linux-kernel - Re: [PATCH v2] jump_label: fix jump

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Message-ID: <20110621154712.GC2495@redhat.com>
Date:	Tue, 21 Jun 2011 11:47:12 -0400
From:	Jason Baron <jbaron@...hat.com>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] jump_label: fix jump_label update

On Tue, Jun 21, 2011 at 11:44:55AM +0200, Jiri Olsa wrote:
> On Tue, Jun 21, 2011 at 10:35:55AM +0800, Xiao Guangrong wrote:
> > The key of module is out of __stop___jump_table, it causes the events
> > of modules does not work
> > 
> > Signed-off-by: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
> > ---
> >  kernel/jump_label.c |   14 +++++++++-----
> >  1 files changed, 9 insertions(+), 5 deletions(-)
> > 
> > diff --git a/kernel/jump_label.c b/kernel/jump_label.c
> > index fa27e75..a8ce450 100644
> > --- a/kernel/jump_label.c
> > +++ b/kernel/jump_label.c
> > @@ -375,15 +375,19 @@ int jump_label_text_reserved(void *start, void *end)
> >  
> >  static void jump_label_update(struct jump_label_key *key, int enable)
> >  {
> > -	struct jump_entry *entry = key->entries;
> > -
> > -	/* if there are no users, entry can be NULL */
> > -	if (entry)
> > -		__jump_label_update(key, entry, __stop___jump_table, enable);
> > +	struct jump_entry *entry = key->entries, *stop = __stop___jump_table;
> >  
> >  #ifdef CONFIG_MODULES
> > +	struct module *mod = __module_address((jump_label_t)key);
> > +
> >  	__jump_label_mod_update(key, enable);
> > +
> > +	if (mod)
> > +		stop = mod->jump_entries + mod->num_jump_entries;
> >  #endif
> > +	/* if there are no users, entry can be NULL */
> > +	if (entry)
> > +		__jump_label_update(key, entry, stop, enable);
> >  }
> >  
> >  #endif
> > -- 
> > 1.7.5.4
> 
> That works for me, but in order to test it I needed to export
> jump_label_inc/jump_label_dec functions.
> 
> Not sure I'm missing something, but to manage a key that is local
> to the module, we need to call jump_label_inc/jump_label_dec
> from within the module code, so we need some of the jump_label
> functions exported.. it'd be probably:
> 
> 	jump_label_inc/jump_label_dec/jump_label_enabled
> 

You're not missing anything, right now all the enabling/disabling is
done in the core kernel, hence no need for the export. I'd prefer to
keep them non-exported until we had a real use-case that required them
to be exported. But I don't feel that strongly about it.

Thanks,

-Jason
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