semaphore
 
SDL_SemaphoreSDL_CreateSemaphore (Uint32 initial_value)
 
void SDL_DestroySemaphore (SDL_Semaphore *sem)
 
int SDL_WaitSemaphore (SDL_Semaphore *sem)
 
int SDL_TryWaitSemaphore (SDL_Semaphore *sem)
 
int SDL_WaitSemaphoreTimeout (SDL_Semaphore *sem, Sint32 timeoutMS)
 
int SDL_PostSemaphore (SDL_Semaphore *sem)
 
Uint32 SDL_GetSemaphoreValue (SDL_Semaphore *sem)
 

Condition variable functions

typedef struct SDL_Condition SDL_Condition
 
SDL_ConditionSDL_CreateCondition (void)
 
void SDL_DestroyCondition (SDL_Condition *cond)
 
int SDL_SignalCondition (SDL_Condition *cond)
 
int SDL_BroadcastCondition (SDL_Condition *cond)
 
int SDL_WaitCondition (SDL_Condition *cond, SDL_Mutex *mutex)
 
int SDL_WaitConditionTimeout (SDL_Condition *cond, SDL_Mutex *mutex, Sint32 timeoutMS)
 

Detailed Description

Functions to provide thread synchronization primitives.

Definition in file SDL_mutex.h.

Macro Definition Documentation

◆ SDL_ACQUIRE

#define SDL_ACQUIRE (   x)     SDL_THREAD_ANNOTATION_ATTRIBUTE__(acquire_capability(x))

Definition at line 73 of file SDL_mutex.h.

◆ SDL_ACQUIRE_SHARED

#define SDL_ACQUIRE_SHARED (   x)     SDL_THREAD_ANNOTATION_ATTRIBUTE__(acquire_shared_capability(x))

Definition at line 76 of file SDL_mutex.h.

◆ SDL_ACQUIRED_AFTER

#define SDL_ACQUIRED_AFTER (   x)     SDL_THREAD_ANNOTATION_ATTRIBUTE__(acquired_after(x))

Definition at line 64 of file SDL_mutex.h.

◆ SDL_ACQUIRED_BEFORE

#define SDL_ACQUIRED_BEFORE (   x)     SDL_THREAD_ANNOTATION_ATTRIBUTE__(acquired_before(x))

Definition at line 61 of file SDL_mutex.h.

◆ SDL_ASSERT_CAPABILITY

#define SDL_ASSERT_CAPABILITY (   x)     SDL_THREAD_ANNOTATION_ATTRIBUTE__(assert_capability(x))

Definition at line 97 of file SDL_mutex.h.

◆ SDL_ASSERT_SHARED_CAPABILITY

#define SDL_ASSERT_SHARED_CAPABILITY (   x)     SDL_THREAD_ANNOTATION_ATTRIBUTE__(assert_shared_capability(x))

Definition at line 100 of file SDL_mutex.h.

◆ SDL_CAPABILITY

#define SDL_CAPABILITY (   x)     SDL_THREAD_ANNOTATION_ATTRIBUTE__(capability(x))

Definition at line 49 of file SDL_mutex.h.

◆ SDL_EXCLUDES

#define SDL_EXCLUDES (   x)     SDL_THREAD_ANNOTATION_ATTRIBUTE__(locks_excluded(x))

Definition at line 94 of file SDL_mutex.h.

◆ SDL_GUARDED_BY

#define SDL_GUARDED_BY (   x)     SDL_THREAD_ANNOTATION_ATTRIBUTE__(guarded_by(x))

Definition at line 55 of file SDL_mutex.h.

◆ SDL_MUTEX_MAXWAIT

#define SDL_MUTEX_MAXWAIT   -1

This is the timeout value which corresponds to never time out.

Definition at line 127 of file SDL_mutex.h.

◆ SDL_MUTEX_TIMEDOUT

#define SDL_MUTEX_TIMEDOUT   1

Synchronization functions which can time out return this value if they time out.

Definition at line 122 of file SDL_mutex.h.

◆ SDL_NO_THREAD_SAFETY_ANALYSIS

#define SDL_NO_THREAD_SAFETY_ANALYSIS    SDL_THREAD_ANNOTATION_ATTRIBUTE__(no_thread_safety_analysis)

Definition at line 106 of file SDL_mutex.h.

◆ SDL_PT_GUARDED_BY

#define SDL_PT_GUARDED_BY (   x)     SDL_THREAD_ANNOTATION_ATTRIBUTE__(pt_guarded_by(x))

Definition at line 58 of file SDL_mutex.h.

◆ SDL_RELEASE

#define SDL_RELEASE (   x)     SDL_THREAD_ANNOTATION_ATTRIBUTE__(release_capability(x))

Definition at line 79 of file SDL_mutex.h.

◆ SDL_RELEASE_GENERIC

#define SDL_RELEASE_GENERIC (   x)     SDL_THREAD_ANNOTATION_ATTRIBUTE__(release_generic_capability(x))

Definition at line 85 of file SDL_mutex.h.

◆ SDL_RELEASE_SHARED

#define SDL_RELEASE_SHARED (   x)     SDL_THREAD_ANNOTATION_ATTRIBUTE__(release_shared_capability(x))

Definition at line 82 of file SDL_mutex.h.

◆ SDL_REQUIRES

#define SDL_REQUIRES (   x)     SDL_THREAD_ANNOTATION_ATTRIBUTE__(requires_capability(x))

Definition at line 67 of file SDL_mutex.h.

◆ SDL_REQUIRES_SHARED

#define SDL_REQUIRES_SHARED (   x)     SDL_THREAD_ANNOTATION_ATTRIBUTE__(requires_shared_capability(x))

Definition at line 70 of file SDL_mutex.h.

◆ SDL_RETURN_CAPABILITY

#define SDL_RETURN_CAPABILITY (   x)     SDL_THREAD_ANNOTATION_ATTRIBUTE__(lock_returned(x))

Definition at line 103 of file SDL_mutex.h.

◆ SDL_RWLOCK_TIMEDOUT

#define SDL_RWLOCK_TIMEDOUT   SDL_MUTEX_TIMEDOUT

Definition at line 256 of file SDL_mutex.h.

◆ SDL_SCOPED_CAPABILITY

#define SDL_SCOPED_CAPABILITY    SDL_THREAD_ANNOTATION_ATTRIBUTE__(scoped_lockable)

Definition at line 52 of file SDL_mutex.h.

◆ SDL_THREAD_ANNOTATION_ATTRIBUTE__

#define SDL_THREAD_ANNOTATION_ATTRIBUTE__ (   x)    /* no-op */

Definition at line 46 of file SDL_mutex.h.

◆ SDL_TRY_ACQUIRE

#define SDL_TRY_ACQUIRE (   x,
 
)     SDL_THREAD_ANNOTATION_ATTRIBUTE__(try_acquire_capability(x, y))

Definition at line 88 of file SDL_mutex.h.

◆ SDL_TRY_ACQUIRE_SHARED

#define SDL_TRY_ACQUIRE_SHARED (   x,
 
)     SDL_THREAD_ANNOTATION_ATTRIBUTE__(try_acquire_shared_capability(x, y))

Definition at line 91 of file SDL_mutex.h.

Typedef Documentation

◆ SDL_Condition

typedef struct SDL_Condition SDL_Condition

Definition at line 631 of file SDL_mutex.h.

◆ SDL_Mutex

typedef struct SDL_Mutex SDL_Mutex

Definition at line 137 of file SDL_mutex.h.

◆ SDL_RWLock

typedef struct SDL_RWLock SDL_RWLock

Definition at line 250 of file SDL_mutex.h.

◆ SDL_Semaphore

typedef struct SDL_Semaphore SDL_Semaphore

Definition at line 470 of file SDL_mutex.h.

Function Documentation

◆ SDL_BroadcastCondition()

int SDL_BroadcastCondition ( SDL_Condition cond)

Restart all threads that are waiting on the condition variable.

Parameters
condthe condition variable to signal
Returns
0 on success or a negative error code on failure; call SDL_GetError() for more information.
Since
This function is available since SDL 3.0.0.
See also
SDL_SignalCondition
SDL_WaitCondition
SDL_WaitConditionTimeout
SDL_CreateCondition
SDL_DestroyCondition

◆ SDL_CreateCondition()

SDL_Condition * SDL_CreateCondition ( void  )

Create a condition variable.

Returns
a new condition variable or NULL on failure; call SDL_GetError() for more information.
Since
This function is available since SDL 3.0.0.
See also
SDL_BroadcastCondition
SDL_SignalCondition
SDL_WaitCondition
SDL_WaitConditionTimeout
SDL_DestroyCondition

◆ SDL_CreateMutex()

SDL_Mutex * SDL_CreateMutex ( void  )

Create a new mutex.

All newly-created mutexes begin in the unlocked state.

Calls to SDL_LockMutex() will not return while the mutex is locked by another thread. See SDL_TryLockMutex() to attempt to lock without blocking.

SDL mutexes are reentrant.

Returns
the initialized and unlocked mutex or NULL on failure; call SDL_GetError() for more information.
Since
This function is available since SDL 3.0.0.
See also
SDL_DestroyMutex
SDL_LockMutex
SDL_TryLockMutex
SDL_UnlockMutex

◆ SDL_CreateRWLock()

SDL_RWLock * SDL_CreateRWLock ( void  )

Create a new read/write lock.

A read/write lock is useful for situations where you have multiple threads trying to access a resource that is rarely updated. All threads requesting a read-only lock will be allowed to run in parallel; if a thread requests a write lock, it will be provided exclusive access. This makes it safe for multiple threads to use a resource at the same time if they promise not to change it, and when it has to be changed, the rwlock will serve as a gateway to make sure those changes can be made safely.

In the right situation, a rwlock can be more efficient than a mutex, which only lets a single thread proceed at a time, even if it won't be modifying the data.

All newly-created read/write locks begin in the unlocked state.

Calls to SDL_LockRWLockForReading() and SDL_LockRWLockForWriting will not return while the rwlock is locked for writing by another thread. See SDL_TryLockRWLockForReading() and SDL_TryLockRWLockForWriting() to attempt to lock without blocking.

SDL read/write locks are only recursive for read-only locks! They are not guaranteed to be fair, or provide access in a FIFO manner! They are not guaranteed to favor writers. You may not lock a rwlock for both read-only and write access at the same time from the same thread (so you can't promote your read-only lock to a write lock without unlocking first).

Returns
the initialized and unlocked read/write lock or NULL on failure; call SDL_GetError() for more information.
Since
This function is available since SDL 3.0.0.
See also
SDL_DestroyRWLock
SDL_LockRWLockForReading
SDL_TryLockRWLockForReading
SDL_LockRWLockForWriting
SDL_TryLockRWLockForWriting
SDL_UnlockRWLock

◆ SDL_CreateSemaphore()

SDL_Semaphore * SDL_CreateSemaphore ( Uint32  initial_value)

Create a semaphore.

This function creates a new semaphore and initializes it with the value initial_value. Each wait operation on the semaphore will atomically decrement the semaphore value and potentially block if the semaphore value is 0. Each post operation will atomically increment the semaphore value and wake waiting threads and allow them to retry the wait operation.

Parameters
initial_valuethe starting value of the semaphore
Returns
a new semaphore or NULL on failure; call SDL_GetError() for more information.
Since
This function is available since SDL 3.0.0.
See also
SDL_DestroySemaphore
SDL_PostSemaphore
SDL_TryWaitSemaphore
SDL_GetSemaphoreValue
SDL_WaitSemaphore
SDL_WaitSemaphoreTimeout

◆ SDL_DestroyCondition()

void SDL_DestroyCondition ( SDL_Condition cond)

Destroy a condition variable.

Parameters
condthe condition variable to destroy
Since
This function is available since SDL 3.0.0.
See also
SDL_BroadcastCondition
SDL_SignalCondition
SDL_WaitCondition
SDL_WaitConditionTimeout
SDL_CreateCondition

◆ SDL_DestroyMutex()

void SDL_DestroyMutex ( SDL_Mutex mutex)

Destroy a mutex created with SDL_CreateMutex().

This function must be called on any mutex that is no longer needed. Failure to destroy a mutex will result in a system memory or resource leak. While it is safe to destroy a mutex that is unlocked, it is not safe to attempt to destroy a locked mutex, and may result in undefined behavior depending on the platform.

Parameters
mutexthe mutex to destroy
Since
This function is available since SDL 3.0.0.
See also
SDL_CreateMutex
SDL_LockMutex
SDL_TryLockMutex
SDL_UnlockMutex

◆ SDL_DestroyRWLock()

void SDL_DestroyRWLock ( SDL_RWLock rwlock)

Destroy a read/write lock created with SDL_CreateRWLock().

This function must be called on any read/write lock that is no longer needed. Failure to destroy a rwlock will result in a system memory or resource leak. While it is safe to destroy a rwlock that is unlocked, it is not safe to attempt to destroy a locked rwlock, and may result in undefined behavior depending on the platform.

Parameters
rwlockthe rwlock to destroy
Since
This function is available since SDL 3.0.0.
See also
SDL_CreateRWLock
SDL_LockRWLockForReading
SDL_LockRWLockForWriting
SDL_TryLockRWLockForReading
SDL_TryLockRWLockForWriting
SDL_UnlockRWLock

◆ SDL_DestroySemaphore()

void SDL_DestroySemaphore ( SDL_Semaphore sem)

Destroy a semaphore.

It is not safe to destroy a semaphore if there are threads currently waiting on it.

Parameters
semthe semaphore to destroy
Since
This function is available since SDL 3.0.0.
See also
SDL_CreateSemaphore
SDL_PostSemaphore
SDL_TryWaitSemaphore
SDL_GetSemaphoreValue
SDL_WaitSemaphore
SDL_WaitSemaphoreTimeout

◆ SDL_GetSemaphoreValue()

Uint32 SDL_GetSemaphoreValue ( SDL_Semaphore sem)

Get the current value of a semaphore.

Parameters
semthe semaphore to query
Returns
the current value of the semaphore.
Since
This function is available since SDL 3.0.0.
See also
SDL_CreateSemaphore

◆ SDL_LockMutex()

int SDL_LockMutex ( SDL_Mutex mutex)

Lock the mutex.

This will block until the mutex is available, which is to say it is in the unlocked state and the OS has chosen the caller as the next thread to lock it. Of all threads waiting to lock the mutex, only one may do so at a time.

It is legal for the owning thread to lock an already-locked mutex. It must unlock it the same number of times before it is actually made available for other threads in the system (this is known as a "recursive mutex").

Parameters
mutexthe mutex to lock
Returns
0 on success or a negative error code on failure; call SDL_GetError() for more information.
Since
This function is available since SDL 3.0.0.

◆ SDL_LockRWLockForReading()

int SDL_LockRWLockForReading ( SDL_RWLock rwlock)

Lock the read/write lock for read only operations.

This will block until the rwlock is available, which is to say it is not locked for writing by any other thread. Of all threads waiting to lock the rwlock, all may do so at the same time as long as they are requesting read-only access; if a thread wants to lock for writing, only one may do so at a time, and no other threads, read-only or not, may hold the lock at the same time.

It is legal for the owning thread to lock an already-locked rwlock for reading. It must unlock it the same number of times before it is actually made available for other threads in the system (this is known as a "recursive rwlock").

Note that locking for writing is not recursive (this is only available to read-only locks).

It is illegal to request a read-only lock from a thread that already holds the write lock. Doing so results in undefined behavior. Unlock the write lock before requesting a read-only lock. (But, of course, if you have the write lock, you don't need further locks to read in any case.)

Parameters
rwlockthe read/write lock to lock
Returns
0 on success or a negative error code on failure; call SDL_GetError() for more information.
Since
This function is available since SDL 3.0.0.
See also
SDL_UnlockRWLock

◆ SDL_LockRWLockForWriting()

int SDL_LockRWLockForWriting ( SDL_RWLock rwlock)

Lock the read/write lock for write operations.

This will block until the rwlock is available, which is to say it is not locked for reading or writing by any other thread. Only one thread may hold the lock when it requests write access; all other threads, whether they also want to write or only want read-only access, must wait until the writer thread has released the lock.

It is illegal for the owning thread to lock an already-locked rwlock for writing (read-only may be locked recursively, writing can not). Doing so results in undefined behavior.

It is illegal to request a write lock from a thread that already holds a read-only lock. Doing so results in undefined behavior. Unlock the read-only lock before requesting a write lock.

Parameters
rwlockthe read/write lock to lock
Returns
0 on success or a negative error code on failure; call SDL_GetError() for more information.
Since
This function is available since SDL 3.0.0.
See also
SDL_UnlockRWLock

◆ SDL_PostSemaphore()

int SDL_PostSemaphore ( SDL_Semaphore sem)

Atomically increment a semaphore's value and wake waiting threads.

Parameters
semthe semaphore to increment
Returns
0 on success or a negative error code on failure; call SDL_GetError() for more information.
Since
This function is available since SDL 3.0.0.
See also
SDL_CreateSemaphore
SDL_DestroySemaphore
SDL_TryWaitSemaphore
SDL_GetSemaphoreValue
SDL_WaitSemaphore
SDL_WaitSemaphoreTimeout

◆ SDL_SignalCondition()

int SDL_SignalCondition ( SDL_Condition cond)

Restart one of the threads that are waiting on the condition variable.

Parameters
condthe condition variable to signal
Returns
0 on success or a negative error code on failure; call SDL_GetError() for more information.
Since
This function is available since SDL 3.0.0.
See also
SDL_BroadcastCondition
SDL_WaitCondition
SDL_WaitConditionTimeout
SDL_CreateCondition
SDL_DestroyCondition

◆ SDL_TryLockMutex()

int SDL_TryLockMutex ( SDL_Mutex mutex)

Try to lock a mutex without blocking.

This works just like SDL_LockMutex(), but if the mutex is not available, this function returns SDL_MUTEX_TIMEDOUT immediately.

This technique is useful if you need exclusive access to a resource but don't want to wait for it, and will return to it to try again later.

Parameters
mutexthe mutex to try to lock
Returns
0, SDL_MUTEX_TIMEDOUT, or -1 on error; call SDL_GetError() for more information.
Since
This function is available since SDL 3.0.0.
See also
SDL_CreateMutex
SDL_DestroyMutex
SDL_LockMutex
SDL_UnlockMutex

◆ SDL_TryLockRWLockForReading()

int SDL_TryLockRWLockForReading ( SDL_RWLock rwlock)

Try to lock a read/write lock for reading without blocking.

This works just like SDL_LockRWLockForReading(), but if the rwlock is not available, then this function returns SDL_RWLOCK_TIMEDOUT immediately.

This technique is useful if you need access to a resource but don't want to wait for it, and will return to it to try again later.

Trying to lock for read-only access can succeed if other threads are holding read-only locks, as this won't prevent access.

Parameters
rwlockthe rwlock to try to lock
Returns
0, SDL_RWLOCK_TIMEDOUT, or -1 on error; call SDL_GetError() for more information.
Since
This function is available since SDL 3.0.0.
See also
SDL_CreateRWLock
SDL_DestroyRWLock
SDL_TryLockRWLockForReading
SDL_UnlockRWLock

◆ SDL_TryLockRWLockForWriting()

int SDL_TryLockRWLockForWriting ( SDL_RWLock rwlock)

Try to lock a read/write lock for writing without blocking.

This works just like SDL_LockRWLockForWriting(), but if the rwlock is not available, this function returns SDL_RWLOCK_TIMEDOUT immediately.

This technique is useful if you need exclusive access to a resource but don't want to wait for it, and will return to it to try again later.

It is illegal for the owning thread to lock an already-locked rwlock for writing (read-only may be locked recursively, writing can not). Doing so results in undefined behavior.

It is illegal to request a write lock from a thread that already holds a read-only lock. Doing so results in undefined behavior. Unlock the read-only lock before requesting a write lock.

Parameters
rwlockthe rwlock to try to lock
Returns
0, SDL_RWLOCK_TIMEDOUT, or -1 on error; call SDL_GetError() for more information.
Since
This function is available since SDL 3.0.0.
See also
SDL_CreateRWLock
SDL_DestroyRWLock
SDL_TryLockRWLockForWriting
SDL_UnlockRWLock

◆ SDL_TryWaitSemaphore()

int SDL_TryWaitSemaphore ( SDL_Semaphore sem)

See if a semaphore has a positive value and decrement it if it does.

This function checks to see if the semaphore pointed to by sem has a positive value and atomically decrements the semaphore value if it does. If the semaphore doesn't have a positive value, the function immediately returns SDL_MUTEX_TIMEDOUT.

Parameters
semthe semaphore to wait on
Returns
0 if the wait succeeds, SDL_MUTEX_TIMEDOUT if the wait would block, or a negative error code on failure; call SDL_GetError() for more information.
Since
This function is available since SDL 3.0.0.
See also
SDL_CreateSemaphore
SDL_DestroySemaphore
SDL_PostSemaphore
SDL_GetSemaphoreValue
SDL_WaitSemaphore
SDL_WaitSemaphoreTimeout

◆ SDL_UnlockMutex()

int SDL_UnlockMutex ( SDL_Mutex mutex)

Unlock the mutex.

It is legal for the owning thread to lock an already-locked mutex. It must unlock it the same number of times before it is actually made available for other threads in the system (this is known as a "recursive mutex").

It is illegal to unlock a mutex that has not been locked by the current thread, and doing so results in undefined behavior.

Parameters
mutexthe mutex to unlock.
Returns
0 on success or a negative error code on failure; call SDL_GetError() for more information.
Since
This function is available since SDL 3.0.0.

◆ SDL_UnlockRWLock()

int SDL_UnlockRWLock ( SDL_RWLock rwlock)

Unlock the read/write lock.

Use this function to unlock the rwlock, whether it was locked for read-only or write operations.

It is legal for the owning thread to lock an already-locked read-only lock. It must unlock it the same number of times before it is actually made available for other threads in the system (this is known as a "recursive rwlock").

It is illegal to unlock a rwlock that has not been locked by the current thread, and doing so results in undefined behavior.

Parameters
rwlockthe rwlock to unlock.
Returns
0 on success or a negative error code on failure; call SDL_GetError() for more information.
Since
This function is available since SDL 3.0.0.

◆ SDL_WaitCondition()

int SDL_WaitCondition ( SDL_Condition cond,
SDL_Mutex mutex 
)

Wait until a condition variable is signaled.

This function unlocks the specified mutex and waits for another thread to call SDL_SignalCondition() or SDL_BroadcastCondition() on the condition variable cond. Once the condition variable is signaled, the mutex is re-locked and the function returns.

The mutex must be locked before calling this function. Locking the mutex recursively (more than once) is not supported and leads to undefined behavior.

This function is the equivalent of calling SDL_WaitConditionTimeout() with a time length of SDL_MUTEX_MAXWAIT.

Parameters
condthe condition variable to wait on
mutexthe mutex used to coordinate thread access
Returns
0 when it is signaled or a negative error code on failure; call SDL_GetError() for more information.
Since
This function is available since SDL 3.0.0.
See also
SDL_BroadcastCondition
SDL_SignalCondition
SDL_WaitConditionTimeout
SDL_CreateCondition
SDL_DestroyCondition

◆ SDL_WaitConditionTimeout()

int SDL_WaitConditionTimeout ( SDL_Condition cond,
SDL_Mutex mutex,
Sint32  timeoutMS 
)

Wait until a condition variable is signaled or a certain time has passed.

This function unlocks the specified mutex and waits for another thread to call SDL_SignalCondition() or SDL_BroadcastCondition() on the condition variable cond, or for the specified time to elapse. Once the condition variable is signaled or the time elapsed, the mutex is re-locked and the function returns.

The mutex must be locked before calling this function. Locking the mutex recursively (more than once) is not supported and leads to undefined behavior.

Parameters
condthe condition variable to wait on
mutexthe mutex used to coordinate thread access
timeoutMSthe maximum time to wait, in milliseconds, or SDL_MUTEX_MAXWAIT to wait indefinitely
Returns
0 if the condition variable is signaled, SDL_MUTEX_TIMEDOUT if the condition is not signaled in the allotted time, or a negative error code on failure; call SDL_GetError() for more information.
Since
This function is available since SDL 3.0.0.
See also
SDL_BroadcastCondition
SDL_SignalCondition
SDL_WaitCondition
SDL_CreateCondition
SDL_DestroyCondition

◆ SDL_WaitSemaphore()

int SDL_WaitSemaphore ( SDL_Semaphore sem)

Wait until a semaphore has a positive value and then decrements it.

This function suspends the calling thread until either the semaphore pointed to by sem has a positive value or the call is interrupted by a signal or error. If the call is successful it will atomically decrement the semaphore value.

This function is the equivalent of calling SDL_WaitSemaphoreTimeout() with a time length of SDL_MUTEX_MAXWAIT.

Parameters
semthe semaphore wait on
Returns
0 on success or a negative error code on failure; call SDL_GetError() for more information.
Since
This function is available since SDL 3.0.0.
See also
SDL_CreateSemaphore
SDL_DestroySemaphore
SDL_PostSemaphore
SDL_TryWaitSemaphore
SDL_GetSemaphoreValue
SDL_WaitSemaphore
SDL_WaitSemaphoreTimeout

◆ SDL_WaitSemaphoreTimeout()

int SDL_WaitSemaphoreTimeout ( SDL_Semaphore sem,
Sint32  timeoutMS 
)

Wait until a semaphore has a positive value and then decrements it.

This function suspends the calling thread until either the semaphore pointed to by sem has a positive value, the call is interrupted by a signal or error, or the specified time has elapsed. If the call is successful it will atomically decrement the semaphore value.

Parameters
semthe semaphore to wait on
timeoutMSthe length of the timeout, in milliseconds
Returns
0 if the wait succeeds, SDL_MUTEX_TIMEDOUT if the wait does not succeed in the allotted time, or a negative error code on failure; call SDL_GetError() for more information.
Since
This function is available since SDL 3.0.0.
See also
SDL_CreateSemaphore
SDL_DestroySemaphore
SDL_PostSemaphore
SDL_TryWaitSemaphore
SDL_GetSemaphoreValue
SDL_WaitSemaphore

Variable Documentation

◆ mutex

int mutex

Definition at line 200 of file SDL_mutex.h.

◆ rwlock

int rwlock

Definition at line 384 of file SDL_mutex.h.