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

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Message-ID: <20191121010527.GB191121@google.com>
Date:   Thu, 21 Nov 2019 10:05:27 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...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 (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

> RT guys are going to make printk() fully lockless. It would be
> really great achievement. irq_work is lockless. While wake_up()
> is not.
>
> There must be a better way how to break the infinite loop caused
> by the irq_work.

A lockless wake_up() would do :)

	-ss