Re: [PATCHv3 2/6] tty/ldsem: Update waiter->task before waking up reader

On Tue, Sep 11, 2018 at 02:41:29PM +0900, Sergey Senozhatsky wrote:

On (09/11/18 14:04), Sergey Senozhatsky wrote:

...

...

for (;;) { set_current_state(TASK_UNINTERRUPTIBLE);

I think that set_current_state() also executes memory barrier. Just because it accesses task state.

...

• if (!waiter.task)
  

• if (!READ_ONCE(waiter.task))
  break;
  

  if (!timeout) break;

This READ_ONCE(waiter.task) looks interesting. Maybe could be moved to a loop condition

while (!READ_ONCE(waiter.task)) { ... }

No, it must be after set_current_state(). See that same comment.