Date: Fri, 29 Apr 2016 09:00:39 -0500
From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Minfei Huang <mnghuan@gmail.com>
Cc: Jessica Yu <jeyu@redhat.com>, Jiri Kosina <jikos@kernel.org>,
        Miroslav Benes <mbenes@suse.cz>, Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        live-patching@vger.kernel.org, linux-kernel@vger.kernel.org,
        x86@kernel.org, linuxppc-dev@lists.ozlabs.org,
        linux-s390@vger.kernel.org, Vojtech Pavlik <vojtech@suse.com>,
        Jiri Slaby <jslaby@suse.cz>, Petr Mladek <pmladek@suse.com>,
        Chris J Arges <chris.j.arges@canonical.com>,
        Andy Lutomirski <luto@kernel.org>
Subject: Re: [RFC PATCH v2 06/18] x86: dump_trace() error handling
Message-ID: <20160429140039.w7nykasabm5kzhns@treble>
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 <20160429134558.GA17476@dhcp-128-44.nay.redhat.com>
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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