Re: [PATCH v4 04/16] locking/rwsem: Implement a new locking scheme

[Peter Zijlstra]

On Sat, Apr 13, 2019 at 01:22:47PM -0400, Waiman Long wrote:
> +#define RWSEM_COUNT_LOCKED(c)        ((c) & RWSEM_LOCK_MASK)

The above doesn't seem to make it more readable or shorter.

--- a/kernel/locking/rwsem-xadd.c
+++ b/kernel/locking/rwsem-xadd.c
@@ -192,7 +192,7 @@ static inline bool rwsem_try_write_lock(
 {
        long new;
 
-       if (RWSEM_COUNT_LOCKED(count))
+       if (count & RWSEM_LOCK_MASK)
                return false;
 
        new = count + RWSEM_WRITER_LOCKED -
@@ -214,7 +214,7 @@ static inline bool rwsem_try_write_lock_
 {
        long count = atomic_long_read(&sem->count);
 
-       while (!RWSEM_COUNT_LOCKED(count)) {
+       while (!(count & RWSEM_LOCK_MASK)) {
                if (atomic_long_try_cmpxchg_acquire(&sem->count, &count,
                                        count + RWSEM_WRITER_LOCKED)) {
                        rwsem_set_owner(sem);
@@ -393,7 +393,7 @@ __rwsem_down_read_failed_common(struct r
         * If there are no writers and we are first in the queue,
         * wake our own waiter to join the existing active readers !
         */
-       if (!RWSEM_COUNT_LOCKED(count) ||
+       if (!(count & RWSEM_LOCK_MASK) ||
           (!(count & RWSEM_WRITER_MASK) && (adjustment & RWSEM_FLAG_WAITERS)))
                __rwsem_mark_wake(sem, RWSEM_WAKE_ANY, &wake_q);
 
@@ -522,7 +522,7 @@ __rwsem_down_write_failed_common(struct
                        lockevent_inc(rwsem_sleep_writer);
                        set_current_state(state);
                        count = atomic_long_read(&sem->count);
-               } while (RWSEM_COUNT_LOCKED(count));
+               } while (count & RWSEM_LOCK_MASK);
 
                raw_spin_lock_irq(&sem->wait_lock);
        }