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)));