locking/static_key: Don't take sleeping locks in __static_key_slow_dec_deferred()

Changing jump_label state is protected by jump_label_lock().
Rate limited static_key_slow_dec(), however, will never
directly call jump_label_update(), it will schedule a delayed
work instead.  Therefore it's unnecessary to take both the
cpus_read_lock() and jump_label_lock().

This allows static_key_slow_dec_deferred() to be called
from atomic contexts, like socket destructing in net/tls,
without the need for another indirection.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
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: Will Deacon <will.deacon@arm.com>
Cc: alexei.starovoitov@gmail.com
Cc: ard.biesheuvel@linaro.org
Cc: oss-drivers@netronome.com
Cc: yamada.masahiro@socionext.com
Link: https://lkml.kernel.org/r/20190330000854.30142-4-jakub.kicinski@netronome.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 02c3d11..de6efde 100644 (file)
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -221,9 +221,7 @@ static bool static_key_slow_try_dec(struct static_key *key)
        return true;
 }
 
-static void __static_key_slow_dec_cpuslocked(struct static_key *key,
-                                          unsigned long rate_limit,
-                                          struct delayed_work *work)
+static void __static_key_slow_dec_cpuslocked(struct static_key *key)
 {
        lockdep_assert_cpus_held();
 
@@ -231,23 +229,15 @@ static void __static_key_slow_dec_cpuslocked(struct static_key *key,
                return;
 
        jump_label_lock();
-       if (atomic_dec_and_test(&key->enabled)) {
-               if (rate_limit) {
-                       atomic_inc(&key->enabled);
-                       schedule_delayed_work(work, rate_limit);
-               } else {
-                       jump_label_update(key);
-               }
-       }
+       if (atomic_dec_and_test(&key->enabled))
+               jump_label_update(key);
        jump_label_unlock();
 }
 
-static void __static_key_slow_dec(struct static_key *key,
-                                 unsigned long rate_limit,
-                                 struct delayed_work *work)
+static void __static_key_slow_dec(struct static_key *key)
 {
        cpus_read_lock();
-       __static_key_slow_dec_cpuslocked(key, rate_limit, work);
+       __static_key_slow_dec_cpuslocked(key);
        cpus_read_unlock();
 }
 
@@ -255,21 +245,21 @@ void jump_label_update_timeout(struct work_struct *work)
 {
        struct static_key_deferred *key =
                container_of(work, struct static_key_deferred, work.work);
-       __static_key_slow_dec(&key->key, 0, NULL);
+       __static_key_slow_dec(&key->key);
 }
 EXPORT_SYMBOL_GPL(jump_label_update_timeout);
 
 void static_key_slow_dec(struct static_key *key)
 {
        STATIC_KEY_CHECK_USE(key);
-       __static_key_slow_dec(key, 0, NULL);
+       __static_key_slow_dec(key);
 }
 EXPORT_SYMBOL_GPL(static_key_slow_dec);
 
 void static_key_slow_dec_cpuslocked(struct static_key *key)
 {
        STATIC_KEY_CHECK_USE(key);
-       __static_key_slow_dec_cpuslocked(key, 0, NULL);
+       __static_key_slow_dec_cpuslocked(key);
 }
 
 void __static_key_slow_dec_deferred(struct static_key *key,
@@ -277,7 +267,11 @@ void __static_key_slow_dec_deferred(struct static_key *key,
                                    unsigned long timeout)
 {
        STATIC_KEY_CHECK_USE(key);
-       __static_key_slow_dec(key, timeout, work);
+
+       if (static_key_slow_try_dec(key))
+               return;
+
+       schedule_delayed_work(work, timeout);
 }
 EXPORT_SYMBOL_GPL(__static_key_slow_dec_deferred);