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From: Steven Rostedt <rostedt@goodmis.org>
To: Qian Cai <cai@lca.pw>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	Petr Mladek <pmladek@suse.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Michal Hocko <mhocko@kernel.org>,
	Eric Dumazet <eric.dumazet@gmail.com>,
	davem@davemloft.net, netdev@vger.kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] net/skbuff: silence warnings under memory pressure
Date: Thu, 5 Sep 2019 13:14:13 -0400	[thread overview]
Message-ID: <20190905131413.0aa4e4f1@oasis.local.home> (raw)
In-Reply-To: <1567699393.5576.96.camel@lca.pw>

On Thu, 05 Sep 2019 12:03:13 -0400
Qian Cai <cai@lca.pw> wrote:

> > > and could deal with console hardware that involve irq_exit() anyway.  
> > 
> > printk->console_driver->write() does not involve irq.  
> 
> Hmm, from the article,
> 
> https://en.wikipedia.org/wiki/Universal_asynchronous_receiver-transmitter
> 
> "Since transmission of a single or multiple characters may take a long time
> relative to CPU speeds, a UART maintains a flag showing busy status so that the
> host system knows if there is at least one character in the transmit buffer or
> shift register; "ready for next character(s)" may also be signaled with an
> interrupt."

I'm pretty sure all serial consoles do a busy loop on the UART and not
use interrupts to notify when it's available. That would require an
asynchronous implementation of printk() which would be quite complex to
implement.

-- Steve

  reply	other threads:[~2019-09-05 17:14 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 [this message]
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
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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