Commit 10476e63 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

locking/lockdep: Fix bad recursion pattern 



There were two patterns for lockdep_recursion:

Pattern-A:
	if (current->lockdep_recursion)
		return

	current->lockdep_recursion = 1;
	/* do stuff */
	current->lockdep_recursion = 0;

Pattern-B:
	current->lockdep_recursion++;
	/* do stuff */
	current->lockdep_recursion--;

But a third pattern has emerged:

Pattern-C:
	current->lockdep_recursion = 1;
	/* do stuff */
	current->lockdep_recursion = 0;

And while this isn't broken per-se, it is highly dangerous because it
doesn't nest properly.

Get rid of all Pattern-C instances and shore up Pattern-A with a
warning.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200313093325.GW12561@hirez.programming.kicks-ass.net
parent 25016bd7

kernel/locking/lockdep.c

+40 −34
Original line number Diff line number Diff line
@@ -390,6 +390,12 @@ void lockdep_on(void) 
}

EXPORT_SYMBOL(lockdep_on);



static inline void lockdep_recursion_finish(void)

{

	if (WARN_ON_ONCE(--current->lockdep_recursion))

		current->lockdep_recursion = 0;

}



void lockdep_set_selftest_task(struct task_struct *task)

{

	lockdep_selftest_task_struct = task;
@@ -1723,11 +1729,11 @@ unsigned long lockdep_count_forward_deps(struct lock_class *class) 
	this.class = class;



	raw_local_irq_save(flags);

	current->lockdep_recursion = 1;

	current->lockdep_recursion++;

	arch_spin_lock(&lockdep_lock);

	ret = __lockdep_count_forward_deps(&this);

	arch_spin_unlock(&lockdep_lock);

	current->lockdep_recursion = 0;

	current->lockdep_recursion--;

	raw_local_irq_restore(flags);



	return ret;
@@ -1752,11 +1758,11 @@ unsigned long lockdep_count_backward_deps(struct lock_class *class) 
	this.class = class;



	raw_local_irq_save(flags);

	current->lockdep_recursion = 1;

	current->lockdep_recursion++;

	arch_spin_lock(&lockdep_lock);

	ret = __lockdep_count_backward_deps(&this);

	arch_spin_unlock(&lockdep_lock);

	current->lockdep_recursion = 0;

	current->lockdep_recursion--;

	raw_local_irq_restore(flags);



	return ret;
@@ -3668,9 +3674,9 @@ void lockdep_hardirqs_on(unsigned long ip) 
	if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))

		return;



	current->lockdep_recursion = 1;

	current->lockdep_recursion++;

	__trace_hardirqs_on_caller(ip);

	current->lockdep_recursion = 0;

	lockdep_recursion_finish();

}

NOKPROBE_SYMBOL(lockdep_hardirqs_on);
@@ -3726,7 +3732,7 @@ void trace_softirqs_on(unsigned long ip) 
		return;

	}



	current->lockdep_recursion = 1;

	current->lockdep_recursion++;

	/*

	 * We'll do an OFF -> ON transition:

	 */
@@ -3741,7 +3747,7 @@ void trace_softirqs_on(unsigned long ip) 
	 */

	if (curr->hardirqs_enabled)

		mark_held_locks(curr, LOCK_ENABLED_SOFTIRQ);

	current->lockdep_recursion = 0;

	lockdep_recursion_finish();

}



/*
@@ -3995,9 +4001,9 @@ void lockdep_init_map(struct lockdep_map *lock, const char *name, 
			return;



		raw_local_irq_save(flags);

		current->lockdep_recursion = 1;

		current->lockdep_recursion++;

		register_lock_class(lock, subclass, 1);

		current->lockdep_recursion = 0;

		lockdep_recursion_finish();

		raw_local_irq_restore(flags);

	}

}
@@ -4677,11 +4683,11 @@ void lock_set_class(struct lockdep_map *lock, const char *name, 
		return;



	raw_local_irq_save(flags);

	current->lockdep_recursion = 1;

	current->lockdep_recursion++;

	check_flags(flags);

	if (__lock_set_class(lock, name, key, subclass, ip))

		check_chain_key(current);

	current->lockdep_recursion = 0;

	lockdep_recursion_finish();

	raw_local_irq_restore(flags);

}

EXPORT_SYMBOL_GPL(lock_set_class);
@@ -4694,11 +4700,11 @@ void lock_downgrade(struct lockdep_map *lock, unsigned long ip) 
		return;



	raw_local_irq_save(flags);

	current->lockdep_recursion = 1;

	current->lockdep_recursion++;

	check_flags(flags);

	if (__lock_downgrade(lock, ip))

		check_chain_key(current);

	current->lockdep_recursion = 0;

	lockdep_recursion_finish();

	raw_local_irq_restore(flags);

}

EXPORT_SYMBOL_GPL(lock_downgrade);
@@ -4719,11 +4725,11 @@ void lock_acquire(struct lockdep_map *lock, unsigned int subclass, 
	raw_local_irq_save(flags);

	check_flags(flags);



	current->lockdep_recursion = 1;

	current->lockdep_recursion++;

	trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);

	__lock_acquire(lock, subclass, trylock, read, check,

		       irqs_disabled_flags(flags), nest_lock, ip, 0, 0);

	current->lockdep_recursion = 0;

	lockdep_recursion_finish();

	raw_local_irq_restore(flags);

}

EXPORT_SYMBOL_GPL(lock_acquire);
@@ -4737,11 +4743,11 @@ void lock_release(struct lockdep_map *lock, unsigned long ip) 


	raw_local_irq_save(flags);

	check_flags(flags);

	current->lockdep_recursion = 1;

	current->lockdep_recursion++;

	trace_lock_release(lock, ip);

	if (__lock_release(lock, ip))

		check_chain_key(current);

	current->lockdep_recursion = 0;

	lockdep_recursion_finish();

	raw_local_irq_restore(flags);

}

EXPORT_SYMBOL_GPL(lock_release);
@@ -4757,9 +4763,9 @@ int lock_is_held_type(const struct lockdep_map *lock, int read) 
	raw_local_irq_save(flags);

	check_flags(flags);



	current->lockdep_recursion = 1;

	current->lockdep_recursion++;

	ret = __lock_is_held(lock, read);

	current->lockdep_recursion = 0;

	lockdep_recursion_finish();

	raw_local_irq_restore(flags);



	return ret;
@@ -4778,9 +4784,9 @@ struct pin_cookie lock_pin_lock(struct lockdep_map *lock) 
	raw_local_irq_save(flags);

	check_flags(flags);



	current->lockdep_recursion = 1;

	current->lockdep_recursion++;

	cookie = __lock_pin_lock(lock);

	current->lockdep_recursion = 0;

	lockdep_recursion_finish();

	raw_local_irq_restore(flags);



	return cookie;
@@ -4797,9 +4803,9 @@ void lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie) 
	raw_local_irq_save(flags);

	check_flags(flags);



	current->lockdep_recursion = 1;

	current->lockdep_recursion++;

	__lock_repin_lock(lock, cookie);

	current->lockdep_recursion = 0;

	lockdep_recursion_finish();

	raw_local_irq_restore(flags);

}

EXPORT_SYMBOL_GPL(lock_repin_lock);
@@ -4814,9 +4820,9 @@ void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie) 
	raw_local_irq_save(flags);

	check_flags(flags);



	current->lockdep_recursion = 1;

	current->lockdep_recursion++;

	__lock_unpin_lock(lock, cookie);

	current->lockdep_recursion = 0;

	lockdep_recursion_finish();

	raw_local_irq_restore(flags);

}

EXPORT_SYMBOL_GPL(lock_unpin_lock);
@@ -4952,10 +4958,10 @@ void lock_contended(struct lockdep_map *lock, unsigned long ip) 


	raw_local_irq_save(flags);

	check_flags(flags);

	current->lockdep_recursion = 1;

	current->lockdep_recursion++;

	trace_lock_contended(lock, ip);

	__lock_contended(lock, ip);

	current->lockdep_recursion = 0;

	lockdep_recursion_finish();

	raw_local_irq_restore(flags);

}

EXPORT_SYMBOL_GPL(lock_contended);
@@ -4972,9 +4978,9 @@ void lock_acquired(struct lockdep_map *lock, unsigned long ip) 


	raw_local_irq_save(flags);

	check_flags(flags);

	current->lockdep_recursion = 1;

	current->lockdep_recursion++;

	__lock_acquired(lock, ip);

	current->lockdep_recursion = 0;

	lockdep_recursion_finish();

	raw_local_irq_restore(flags);

}

EXPORT_SYMBOL_GPL(lock_acquired);
@@ -5176,7 +5182,7 @@ static void free_zapped_rcu(struct rcu_head *ch) 


	raw_local_irq_save(flags);

	arch_spin_lock(&lockdep_lock);

	current->lockdep_recursion = 1;

	current->lockdep_recursion++;



	/* closed head */

	pf = delayed_free.pf + (delayed_free.index ^ 1);
@@ -5188,7 +5194,7 @@ static void free_zapped_rcu(struct rcu_head *ch) 
	 */

	call_rcu_zapped(delayed_free.pf + delayed_free.index);



	current->lockdep_recursion = 0;

	current->lockdep_recursion--;

	arch_spin_unlock(&lockdep_lock);

	raw_local_irq_restore(flags);

}
@@ -5235,11 +5241,11 @@ static void lockdep_free_key_range_reg(void *start, unsigned long size) 


	raw_local_irq_save(flags);

	arch_spin_lock(&lockdep_lock);

	current->lockdep_recursion = 1;

	current->lockdep_recursion++;

	pf = get_pending_free();

	__lockdep_free_key_range(pf, start, size);

	call_rcu_zapped(pf);

	current->lockdep_recursion = 0;

	current->lockdep_recursion--;

	arch_spin_unlock(&lockdep_lock);

	raw_local_irq_restore(flags);

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