-/* -*- mode: C; c-file-style: "gnu" -*- */
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
/* dbus-sysdeps-pthread.c Implements threads using pthreads (internal to libdbus)
*
* Copyright (C) 2002, 2003, 2006 Red Hat, Inc.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
*/
+#include <config.h>
#include "dbus-internals.h"
#include "dbus-sysdeps.h"
#include "dbus-threads.h"
#include <pthread.h>
#include <string.h>
+#ifdef HAVE_ERRNO_H
+#include <errno.h>
+#endif
+
+#include <config.h>
+
+/* Whether we have a "monotonic" clock; i.e. a clock not affected by
+ * changes in system time.
+ * This is initialized once in check_monotonic_clock below.
+ * https://bugs.freedesktop.org/show_bug.cgi?id=18121
+ */
+static dbus_bool_t have_monotonic_clock = 0;
+
typedef struct {
- pthread_mutex_t lock;
+ pthread_mutex_t lock; /**< lock protecting count field */
+ volatile int count; /**< count of how many times lock holder has recursively locked */
+ volatile pthread_t holder; /**< holder of the lock if count >0,
+ valid but arbitrary thread if count
+ has ever been >0, uninitialized memory
+ if count has never been >0 */
} DBusMutexPThread;
typedef struct {
- pthread_cond_t cond;
+ pthread_cond_t cond; /**< the condition */
} DBusCondVarPThread;
#define DBUS_MUTEX(m) ((DBusMutex*) m)
#define DBUS_COND_VAR_PTHREAD(c) ((DBusCondVarPThread*) c)
+#ifdef DBUS_DISABLE_ASSERT
+/* (tmp != 0) is a no-op usage to silence compiler */
+#define PTHREAD_CHECK(func_name, result_or_call) \
+ do { int tmp = (result_or_call); if (tmp != 0) {;} } while (0)
+#else
#define PTHREAD_CHECK(func_name, result_or_call) do { \
int tmp = (result_or_call); \
if (tmp != 0) { \
func_name, tmp, strerror(tmp), _DBUS_FUNCTION_NAME); \
} \
} while (0)
-
+#endif /* !DBUS_DISABLE_ASSERT */
+
static DBusMutex*
_dbus_pthread_mutex_new (void)
{
PTHREAD_CHECK ("pthread_mutex_init", result);
}
+ /* Only written */
+ pmutex->count = 0;
+
+ /* There's no portable way to have a "null" pthread afaik so we
+ * can't set pmutex->holder to anything sensible. We only access it
+ * once the lock is held (which means we've set it).
+ */
+
return DBUS_MUTEX (pmutex);
}
_dbus_pthread_mutex_free (DBusMutex *mutex)
{
DBusMutexPThread *pmutex = DBUS_MUTEX_PTHREAD (mutex);
+
+ _dbus_assert (pmutex->count == 0);
PTHREAD_CHECK ("pthread_mutex_destroy", pthread_mutex_destroy (&pmutex->lock));
dbus_free (pmutex);
}
-static dbus_bool_t
+static void
_dbus_pthread_mutex_lock (DBusMutex *mutex)
{
DBusMutexPThread *pmutex = DBUS_MUTEX_PTHREAD (mutex);
-
- PTHREAD_CHECK ("pthread_mutex_lock", pthread_mutex_lock (&pmutex->lock));
-
- return TRUE;
+ pthread_t self = pthread_self ();
+
+ /* If the count is > 0 then someone had the lock, maybe us. If it is
+ * 0, then it might immediately change right after we read it,
+ * but it will be changed by another thread; i.e. if we read 0,
+ * we assume that this thread doesn't have the lock.
+ *
+ * Not 100% sure this is safe, but ... seems like it should be.
+ */
+ if (pmutex->count == 0)
+ {
+ /* We know we don't have the lock; someone may have the lock. */
+
+ PTHREAD_CHECK ("pthread_mutex_lock", pthread_mutex_lock (&pmutex->lock));
+
+ /* We now have the lock. Count must be 0 since it must be 0 when
+ * the lock is released by another thread, and we just now got
+ * the lock.
+ */
+ _dbus_assert (pmutex->count == 0);
+
+ pmutex->holder = self;
+ pmutex->count = 1;
+ }
+ else
+ {
+ /* We know someone had the lock, possibly us. Thus
+ * pmutex->holder is not pointing to junk, though it may not be
+ * the lock holder anymore if the lock holder is not us. If the
+ * lock holder is us, then we definitely have the lock.
+ */
+
+ if (pthread_equal (pmutex->holder, self))
+ {
+ /* We already have the lock. */
+ _dbus_assert (pmutex->count > 0);
+ }
+ else
+ {
+ /* Wait for the lock */
+ PTHREAD_CHECK ("pthread_mutex_lock", pthread_mutex_lock (&pmutex->lock));
+ pmutex->holder = self;
+ _dbus_assert (pmutex->count == 0);
+ }
+
+ pmutex->count += 1;
+ }
}
-static dbus_bool_t
+static void
_dbus_pthread_mutex_unlock (DBusMutex *mutex)
{
DBusMutexPThread *pmutex = DBUS_MUTEX_PTHREAD (mutex);
- PTHREAD_CHECK ("pthread_mutex_unlock", pthread_mutex_unlock (&pmutex->lock));
+ _dbus_assert (pmutex->count > 0);
+
+ pmutex->count -= 1;
- return TRUE;
+ if (pmutex->count == 0)
+ PTHREAD_CHECK ("pthread_mutex_unlock", pthread_mutex_unlock (&pmutex->lock));
+
+ /* We leave pmutex->holder set to ourselves, its content is undefined if count is 0 */
}
static DBusCondVar *
_dbus_pthread_condvar_new (void)
{
DBusCondVarPThread *pcond;
+ pthread_condattr_t attr;
int result;
pcond = dbus_new (DBusCondVarPThread, 1);
if (pcond == NULL)
return NULL;
- result = pthread_cond_init (&pcond->cond, NULL);
+ pthread_condattr_init (&attr);
+#ifdef HAVE_MONOTONIC_CLOCK
+ if (have_monotonic_clock)
+ pthread_condattr_setclock (&attr, CLOCK_MONOTONIC);
+#endif
+
+ result = pthread_cond_init (&pcond->cond, &attr);
+ pthread_condattr_destroy (&attr);
if (result == EAGAIN || result == ENOMEM)
{
{
DBusMutexPThread *pmutex = DBUS_MUTEX_PTHREAD (mutex);
DBusCondVarPThread *pcond = DBUS_COND_VAR_PTHREAD (cond);
+ int old_count;
+ _dbus_assert (pmutex->count > 0);
+ _dbus_assert (pthread_equal (pmutex->holder, pthread_self ()));
+
+ old_count = pmutex->count;
+ pmutex->count = 0; /* allow other threads to lock */
PTHREAD_CHECK ("pthread_cond_wait", pthread_cond_wait (&pcond->cond, &pmutex->lock));
+ _dbus_assert (pmutex->count == 0);
+ pmutex->count = old_count;
+ pmutex->holder = pthread_self(); /* other threads may have locked the mutex in the meantime */
}
static dbus_bool_t
struct timeval time_now;
struct timespec end_time;
int result;
+ int old_count;
+ _dbus_assert (pmutex->count > 0);
+ _dbus_assert (pthread_equal (pmutex->holder, pthread_self ()));
+
+#ifdef HAVE_MONOTONIC_CLOCK
+ if (have_monotonic_clock)
+ {
+ struct timespec monotonic_timer;
+ clock_gettime (CLOCK_MONOTONIC,&monotonic_timer);
+ time_now.tv_sec = monotonic_timer.tv_sec;
+ time_now.tv_usec = monotonic_timer.tv_nsec / 1000;
+ }
+ else
+ /* This else falls through to gettimeofday */
+#endif
gettimeofday (&time_now, NULL);
end_time.tv_sec = time_now.tv_sec + timeout_milliseconds / 1000;
end_time.tv_nsec -= 1000*1000*1000;
}
+ old_count = pmutex->count;
+ pmutex->count = 0;
result = pthread_cond_timedwait (&pcond->cond, &pmutex->lock, &end_time);
-
+
if (result != ETIMEDOUT)
{
PTHREAD_CHECK ("pthread_cond_timedwait", result);
}
+
+ _dbus_assert (pmutex->count == 0);
+ pmutex->count = old_count;
+ pmutex->holder = pthread_self(); /* other threads may have locked the mutex in the meantime */
/* return true if we did not time out */
return result != ETIMEDOUT;
static const DBusThreadFunctions pthread_functions =
{
- DBUS_THREAD_FUNCTIONS_MUTEX_NEW_MASK |
- DBUS_THREAD_FUNCTIONS_MUTEX_FREE_MASK |
- DBUS_THREAD_FUNCTIONS_MUTEX_LOCK_MASK |
- DBUS_THREAD_FUNCTIONS_MUTEX_UNLOCK_MASK |
+ DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_NEW_MASK |
+ DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_FREE_MASK |
+ DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_LOCK_MASK |
+ DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_UNLOCK_MASK |
DBUS_THREAD_FUNCTIONS_CONDVAR_NEW_MASK |
DBUS_THREAD_FUNCTIONS_CONDVAR_FREE_MASK |
DBUS_THREAD_FUNCTIONS_CONDVAR_WAIT_MASK |
DBUS_THREAD_FUNCTIONS_CONDVAR_WAIT_TIMEOUT_MASK |
DBUS_THREAD_FUNCTIONS_CONDVAR_WAKE_ONE_MASK|
DBUS_THREAD_FUNCTIONS_CONDVAR_WAKE_ALL_MASK,
- _dbus_pthread_mutex_new,
- _dbus_pthread_mutex_free,
- _dbus_pthread_mutex_lock,
- _dbus_pthread_mutex_unlock,
+ NULL, NULL, NULL, NULL,
_dbus_pthread_condvar_new,
_dbus_pthread_condvar_free,
_dbus_pthread_condvar_wait,
_dbus_pthread_condvar_wait_timeout,
_dbus_pthread_condvar_wake_one,
- _dbus_pthread_condvar_wake_all
+ _dbus_pthread_condvar_wake_all,
+ _dbus_pthread_mutex_new,
+ _dbus_pthread_mutex_free,
+ _dbus_pthread_mutex_lock,
+ _dbus_pthread_mutex_unlock
};
+static void
+check_monotonic_clock (void)
+{
+#ifdef HAVE_MONOTONIC_CLOCK
+ struct timespec dummy;
+ if (clock_getres (CLOCK_MONOTONIC, &dummy) == 0)
+ have_monotonic_clock = TRUE;
+#endif
+}
+
dbus_bool_t
_dbus_threads_init_platform_specific (void)
{
+ check_monotonic_clock ();
return dbus_threads_init (&pthread_functions);
}
projects / platform / upstream / dbus.git / blobdiff