linux-kernel - Re: [PATCH] net/skbuff: silence warnings under memory pressure

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Date:   Thu, 21 Nov 2019 10:15:18 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Qian Cai <cai@....pw>, Steven Rostedt <rostedt@...dmis.org>,
        Michal Hocko <mhocko@...nel.org>,
        Eric Dumazet <eric.dumazet@...il.com>, davem@...emloft.net,
        netdev@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net/skbuff: silence warnings under memory pressure

On Thu 2019-11-21 10:05:27, Sergey Senozhatsky wrote:
> On (19/11/20 17:13), Petr Mladek wrote:
> [..]
> > It is the first time that I hear about problem caused by the
> > irq_work(). But we deal with deadlocks caused by wake_up() for years.
> > It would be like replacing a lightly dripping tap with a heavily
> > dripping one.
> > 
> > I see reports with WARN() from scheduler code from time to time.
> > I would get reports about silent death instead.
> 
> Just curious, how many of those WARN() come under rq lock or pi_lock?
> // this is real question

I guess that all SCHED_WARN_ON() would stop working.

I am not 100% sure but I think that all WARN_ON*() in
set_task_cpu(), finish_task_switch(), migrate_tasks()
are affected.

I have seen many reports with the WARN() from
native_smp_send_reschedule() about offline CPU.

Best Regards,
Petr