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Remove almost all instances of "volatile" keyword.

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As Tiffany pointed out in Bugzilla, volatile is not useful for thread safety:

https://software.intel.com/en-us/blogs/2007/11/30/volatile-almost-useless-for-multi-threaded-programming/

Some of these volatiles didn't need to be, some were otherwise protected by
spinlocks or mutexes, and some got moved over to SDL_atomic_t data, etc.

Fixes Bugzilla #3220.
This commit is contained in:
Ryan C. Gordon 2016-01-03 06:50:50 -05:00
parent 21f66ea295
commit fa8c83c1c1
11 changed files with 66 additions and 72 deletions
Download patch file Download diff file Expand all files Collapse all files

12
test/testatomic.c
View file

@ -284,7 +284,7 @@ typedef struct
char cache_pad4[SDL_CACHELINE_SIZE-sizeof(SDL_SpinLock)-2*sizeof(SDL_atomic_t)];
#endif
volatile SDL_bool active;
SDL_atomic_t active;
/* Only needed for the mutex test */
SDL_mutex *mutex;
@ -305,7 +305,7 @@ static void InitEventQueue(SDL_EventQueue *queue)
SDL_AtomicSet(&queue->rwcount, 0);
SDL_AtomicSet(&queue->watcher, 0);
#endif
queue->active = SDL_TRUE;
SDL_AtomicSet(&queue->active, 1);
}
static SDL_bool EnqueueEvent_LockFree(SDL_EventQueue *queue, const SDL_Event *event)
@ -538,7 +538,7 @@ static int FIFO_Reader(void* _data)
if (DequeueEvent_LockFree(queue, &event)) {
WriterData *writer = (WriterData*)event.user.data1;
++data->counters[writer->index];
} else if (queue->active) {
} else if (SDL_AtomicGet(&queue->active)) {
++data->waits;
SDL_Delay(0);
} else {
@ -551,7 +551,7 @@ static int FIFO_Reader(void* _data)
if (DequeueEvent_Mutex(queue, &event)) {
WriterData *writer = (WriterData*)event.user.data1;
++data->counters[writer->index];
} else if (queue->active) {
} else if (SDL_AtomicGet(&queue->active)) {
++data->waits;
SDL_Delay(0);
} else {
@ -571,7 +571,7 @@ static int FIFO_Watcher(void* _data)
{
SDL_EventQueue *queue = (SDL_EventQueue *)_data;
while (queue->active) {
while (SDL_AtomicGet(&queue->active)) {
SDL_AtomicLock(&queue->lock);
SDL_AtomicIncRef(&queue->watcher);
while (SDL_AtomicGet(&queue->rwcount) > 0) {
@ -652,7 +652,7 @@ static void RunFIFOTest(SDL_bool lock_free)
}
/* Shut down the queue so readers exit */
queue.active = SDL_FALSE;
SDL_AtomicSet(&queue.active, 0);
/* Wait for the readers */
while (SDL_AtomicGet(&readersRunning) > 0) {