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.
-Peff
