linux-kernel - Re: [RFC PATCH v2 06/18] x86: dump

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Date:	Fri, 29 Apr 2016 09:00:39 -0500
From:	Josh Poimboeuf <jpoimboe@...hat.com>
To:	Minfei Huang <mnghuan@...il.com>
Cc:	Jessica Yu <jeyu@...hat.com>, Jiri Kosina <jikos@...nel.org>,
	Miroslav Benes <mbenes@...e.cz>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
	x86@...nel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-s390@...r.kernel.org, Vojtech Pavlik <vojtech@...e.com>,
	Jiri Slaby <jslaby@...e.cz>, Petr Mladek <pmladek@...e.com>,
	Chris J Arges <chris.j.arges@...onical.com>,
	Andy Lutomirski <luto@...nel.org>
Subject: Re: [RFC PATCH v2 06/18] x86: dump_trace() error handling

On Fri, Apr 29, 2016 at 09:45:58PM +0800, Minfei Huang wrote:
> On 04/28/16 at 03:44P, Josh Poimboeuf wrote:
> > In preparation for being able to determine whether a given stack trace
> > is reliable, allow the stacktrace_ops functions to propagate errors to
> > dump_trace().
> 
> Hi, Josh.
> 
> Have you considered to make walk_stack function as non-return function,
> since there is no obvious error during detecting the frame points?

If you look at the next patch 07/18, there are several cases where
walk_stack (print_context_stack_reliable) returns an error.

For example, if a function gets preempted before it gets a chance to
save the frame pointer, the function's caller would get skipped on the
stack trace.  So for preempted tasks, we always have to consider their
stacks unreliable.

-- 
Josh