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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) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2015-07-24 15:06:37 +02:00 committed by Ingo Molnar
parent e33886b38c
commit 706249c222
1 changed files with 39 additions and 51 deletions
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90
kernel/jump_label.c
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@ -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); sort(start, size, sizeof(struct jump_entry), jump_label_cmp, NULL);
} }
static void jump_label_update(struct static_key *key, int enable); static void jump_label_update(struct static_key *key);
static inline bool static_key_type(struct static_key *key)
{
return (unsigned long)key->entries & JUMP_TYPE_MASK;
}
void static_key_slow_inc(struct static_key *key) void static_key_slow_inc(struct static_key *key)
{ {
@ -68,13 +63,8 @@ void static_key_slow_inc(struct static_key *key)
return; return;
jump_label_lock(); jump_label_lock();
if (atomic_read(&key->enabled) == 0) { if (atomic_inc_return(&key->enabled) == 1)
if (!static_key_type(key)) jump_label_update(key);
jump_label_update(key, JUMP_LABEL_JMP);
else
jump_label_update(key, JUMP_LABEL_NOP);
}
atomic_inc(&key->enabled);
jump_label_unlock(); jump_label_unlock();
} }
EXPORT_SYMBOL_GPL(static_key_slow_inc); EXPORT_SYMBOL_GPL(static_key_slow_inc);
@ -92,10 +82,7 @@ static void __static_key_slow_dec(struct static_key *key,
atomic_inc(&key->enabled); atomic_inc(&key->enabled);
schedule_delayed_work(work, rate_limit); schedule_delayed_work(work, rate_limit);
} else { } else {
if (!static_key_type(key)) jump_label_update(key);
jump_label_update(key, JUMP_LABEL_NOP);
else
jump_label_update(key, JUMP_LABEL_JMP);
} }
jump_label_unlock(); jump_label_unlock();
} }
@ -154,7 +141,7 @@ static int __jump_label_text_reserved(struct jump_entry *iter_start,
return 0; return 0;
} }
/* /*
* Update code which is definitely not currently executing. * Update code which is definitely not currently executing.
* Architectures which need heavyweight synchronization to modify * Architectures which need heavyweight synchronization to modify
* running code can override this to make the non-live update case * running code can override this to make the non-live update case
@ -163,24 +150,7 @@ 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, void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
enum jump_label_type type) 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)
{
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);
}
} }
static inline struct jump_entry *static_key_entries(struct static_key *key) static inline struct jump_entry *static_key_entries(struct static_key *key)
@ -188,19 +158,40 @@ static inline struct jump_entry *static_key_entries(struct static_key *key)
return (struct jump_entry *)((unsigned long)key->entries & ~JUMP_TYPE_MASK); return (struct jump_entry *)((unsigned long)key->entries & ~JUMP_TYPE_MASK);
} }
static inline bool static_key_type(struct static_key *key)
{
return (unsigned long)key->entries & JUMP_TYPE_MASK;
}
static inline struct static_key *jump_entry_key(struct jump_entry *entry) static inline struct static_key *jump_entry_key(struct jump_entry *entry)
{ {
return (struct static_key *)((unsigned long)entry->key); 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 enabled = static_key_enabled(key);
bool type = static_key_type(key); bool type = static_key_type(key);
return enabled ^ type; 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) void __init jump_label_init(void)
{ {
struct jump_entry *iter_start = __start___jump_table; struct jump_entry *iter_start = __start___jump_table;
@ -214,8 +205,8 @@ void __init jump_label_init(void)
for (iter = iter_start; iter < iter_stop; iter++) { for (iter = iter_start; iter < iter_stop; iter++) {
struct static_key *iterk; struct static_key *iterk;
arch_jump_label_transform_static(iter, jump_label_type(iter));
iterk = jump_entry_key(iter); iterk = jump_entry_key(iter);
arch_jump_label_transform_static(iter, jump_label_type(iterk));
if (iterk == key) if (iterk == key)
continue; continue;
@ -255,17 +246,15 @@ static int __jump_label_mod_text_reserved(void *start, void *end)
start, 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; struct module *m = mod->mod;
__jump_label_update(key, mod->entries, __jump_label_update(key, mod->entries,
m->jump_entries + m->num_jump_entries, m->jump_entries + m->num_jump_entries);
enable);
mod = mod->next;
} }
} }
@ -287,9 +276,8 @@ void jump_label_apply_nops(struct module *mod)
if (iter_start == iter_stop) if (iter_start == iter_stop)
return; 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); arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
}
} }
static int jump_label_add_module(struct module *mod) static int jump_label_add_module(struct module *mod)
@ -330,8 +318,8 @@ static int jump_label_add_module(struct module *mod)
jlm->next = key->next; jlm->next = key->next;
key->next = jlm; key->next = jlm;
if (jump_label_type(key) == JUMP_LABEL_JMP) if (jump_label_type(iter) == JUMP_LABEL_JMP)
__jump_label_update(key, iter, iter_stop, JUMP_LABEL_JMP); __jump_label_update(key, iter, iter_stop);
} }
return 0; return 0;
@ -451,14 +439,14 @@ int jump_label_text_reserved(void *start, void *end)
return ret; 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 *stop = __stop___jump_table;
struct jump_entry *entry = static_key_entries(key); struct jump_entry *entry = static_key_entries(key);
#ifdef CONFIG_MODULES #ifdef CONFIG_MODULES
struct module *mod; struct module *mod;
__jump_label_mod_update(key, enable); __jump_label_mod_update(key);
preempt_disable(); preempt_disable();
mod = __module_address((unsigned long)key); mod = __module_address((unsigned long)key);
@ -468,7 +456,7 @@ static void jump_label_update(struct static_key *key, int enable)
#endif #endif
/* if there are no users, entry can be NULL */ /* if there are no users, entry can be NULL */
if (entry) if (entry)
__jump_label_update(key, entry, stop, enable); __jump_label_update(key, entry, stop);
} }
#endif #endif