Re: [PATCH] Documentation: atomic_t.txt: Explain ordering provided by smp_mb__{before,after}_atomic()

[Peter Zijlstra]

On Tue, Apr 23, 2019 at 06:30:10AM -0700, Paul E. McKenney wrote:
> There are a great many that look like this:
> 
> 	smp_mb__before_atomic();
> 	clear_bit(NFSD4_CLIENT_UPCALL_LOCK, &clp->cl_flags);
> 	smp_mb__after_atomic();

Ooh, marvel at the comment describing the ordering there. Oh wait :-(
So much for checkpatch.pl I suppose.

I think the first is a release order for the 'LOCK' bit and the second
is because of wake_up_bit() being a shitty interface.

So maybe that should've been:

	clear_bit_unlock(NFSD4_CLIENT_UPCALL_LOCK, &clp->cl_flags);
	smp_mb__after_atomic();
	wake_up_bit(&clp->cl_flags, NFSD4_CLIENT_UPCALL_LOCK);

instead?