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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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12
test/testlock.c
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@@ -23,7 +23,7 @@
static SDL_mutex *mutex = NULL;
static SDL_threadID mainthread;
static SDL_Thread *threads[6];
static volatile int doterminate = 0;
static SDL_atomic_t doterminate;
/*
* SDL_Quit() shouldn't be used with atexit() directly because
@@ -45,7 +45,7 @@ void
terminate(int sig)
{
signal(SIGINT, terminate);
doterminate = 1;
SDL_AtomicSet(&doterminate, 1);
}
void
@@ -54,7 +54,7 @@ closemutex(int sig)
SDL_threadID id = SDL_ThreadID();
int i;
SDL_Log("Process %lu: Cleaning up...\n", id == mainthread ? 0 : id);
doterminate = 1;
SDL_AtomicSet(&doterminate, 1);
for (i = 0; i < 6; ++i)
SDL_WaitThread(threads[i], NULL);
SDL_DestroyMutex(mutex);
@@ -66,7 +66,7 @@ Run(void *data)
{
if (SDL_ThreadID() == mainthread)
signal(SIGTERM, closemutex);
while (!doterminate) {
while (!SDL_AtomicGet(&doterminate)) {
SDL_Log("Process %lu ready to work\n", SDL_ThreadID());
if (SDL_LockMutex(mutex) < 0) {
SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Couldn't lock mutex: %s", SDL_GetError());
@@ -82,7 +82,7 @@ Run(void *data)
/* If this sleep isn't done, then threads may starve */
SDL_Delay(10);
}
if (SDL_ThreadID() == mainthread && doterminate) {
if (SDL_ThreadID() == mainthread && SDL_AtomicGet(&doterminate)) {
SDL_Log("Process %lu: raising SIGTERM\n", SDL_ThreadID());
raise(SIGTERM);
}
@@ -105,6 +105,8 @@ main(int argc, char *argv[])
}
atexit(SDL_Quit_Wrapper);
SDL_AtomicSet(&doterminate, 0);
if ((mutex = SDL_CreateMutex()) == NULL) {
SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Couldn't create mutex: %s\n", SDL_GetError());
exit(1);