Re: [PATCH v15 12/16] cpuidle/poll_state: Wait for need-resched via tif_need_resched_relaxed_wait()

[Catalin Marinas <catalin.marinas@arm.com>]

On Wed, Oct 14, 2026 at 03:03:06PM +0200, Peter Zijlstra wrote:
> On Wed, Oct 14, 2026 at 10:00:18AM +0100, Catalin Marinas wrote:
> > It
> > would also be nice to get some acks from the atomic infrastructure
> > maintainers.
> 
> That'd be Mark and me I suppose. I don't see anything substantial
> happening, just plumbing the new function.

Thanks!

> Now, I really rather dislike timeout based schemes, but given we have
> users, I suppose this does improve things. We should however be weary of
> new ones I suppose.

There's some arm64 precedent in commit ebababcd0372 ("rqspinlock:
Hardcode cond_acquire loops for arm64"). This one went in without any of
the arm64 maintainers' ack and we've since been trying to come up with a
generic interface instead of reverting it. It was fixing a bug where
arm64 smp_cond_load_acquire() does not evaluate cond_expr unless the
pointer is also written by another CPU. Arguably the bug was in the
rqspinlock code for not using a plain cpu_relax() loop.

Anyway, we had several incarnations of this series, some with a default
timeout but others objected to it (Arnd and Rafael IIRC), hence the
proposal here that pleased most people (not all though ;)).

-- 
Catalin