diff options
Diffstat (limited to 'nptl/pthread_rwlock_timedwrlock.c')
| -rw-r--r-- | nptl/pthread_rwlock_timedwrlock.c | 127 |
1 files changed, 14 insertions, 113 deletions
diff --git a/nptl/pthread_rwlock_timedwrlock.c b/nptl/pthread_rwlock_timedwrlock.c index 9f024be819..5626505d2c 100644 --- a/nptl/pthread_rwlock_timedwrlock.c +++ b/nptl/pthread_rwlock_timedwrlock.c @@ -16,121 +16,22 @@ License along with the GNU C Library; if not, see <http://www.gnu.org/licenses/>. */ -#include <errno.h> -#include <sysdep.h> -#include <lowlevellock.h> -#include <futex-internal.h> -#include <pthread.h> -#include <pthreadP.h> -#include <sys/time.h> -#include <stdbool.h> +#include "pthread_rwlock_common.c" - -/* Try to acquire write lock for RWLOCK or return after specfied time. */ +/* See pthread_rwlock_common.c. */ int pthread_rwlock_timedwrlock (pthread_rwlock_t *rwlock, - const struct timespec *abstime) + const struct timespec *abstime) { - int result = 0; - bool wake_readers = false; - int futex_shared = - rwlock->__data.__shared == LLL_PRIVATE ? FUTEX_PRIVATE : FUTEX_SHARED; - - /* Make sure we are alone. */ - lll_lock (rwlock->__data.__lock, rwlock->__data.__shared); - - while (1) - { - int err; - - /* Get the rwlock if there is no writer and no reader. */ - if (rwlock->__data.__writer == 0 && rwlock->__data.__nr_readers == 0) - { - /* Mark self as writer. */ - rwlock->__data.__writer = THREAD_GETMEM (THREAD_SELF, tid); - break; - } - - /* Make sure we are not holding the rwlock as a writer. This is - a deadlock situation we recognize and report. */ - if (__builtin_expect (rwlock->__data.__writer - == THREAD_GETMEM (THREAD_SELF, tid), 0)) - { - result = EDEADLK; - break; - } - - /* Make sure the passed in timeout value is valid. Ideally this - test would be executed once. But since it must not be - performed if we would not block at all simply moving the test - to the front is no option. Replicating all the code is - costly while this test is not. */ - if (__builtin_expect (abstime->tv_nsec >= 1000000000 - || abstime->tv_nsec < 0, 0)) - { - result = EINVAL; - break; - } - - /* Remember that we are a writer. */ - if (++rwlock->__data.__nr_writers_queued == 0) - { - /* Overflow on number of queued writers. */ - --rwlock->__data.__nr_writers_queued; - result = EAGAIN; - break; - } - - int waitval = rwlock->__data.__writer_wakeup; - - /* Free the lock. */ - lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared); - - /* Wait for the writer or reader(s) to finish. We handle ETIMEDOUT - below; on other return values, we decide how to continue based on - the state of the rwlock. */ - err = futex_abstimed_wait (&rwlock->__data.__writer_wakeup, waitval, - abstime, futex_shared); - - /* Get the lock. */ - lll_lock (rwlock->__data.__lock, rwlock->__data.__shared); - - /* To start over again, remove the thread from the writer list. */ - --rwlock->__data.__nr_writers_queued; - - /* Did the futex call time out? */ - if (err == ETIMEDOUT) - { - result = ETIMEDOUT; - /* If we prefer writers, it can have happened that readers blocked - for us to acquire the lock first. If we have timed out, we need - to wake such readers if there are any, and if there is no writer - currently (otherwise, the writer will take care of wake-up). - Likewise, even if we prefer readers, we can be responsible for - wake-up (see pthread_rwlock_unlock) if no reader or writer has - acquired the lock. We have timed out and thus not consumed a - futex wake-up; therefore, if there is no other blocked writer - that would consume the wake-up and thus take over responsibility, - we need to wake blocked readers. */ - if ((!PTHREAD_RWLOCK_PREFER_READER_P (rwlock) - || ((rwlock->__data.__nr_readers == 0) - && (rwlock->__data.__nr_writers_queued == 0))) - && (rwlock->__data.__nr_readers_queued > 0) - && (rwlock->__data.__writer == 0)) - { - ++rwlock->__data.__readers_wakeup; - wake_readers = true; - } - break; - } - } - - /* We are done, free the lock. */ - lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared); - - /* Might be required after timeouts. */ - if (wake_readers) - futex_wake (&rwlock->__data.__readers_wakeup, INT_MAX, futex_shared); - - return result; + /* Make sure the passed in timeout value is valid. Note that the previous + implementation assumed that this check *must* not be performed if there + would in fact be no blocking; however, POSIX only requires that "the + validity of the abstime parameter need not be checked if the lock can be + immediately acquired" (i.e., we need not but may check it). */ + /* ??? Just move this to __pthread_rwlock_wrlock_full? */ + if (__glibc_unlikely (abstime->tv_nsec >= 1000000000 + || abstime->tv_nsec < 0)) + return EINVAL; + + return __pthread_rwlock_wrlock_full (rwlock, abstime); } |