Re: [msysGit] Re: [PATCH/RFC] mingw: implement PTHREAD_MUTEX_INITIALIZER
On Wed, Oct 26, 2011 at 5:05 AM, Atsushi Nakagawa <atnak@chejz.com> wrote:
Show 21 quoted lines
> On Oct 25, 11:55 pm, Erik Faye-Lund <kusmab...@gmail.com> wrote:
>> [...]
>> +int pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t
>> *attr)
>> +{
>> + InitializeCriticalSection(&mutex->cs);
>> + mutex->autoinit = 0;
>> + return 0;
>> +}
>> +
>> +int pthread_mutex_lock(pthread_mutex_t *mutex)
>> +{
>> + if (mutex->autoinit) {
>> + if (InterlockedCompareExchange(&mutex->autoinit, -1, 1) !=
>> -1) {
> I'm making the assumption that mutex->autoinit starts off as 1 before things
> get multi-threaded..
> I've only looked at what's in the patch so I could be missing vital
> context.. Anyways, is there a reason why you made this
> "InterlockedCompareExchange(..., -1, 1) != -1" and not
> "InterlockedCompareExchange(..., -1, 1) == 1"?> It looks to me the former adds a race condition after "if (mutex->autoinit)
> {". e.g. A second thread could reinitialize mutex->cs after the first
> thread has already entered EnterCriticalSection(...).You are indeed correct, thanks for spotting :)
Erik Faye-Lund <kusmabite@gmail.com>