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N3DS: Backport semaphore fixes from #6776.
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parent
b79732b967
commit
e580e087ff
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@ -25,3 +25,4 @@ cmake --install build
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- SDL2main should be used to ensure ROMFS is enabled.
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- SDL2main should be used to ensure ROMFS is enabled.
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- By default, the extra L2 cache and higher clock speeds of the New 2/3DS lineup are enabled. If you wish to turn it off, use `osSetSpeedupEnable(false)` in your main function.
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- By default, the extra L2 cache and higher clock speeds of the New 2/3DS lineup are enabled. If you wish to turn it off, use `osSetSpeedupEnable(false)` in your main function.
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- `SDL_GetBasePath` returns the romfs root instead of the executable's directory.
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- `SDL_GetBasePath` returns the romfs root instead of the executable's directory.
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- The Nintendo 3DS uses a cooperative threading model on a single core, meaning a thread will never yield unless done manually through the `SDL_Delay` functions, or blocking waits (`SDL_LockMutex`, `SDL_SemWait`, `SDL_CondWait`, `SDL_WaitThread`). To avoid starving other threads, `SDL_SemTryWait` and `SDL_SemWaitTimeout` will yield if they fail to acquire the semaphore, see https://github.com/libsdl-org/SDL/pull/6776 for more information.
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@ -27,14 +27,16 @@
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#include <3ds.h>
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#include <3ds.h>
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#include "SDL_thread.h"
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#include "SDL_thread.h"
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#include "SDL_timer.h"
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int WaitOnSemaphoreFor(SDL_sem *sem, Uint32 timeout);
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struct SDL_semaphore
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struct SDL_semaphore
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{
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{
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LightSemaphore semaphore;
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LightSemaphore semaphore;
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};
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};
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SDL_sem *
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SDL_sem *SDL_CreateSemaphore(Uint32 initial_value)
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SDL_CreateSemaphore(Uint32 initial_value)
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{
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{
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SDL_sem *sem;
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SDL_sem *sem;
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@ -59,9 +61,7 @@ SDL_CreateSemaphore(Uint32 initial_value)
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*/
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*/
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void SDL_DestroySemaphore(SDL_sem *sem)
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void SDL_DestroySemaphore(SDL_sem *sem)
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{
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{
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if (sem) {
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SDL_free(sem);
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SDL_free(sem);
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}
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}
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}
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int SDL_SemTryWait(SDL_sem *sem)
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int SDL_SemTryWait(SDL_sem *sem)
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@ -70,35 +70,49 @@ int SDL_SemTryWait(SDL_sem *sem)
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return SDL_InvalidParamError("sem");
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return SDL_InvalidParamError("sem");
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}
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}
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return SDL_SemWaitTimeout(sem, 0);
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if (LightSemaphore_TryAcquire(&sem->semaphore, 1) != 0) {
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/* If we failed, yield to avoid starvation on busy waits */
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svcSleepThread(1);
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return SDL_MUTEX_TIMEDOUT;
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}
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return 0;
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}
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}
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int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout)
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int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout)
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{
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{
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int retval;
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if (sem == NULL) {
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if (sem == NULL) {
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return SDL_InvalidParamError("sem");
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return SDL_InvalidParamError("sem");
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}
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}
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if (timeout == SDL_MUTEX_MAXWAIT) {
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if (timeout == SDL_MUTEX_MAXWAIT) {
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LightSemaphore_Acquire(&sem->semaphore, 1);
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LightSemaphore_Acquire(&sem->semaphore, 1);
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retval = 0;
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return 0;
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} else {
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int return_code = LightSemaphore_TryAcquire(&sem->semaphore, 1);
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if (return_code != 0) {
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for (u32 i = 0; i < timeout; i++) {
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svcSleepThread(1000000LL);
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return_code = LightSemaphore_TryAcquire(&sem->semaphore, 1);
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if (return_code == 0) {
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break;
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}
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}
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}
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retval = return_code != 0 ? SDL_MUTEX_TIMEDOUT : 0;
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}
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}
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return retval;
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if (LightSemaphore_TryAcquire(&sem->semaphore, 1) != 0) {
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return WaitOnSemaphoreFor(sem, timeout);
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}
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return 0;
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}
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int WaitOnSemaphoreFor(SDL_sem *sem, Uint32 timeout)
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{
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Uint64 stop_time = SDL_GetTicks64() + timeout;
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Uint64 current_time = SDL_GetTicks64();
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while (current_time < stop_time) {
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if (LightSemaphore_TryAcquire(&sem->semaphore, 1) == 0) {
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return 0;
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}
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/* 100 microseconds seems to be the sweet spot */
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svcSleepThread(100000LL);
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current_time = SDL_GetTicks64();
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}
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/* If we failed, yield to avoid starvation on busy waits */
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svcSleepThread(1);
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return SDL_MUTEX_TIMEDOUT;
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}
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}
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int SDL_SemWait(SDL_sem *sem)
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int SDL_SemWait(SDL_sem *sem)
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@ -106,8 +120,7 @@ int SDL_SemWait(SDL_sem *sem)
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return SDL_SemWaitTimeout(sem, SDL_MUTEX_MAXWAIT);
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return SDL_SemWaitTimeout(sem, SDL_MUTEX_MAXWAIT);
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}
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}
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Uint32
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Uint32 SDL_SemValue(SDL_sem *sem)
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SDL_SemValue(SDL_sem *sem)
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{
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{
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if (sem == NULL) {
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if (sem == NULL) {
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SDL_InvalidParamError("sem");
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SDL_InvalidParamError("sem");
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@ -49,8 +49,9 @@ static void ThreadEntry(void *arg)
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int SDL_SYS_CreateThread(SDL_Thread *thread)
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int SDL_SYS_CreateThread(SDL_Thread *thread)
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{
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{
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s32 priority = N3DS_THREAD_PRIORITY_MEDIUM;
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s32 priority;
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size_t stack_size = GetStackSize(thread->stacksize);
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size_t stack_size = GetStackSize(thread->stacksize);
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svcGetThreadPriority(&priority, CUR_THREAD_HANDLE);
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thread->handle = threadCreate(ThreadEntry,
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thread->handle = threadCreate(ThreadEntry,
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thread,
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thread,
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@ -210,6 +210,8 @@ TestOverheadContended(SDL_bool try_wait)
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}
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}
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/* Make sure threads consumed everything */
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/* Make sure threads consumed everything */
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while (SDL_SemValue(sem)) {
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while (SDL_SemValue(sem)) {
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/* Friendlier with cooperative threading models */
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SDL_Delay(1);
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}
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}
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}
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}
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end_ticks = SDL_GetTicks();
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end_ticks = SDL_GetTicks();
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