Re: [PATCH 1/4] sched/wakeup: Strengthen current_save_and_set_rtlock_wait_state()

[Peter Zijlstra]

On Fri, Sep 10, 2021 at 01:57:26PM +0100, Will Deacon wrote:
> On Thu, Sep 09, 2021 at 04:27:46PM +0200, Peter Zijlstra wrote:
> > Moo yes, so the earlier changelog I wrote was something like:
> > 
> > 	current_save_and_set_rtlock_wait_state();
> > 	for (;;) {
> > 		if (try_lock())
> > 			break;
> > 
> > 		raw_spin_unlock_irq(&lock->wait_lock);
> > 		if (!cond)
> > 			schedule();
> > 		raw_spin_lock_irq(&lock->wait_lock);
> > 
> > 		set_current_state(TASK_RTLOCK_WAIT);
> > 	}
> > 	current_restore_rtlock_saved_state();
> > 
> > which is more what the code looks like before these patches, and in that
> > case the @cond load can be lifted before __state.
> 
> Ah, so that makes more sense, thanks. I can't see how the try_lock() could
> be reordered though, as it's going to have to do an atomic rmw.

OK, lemme go update the Changelog and make it __flags for bigeasy :-)