Messages in this thread Patch in this message | | | Date | Mon, 3 Oct 2011 11:02:06 -0400 | From | Jason Baron <> | Subject | Re: [PATCH RFC V2 3/5] jump_label: if a key has already been initialized, don't nop it out |
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Hi,
(Sorry for the late reply - I was away for a few days).
The early enable is really nice - it means there are not restrictions on when jump_label_inc()/dec() can be called which is nice.
comments below.
On Sat, Oct 01, 2011 at 02:55:35PM -0700, Jeremy Fitzhardinge wrote: > From: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> > > 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@citrix.com> > --- > 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);
The only reason I called this at boot-time was that the 'ideal' x86 no-op isn't known until boot time. Thus, in the enabled case we could skip the the arch_jump_label_transform() call. ie:
if (!enabled) arch_jump_label_transform(iter, 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 >
hmmm...this is used on module load in smp - so this would introduce a number of calls to stop_machine() where we didn't have them before. Yes, module load is a very slow path to begin with, but I think its at least worth pointing out...
thanks,
-Jason
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