linux-kernel - Re: [PATCH 0/7] Serialise oopses, BUGs, WARNs, dump

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Message-ID: <20150224104339.GT8656@n2100.arm.linux.org.uk>
Date:	Tue, 24 Feb 2015 10:43:40 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Arjan van de Ven <arjanvandeven@...il.com>
Cc:	Ingo Molnar <mingo@...nel.org>, Anton Blanchard <anton@...ba.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Paul Mackerras <paulus@...ba.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	sam.bobroff@....ibm.com, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Don Zickus <dzickus@...hat.com>,
	linux-arm-kernel@...ts.infradead.org,
	LKML <linux-kernel@...r.kernel.org>,
	ppc-dev <linuxppc-dev@...ts.ozlabs.org>, X86 ML <x86@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: [PATCH 0/7] Serialise oopses, BUGs, WARNs, dump_stack, soft
 lockups and hard lockups

On Tue, Feb 24, 2015 at 01:39:46AM -0800, Arjan van de Ven wrote:
> one of the question is if you want to serialize, or if you just want
> to label.  If you take a cookie (could just be a monotonic increasing
> number) at the start of the oops and then prefix/postfix the stack
> printing with that number, you don't serialize (risk of locking up),
> but you can pretty trivially see which line came from where..
> if you do the monotonic increasing number approach, you even get an
> ordering out of it. it does mean changing the dump_stack() and co
> function fingerprint to take an extra argument, but that is not TOO
> insane.

I like that idea, but it relies on ensuring that each line is printed
by one printk() statement - which in itself is a good idea.

I'd actually like a version of print_hex_dump() which we could use for
stack and code dumping - the existing print_hex_dump() assumes that it's
fine to dereference the pointer, whereas for stack and code dumping,
we can't always make that assumption.  That's a separate issue though.

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