Re: [PATCH] sched/ext: Suppress warning in __this_cpu_write() by disabling preemption

[Peter Zijlstra]

On Wed, Jul 16, 2025 at 03:15:12PM +0200, Andrea Righi wrote:

> The idea is to track the scx callbacks that are invoked with a rq lock held
> and, in those cases, store the locked rq. However, some callbacks may also
> be invoked from an unlocked context, where no rq is locked and in this case
> rq should be NULL.
> 
> In the latter case, it's acceptable for preemption to remain enabled, but
> we still want to explicitly set locked_rq = NULL. If during the execution
> of the callback we jump on another CPU, it'd still be in an unlocked state,
> so it's locked_rq is still NULL.

Right; but doing superfluous NULL stores seems pointless. So better to
avoid the store entirely, rather than making it more expensive and no
less pointless, right?