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-rw-r--r--kernel/locking/rwsem.h174
1 files changed, 172 insertions, 2 deletions
diff --git a/kernel/locking/rwsem.h b/kernel/locking/rwsem.h
index bad2bca0268b..64877f5294e3 100644
--- a/kernel/locking/rwsem.h
+++ b/kernel/locking/rwsem.h
@@ -23,15 +23,44 @@
* is involved. Ideally we would like to track all the readers that own
* a rwsem, but the overhead is simply too big.
*/
+#include "lock_events.h"
+
#define RWSEM_READER_OWNED (1UL << 0)
#define RWSEM_ANONYMOUSLY_OWNED (1UL << 1)
#ifdef CONFIG_DEBUG_RWSEMS
-# define DEBUG_RWSEMS_WARN_ON(c) DEBUG_LOCKS_WARN_ON(c)
+# define DEBUG_RWSEMS_WARN_ON(c, sem) do { \
+ if (!debug_locks_silent && \
+ WARN_ONCE(c, "DEBUG_RWSEMS_WARN_ON(%s): count = 0x%lx, owner = 0x%lx, curr 0x%lx, list %sempty\n",\
+ #c, atomic_long_read(&(sem)->count), \
+ (long)((sem)->owner), (long)current, \
+ list_empty(&(sem)->wait_list) ? "" : "not ")) \
+ debug_locks_off(); \
+ } while (0)
+#else
+# define DEBUG_RWSEMS_WARN_ON(c, sem)
+#endif
+
+/*
+ * R/W semaphores originally for PPC using the stuff in lib/rwsem.c.
+ * Adapted largely from include/asm-i386/rwsem.h
+ * by Paul Mackerras <paulus@samba.org>.
+ */
+
+/*
+ * the semaphore definition
+ */
+#ifdef CONFIG_64BIT
+# define RWSEM_ACTIVE_MASK 0xffffffffL
#else
-# define DEBUG_RWSEMS_WARN_ON(c)
+# define RWSEM_ACTIVE_MASK 0x0000ffffL
#endif
+#define RWSEM_ACTIVE_BIAS 0x00000001L
+#define RWSEM_WAITING_BIAS (-RWSEM_ACTIVE_MASK-1)
+#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
+#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
+
#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
/*
* All writes to owner are protected by WRITE_ONCE() to make sure that
@@ -132,3 +161,144 @@ static inline void rwsem_clear_reader_owned(struct rw_semaphore *sem)
{
}
#endif
+
+extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
+extern struct rw_semaphore *rwsem_down_read_failed_killable(struct rw_semaphore *sem);
+extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
+extern struct rw_semaphore *rwsem_down_write_failed_killable(struct rw_semaphore *sem);
+extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem);
+extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
+
+/*
+ * lock for reading
+ */
+static inline void __down_read(struct rw_semaphore *sem)
+{
+ if (unlikely(atomic_long_inc_return_acquire(&sem->count) <= 0)) {
+ rwsem_down_read_failed(sem);
+ DEBUG_RWSEMS_WARN_ON(!((unsigned long)sem->owner &
+ RWSEM_READER_OWNED), sem);
+ } else {
+ rwsem_set_reader_owned(sem);
+ }
+}
+
+static inline int __down_read_killable(struct rw_semaphore *sem)
+{
+ if (unlikely(atomic_long_inc_return_acquire(&sem->count) <= 0)) {
+ if (IS_ERR(rwsem_down_read_failed_killable(sem)))
+ return -EINTR;
+ DEBUG_RWSEMS_WARN_ON(!((unsigned long)sem->owner &
+ RWSEM_READER_OWNED), sem);
+ } else {
+ rwsem_set_reader_owned(sem);
+ }
+ return 0;
+}
+
+static inline int __down_read_trylock(struct rw_semaphore *sem)
+{
+ /*
+ * Optimize for the case when the rwsem is not locked at all.
+ */
+ long tmp = RWSEM_UNLOCKED_VALUE;
+
+ lockevent_inc(rwsem_rtrylock);
+ do {
+ if (atomic_long_try_cmpxchg_acquire(&sem->count, &tmp,
+ tmp + RWSEM_ACTIVE_READ_BIAS)) {
+ rwsem_set_reader_owned(sem);
+ return 1;
+ }
+ } while (tmp >= 0);
+ return 0;
+}
+
+/*
+ * lock for writing
+ */
+static inline void __down_write(struct rw_semaphore *sem)
+{
+ long tmp;
+
+ tmp = atomic_long_add_return_acquire(RWSEM_ACTIVE_WRITE_BIAS,
+ &sem->count);
+ if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
+ rwsem_down_write_failed(sem);
+ rwsem_set_owner(sem);
+}
+
+static inline int __down_write_killable(struct rw_semaphore *sem)
+{
+ long tmp;
+
+ tmp = atomic_long_add_return_acquire(RWSEM_ACTIVE_WRITE_BIAS,
+ &sem->count);
+ if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
+ if (IS_ERR(rwsem_down_write_failed_killable(sem)))
+ return -EINTR;
+ rwsem_set_owner(sem);
+ return 0;
+}
+
+static inline int __down_write_trylock(struct rw_semaphore *sem)
+{
+ long tmp;
+
+ lockevent_inc(rwsem_wtrylock);
+ tmp = atomic_long_cmpxchg_acquire(&sem->count, RWSEM_UNLOCKED_VALUE,
+ RWSEM_ACTIVE_WRITE_BIAS);
+ if (tmp == RWSEM_UNLOCKED_VALUE) {
+ rwsem_set_owner(sem);
+ return true;
+ }
+ return false;
+}
+
+/*
+ * unlock after reading
+ */
+static inline void __up_read(struct rw_semaphore *sem)
+{
+ long tmp;
+
+ DEBUG_RWSEMS_WARN_ON(!((unsigned long)sem->owner & RWSEM_READER_OWNED),
+ sem);
+ rwsem_clear_reader_owned(sem);
+ tmp = atomic_long_dec_return_release(&sem->count);
+ if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0))
+ rwsem_wake(sem);
+}
+
+/*
+ * unlock after writing
+ */
+static inline void __up_write(struct rw_semaphore *sem)
+{
+ DEBUG_RWSEMS_WARN_ON(sem->owner != current, sem);
+ rwsem_clear_owner(sem);
+ if (unlikely(atomic_long_sub_return_release(RWSEM_ACTIVE_WRITE_BIAS,
+ &sem->count) < 0))
+ rwsem_wake(sem);
+}
+
+/*
+ * downgrade write lock to read lock
+ */
+static inline void __downgrade_write(struct rw_semaphore *sem)
+{
+ long tmp;
+
+ /*
+ * When downgrading from exclusive to shared ownership,
+ * anything inside the write-locked region cannot leak
+ * into the read side. In contrast, anything in the
+ * read-locked region is ok to be re-ordered into the
+ * write side. As such, rely on RELEASE semantics.
+ */
+ DEBUG_RWSEMS_WARN_ON(sem->owner != current, sem);
+ tmp = atomic_long_add_return_release(-RWSEM_WAITING_BIAS, &sem->count);
+ rwsem_set_reader_owned(sem);
+ if (tmp < 0)
+ rwsem_downgrade_wake(sem);
+}