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jump_label: add arch_jump_label_transform_static() to optimise non-live code updates

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When updating a newly loaded module, the code is definitely not yet
executing on any processor, so it can be updated with no need for any
heavyweight synchronization.

This patch adds arch_jump_label_static() which is implemented as
arch_jump_label_transform() by default, but architectures can override
it if it avoids, say, a call to stop_machine().

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Acked-by: Jason Baron <jbaron@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
This commit is contained in:
Jeremy Fitzhardinge 2011-10-03 11:01:46 -07:00
parent 92e02396d7
commit 20284aa77c
2 changed files with 17 additions and 3 deletions
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2
include/linux/jump_label.h
View File

@ -45,6 +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_transform_static(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);

18
kernel/jump_label.c
View File

@ -104,6 +104,18 @@ static int __jump_label_text_reserved(struct jump_entry *iter_start,
return 0;
}
/*
* Update code which is definitely not currently executing.
* Architectures which need heavyweight synchronization to modify
* running code can override this to make the non-live update case
* cheaper.
*/
void __weak arch_jump_label_transform_static(struct jump_entry *entry,
enum jump_label_type type)
{
arch_jump_label_transform(entry, type);
}
static void __jump_label_update(struct jump_label_key *key,
struct jump_entry *entry,
struct jump_entry *stop, int enable)
@ -135,8 +147,8 @@ static __init int jump_label_init(void)
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);
arch_jump_label_transform_static(iter, jump_label_enabled(iterk) ?
JUMP_LABEL_ENABLE : JUMP_LABEL_DISABLE);
if (iterk == key)
continue;
@ -208,7 +220,7 @@ void jump_label_apply_nops(struct module *mod)
return;
for (iter = iter_start; iter < iter_stop; iter++)
arch_jump_label_transform(iter, JUMP_LABEL_DISABLE);
arch_jump_label_transform_static(iter, JUMP_LABEL_DISABLE);
}
static int jump_label_add_module(struct module *mod)