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Implement light semaphores (#369)

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TuxSH 2017-08-01 15:35:45 +02:00 committed by Dave Murphy
parent 4dafd78e26
commit f132a7a2a9
2 changed files with 129 additions and 0 deletions
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80
libctru/include/3ds/synchronization.h
View File

@ -19,6 +19,14 @@ typedef struct
LightLock lock; ///< Lock used for sticky timer operation
} LightEvent;
/// A light semaphore.
typedef struct
{
s32 current_count; ///< The current release count of the semaphore
s16 num_threads_acq; ///< Number of threads concurrently acquiring the semaphore
s16 max_count; ///< The maximum release count of the semaphore
} LightSemaphore;
/// Performs a Data Synchronization Barrier operation.
static inline void __dsb(void)
{
@ -56,6 +64,56 @@ static inline bool __strex(s32* addr, s32 val)
return res;
}
/**
* @brief Performs a ldrexh operation.
* @param addr Address to perform the operation on.
* @return The resulting value.
*/
static inline u16 __ldrexh(u16* addr)
{
u16 val;
__asm__ __volatile__("ldrexh %[val], %[addr]" : [val] "=r" (val) : [addr] "Q" (*addr));
return val;
}
/**
* @brief Performs a strexh operation.
* @param addr Address to perform the operation on.
* @param val Value to store.
* @return Whether the operation was successful.
*/
static inline bool __strexh(u16* addr, u16 val)
{
bool res;
__asm__ __volatile__("strexh %[res], %[val], %[addr]" : [res] "=&r" (res) : [val] "r" (val), [addr] "Q" (*addr));
return res;
}
/**
* @brief Performs a ldrexb operation.
* @param addr Address to perform the operation on.
* @return The resulting value.
*/
static inline u8 __ldrexb(u8* addr)
{
u8 val;
__asm__ __volatile__("ldrexb %[val], %[addr]" : [val] "=r" (val) : [addr] "Q" (*addr));
return val;
}
/**
* @brief Performs a strexb operation.
* @param addr Address to perform the operation on.
* @param val Value to store.
* @return Whether the operation was successful.
*/
static inline bool __strexb(u8* addr, u8 val)
{
bool res;
__asm__ __volatile__("strexb %[res], %[val], %[addr]" : [res] "=&r" (res) : [val] "r" (val), [addr] "Q" (*addr));
return res;
}
/// Performs an atomic pre-increment operation.
#define AtomicIncrement(ptr) __atomic_add_fetch((u32*)(ptr), 1, __ATOMIC_SEQ_CST)
/// Performs an atomic pre-decrement operation.
@ -160,3 +218,25 @@ int LightEvent_TryWait(LightEvent* event);
* @param event Pointer to the event.
*/
void LightEvent_Wait(LightEvent* event);
/**
* @brief Initializes a light semaphore.
* @param event Pointer to the semaphore.
* @param max_count Initial count of the semaphore.
* @param max_count Maximum count of the semaphore.
*/
void LightSemaphore_Init(LightSemaphore* semaphore, s16 initial_count, s16 max_count);
/**
* @brief Acquires a light semaphore.
* @param semaphore Pointer to the semaphore.
* @param count Acquire count
*/
void LightSemaphore_Acquire(LightSemaphore* semaphore, s32 count);
/**
* @brief Releases a light semaphore.
* @param semaphore Pointer to the semaphore.
* @param count Release count
*/
void LightSemaphore_Release(LightSemaphore* semaphore, s32 count);

49
libctru/source/synchronization.c
View File

@ -216,3 +216,52 @@ void LightEvent_Wait(LightEvent* event)
svcArbitrateAddress(arbiter, (u32)event, ARBITRATION_WAIT_IF_LESS_THAN, 0, 0);
}
}
void LightSemaphore_Init(LightSemaphore* semaphore, s16 initial_count, s16 max_count)
{
semaphore->current_count = (s32)initial_count;
semaphore->num_threads_acq = 0;
semaphore->max_count = max_count;
}
void LightSemaphore_Acquire(LightSemaphore* semaphore, s32 count)
{
s32 old_count;
s16 num_threads_acq;
do
{
for (;;)
{
old_count = __ldrex(&semaphore->current_count);
if (old_count > 0)
break;
__clrex();
do
num_threads_acq = (s16)__ldrexh((u16 *)&semaphore->num_threads_acq);
while (__strexh((u16 *)&semaphore->num_threads_acq, num_threads_acq + 1));
svcArbitrateAddress(arbiter, (u32)semaphore, ARBITRATION_WAIT_IF_LESS_THAN, count, 0);
do
num_threads_acq = (s16)__ldrexh((u16 *)&semaphore->num_threads_acq);
while (__strexh((u16 *)&semaphore->num_threads_acq, num_threads_acq - 1));
}
} while (__strex(&semaphore->current_count, old_count - count));
}
void LightSemaphore_Release(LightSemaphore* semaphore, s32 count)
{
s32 old_count, new_count;
do
{
old_count = __ldrex(&semaphore->current_count);
new_count = old_count + count;
if (new_count >= semaphore->max_count)
new_count = semaphore->max_count;
} while (__strex(&semaphore->current_count, new_count));
if(old_count <= 0 || semaphore->num_threads_acq > 0)
svcArbitrateAddress(arbiter, (u32)semaphore, ARBITRATION_SIGNAL, count, 0);
}