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

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Date:   Fri, 6 Sep 2019 12:39:00 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Qian Cai <cai@....pw>, Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        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 (09/05/19 13:23), Steven Rostedt wrote:
> > I think we can queue significantly much less irq_work-s from printk().
> > 
> > Petr, Steven, what do you think?

[..]
> I mean, really, do we need to keep calling wake up if it
> probably never even executed?

I guess ratelimiting you are talking about ("if it probably never even
executed") would be to check if we have already called wake up on the
log_wait ->head. For that we need to, at least, take log_wait spin_lock
and check that ->head is still in TASK_INTERRUPTIBLE; which is (quite,
but not exactly) close to what wake_up_interruptible() does - it doesn't
wake up the same task twice, it bails out on `p->state & state' check.

Or did I miss something?

	-ss