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Commit 1dbb6704 authored by Paolo Bonzini's avatar Paolo Bonzini Committed by Ingo Molnar
Browse files

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: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarPeter 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: default avatarIngo Molnar <mingo@kernel.org>
parent 83ced169

include/linux/jump_label.h

+12 −10
Original line number Diff line number Diff line
@@ -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) }

kernel/jump_label.c

+37 −22
Original line number Diff line number Diff line
@@ -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)

{