Re: [PATCH 1/2] Add for_each_module iterator function v2

[Frederic Weisbecker <fweisbec@gmail.com>]

On Wed, Sep 22, 2010 at 04:35:15PM +0200, Andi Kleen wrote:
> On Wed, Sep 22, 2010 at 10:14:32AM -0400, Mathieu Desnoyers wrote:
> > * Andi Kleen (andi@firstfloor.org) wrote:
> > > From: Andi Kleen <ak@linux.intel.com>
> > > 
> > > This is a generic function to iterate over all modules.
> > > To be used in the next patch.
> > > 
> > > v2: Use module_mutex instead of preempt disabling
> > > 
> > > Signed-off-by: Andi Kleen <ak@linux.intel.com>
> > > ---
> > >  include/linux/module.h |    1 +
> > >  kernel/module.c        |   10 ++++++++++
> > >  2 files changed, 11 insertions(+), 0 deletions(-)
> > > 
> > > diff --git a/include/linux/module.h b/include/linux/module.h
> > > index 403ac26..809b6db 100644
> > > --- a/include/linux/module.h
> > > +++ b/include/linux/module.h
> > > @@ -410,6 +410,7 @@ struct module *__module_address(unsigned long addr);
> > >  bool is_module_address(unsigned long addr);
> > >  bool is_module_percpu_address(unsigned long addr);
> > >  bool is_module_text_address(unsigned long addr);
> > > +void for_each_module(void (*op)(struct module *, void *arg), void *arg);
> > >  
> > >  static inline int within_module_core(unsigned long addr, struct module *mod)
> > >  {
> > > diff --git a/kernel/module.c b/kernel/module.c
> > > index eba1341..9e2a561 100644
> > > --- a/kernel/module.c
> > > +++ b/kernel/module.c
> > > @@ -384,6 +384,16 @@ struct module *find_module(const char *name)
> > >  }
> > >  EXPORT_SYMBOL_GPL(find_module);
> > >  
> > > +void for_each_module(void (*op)(struct module *, void *arg), void *arg)
> > > +{
> > > +	struct module *mod;
> > > +
> > > +	mutex_lock(&module_mutex);
> > 
> > I'm concerned about the following mutex dependency chain:
> > 
> > module_mutex -> jump_label_mutex (on module load)
> > jump_label_mutex -> module_mutex (on jump_label_update)
> 
> There are actually more problems in this version with using
> module_mutex().  Looking at a fix.
> 
> > 
> > Actually, I think your module notifier is missing in your version. This
> > is why you don't see this dependency problem.
> 
> The module notifier is not needed anymore, but there's another 
> callback through the trace point code on module load.
> 
> Unload notifier is not needed anymore because there is no
> state to tear down.
> 
> -Andi


If possible, could you please also join a git url with your next version,
it becomes hard to review as it's delta on top of others patches.

Thanks.