On Wed, Oct 26, 2016 at 5:15 AM, Jeff King <peff@xxxxxxxx> wrote:
> On Wed, Oct 26, 2016 at 11:35:58AM +0200, Simon Ruderich wrote:
>
>> > static pthread_mutex_t attr_mutex;
>> > -#define attr_lock()pthread_mutex_lock(&attr_mutex)
>> > +static inline void attr_lock(void)
>> > +{
>> > + static int initialized;
>> > +
>> > + if (!initialized) {
>> > + pthread_mutex_init(&attr_mutex, NULL);
>> > + initialized = 1;
>> > + }
>> > + pthread_mutex_lock(&attr_mutex);
>> > +}
>>
>> This may initialize the mutex multiple times during the first
>> lock (which may happen in parallel).
>>
>> pthread provides static initializers. To quote the man page:
>>
>> Variables of type pthread_mutex_t can also be initialized
>> statically, using the constants PTHREAD_MUTEX_INITIALIZER
>> (for fast mutexes), PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP
>> (for recursive mutexes), and
>> PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP (for error checking
>> mutexes).
>
> I seem to recall this does not work on Windows, where the pthread
> functions are thin wrappers over CRITICAL_SECTION. Other threaded code
> in git does an explicit setup step before entering threaded sections.
> E.g., see start_threads() in builtin/grep.c.
>
I wonder if we can have a similar thing as
http://stackoverflow.com/a/9490113 in compat/win32/pthread.{h.c} as it is
very convenient to not have to explicitly initialize mutexes?