diff options
Diffstat (limited to 'pthread_once.c')
| -rw-r--r-- | pthread_once.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/pthread_once.c b/pthread_once.c index d37ee3d..34dacea 100644 --- a/pthread_once.c +++ b/pthread_once.c @@ -86,6 +86,18 @@ pthread_once (pthread_once_t * once_control, void (*init_routine) (void)) result = 0; } + /* + * The race condition involving once_control->done is harmless. + * The problem experienced in MPU environments with multibyte variables + * is also not a problem because the value (initially zero i.e. PTW32_FALSE) + * is only ever tested for non-zero. In the event of a race occuring, the + * worst result is that up to N-1 threads (N = number of CPUs) may enter the + * while loop and yield their run state unnecessarily, and this can only + * ever occur at most once. + * + * The alternatives are to use a condition variable (overkill?), or + * InterlockedCompareExchange() to test/set once_control->done. + */ if (!once_control->done) { if (InterlockedIncrement (&(once_control->started)) == 0) |