Provide writer preference option in rwlock.
Previous implementation of rwlock contains four atomic variables, which
is hard to maintain and change. So I make following changes in this CL:
1. Add pending flags in rwlock.state, so we don't need to synchronize
between different atomic variables. Using compare_and_swap operations
on rwlock.state is enough for all state change.
2. Add pending_lock to protect readers/writers waiting and wake up
operations. As waiting/wakeup is not performance critical, using a
lock is easier to maintain.
3. Add writer preference option.
4. Add unit tests for rwlock.
Bug: 19109156
Change-Id: Idcaa58d695ea401d64445610b465ac5cff23ec7c
diff --git a/libc/include/pthread.h b/libc/include/pthread.h
index 83a56d6..26d68e4 100644
--- a/libc/include/pthread.h
+++ b/libc/include/pthread.h
@@ -85,6 +85,11 @@
#define PTHREAD_RWLOCK_INITIALIZER { { 0 } }
+enum {
+ PTHREAD_RWLOCK_PREFER_READER_NP = 0,
+ PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP = 1,
+};
+
typedef int pthread_key_t;
typedef int pthread_once_t;
@@ -178,10 +183,12 @@
int pthread_once(pthread_once_t*, void (*)(void)) __nonnull((1, 2));
+int pthread_rwlockattr_init(pthread_rwlockattr_t*) __nonnull((1));
int pthread_rwlockattr_destroy(pthread_rwlockattr_t*) __nonnull((1));
int pthread_rwlockattr_getpshared(const pthread_rwlockattr_t*, int*) __nonnull((1, 2));
-int pthread_rwlockattr_init(pthread_rwlockattr_t*) __nonnull((1));
int pthread_rwlockattr_setpshared(pthread_rwlockattr_t*, int) __nonnull((1));
+int pthread_rwlockattr_getkind_np(const pthread_rwlockattr_t*, int*) __nonnull((1, 2));
+int pthread_rwlockattr_setkind_np(pthread_rwlockattr_t*, int) __nonnull((1));
int pthread_rwlock_destroy(pthread_rwlock_t*) __nonnull((1));
int pthread_rwlock_init(pthread_rwlock_t*, const pthread_rwlockattr_t*) __nonnull((1));