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authorPeter Zijlstra <peterz@infradead.org>2020-03-13 09:56:38 +0100
committerPeter Zijlstra <peterz@infradead.org>2020-03-20 13:06:25 +0100
commit10476e6304222ced7df9b3d5fb0a043b3c2a1ad8 (patch)
treeffabb7c1514caad90cace22b593c01300d05a7a8 /kernel/locking
parentlocking/lockdep: Avoid recursion in lockdep_count_{for,back}ward_deps() (diff)
downloadlinux-10476e6304222ced7df9b3d5fb0a043b3c2a1ad8.tar.xz
linux-10476e6304222ced7df9b3d5fb0a043b3c2a1ad8.zip
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: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200313093325.GW12561@hirez.programming.kicks-ass.net
Diffstat (limited to 'kernel/locking')
-rw-r--r--kernel/locking/lockdep.c74
1 files changed, 40 insertions, 34 deletions
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 2564950a402c..64ea69f94b3a 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -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);