linux-kernel - Re: [PATCH v6 1/8] x86: allow to handle errors in text

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Message-ID: <1390309237.14199.16.camel@pathway.suse.cz>
Date:	Tue, 21 Jan 2014 14:00:37 +0100
From:	Petr Mladek <pmladek@...e.cz>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Jiri Kosina <jkosina@...e.cz>, linux-kernel@...r.kernel.org,
	x86@...nel.org
Subject: Re: [PATCH v6 1/8] x86: allow to handle errors in text_poke
 function family

On Tue, 2014-01-14 at 18:20 -0500, Steven Rostedt wrote:
> FYI, for future patches, start the subject with a capital letter. ie:
>  x86: Allow to handle errors in text_poke function family
> 
> On Tue, 10 Dec 2013 16:42:13 +0100
> Petr Mladek <pmladek@...e.cz> wrote:
> 
> > The text_poke functions called BUG() in case of error. This was too strict.
> > There are situations when the system is still usable even when the patching
> > has failed, for example when enabling the dynamic ftrace.
> > 
> > This commit modifies text_poke and text_poke_bp functions to return an error
> > code instead of calling BUG(). They used to return the patched address. But
> > the address was just copied from the first parameter. It was no extra
> > information and it has not been used anywhere yet.
> > 
> > There are some situations where it is hard to recover from an error. Masami
> > Hiramatsu <masami.hiramatsu.pt@...achi.com> suggested to create
> > text_poke*_or_die() variants for this purpose.
> 
> I don't like the "_or_die()". Although I don't care much about it, I'm
> thinking the x86 maintainers might not like it either.
> 
> What about just doing the test in the places that would call "or_die"?
> 
> 	ret = text_poke*();
> 	BUG_ON(ret);

Exactly this solution has been used in v5 of this patch set, see 
https://lkml.org/lkml/2013/12/3/258

Masami suggested to use the "or_die()" because BUG_ON() was used on most
locations, see https://lkml.org/lkml/2013/12/6/1107

I personally do not have any strong opinion about it and will do
whatever makes x86 maintainers happy :-)

Best Regards,
Petr

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