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From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>, Qian Cai <cai@lca.pw>,
	davem@davemloft.net, Eric Dumazet <eric.dumazet@gmail.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Michal Hocko <mhocko@kernel.org>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	netdev@vger.kernel.org
Subject: Re: [PATCH] net/skbuff: silence warnings under memory pressure
Date: Sat, 7 Sep 2019 04:51:35 +0900	[thread overview]
Message-ID: <20190906195135.GA69785@tigerII.localdomain> (raw)
In-Reply-To: <20190906145533.4uw43a5pvsawmdov@pathway.suse.cz>

On (09/06/19 16:55), Petr Mladek wrote:
> > I think we can queue significantly much less irq_work-s from printk().
> > 
> > Petr, Steven, what do you think?
> > 
> > Something like this. Call wake_up_interruptible(), switch to
> > wake_up_klogd() only when called from sched code.
> 
> Replacing irq_work_queue() with wake_up_interruptible() looks
> dangerous to me.
> 
> As a result, all "normal" printk() calls from the scheduler
> code will deadlock. There is almost always a userspace
> logger registered.

I don't see why all printk()-s should deadlock.

A "normal" printk() call will deadlock only when scheduler calls
"normal" printk() under rq or pi locks. But this is illegal anyway,
because console_sem up() calls wake_up_process() - the same function
wake_up_interruptible() calls. IOW "normal" printk() calls from
scheduler end up in scheduler, via console_sem->sched chain. We
already execute wake_up_process()->try_to_wake_up() in printk(),
even when a non-LOGLEVEL_SCHED printk() comes from scheduler.

What am I missing something?

	-ss

  reply	other threads:[~2019-09-06 19:51 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-30 14:57 [PATCH] net/skbuff: silence warnings under memory pressure Qian Cai
2019-08-30 15:11 ` Eric Dumazet
2019-08-30 15:25   ` Qian Cai
2019-08-30 16:15     ` Eric Dumazet
2019-08-30 18:06       ` Qian Cai
2019-09-03 13:22       ` Michal Hocko
2019-09-03 15:42         ` Qian Cai
2019-09-03 18:53           ` Michal Hocko
2019-09-03 21:42             ` Qian Cai
2019-09-04  6:15               ` Michal Hocko
2019-09-04  6:41                 ` Sergey Senozhatsky
2019-09-04  6:54                   ` Michal Hocko
2019-09-04  7:19                     ` Sergey Senozhatsky
2019-09-04  7:43                       ` Sergey Senozhatsky
2019-09-04 12:14                         ` Qian Cai
2019-09-04 14:48                           ` Sergey Senozhatsky
2019-09-04 15:07                             ` Qian Cai
2019-09-04 20:42                             ` Qian Cai
2019-09-05  8:32                               ` Eric Dumazet
2019-09-05 14:09                                 ` Qian Cai
2019-09-05 15:06                                   ` Eric Dumazet
2019-09-05 15:14                                   ` Eric Dumazet
2019-09-05 11:32                               ` Sergey Senozhatsky
2019-09-05 16:03                                 ` Qian Cai
2019-09-05 17:14                                   ` Steven Rostedt
2019-09-06  2:50                                     ` Sergey Senozhatsky
2019-09-06  4:32                                   ` Sergey Senozhatsky
2019-09-06 21:17                                     ` Qian Cai
2019-09-05 17:23                                 ` Steven Rostedt
2019-09-06  3:39                                   ` Sergey Senozhatsky
2019-09-06 15:32                                     ` Petr Mladek
2019-09-09  1:10                                       ` Sergey Senozhatsky
2019-09-06 14:55                                 ` Petr Mladek
2019-09-06 19:51                                   ` Sergey Senozhatsky [this message]
2019-11-14 17:12                                 ` Qian Cai
2019-11-18 15:27                                   ` Petr Mladek
2019-11-19  0:41                                     ` Sergey Senozhatsky
2019-11-19  9:41                                       ` Petr Mladek
2019-11-19 15:58                                         ` Qian Cai
2019-11-20  1:30                                         ` Sergey Senozhatsky
2019-11-20 16:13                                           ` Petr Mladek
2019-11-21  1:05                                             ` Sergey Senozhatsky
2019-11-21  9:15                                               ` Petr Mladek
2019-09-04  7:00                   ` Sergey Senozhatsky
2019-09-04  8:25                     ` Michal Hocko
2019-09-04 11:59                       ` Qian Cai
2019-09-04 12:07                         ` Michal Hocko
2019-09-04 12:28                           ` Qian Cai
2019-09-07 11:00                       ` Tetsuo Handa
2019-09-04  6:15               ` Michal Hocko
2019-09-02 14:24     ` Vlastimil Babka

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