diff options
Diffstat (limited to 'nptl/pthread_rwlock_rdlock.c')
| -rw-r--r-- | nptl/pthread_rwlock_rdlock.c | 88 |
1 files changed, 61 insertions, 27 deletions
diff --git a/nptl/pthread_rwlock_rdlock.c b/nptl/pthread_rwlock_rdlock.c index 3773f7db2a..1df0327a22 100644 --- a/nptl/pthread_rwlock_rdlock.c +++ b/nptl/pthread_rwlock_rdlock.c @@ -24,39 +24,16 @@ #include <stap-probe.h> -/* Acquire read lock for RWLOCK. */ -int -__pthread_rwlock_rdlock (rwlock) - pthread_rwlock_t *rwlock; +/* Acquire read lock for RWLOCK. Slow path. */ +static int __attribute__((noinline)) +__pthread_rwlock_rdlock_slow (pthread_rwlock_t *rwlock) { int result = 0; - LIBC_PROBE (rdlock_entry, 1, rwlock); - - /* Make sure we are alone. */ - lll_lock (rwlock->__data.__lock, rwlock->__data.__shared); + /* Lock is taken in caller. */ while (1) { - /* 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 (__glibc_unlikely (++rwlock->__data.__nr_readers == 0)) - { - /* Overflow on number of readers. */ - --rwlock->__data.__nr_readers; - result = EAGAIN; - } - else - LIBC_PROBE (rdlock_acquire_read, 1, rwlock); - - 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 @@ -88,6 +65,25 @@ __pthread_rwlock_rdlock (rwlock) lll_lock (rwlock->__data.__lock, rwlock->__data.__shared); --rwlock->__data.__nr_readers_queued; + + /* 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 (__glibc_unlikely (++rwlock->__data.__nr_readers == 0)) + { + /* Overflow on number of readers. */ + --rwlock->__data.__nr_readers; + result = EAGAIN; + } + else + LIBC_PROBE (rdlock_acquire_read, 1, rwlock); + + break; + } } /* We are done, free the lock. */ @@ -96,5 +92,43 @@ __pthread_rwlock_rdlock (rwlock) return result; } + +/* Fast path of acquiring read lock on RWLOCK. */ + +int +__pthread_rwlock_rdlock (pthread_rwlock_t *rwlock) +{ + int result = 0; + + LIBC_PROBE (rdlock_entry, 1, rwlock); + + /* Make sure we are alone. */ + lll_lock (rwlock->__data.__lock, rwlock->__data.__shared); + + /* 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 (__glibc_unlikely (++rwlock->__data.__nr_readers == 0)) + { + /* Overflow on number of readers. */ + --rwlock->__data.__nr_readers; + result = EAGAIN; + } + else + LIBC_PROBE (rdlock_acquire_read, 1, rwlock); + + /* We are done, free the lock. */ + lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared); + + return result; + } + + return __pthread_rwlock_rdlock_slow (rwlock); +} + weak_alias (__pthread_rwlock_rdlock, pthread_rwlock_rdlock) hidden_def (__pthread_rwlock_rdlock) |