Commit 94b5f312 authored by Jakub Kicinski's avatar Jakub Kicinski Committed by Ingo Molnar
Browse files

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: default avatarJakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarSimon 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: default avatarIngo Molnar <mingo@kernel.org>
parent b92e793b

kernel/jump_label.c

+13 −19
Original line number Diff line number Diff line
@@ -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 {

	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);

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