Re: [PATCH v4 30/39] unwind_user/deferred: Make unwind deferral requests NMI-safe

[Peter Zijlstra]

On Thu, Jan 23, 2025 at 11:48:07AM -0800, Josh Poimboeuf wrote:
> > > >         cookie = READ_ONCE(current->unwind_info.cookie);
> > > >         do {
> > > >                 if (cookie)
> > > >                         return cookie;
> > > >                 cookie = ctx_to_cookie(cpu, ctr+1);
> > > >         } while (!try_cmpxchg64(&current->unwind_info.cookie, &cookie, 
> > > > cookie));
> 
> Should not the 2nd argument be &zero?

This I suppose

        cookie = READ_ONCE(current->unwind_info.cookie);
        do {
                if (cookie)
                        return cookie;
        } while (!try_cmpxchg64(&current->unwind_info.cookie, &cookie,
                                ctx_to_cookie(cpu, ctr+1)));