Fixed bug 4097 - Segmentation fault by SDL_CreateThreadWithStackSize

Dongsun Kim

Normal case
1. [thread 1] SDL_CreateThreadWithStackSize calls SDL_SYS_CreateThread.
2. [thread 1] If successful, it calls SDL_SemWait.
3. [thread 2] SDL_RunThread calls SDL_SYS_SetupThread, SDL_ThreadID, SDL_SemPost.
4. [thread 1] SDL_CreateThreadWithStackSize calls SDL_DestroySemaphore, SDL_free.

Crash case (Segmentation fault)
1. [thread 1] SDL_CreateThreadWithStackSize calls SDL_SYS_CreateThread.
2. [thread 1] If successful, it calls SDL_SemWait.
--> Error return due to SIGNAL(SYSTEM or Real Time) at sem_wait(pthread).
3. [thread 1] SDL_CreateThreadWithStackSize calls SDL_DestroySemaphore, SDL_free.
4. [thread 2] SDL_RunThread calls SDL_SYS_SetupThread, SDL_ThreadID, SDL_SemPost.
--> Segmentation fault at strlen or sem_post.

src/thread/pthread/SDL_syssem.c

@@ -91,7 +91,10 @@ SDL_SemWait(SDL_sem * sem)
         return SDL_SetError("Passed a NULL semaphore");
     }
 
+    do {
         retval = sem_wait(&sem->sem);
+    } while (retval < 0 && errno == EINTR);
+
     if (retval < 0) {
         retval = SDL_SetError("sem_wait() failed");
     }