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From: Thomas Gleixner <tglx@linutronix.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	John Ogness <john.ogness@linutronix.de>,
	Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
	Petr Mladek <pmladek@suse.com>,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Andrea Parri <andrea.parri@amarulasolutions.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Brendan Higgins <brendanhiggins@google.com>
Subject: Re: [RFC PATCH v4 9/9] printk: use a new ringbuffer implementation
Date: Sat, 10 Aug 2019 07:53:56 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.21.1908100745260.7324@nanos.tec.linutronix.de> (raw)
In-Reply-To: <CAHk-=wiG55kT0MRprt+Opbpcc=ebugC_rz4d6-whtAGXri3TwQ@mail.gmail.com>

On Fri, 9 Aug 2019, Linus Torvalds wrote:
> On Thu, Aug 8, 2019 at 11:14 PM Peter Zijlstra <peterz@infradead.org> wrote:
> > Note that you can hook this into printk as a fake early serial device;
> > just have the serial device write to the DRAM buffer.
> 
> No, you really really can't.
...
> Even the "early console" stuff tries to honor serialization by
> console_lock and console_suspended etc. Or things like the "I'm in the
> middle of the scheduler, so I won't be doing any real logging".

If you think of it as the classic console you are right. What Peter has in
mind is the extra stuff on top of this buffer patchset, which implements
emergency write to consoles. That's an extra callback in the console
struct, which can be invoked in such situations igoring context and console
lock completely.

Right now we have an implementation for serial only, but that already is
useful. I nicely got (minimaly garbled) crash dumps out of an NMI
handler. With the current mainline console code the machine just hung.

So with this scheme we actually could hook your smart buffer into the
console stuff and still achieve what you want.

Thanks,

	tglx

  reply	other threads:[~2019-08-10  5:54 UTC|newest]

Thread overview: 131+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-07 22:26 [RFC PATCH v4 0/9] printk: new ringbuffer implementation John Ogness
2019-08-07 22:26 ` [RFC PATCH v4 1/9] printk-rb: add a new printk " John Ogness
2019-08-20  8:15   ` numlist_pop(): " Petr Mladek
2019-08-21  5:41     ` John Ogness
2019-09-04 12:19     ` Peter Zijlstra
2019-08-20  8:22   ` assign_desc() barriers: " Petr Mladek
2019-08-20 14:14     ` Petr Mladek
2019-08-21  5:52       ` John Ogness
2019-08-22 11:53         ` Petr Mladek
2019-08-25  2:06           ` John Ogness
2019-08-26  8:21             ` John Ogness
2019-08-20  8:55   ` comments style: " Petr Mladek
2019-08-20  9:27     ` Sergey Senozhatsky
2019-08-21  5:46       ` John Ogness
2019-08-22 13:50         ` Petr Mladek
2019-08-22 17:38           ` Andrea Parri
2019-08-23 10:47             ` Petr Mladek
2019-08-23 14:27               ` Andrea Parri
2019-08-23  9:49           ` Sergey Senozhatsky
2019-08-23  5:54         ` Sergey Senozhatsky
2019-08-23 10:29           ` Petr Mladek
2019-08-21  5:42     ` John Ogness
2019-08-22 12:44       ` Petr Mladek
2019-08-20 13:50   ` dataring_push() barriers " Petr Mladek
2019-08-25  2:42     ` John Ogness
2019-08-27 14:36       ` Petr Mladek
2019-08-28 13:43         ` John Ogness
2019-08-20 15:12   ` datablock reuse races " Petr Mladek
2019-08-23  9:21   ` numlist_push() barriers " Petr Mladek
2019-08-26  8:34     ` Andrea Parri
2019-08-26  8:43       ` Andrea Parri
2019-08-26 14:10       ` Petr Mladek
2019-08-26 16:01         ` Andrea Parri
2019-08-26 22:36     ` John Ogness
2019-08-27  7:40       ` Petr Mladek
2019-08-27 14:28         ` John Ogness
2019-08-27 15:07           ` Petr Mladek
2019-08-28 10:24             ` John Ogness
2019-08-23 17:18   ` numlist API " Petr Mladek
2019-08-26 23:57     ` John Ogness
2019-08-27 13:03       ` Petr Mladek
2019-08-28  7:13         ` John Ogness
2019-08-28  8:58           ` Petr Mladek
2019-08-28 14:03             ` John Ogness
2019-08-29 11:28               ` Petr Mladek
2019-09-03  7:58         ` Sergey Senozhatsky
2019-08-30 14:48   ` dataring " Petr Mladek
2019-08-07 22:26 ` [RFC PATCH v4 2/9] printk-rb: add test module John Ogness
2019-08-07 22:26 ` [RFC PATCH v4 3/9] printk-rb: fix missing includes/exports John Ogness
2019-08-07 22:26 ` [RFC PATCH v4 4/9] printk-rb: initialize new descriptors as invalid John Ogness
2019-08-20  9:23   ` Petr Mladek
2019-08-20 10:16     ` Sergey Senozhatsky
2019-08-21  5:56     ` John Ogness
2019-08-07 22:26 ` [RFC PATCH v4 5/9] printk-rb: remove extra data buffer size allocation John Ogness
2019-08-07 22:26 ` [RFC PATCH v4 6/9] printk-rb: adjust test module ringbuffer sizes John Ogness
2019-08-19 21:29   ` [PATCH] printk-rb: fix test module macro usage John Ogness
2019-08-07 22:26 ` [RFC PATCH v4 7/9] printk-rb: increase size of seq and size variables John Ogness
2019-08-07 22:26 ` [RFC PATCH v4 8/9] printk-rb: new functionality to support printk John Ogness
2019-08-20  9:59   ` Sergey Senozhatsky
2019-08-21  5:47     ` John Ogness
2019-08-07 22:26 ` [RFC PATCH v4 9/9] printk: use a new ringbuffer implementation John Ogness
2019-08-08 19:07   ` Linus Torvalds
2019-08-08 22:55     ` John Ogness
2019-08-08 23:33       ` Linus Torvalds
2019-08-08 23:45         ` Steven Rostedt
2019-08-09  0:21           ` Linus Torvalds
2019-08-09  0:48             ` Steven Rostedt
2019-08-09  1:15               ` Linus Torvalds
2019-08-09 11:15                 ` Thomas Gleixner
2019-08-09 16:00                   ` Linus Torvalds
2019-08-09 20:07                     ` Thomas Gleixner
2019-08-09 20:20                       ` Linus Torvalds
2019-08-09  6:14     ` Peter Zijlstra
2019-08-09  7:08       ` John Ogness
2019-08-09 15:57       ` Linus Torvalds
2019-08-10  5:53         ` Thomas Gleixner [this message]
2019-09-10  3:19           ` Sergey Senozhatsky
2019-08-12  9:54       ` Geert Uytterhoeven
2019-08-16  5:46   ` Dave Young
2019-08-16  5:54     ` Dave Young
2019-08-16  9:40     ` John Ogness
2019-09-04 12:35 ` [RFC PATCH v4 0/9] printk: " Peter Zijlstra
2019-09-05 13:05   ` Petr Mladek
2019-09-05 14:31     ` Peter Zijlstra
2019-09-05 15:38       ` Thomas Gleixner
2019-09-05 16:11         ` Steven Rostedt
2019-09-05 21:10           ` John Ogness
2019-09-06  9:39           ` Petr Mladek
2019-09-09 14:11           ` printk meeting at LPC Thomas Gleixner
2019-09-13 13:26             ` John Ogness
2019-09-13 14:48               ` Daniel Vetter
2019-09-15 13:47                 ` John Ogness
2019-09-16  8:44                   ` Daniel Vetter
2019-09-16  4:30               ` Tetsuo Handa
2019-09-16 10:46                 ` Petr Mladek
2019-09-16 13:43                   ` Steven Rostedt
2019-09-16 14:28                     ` John Ogness
2019-09-17  8:11                       ` Petr Mladek
2019-09-17  7:52                     ` Petr Mladek
2019-09-17 13:02                       ` Steven Rostedt
2019-09-17 13:12                         ` Greg Kroah-Hartman
2019-09-17 13:37                           ` Steven Rostedt
2019-09-17 14:08                             ` Tetsuo Handa
2019-09-17  7:51                   ` Sergey Senozhatsky
2019-09-18  1:25               ` Sergey Senozhatsky
2019-09-18  2:08                 ` Steven Rostedt
2019-09-18  2:36                   ` Sergey Senozhatsky
2019-09-18  5:19                     ` Sergey Senozhatsky
2019-09-18  7:42                       ` John Ogness
2019-09-18  8:10                         ` Sergey Senozhatsky
2019-09-18  9:05                           ` John Ogness
2019-09-18  9:11                             ` Sergey Senozhatsky
2019-09-18 16:41                             ` Petr Mladek
2019-09-18 16:48                               ` Steven Rostedt
2019-09-24 14:24                                 ` Petr Mladek
2019-09-19  8:06                         ` Daniel Vetter
2019-09-18  7:33                     ` John Ogness
2019-09-18  8:08                       ` Sergey Senozhatsky
2019-10-04 14:48               ` Tony Asleson
2019-10-07 12:01                 ` Petr Mladek
2019-09-06  9:06       ` [RFC PATCH v4 0/9] printk: new ringbuffer implementation Peter Zijlstra
2019-09-06 10:09         ` Sergey Senozhatsky
2019-09-06 10:49           ` Peter Zijlstra
2019-09-06 13:44             ` Sergey Senozhatsky
2019-09-06 12:42         ` Petr Mladek
2019-09-06 14:01           ` Peter Zijlstra
2019-09-06 14:22             ` Peter Zijlstra
2019-09-06 19:53             ` Sergey Senozhatsky
2019-09-06 22:47             ` John Ogness
2019-09-08 22:18             ` Peter Zijlstra
2019-09-10  3:22             ` Sergey Senozhatsky

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