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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
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38
src/events/SDL_events.c
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@@ -73,15 +73,15 @@ typedef struct _SDL_SysWMEntry
static struct
{
SDL_mutex *lock;
volatile SDL_bool active;
volatile int count;
volatile int max_events_seen;
SDL_atomic_t active;
SDL_atomic_t count;
int max_events_seen;
SDL_EventEntry *head;
SDL_EventEntry *tail;
SDL_EventEntry *free;
SDL_SysWMEntry *wmmsg_used;
SDL_SysWMEntry *wmmsg_free;
} SDL_EventQ = { NULL, SDL_TRUE, 0, 0, NULL, NULL, NULL, NULL, NULL };
} SDL_EventQ = { NULL, { 1 }, { 0 }, 0, NULL, NULL, NULL, NULL, NULL };
/* Public functions */
@@ -98,7 +98,7 @@ SDL_StopEventLoop(void)
SDL_LockMutex(SDL_EventQ.lock);
}
SDL_EventQ.active = SDL_FALSE;
SDL_AtomicSet(&SDL_EventQ.active, 0);
if (report && SDL_atoi(report)) {
SDL_Log("SDL EVENT QUEUE: Maximum events in-flight: %d\n",
@@ -127,7 +127,7 @@ SDL_StopEventLoop(void)
wmmsg = next;
}
SDL_EventQ.count = 0;
SDL_AtomicSet(&SDL_EventQ.count, 0);
SDL_EventQ.max_events_seen = 0;
SDL_EventQ.head = NULL;
SDL_EventQ.tail = NULL;
@@ -171,7 +171,7 @@ SDL_StartEventLoop(void)
SDL_EventQ.lock = SDL_CreateMutex();
}
if (SDL_EventQ.lock == NULL) {
return (-1);
return -1;
}
#endif /* !SDL_THREADS_DISABLED */
@@ -180,9 +180,9 @@ SDL_StartEventLoop(void)
SDL_EventState(SDL_TEXTEDITING, SDL_DISABLE);
SDL_EventState(SDL_SYSWMEVENT, SDL_DISABLE);
SDL_EventQ.active = SDL_TRUE;
SDL_AtomicSet(&SDL_EventQ.active, 1);
return (0);
return 0;
}
@@ -191,9 +191,11 @@ static int
SDL_AddEvent(SDL_Event * event)
{
SDL_EventEntry *entry;
const int initial_count = SDL_AtomicGet(&SDL_EventQ.count);
int final_count;
if (SDL_EventQ.count >= SDL_MAX_QUEUED_EVENTS) {
SDL_SetError("Event queue is full (%d events)", SDL_EventQ.count);
if (initial_count >= SDL_MAX_QUEUED_EVENTS) {
SDL_SetError("Event queue is full (%d events)", initial_count);
return 0;
}
@@ -225,10 +227,10 @@ SDL_AddEvent(SDL_Event * event)
entry->prev = NULL;
entry->next = NULL;
}
++SDL_EventQ.count;
if (SDL_EventQ.count > SDL_EventQ.max_events_seen) {
SDL_EventQ.max_events_seen = SDL_EventQ.count;
final_count = SDL_AtomicAdd(&SDL_EventQ.count, 1) + 1;
if (final_count > SDL_EventQ.max_events_seen) {
SDL_EventQ.max_events_seen = final_count;
}
return 1;
@@ -256,8 +258,8 @@ SDL_CutEvent(SDL_EventEntry *entry)
entry->next = SDL_EventQ.free;
SDL_EventQ.free = entry;
SDL_assert(SDL_EventQ.count > 0);
--SDL_EventQ.count;
SDL_assert(SDL_AtomicGet(&SDL_EventQ.count) > 0);
SDL_AtomicAdd(&SDL_EventQ.count, -1);
}
/* Lock the event queue, take a peep at it, and unlock it */
@@ -268,7 +270,7 @@ SDL_PeepEvents(SDL_Event * events, int numevents, SDL_eventaction action,
int i, used;
/* Don't look after we've quit */
if (!SDL_EventQ.active) {
if (!SDL_AtomicGet(&SDL_EventQ.active)) {
/* We get a few spurious events at shutdown, so don't warn then */
if (action != SDL_ADDEVENT) {
SDL_SetError("The event system has been shut down");
@@ -363,7 +365,7 @@ void
SDL_FlushEvents(Uint32 minType, Uint32 maxType)
{
/* Don't look after we've quit */
if (!SDL_EventQ.active) {
if (!SDL_AtomicGet(&SDL_EventQ.active)) {
return;
}