linux-kernel - Re: [PATCH RESEND 1/3] printk: convert byte-buffer to variable-length record buffer

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Message-ID: <CA+55aFxhQ3SQrZJ6KGDu0xQ6sWSDxrS1C-V_fBcgCYmSqAKSWQ@mail.gmail.com>
Date:	Thu, 3 May 2012 12:56:48 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Kay Sievers <kay@...y.org>, Greg Kroah-Hartmann <greg@...ah.com>,
	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND 1/3] printk: convert byte-buffer to variable-length
 record buffer

On Thu, May 3, 2012 at 12:48 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Thu, 2012-05-03 at 02:29 +0200, Kay Sievers wrote:
>> + * This is printk(). It can be called from any context. We want it to work.
>
> This is not true..

Well, it is very very nearly true, and people should basically expect it to be.

There are exceptions, but they are ridiculously specific
 - no NMI context
 - we've had trouble with the percpu runqueue lock (due to the stupid wakeup)
 - for similar reasons, we've had trouble with printk called from
within some terminal locks.

But basically, it damn well should be considered a hard rule that you
can printk from pretty much anything. The few cases where that is not
true are big problems, and should be considered to be real problems,
not "oh, you can't printk from here".

                     Linus
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