Re: recursive mutexes in Lion?

31 Jan 2012

      What are you hoping the test program to exercise, given that you're not initializing the mutexattr, nor are you associating the mutexattr with the mutex in any way? Using the compile-time mutex initializer gets you a default non-recursive mutex unless you use PTHREAD_RECURSIVE_MUTEX_INITIALIZER, which you're not using. This test program is really difficult to decipher.

The following using either the proper static initializer or the proper mutexattr both seem to work for me. Are you seeing otherwise?

$ cat test.c
#include <pthread.h>
#include <stdio.h>
#include <err.h>
#include <errno.h>

int main(int argc, char *argv[])
{
	int result;

#if USE_MUTEXATTR
	pthread_mutex_t       mutex;
	pthread_mutexattr_t   mta;

	result = pthread_mutexattr_init(&mta);
	if (result)
		err(1, "pthread_mutexattr_init");

	result = pthread_mutexattr_settype(&mta, PTHREAD_MUTEX_RECURSIVE);
	if (result)
		err(1, "pthread_mutexattr_settype");

	result = pthread_mutex_init(&mutex, &mta);
	if (result)
		err(1, "pthread_mutex_init");

	result = pthread_mutexattr_destroy(&mta);
	if (result)
		err(1, "pthread_mutexattr_destroy");
#else
	pthread_mutex_t       mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER;
#endif

	result = pthread_mutex_lock(&mutex);
	if (result)
		err(1, "pthread_mutex_lock 1");

	result = pthread_mutex_lock(&mutex);
	if (result)
		err(1, "pthread_mutex_lock 2");

	result = pthread_mutex_trylock(&mutex);
	if (result) {
		if (errno != EBUSY) {
			err(1, "pthread_mutex_trylock");
		}
	} else {
		result = pthread_mutex_unlock(&mutex);
		if (result)
			err(1, "pthread_mutex_unlock trylock");
	}

	result = pthread_mutex_unlock(&mutex);
	if (result)
		err(1, "pthread_mutex_unlock 2");

	result = pthread_mutex_unlock(&mutex);
	if (result)
		err(1, "pthread_mutex_unlock 1");

	result = pthread_mutex_destroy(&mutex);
	if (result)
		err(1, "pthread_mutex_destroy");

	return 0;
}
$ cc -g -O0 test.c
$ ./a.out
$ cc -g -O0 test.c -DUSE_MUTEXATTR=1
$ ./a.out
$

Shantonu

On Jan 31, 2012, at 11:58 AM, Jack Howarth <howarth@bromo.med.uc.edu> wrote:
...
The upcoming FSF gcc 4.7 release seems to have uncovered that the claimed
recursive mutex support in pthread.h for Lion is broken...
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51906
WARNING: program timed out.
FAIL: 30_threads/lock/3.cc execution test
FAIL: 30_threads/recursive_mutex/try_lock/1.cc execution test
FAIL: 30_threads/try_lock/3.cc execution test
Recursive mutexes are used due to the presence of...
#if (!defined(_POSIX_C_SOURCE) && !defined(_XOPEN_SOURCE)) || defined(_DARWIN_C_SOURCE)
#define PTHREAD_ERRORCHECK_MUTEX_INITIALIZER {_PTHREAD_ERRORCHECK_MUTEX_SIG_init, {0}}
#define PTHREAD_RECURSIVE_MUTEX_INITIALIZER {_PTHREAD_RECURSIVE_MUTEX_SIG_init, {0}}
#endif /* (!_POSIX_C_SOURCE && !_XOPEN_SOURCE) || _DARWIN_C_SOURCE */
in /usr/include/pthread.h on Lion (but on SL which lacks that pthread.h change).
While a small test program like...
---- pthread_test.C ----
#include <pthread.h>
#include <stdio.h>
/* int pthread_mutexatttr_settype(pthread_mutexattr_t *attr, int type); */
int main()
{
/* or PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP */
pthread_mutex_t       mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_mutexattr_t   mta;
/* pthread_mutexattr_init(&mta);  */
/* or PTHREAD_MUTEX_RECURSIVE_NP */
printf(" returned %d\n",pthread_mutexattr_settype(&mta, PTHREAD_MUTEX_RECURSIVE));
printf(" returned %d\n",pthread_mutex_trylock(&mutex));
}
---------------------------
which can be compiled gcc-4.6 using "g++ -std=c++0x -g -O0  pthread_test.c -lpthread" on linux and produces...
returned 0
returned 0
it fails on darwin11 when using clang++ with " clang++ -std=c++0x -g -O0 pthread_test.c" where the resulting
binary produces...
returned 22
returned 0
suggesting that PTHREAD_MUTEX_RECURSIVE isn't a valid type. Is this breakage expected for lion?
            Jack
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Shantonu Sen

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