linux-kernel - Re: [PATCH 07/10] module: _

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Message-Id: <201002242126.09994.arnd@arndb.de>
Date:	Wed, 24 Feb 2010 21:26:09 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Alexey Dobriyan <adobriyan@...il.com>
Cc:	paulmck@...ux.vnet.ibm.com,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	josh@...htriplett.org, dvhltc@...ibm.com, niv@...ibm.com,
	tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org,
	Valdis.Kletnieks@...edu, dhowells@...hat.com
Subject: Re: [PATCH 07/10] module: __rcu annotations

On Wednesday 24 February 2010, Alexey Dobriyan wrote:
> On Wed, Feb 24, 2010 at 09:04:03PM +0100, Arnd Bergmann wrote:
> > @@ -360,10 +360,12 @@ struct module *find_module(const char *name)
> >  {
> >       struct module *mod;
> >  
> > -     list_for_each_entry(mod, &modules, list) {
> > +     rcu_read_lock();
> > +     list_for_each_entry_rcu(mod, &modules, list) {
> >               if (strcmp(mod->name, name) == 0)
> >                       return mod;
> >       }
> > +     rcu_read_unlock();
> >       return NULL;
> >  }
> >  EXPORT_SYMBOL_GPL(find_module);
> 
> modules list is under module_mutex, nothing should be done here.

Ok, this is a significant limitation of the list rcu annotation
then, it's not possible to pass the same list into list_for_each_entry
and list_for_each_entry_rcu with the way I changed the rcu list
definition. I would be possible to do a __list_for_each_entry_rcu
macro that takes an rcu_list_head but does not actually use
rcu_dereference, but I'm not sure if that's good enough.

	Arnd

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