Re: [RFC][PATCH 4/4] futex: Rewrite FUTEX_UNLOCK_PI

[Peter Zijlstra]

On Mon, Oct 03, 2016 at 11:36:24AM -0400, Steven Rostedt wrote:

> > +	WARN_ON_ONCE(!atomic_inc_not_zero(&pi_state->refcount));
> 
> Don't we have a rule where WARN_ON() and BUG_ON() should never have
> "side effects"? That is, they should only check values, but their
> contents should not update values.

not that I'm aware, there's various places in the kernel (including
kref.h) that relies on WARN_ON*() having side effects.