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Message-ID: <20150727104714.GT19282@twins.programming.kicks-ass.net>
Date: Mon, 27 Jul 2015 12:47:14 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: linux-kernel@...r.kernel.org, mingo@...nel.org
Cc: jasonbaron0@...il.com, bp@...en8.de, luto@...capital.net,
tglx@...utronix.de, rostedt@...dmis.org, will.deacon@....com,
liuj97@...il.com, rabin@....in, ralf@...ux-mips.org,
ddaney@...iumnetworks.com, benh@...nel.crashing.org,
michael@...erman.id.au, heiko.carstens@...ibm.com,
davem@...emloft.net
Subject: Re: [RFC][PATCH 5/7] jump_label: Rework update logic
Fixes jump_label_add_module()
---
Subject: jump_label: Rework update logic
From: Peter Zijlstra <peterz@...radead.org>
Date: Fri Jul 24 15:06:37 CEST 2015
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 they enabled
count _before_ calling the update path, otherwise jump_label_type()
will not see the right state.
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
kernel/jump_label.c | 88 ++++++++++++++++++++++------------------------------
1 file changed, 38 insertions(+), 50 deletions(-)
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -54,12 +54,7 @@ jump_label_sort_entries(struct jump_entr
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)
{
@@ -68,13 +63,8 @@ void static_key_slow_inc(struct static_k
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_and_test(&key->enabled))
+ jump_label_update(key);
jump_label_unlock();
}
EXPORT_SYMBOL_GPL(static_key_slow_inc);
@@ -92,10 +82,7 @@ static void __static_key_slow_dec(struct
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();
}
@@ -154,7 +141,7 @@ static int __jump_label_text_reserved(st
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
@@ -163,29 +150,17 @@ static int __jump_label_text_reserved(st
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)
@@ -193,14 +168,30 @@ static inline struct static_key *jump_en
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;
@@ -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;
@@ -255,17 +246,15 @@ static int __jump_label_mod_text_reserve
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);
}
}
@@ -287,9 +276,8 @@ void jump_label_apply_nops(struct module
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)
@@ -330,8 +318,8 @@ static int jump_label_add_module(struct
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;
@@ -451,14 +439,14 @@ int jump_label_text_reserved(void *start
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);
@@ -468,7 +456,7 @@ static void jump_label_update(struct sta
#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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