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Use actual recursive pthreads mutexes, rather than NIH'ing them, wrong

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Very loosely based on a patch from Sigmund Augdal.

For the moment, we make PTHREAD_MUTEX_RECURSIVE a hard requirement:
it's required by POSIX 2008 Base and SUSv2.

If your (non-Windows) platform doesn't have PTHREAD_MUTEX_RECURSIVE,
please report a bug on freedesktop.org bugzilla with details of the
platform in question.

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=43744
Signed-off-by: Simon McVittie <simon.mcvittie@collabora.co.uk>
Reviewed-by: Thiago Macieira <thiago@kde.org>
This commit is contained in:
Simon McVittie 2012-02-14 19:02:20 +00:00
parent f85ca5fac1
commit f025158dd9
1 changed files with 49 additions and 98 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

147
dbus/dbus-sysdeps-pthread.c
View file

@ -44,12 +44,7 @@
static dbus_bool_t have_monotonic_clock = 0;
typedef struct {
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 */
pthread_mutex_t lock; /**< the lock */
} DBusMutexPThread;
typedef struct {
@ -77,12 +72,12 @@ typedef struct {
} while (0)
#endif /* !DBUS_DISABLE_ASSERT */
static DBusMutex*
_dbus_pthread_mutex_new (void)
static DBusMutex *
_dbus_pthread_cmutex_new (void)
{
DBusMutexPThread *pmutex;
int result;
pmutex = dbus_new (DBusMutexPThread, 1);
if (pmutex == NULL)
return NULL;
@ -99,14 +94,35 @@ _dbus_pthread_mutex_new (void)
PTHREAD_CHECK ("pthread_mutex_init", result);
}
/* Only written */
pmutex->count = 0;
return DBUS_MUTEX (pmutex);
}
static DBusMutex *
_dbus_pthread_rmutex_new (void)
{
DBusMutexPThread *pmutex;
pthread_mutexattr_t mutexattr;
int result;
pmutex = dbus_new (DBusMutexPThread, 1);
if (pmutex == NULL)
return NULL;
pthread_mutexattr_init (&mutexattr);
pthread_mutexattr_settype (&mutexattr, PTHREAD_MUTEX_RECURSIVE);
result = pthread_mutex_init (&pmutex->lock, &mutexattr);
pthread_mutexattr_destroy (&mutexattr);
if (result == ENOMEM || result == EAGAIN)
{
dbus_free (pmutex);
return NULL;
}
else
{
PTHREAD_CHECK ("pthread_mutex_init", result);
}
/* 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);
}
@ -115,79 +131,26 @@ _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 void
static dbus_bool_t
_dbus_pthread_mutex_lock (DBusMutex *mutex)
{
DBusMutexPThread *pmutex = DBUS_MUTEX_PTHREAD (mutex);
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;
}
PTHREAD_CHECK ("pthread_mutex_lock", pthread_mutex_lock (&pmutex->lock));
return TRUE;
}
static void
static dbus_bool_t
_dbus_pthread_mutex_unlock (DBusMutex *mutex)
{
DBusMutexPThread *pmutex = DBUS_MUTEX_PTHREAD (mutex);
_dbus_assert (pmutex->count > 0);
pmutex->count -= 1;
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 */
PTHREAD_CHECK ("pthread_mutex_unlock", pthread_mutex_unlock (&pmutex->lock));
return TRUE;
}
static DBusCondVar *
@ -239,17 +202,8 @@ _dbus_pthread_condvar_wait (DBusCondVar *cond,
{
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
@ -262,10 +216,6 @@ _dbus_pthread_condvar_wait_timeout (DBusCondVar *cond,
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)
@ -288,8 +238,6 @@ _dbus_pthread_condvar_wait_timeout (DBusCondVar *cond,
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)
@ -297,10 +245,6 @@ _dbus_pthread_condvar_wait_timeout (DBusCondVar *cond,
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;
}
@ -323,6 +267,10 @@ _dbus_pthread_condvar_wake_all (DBusCondVar *cond)
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 |
@ -333,17 +281,20 @@ static const DBusThreadFunctions pthread_functions =
DBUS_THREAD_FUNCTIONS_CONDVAR_WAIT_TIMEOUT_MASK |
DBUS_THREAD_FUNCTIONS_CONDVAR_WAKE_ONE_MASK|
DBUS_THREAD_FUNCTIONS_CONDVAR_WAKE_ALL_MASK,
NULL, NULL, NULL, NULL,
_dbus_pthread_cmutex_new,
_dbus_pthread_mutex_free,
_dbus_pthread_mutex_lock,
_dbus_pthread_mutex_unlock,
_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_mutex_new,
_dbus_pthread_rmutex_new,
_dbus_pthread_mutex_free,
_dbus_pthread_mutex_lock,
_dbus_pthread_mutex_unlock
(void (*) (DBusMutex *)) _dbus_pthread_mutex_lock,
(void (*) (DBusMutex *)) _dbus_pthread_mutex_unlock
};
static void