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authorTorvald Riegel <triegel@redhat.com>2014-05-22 16:00:12 +0200
committerTorvald Riegel <triegel@redhat.com>2017-01-10 11:50:17 +0100
commitcc25c8b4c1196a8c29e9a45b1e096b99a87b7f8c (patch)
tree52c5358896bc1ce9ad2081f179e72a1edac5fa6f /nptl/pthread_rwlock_timedrdlock.c
parentfbb31e20bc41957c5f3d6550f0178590cf473043 (diff)
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New pthread rwlock that is more scalable.
This replaces the pthread rwlock with a new implementation that uses a more scalable algorithm (primarily through not using a critical section anymore to make state changes). The fast path for rdlock acquisition and release is now basically a single atomic read-modify write or CAS and a few branches. See nptl/pthread_rwlock_common.c for details. * nptl/DESIGN-rwlock.txt: Remove. * nptl/lowlevelrwlock.sym: Remove. * nptl/Makefile: Add new tests. * nptl/pthread_rwlock_common.c: New file. Contains the new rwlock. * nptl/pthreadP.h (PTHREAD_RWLOCK_PREFER_READER_P): Remove. (PTHREAD_RWLOCK_WRPHASE, PTHREAD_RWLOCK_WRLOCKED, PTHREAD_RWLOCK_RWAITING, PTHREAD_RWLOCK_READER_SHIFT, PTHREAD_RWLOCK_READER_OVERFLOW, PTHREAD_RWLOCK_WRHANDOVER, PTHREAD_RWLOCK_FUTEX_USED): New. * nptl/pthread_rwlock_init.c (__pthread_rwlock_init): Adapt to new implementation. * nptl/pthread_rwlock_rdlock.c (__pthread_rwlock_rdlock_slow): Remove. (__pthread_rwlock_rdlock): Adapt. * nptl/pthread_rwlock_timedrdlock.c (pthread_rwlock_timedrdlock): Adapt. * nptl/pthread_rwlock_timedwrlock.c (pthread_rwlock_timedwrlock): Adapt. * nptl/pthread_rwlock_trywrlock.c (pthread_rwlock_trywrlock): Adapt. * nptl/pthread_rwlock_tryrdlock.c (pthread_rwlock_tryrdlock): Adapt. * nptl/pthread_rwlock_unlock.c (pthread_rwlock_unlock): Adapt. * nptl/pthread_rwlock_wrlock.c (__pthread_rwlock_wrlock_slow): Remove. (__pthread_rwlock_wrlock): Adapt. * nptl/tst-rwlock10.c: Adapt. * nptl/tst-rwlock11.c: Adapt. * nptl/tst-rwlock17.c: New file. * nptl/tst-rwlock18.c: New file. * nptl/tst-rwlock19.c: New file. * nptl/tst-rwlock2b.c: New file. * nptl/tst-rwlock8.c: Adapt. * nptl/tst-rwlock9.c: Adapt. * sysdeps/aarch64/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt. * sysdeps/arm/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt. * sysdeps/hppa/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt. * sysdeps/ia64/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt. * sysdeps/m68k/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt. * sysdeps/microblaze/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt. * sysdeps/mips/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt. * sysdeps/nios2/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt. * sysdeps/s390/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt. * sysdeps/sh/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt. * sysdeps/sparc/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt. * sysdeps/tile/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt. * sysdeps/unix/sysv/linux/alpha/bits/pthreadtypes.h (pthread_rwlock_t): Adapt. * sysdeps/unix/sysv/linux/powerpc/bits/pthreadtypes.h (pthread_rwlock_t): Adapt. * sysdeps/x86/bits/pthreadtypes.h (pthread_rwlock_t): Adapt. * nptl/nptl-printers.py (): Adapt. * nptl/nptl_lock_constants.pysym: Adapt. * nptl/test-rwlock-printers.py: Adapt. * nptl/test-rwlockattr-printers.c: Adapt. * nptl/test-rwlockattr-printers.py: Adapt.
Diffstat (limited to 'nptl/pthread_rwlock_timedrdlock.c')
-rw-r--r--nptl/pthread_rwlock_timedrdlock.c127
1 files changed, 14 insertions, 113 deletions
diff --git a/nptl/pthread_rwlock_timedrdlock.c b/nptl/pthread_rwlock_timedrdlock.c
index 003ea573c9..9f084f8c34 100644
--- a/nptl/pthread_rwlock_timedrdlock.c
+++ b/nptl/pthread_rwlock_timedrdlock.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 read lock for RWLOCK or return after specfied time. */
+/* See pthread_rwlock_common.c. */
int
pthread_rwlock_timedrdlock (pthread_rwlock_t *rwlock,
- const struct timespec *abstime)
+ const struct timespec *abstime)
{
- int result = 0;
- bool wake = 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... */
- if (rwlock->__data.__writer == 0
- /* ...and if either no writer is waiting or we prefer readers. */
- && (!rwlock->__data.__nr_writers_queued
- || PTHREAD_RWLOCK_PREFER_READER_P (rwlock)))
- {
- /* Increment the reader counter. Avoid overflow. */
- if (++rwlock->__data.__nr_readers == 0)
- {
- /* Overflow on number of readers. */
- --rwlock->__data.__nr_readers;
- result = EAGAIN;
- }
- else
- {
- /* See pthread_rwlock_rdlock. */
- if (rwlock->__data.__nr_readers == 1
- && rwlock->__data.__nr_readers_queued > 0
- && rwlock->__data.__nr_writers_queued > 0)
- {
- ++rwlock->__data.__readers_wakeup;
- wake = true;
- }
- }
-
- 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 reader. */
- if (++rwlock->__data.__nr_readers_queued == 0)
- {
- /* Overflow on number of queued readers. */
- --rwlock->__data.__nr_readers_queued;
- result = EAGAIN;
- break;
- }
-
- int waitval = rwlock->__data.__readers_wakeup;
-
- /* Free the lock. */
- lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
-
- /* Wait for the writer 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.__readers_wakeup, waitval,
- abstime, futex_shared);
-
- /* Get the lock. */
- lll_lock (rwlock->__data.__lock, rwlock->__data.__shared);
-
- --rwlock->__data.__nr_readers_queued;
-
- /* Did the futex call time out? */
- if (err == ETIMEDOUT)
- {
- /* Yep, report it. */
- result = ETIMEDOUT;
- break;
- }
- }
-
- /* We are done, free the lock. */
- lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
-
- if (wake)
- 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_rdlock_full? */
+ if (__glibc_unlikely (abstime->tv_nsec >= 1000000000
+ || abstime->tv_nsec < 0))
+ return EINVAL;
+
+ return __pthread_rwlock_rdlock_full (rwlock, abstime);
}