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locking/lockdep: Fix bad recursion pattern
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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: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200313093325.GW12561@hirez.programming.kicks-ass.net
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Peter Zijlstra committed Mar 20, 2020
1 parent 25016bd commit 10476e6
Showing 1 changed file with 40 additions and 34 deletions.
74 changes: 40 additions & 34 deletions kernel/locking/lockdep.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down Expand Up @@ -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;
Expand All @@ -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;
Expand Down Expand Up @@ -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);

Expand Down Expand Up @@ -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:
*/
Expand All @@ -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();
}

/*
Expand Down Expand Up @@ -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);
}
}
Expand Down Expand Up @@ -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);
Expand All @@ -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);
Expand All @@ -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);
Expand All @@ -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);
Expand All @@ -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;
Expand All @@ -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;
Expand All @@ -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);
Expand All @@ -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);
Expand Down Expand Up @@ -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);
Expand All @@ -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);
Expand Down Expand Up @@ -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);
Expand All @@ -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);
}
Expand Down Expand Up @@ -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);

Expand Down

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