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authorPaolo Bonzini <pbonzini@redhat.com>2017-08-01 17:24:04 +0200
committerIngo Molnar <mingo@kernel.org>2017-08-10 12:28:56 +0200
commit1dbb6704de91b169a58d0c8221624afd6a95cfc7 (patch)
tree46273515a9b79413d2f00629b7e253189e903219
parent83ced169d9a01f22eb39f1fcc1f89ad9d223238f (diff)
downloadlinux-1dbb6704de91b169a58d0c8221624afd6a95cfc7.tar.bz2
jump_label: Fix concurrent static_key_enable/disable()
static_key_enable/disable are trying to cap the static key count to 0/1. However, their use of key->enabled is outside jump_label_lock so they do not really ensure that. Rewrite them to do a quick check for an already enabled (respectively, already disabled), and then recheck under the jump label lock. Unlike static_key_slow_inc/dec, a failed check under the jump label lock does not modify key->enabled. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: Jason Baron <jbaron@akamai.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1501601046-35683-2-git-send-email-pbonzini@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--include/linux/jump_label.h22
-rw-r--r--kernel/jump_label.c59
2 files changed, 49 insertions, 32 deletions
diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
index 2afd74b9d844..740a42ea7f7f 100644
--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -234,22 +234,24 @@ static inline int jump_label_apply_nops(struct module *mod)
static inline void static_key_enable(struct static_key *key)
{
- int count = static_key_count(key);
-
- WARN_ON_ONCE(count < 0 || count > 1);
+ STATIC_KEY_CHECK_USE();
- if (!count)
- static_key_slow_inc(key);
+ if (atomic_read(&key->enabled) != 0) {
+ WARN_ON_ONCE(atomic_read(&key->enabled) != 1);
+ return;
+ }
+ atomic_set(&key->enabled, 1);
}
static inline void static_key_disable(struct static_key *key)
{
- int count = static_key_count(key);
-
- WARN_ON_ONCE(count < 0 || count > 1);
+ STATIC_KEY_CHECK_USE();
- if (count)
- static_key_slow_dec(key);
+ if (atomic_read(&key->enabled) != 1) {
+ WARN_ON_ONCE(atomic_read(&key->enabled) != 0);
+ return;
+ }
+ atomic_set(&key->enabled, 0);
}
#define STATIC_KEY_INIT_TRUE { .enabled = ATOMIC_INIT(1) }
diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index d11c506a6ac3..833eecae825e 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -79,28 +79,6 @@ int static_key_count(struct static_key *key)
}
EXPORT_SYMBOL_GPL(static_key_count);
-void static_key_enable(struct static_key *key)
-{
- int count = static_key_count(key);
-
- WARN_ON_ONCE(count < 0 || count > 1);
-
- if (!count)
- static_key_slow_inc(key);
-}
-EXPORT_SYMBOL_GPL(static_key_enable);
-
-void static_key_disable(struct static_key *key)
-{
- int count = static_key_count(key);
-
- WARN_ON_ONCE(count < 0 || count > 1);
-
- if (count)
- static_key_slow_dec(key);
-}
-EXPORT_SYMBOL_GPL(static_key_disable);
-
void static_key_slow_inc(struct static_key *key)
{
int v, v1;
@@ -139,6 +117,43 @@ void static_key_slow_inc(struct static_key *key)
}
EXPORT_SYMBOL_GPL(static_key_slow_inc);
+void static_key_enable(struct static_key *key)
+{
+ STATIC_KEY_CHECK_USE();
+ if (atomic_read(&key->enabled) > 0) {
+ WARN_ON_ONCE(atomic_read(&key->enabled) != 1);
+ return;
+ }
+
+ cpus_read_lock();
+ jump_label_lock();
+ if (atomic_read(&key->enabled) == 0) {
+ atomic_set(&key->enabled, -1);
+ jump_label_update(key);
+ atomic_set(&key->enabled, 1);
+ }
+ jump_label_unlock();
+ cpus_read_unlock();
+}
+EXPORT_SYMBOL_GPL(static_key_enable);
+
+void static_key_disable(struct static_key *key)
+{
+ STATIC_KEY_CHECK_USE();
+ if (atomic_read(&key->enabled) != 1) {
+ WARN_ON_ONCE(atomic_read(&key->enabled) != 0);
+ return;
+ }
+
+ cpus_read_lock();
+ jump_label_lock();
+ if (atomic_cmpxchg(&key->enabled, 1, 0))
+ jump_label_update(key);
+ jump_label_unlock();
+ cpus_read_unlock();
+}
+EXPORT_SYMBOL_GPL(static_key_disable);
+
static void __static_key_slow_dec(struct static_key *key,
unsigned long rate_limit, struct delayed_work *work)
{