linux-kernel - Re: printk meeting at LPC

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Message-ID: <20190918012546.GA12090@jagdpanzerIV>
Date:   Wed, 18 Sep 2019 10:25:46 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Petr Mladek <pmladek@...e.com>,
        Andrea Parri <parri.andrea@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Brendan Higgins <brendanhiggins@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Theodore Ts'o <tytso@....edu>, Paul Turner <pjt@...gle.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Prarit Bhargava <prarit@...hat.com>
Subject: Re: printk meeting at LPC

On (09/13/19 15:26), John Ogness wrote:
> 2. A kernel thread will be created for each registered console, each
> responsible for being the sole printers to their respective
> consoles. With this, console printing is _fully_ decoupled from printk()
> callers.

sysrq over serial?

What we currently have is hacky, but, as usual, is a "best effort":

	>> serial driver IRQ

	serial_handle_irq()		[console driver]
	 uart_handle_sysrq_char()
	  handle_sysrq()
	   printk()
	    call_console_drivers()
	     serial_write()		[re-enter console driver]

offloading this to kthread may be unreliable.

	-ss