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locking/static_keys: Rework update logic
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Instead of spreading the branch_default logic all over the place,
concentrate it into the one jump_label_type() function.

This does mean we need to actually increment/decrement the enabled
count _before_ calling the update path, otherwise jump_label_type()
will not see the right state.

Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Signed-off-by: Ingo Molnar <[email protected]>
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Peter Zijlstra authored and Ingo Molnar committed Aug 3, 2015
1 parent e33886b commit 706249c
Showing 1 changed file with 38 additions and 50 deletions.
88 changes: 38 additions & 50 deletions kernel/jump_label.c
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Original file line number Diff line number Diff line change
Expand Up @@ -54,12 +54,7 @@ jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop)
sort(start, size, sizeof(struct jump_entry), jump_label_cmp, NULL);
}

static void jump_label_update(struct static_key *key, int enable);

static inline bool static_key_type(struct static_key *key)
{
return (unsigned long)key->entries & JUMP_TYPE_MASK;
}
static void jump_label_update(struct static_key *key);

void static_key_slow_inc(struct static_key *key)
{
Expand All @@ -68,13 +63,8 @@ void static_key_slow_inc(struct static_key *key)
return;

jump_label_lock();
if (atomic_read(&key->enabled) == 0) {
if (!static_key_type(key))
jump_label_update(key, JUMP_LABEL_JMP);
else
jump_label_update(key, JUMP_LABEL_NOP);
}
atomic_inc(&key->enabled);
if (atomic_inc_return(&key->enabled) == 1)
jump_label_update(key);
jump_label_unlock();
}
EXPORT_SYMBOL_GPL(static_key_slow_inc);
Expand All @@ -92,10 +82,7 @@ static void __static_key_slow_dec(struct static_key *key,
atomic_inc(&key->enabled);
schedule_delayed_work(work, rate_limit);
} else {
if (!static_key_type(key))
jump_label_update(key, JUMP_LABEL_NOP);
else
jump_label_update(key, JUMP_LABEL_JMP);
jump_label_update(key);
}
jump_label_unlock();
}
Expand Down Expand Up @@ -154,7 +141,7 @@ 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
Expand All @@ -163,44 +150,48 @@ static int __jump_label_text_reserved(struct jump_entry *iter_start,
void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
enum jump_label_type type)
{
arch_jump_label_transform(entry, type);
arch_jump_label_transform(entry, type);
}

static void __jump_label_update(struct static_key *key,
struct jump_entry *entry,
struct jump_entry *stop, int enable)
static inline struct jump_entry *static_key_entries(struct static_key *key)
{
for (; (entry < stop) &&
(entry->key == (jump_label_t)(unsigned long)key);
entry++) {
/*
* entry->code set to 0 invalidates module init text sections
* kernel_text_address() verifies we are not in core kernel
* init code, see jump_label_invalidate_module_init().
*/
if (entry->code && kernel_text_address(entry->code))
arch_jump_label_transform(entry, enable);
}
return (struct jump_entry *)((unsigned long)key->entries & ~JUMP_TYPE_MASK);
}

static inline struct jump_entry *static_key_entries(struct static_key *key)
static inline bool static_key_type(struct static_key *key)
{
return (struct jump_entry *)((unsigned long)key->entries & ~JUMP_TYPE_MASK);
return (unsigned long)key->entries & JUMP_TYPE_MASK;
}

static inline struct static_key *jump_entry_key(struct jump_entry *entry)
{
return (struct static_key *)((unsigned long)entry->key);
}

static enum jump_label_type jump_label_type(struct static_key *key)
static enum jump_label_type jump_label_type(struct jump_entry *entry)
{
struct static_key *key = jump_entry_key(entry);
bool enabled = static_key_enabled(key);
bool type = static_key_type(key);

return enabled ^ type;
}

static void __jump_label_update(struct static_key *key,
struct jump_entry *entry,
struct jump_entry *stop)
{
for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
/*
* entry->code set to 0 invalidates module init text sections
* kernel_text_address() verifies we are not in core kernel
* init code, see jump_label_invalidate_module_init().
*/
if (entry->code && kernel_text_address(entry->code))
arch_jump_label_transform(entry, jump_label_type(entry));
}
}

void __init jump_label_init(void)
{
struct jump_entry *iter_start = __start___jump_table;
Expand All @@ -214,8 +205,8 @@ void __init jump_label_init(void)
for (iter = iter_start; iter < iter_stop; iter++) {
struct static_key *iterk;

arch_jump_label_transform_static(iter, jump_label_type(iter));
iterk = jump_entry_key(iter);
arch_jump_label_transform_static(iter, jump_label_type(iterk));
if (iterk == key)
continue;

Expand Down Expand Up @@ -255,17 +246,15 @@ static int __jump_label_mod_text_reserved(void *start, void *end)
start, end);
}

static void __jump_label_mod_update(struct static_key *key, int enable)
static void __jump_label_mod_update(struct static_key *key)
{
struct static_key_mod *mod = key->next;
struct static_key_mod *mod;

while (mod) {
for (mod = key->next; mod; mod = mod->next) {
struct module *m = mod->mod;

__jump_label_update(key, mod->entries,
m->jump_entries + m->num_jump_entries,
enable);
mod = mod->next;
m->jump_entries + m->num_jump_entries);
}
}

Expand All @@ -287,9 +276,8 @@ void jump_label_apply_nops(struct module *mod)
if (iter_start == iter_stop)
return;

for (iter = iter_start; iter < iter_stop; iter++) {
for (iter = iter_start; iter < iter_stop; iter++)
arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
}
}

static int jump_label_add_module(struct module *mod)
Expand Down Expand Up @@ -330,8 +318,8 @@ static int jump_label_add_module(struct module *mod)
jlm->next = key->next;
key->next = jlm;

if (jump_label_type(key) == JUMP_LABEL_JMP)
__jump_label_update(key, iter, iter_stop, JUMP_LABEL_JMP);
if (jump_label_type(iter) == JUMP_LABEL_JMP)
__jump_label_update(key, iter, iter_stop);
}

return 0;
Expand Down Expand Up @@ -451,14 +439,14 @@ int jump_label_text_reserved(void *start, void *end)
return ret;
}

static void jump_label_update(struct static_key *key, int enable)
static void jump_label_update(struct static_key *key)
{
struct jump_entry *stop = __stop___jump_table;
struct jump_entry *entry = static_key_entries(key);
#ifdef CONFIG_MODULES
struct module *mod;

__jump_label_mod_update(key, enable);
__jump_label_mod_update(key);

preempt_disable();
mod = __module_address((unsigned long)key);
Expand All @@ -468,7 +456,7 @@ static void jump_label_update(struct static_key *key, int enable)
#endif
/* if there are no users, entry can be NULL */
if (entry)
__jump_label_update(key, entry, stop, enable);
__jump_label_update(key, entry, stop);
}

#endif

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