On 11/18, Davidlohr Bueso wrote:
>
> @@ -12,7 +12,7 @@ struct percpu_rw_semaphore {
> struct rcu_sync rss;
> unsigned int __percpu *read_count;
> struct rw_semaphore rw_sem;
> - wait_queue_head_t writer;
> + struct swait_queue_head writer;
I won't argue, but even swait_queue_head is overkill in this case.
We can just add "struct task_struct *writer" into percpu_rw_semaphore,
__percpu_up_read:
rcu_read_lock();
writer = task_rcu_dereference(&sem->writer);
if (writer)
wake_up_process(writer);
rcu_read_unlock();
percpu_down_write() can set sem->writer == current and do the simple
while-not-condition-schedule() loop.
But this probably needs a couple of new helpers, and probably they
can have more users.
Oleg.
