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From: David Laight <David.Laight@ACULAB.COM>
To: 'Peter Zijlstra' <peterz@infradead.org>,
	Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Ingo Molnar <mingo@kernel.org>,
	"mingo@redhat.com" <mingo@redhat.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Tetsuo Handa <penguin-kernel@I-love.SKAURA.ne.jp>,
	Andy Lutomirski <luto@amacapital.net>,
	Borislav Petkov <bp@suse.de>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	"Linus Torvalds" <torvalds@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: RE: [PATCH] x86: Avoid pr_cont() in show_opcodes()
Date: Mon, 9 Jul 2018 13:22:39 +0000	[thread overview]
Message-ID: <f3b0dee2b61940b5976571e769692ec9@AcuMS.aculab.com> (raw)
In-Reply-To: <20180709084953.GB2476@hirez.programming.kicks-ass.net>

From: Peter Zijlstra
> Sent: 09 July 2018 09:50
> On Sat, Jul 07, 2018 at 10:54:28PM +0900, Tetsuo Handa wrote:
> > >> Since syzbot is confused by concurrent printk() messages [1],
> > >> this patch changes show_opcodes() to use snprintf().

snprintf() is probably the wrong function.
You want the variant that always returns the number of characters
added to the buffer - not the number that would have been added
were the buffer infinite length.

> But how big of a problem is that really? We can't very well remove all
> pr_cont stuff from the kernel.

On my ubuntu 17.10 system with a 4.13 kernel some messages printed with
pr_cont end up split when displayed by dmesg.
(These are from one of our drivers, I've not looked very hard at it though.)

So maybe removing pr_cont isn't a bad idea.

	David


  reply	other threads:[~2018-07-09 13:21 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-07  6:07 [PATCH] x86: Avoid pr_cont() in show_opcodes() Tetsuo Handa
2018-07-07 11:12 ` Ingo Molnar
2018-07-07 13:54   ` Tetsuo Handa
2018-07-09  8:49     ` Peter Zijlstra
2018-07-09 13:22       ` David Laight [this message]
2018-07-09 19:11       ` Josh Poimboeuf
2018-07-10 11:55         ` Tetsuo Handa
2018-07-10 16:51         ` David Laight
2018-07-10 21:08           ` Tetsuo Handa
2018-07-16 12:47     ` Tetsuo Handa
2018-07-17  9:01     ` Rasmus Villemoes
2018-07-17 13:53       ` Tetsuo Handa
2018-07-17 14:24         ` Rasmus Villemoes
2018-07-17 20:54           ` Tetsuo Handa
2018-07-17 21:19             ` Joe Perches
2018-07-18  8:41               ` Joe Perches
2018-07-17 21:07       ` Andy Shevchenko

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