From 10476e6304222ced7df9b3d5fb0a043b3c2a1ad8 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 13 Mar 2020 09:56:38 +0100 Subject: [PATCH] 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) Link: https://lkml.kernel.org/r/20200313093325.GW12561@hirez.programming.kicks-ass.net --- kernel/locking/lockdep.c | 74 ++++++++++++++++++++++++++---------------------- 1 file changed, 40 insertions(+), 34 deletions(-) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 2564950..64ea69f 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); -- 2.7.4