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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

43
src/timer/SDL_timer.c
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@@ -35,7 +35,7 @@ typedef struct _SDL_Timer
void *param;
Uint32 interval;
Uint32 scheduled;
volatile SDL_bool canceled;
SDL_atomic_t canceled;
struct _SDL_Timer *next;
} SDL_Timer;
@@ -60,9 +60,9 @@ typedef struct {
/* Data used to communicate with the timer thread */
SDL_SpinLock lock;
SDL_sem *sem;
SDL_Timer * volatile pending;
SDL_Timer * volatile freelist;
volatile SDL_bool active;
SDL_Timer *pending;
SDL_Timer *freelist;
SDL_atomic_t active;
/* List of timers - this is only touched by the timer thread */
SDL_Timer *timers;
@@ -138,7 +138,7 @@ SDL_TimerThread(void *_data)
freelist_tail = NULL;
/* Check to see if we're still running, after maintenance */
if (!data->active) {
if (!SDL_AtomicGet(&data->active)) {
break;
}
@@ -160,7 +160,7 @@ SDL_TimerThread(void *_data)
/* We're going to do something with this timer */
data->timers = current->next;
if (current->canceled) {
if (SDL_AtomicGet(&current->canceled)) {
interval = 0;
} else {
interval = current->callback(current->interval, current->param);
@@ -179,7 +179,7 @@ SDL_TimerThread(void *_data)
}
freelist_tail = current;
current->canceled = SDL_TRUE;
SDL_AtomicSet(&current->canceled, 1);
}
}
@@ -207,7 +207,7 @@ SDL_TimerInit(void)
{
SDL_TimerData *data = &SDL_timer_data;
if (!data->active) {
if (!SDL_AtomicGet(&data->active)) {
const char *name = "SDLTimer";
data->timermap_lock = SDL_CreateMutex();
if (!data->timermap_lock) {
@@ -220,7 +220,7 @@ SDL_TimerInit(void)
return -1;
}
data->active = SDL_TRUE;
SDL_AtomicSet(&data->active, 1);
/* !!! FIXME: this is nasty. */
#if defined(__WIN32__) && !defined(HAVE_LIBC)
#undef SDL_CreateThread
@@ -249,9 +249,7 @@ SDL_TimerQuit(void)
SDL_Timer *timer;
SDL_TimerMap *entry;
if (data->active) {
data->active = SDL_FALSE;
if (SDL_AtomicCAS(&data->active, 1, 0)) { /* active? Move to inactive. */
/* Shutdown the timer thread */
if (data->thread) {
SDL_SemPost(data->sem);
@@ -291,21 +289,14 @@ SDL_AddTimer(Uint32 interval, SDL_TimerCallback callback, void *param)
SDL_Timer *timer;
SDL_TimerMap *entry;
if (!data->active) {
int status = 0;
SDL_AtomicLock(&data->lock);
if (!data->active) {
status = SDL_TimerInit();
}
SDL_AtomicUnlock(&data->lock);
if (status < 0) {
SDL_AtomicLock(&data->lock);
if (!SDL_AtomicGet(&data->active)) {
if (SDL_TimerInit() < 0) {
SDL_AtomicUnlock(&data->lock);
return 0;
}
}
SDL_AtomicLock(&data->lock);
timer = data->freelist;
if (timer) {
data->freelist = timer->next;
@@ -326,7 +317,7 @@ SDL_AddTimer(Uint32 interval, SDL_TimerCallback callback, void *param)
timer->param = param;
timer->interval = interval;
timer->scheduled = SDL_GetTicks() + interval;
timer->canceled = SDL_FALSE;
SDL_AtomicSet(&timer->canceled, 0);
entry = (SDL_TimerMap *)SDL_malloc(sizeof(*entry));
if (!entry) {
@@ -377,8 +368,8 @@ SDL_RemoveTimer(SDL_TimerID id)
SDL_UnlockMutex(data->timermap_lock);
if (entry) {
if (!entry->timer->canceled) {
entry->timer->canceled = SDL_TRUE;
if (!SDL_AtomicGet(&entry->timer->canceled)) {
SDL_AtomicSet(&entry->timer->canceled, 1);
canceled = SDL_TRUE;
}
SDL_free(entry);