Re: [PATCH 1/2] sched: Fix balance_callback()

From: Valentin Schneider
Date: Fri Sep 11 2020 - 10:10:56 EST

On 11/09/20 13:25, peterz@xxxxxxxxxxxxx wrote:
> On Fri, Sep 11, 2020 at 01:17:02PM +0100, Valentin Schneider wrote:
>> So that can be say __schedule() tail racing with some setprio; what's the
>> worst that can (currently) happen here? Something like say two consecutive
>> enqueuing of push_rt_tasks() to the callback list?
> Yeah, but that isn't in fact the case I worry most about.
> What can happen (and what I've spotted once before) is that someone
> attempts to enqueue a balance_callback from a rq->lock region that
> doesn't handle the calls.
> Currently that 'works', that is, it will get ran _eventually_. But
> ideally we'd want that to not work and issue a WARN. We want the
> callbacks to be timely.
> So basically all of these machinations we in order to add the WARN :-)

Makes sense, thanks!