Commit 20284aa7 authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge
Browse files

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



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: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Acked-by: default avatarJason Baron <jbaron@redhat.com>
Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
parent 92e02396

include/linux/jump_label.h

+2 −0
Original line number Diff line number Diff line
@@ -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);

kernel/jump_label.c

+15 −3
Original line number Diff line number Diff line
@@ -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)
@@ -135,7 +147,7 @@ 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) ?

		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)

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