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

[Steven Rostedt]

On Mon, 3 Oct 2016 17:45:14 +0200
Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:

> 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.

Looking more into it, I believe the "no side effect" is only with
BUG_ON(), as WARN_ON() can be used within if statements.

-- Steve