linux-kernel - Re: [PATCH v2 4/9] cgroup: rstat: add WARN_ON

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Message-ID: <ZCqQfuprGreGYwFA@dhcp22.suse.cz>
Date:   Mon, 3 Apr 2023 10:38:22 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Yosry Ahmed <yosryahmed@...gle.com>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Shakeel Butt <shakeelb@...gle.com>, Tejun Heo <tj@...nel.org>,
        Josef Bacik <josef@...icpanda.com>,
        Jens Axboe <axboe@...nel.dk>,
        Zefan Li <lizefan.x@...edance.com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Muchun Song <muchun.song@...ux.dev>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Koutný <mkoutny@...e.com>,
        Vasily Averin <vasily.averin@...ux.dev>,
        cgroups@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        bpf@...r.kernel.org
Subject: Re: [PATCH v2 4/9] cgroup: rstat: add WARN_ON_ONCE() if flushing
 outside task context

On Fri 31-03-23 12:03:47, Yosry Ahmed wrote:
> On Fri, Mar 31, 2023 at 4:02 AM Michal Hocko <mhocko@...e.com> wrote:
> >
> > On Thu 30-03-23 01:53:38, Yosry Ahmed wrote:
> > [...]
> > > Maybe we can add a primitive like might_sleep() for this, just food for thought.
> >
> > I do not think it is the correct to abuse might_sleep if the function
> > itself doesn't sleep. If it does might_sleep is already involved.
> 
> Oh, sorry if I wasn't clear, I did not mean to reuse might_sleep() --
> I meant introducing a new similar debug primitive that shouts if irqs
> are disabled.

This is circling back to original concerns about arbitrary decision to
care about IRQs. Is this really any different from spin locks or preempt
disabled critical sections preventing any scheduling and potentially
triggereing soft lockups?
-- 
Michal Hocko
SUSE Labs