WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

[Xen-devel] Re: [PATCH RFC V2 3/5] jump_label: if a key has already been

To: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Subject: [Xen-devel] Re: [PATCH RFC V2 3/5] jump_label: if a key has already been initialized, don't nop it out
From: Jason Baron <jbaron@xxxxxxxxxx>
Date: Mon, 10 Oct 2011 11:36:32 -0400
Cc: Xen Devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Jan Glauber <jang@xxxxxxxxxxxxxxxxxx>, the arch/x86 maintainers <x86@xxxxxxxxxx>, David Daney <david.daney@xxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Steven Rostedt <rostedt@xxxxxxxxxxx>, Michael Ellerman <michael@xxxxxxxxxxxxxx>, Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>, "David S. Miller" <davem@xxxxxxxxxxxxx>
Delivery-date: Mon, 10 Oct 2011 08:37:26 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <477dead9647029012f93c651f2892ed0e86b89e7.1317506051.git.jeremy.fitzhardinge@xxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <cover.1317506051.git.jeremy.fitzhardinge@xxxxxxxxxx> <477dead9647029012f93c651f2892ed0e86b89e7.1317506051.git.jeremy.fitzhardinge@xxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: Mutt/1.5.20 (2009-12-10)
On Sat, Oct 01, 2011 at 02:55:35PM -0700, Jeremy Fitzhardinge wrote:
> From: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
> 
> If a key has been enabled before jump_label_init() is called, don't
> nop it out.
> 
> This removes arch_jump_label_text_poke_early() (which can only nop
> out a site) and uses arch_jump_label_transform() instead.
> 
> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
> ---
>  include/linux/jump_label.h |    3 ++-
>  kernel/jump_label.c        |   20 ++++++++------------
>  2 files changed, 10 insertions(+), 13 deletions(-)
> 
> diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
> index 1213e9d..c8fb1b3 100644
> --- a/include/linux/jump_label.h
> +++ b/include/linux/jump_label.h
> @@ -45,7 +45,8 @@ extern void jump_label_lock(void);
>  extern void jump_label_unlock(void);
>  extern void arch_jump_label_transform(struct jump_entry *entry,
>                                enum jump_label_type type);
> -extern void arch_jump_label_text_poke_early(jump_label_t addr);
> +extern void arch_jump_label_transform_early(struct jump_entry *entry,
> +                              enum jump_label_type type);
>  extern int jump_label_text_reserved(void *start, void *end);
>  extern void jump_label_inc(struct jump_label_key *key);
>  extern void jump_label_dec(struct jump_label_key *key);
> diff --git a/kernel/jump_label.c b/kernel/jump_label.c
> index a8ce450..059202d5 100644
> --- a/kernel/jump_label.c
> +++ b/kernel/jump_label.c
> @@ -121,13 +121,6 @@ static void __jump_label_update(struct jump_label_key 
> *key,
>       }
>  }
>  
> -/*
> - * Not all archs need this.
> - */
> -void __weak arch_jump_label_text_poke_early(jump_label_t addr)
> -{
> -}
> -
>  static __init int jump_label_init(void)
>  {
>       struct jump_entry *iter_start = __start___jump_table;
> @@ -139,12 +132,15 @@ static __init int jump_label_init(void)
>       jump_label_sort_entries(iter_start, iter_stop);
>  
>       for (iter = iter_start; iter < iter_stop; iter++) {
> -             arch_jump_label_text_poke_early(iter->code);
> -             if (iter->key == (jump_label_t)(unsigned long)key)
> +             struct jump_label_key *iterk;
> +
> +             iterk = (struct jump_label_key *)(unsigned long)iter->key;
> +             arch_jump_label_transform(iter, jump_label_enabled(iterk) ?
> +                                       JUMP_LABEL_ENABLE : 
> JUMP_LABEL_DISABLE);
> +             if (iterk == key)
>                       continue;
>  
> -             key = (struct jump_label_key *)(unsigned long)iter->key;
> -             atomic_set(&key->enabled, 0);
> +             key = iterk;
>               key->entries = iter;
>  #ifdef CONFIG_MODULES
>               key->next = NULL;
> @@ -212,7 +208,7 @@ void jump_label_apply_nops(struct module *mod)
>               return;
>  
>       for (iter = iter_start; iter < iter_stop; iter++)
> -             arch_jump_label_text_poke_early(iter->code);
> +             arch_jump_label_transform(iter, JUMP_LABEL_DISABLE);
>  }
>  
>  static int jump_label_add_module(struct module *mod)
> -- 
> 1.7.6.2
> 

Hi,

I just realized that the early call to jump_label_inc(), isn't being
honored with this patch until later when we invoke jump_label_init().
That strikes me as being inconsistent. When jump_label_inc() returns we
should expect the branch to be updated.

Thus, I think what probably want is to add a new 'int jump_label_init'
flag. If its not set we can call 'jump_label_init()' from
jump_label_inc()/dec(). And jump_label_init() can avoid initialization
if its already set.

Thanks,

-Jason 

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel

<Prev in Thread] Current Thread [Next in Thread>