From 4d004099a668c41522242aa146a38cc4eb59cb1e Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 2 Oct 2020 11:04:21 +0200 Subject: [PATCH] lockdep: Fix lockdep recursion Steve reported that lockdep_assert*irq*(), when nested inside lockdep itself, will trigger a false-positive. One example is the stack-trace code, as called from inside lockdep, triggering tracing, which in turn calls RCU, which then uses lockdep_assert_irqs_disabled(). Fixes: a21ee6055c30 ("lockdep: Change hardirq{s_enabled,_context} to per-cpu variables") Reported-by: Steven Rostedt Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar --- include/linux/lockdep.h | 13 ++++-- kernel/locking/lockdep.c | 99 ++++++++++++++++++++++++---------------- 2 files changed, 67 insertions(+), 45 deletions(-) diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index 6a584b3e5c74..b1227be47496 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -534,6 +534,7 @@ do { \ DECLARE_PER_CPU(int, hardirqs_enabled); DECLARE_PER_CPU(int, hardirq_context); +DECLARE_PER_CPU(unsigned int, lockdep_recursion); /* * The below lockdep_assert_*() macros use raw_cpu_read() to access the above @@ -543,25 +544,27 @@ DECLARE_PER_CPU(int, hardirq_context); * read the value from our previous CPU. */ +#define __lockdep_enabled (debug_locks && !raw_cpu_read(lockdep_recursion)) + #define lockdep_assert_irqs_enabled() \ do { \ - WARN_ON_ONCE(debug_locks && !raw_cpu_read(hardirqs_enabled)); \ + WARN_ON_ONCE(__lockdep_enabled && !raw_cpu_read(hardirqs_enabled)); \ } while (0) #define lockdep_assert_irqs_disabled() \ do { \ - WARN_ON_ONCE(debug_locks && raw_cpu_read(hardirqs_enabled)); \ + WARN_ON_ONCE(__lockdep_enabled && raw_cpu_read(hardirqs_enabled)); \ } while (0) #define lockdep_assert_in_irq() \ do { \ - WARN_ON_ONCE(debug_locks && !raw_cpu_read(hardirq_context)); \ + WARN_ON_ONCE(__lockdep_enabled && !raw_cpu_read(hardirq_context)); \ } while (0) #define lockdep_assert_preemption_enabled() \ do { \ WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_COUNT) && \ - debug_locks && \ + __lockdep_enabled && \ (preempt_count() != 0 || \ !raw_cpu_read(hardirqs_enabled))); \ } while (0) @@ -569,7 +572,7 @@ do { \ #define lockdep_assert_preemption_disabled() \ do { \ WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_COUNT) && \ - debug_locks && \ + __lockdep_enabled && \ (preempt_count() == 0 && \ raw_cpu_read(hardirqs_enabled))); \ } while (0) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index a430fbb01eb1..85d15f0362dc 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -76,6 +76,23 @@ module_param(lock_stat, int, 0644); #define lock_stat 0 #endif +DEFINE_PER_CPU(unsigned int, lockdep_recursion); +EXPORT_PER_CPU_SYMBOL_GPL(lockdep_recursion); + +static inline bool lockdep_enabled(void) +{ + if (!debug_locks) + return false; + + if (raw_cpu_read(lockdep_recursion)) + return false; + + if (current->lockdep_recursion) + return false; + + return true; +} + /* * lockdep_lock: protects the lockdep graph, the hashes and the * class/list/hash allocators. @@ -93,7 +110,7 @@ static inline void lockdep_lock(void) arch_spin_lock(&__lock); __owner = current; - current->lockdep_recursion++; + __this_cpu_inc(lockdep_recursion); } static inline void lockdep_unlock(void) @@ -101,7 +118,7 @@ static inline void lockdep_unlock(void) if (debug_locks && DEBUG_LOCKS_WARN_ON(__owner != current)) return; - current->lockdep_recursion--; + __this_cpu_dec(lockdep_recursion); __owner = NULL; arch_spin_unlock(&__lock); } @@ -393,10 +410,15 @@ void lockdep_init_task(struct task_struct *task) task->lockdep_recursion = 0; } +static __always_inline void lockdep_recursion_inc(void) +{ + __this_cpu_inc(lockdep_recursion); +} + static __always_inline void lockdep_recursion_finish(void) { - if (WARN_ON_ONCE((--current->lockdep_recursion) & LOCKDEP_RECURSION_MASK)) - current->lockdep_recursion = 0; + if (WARN_ON_ONCE(__this_cpu_dec_return(lockdep_recursion))) + __this_cpu_write(lockdep_recursion, 0); } void lockdep_set_selftest_task(struct task_struct *task) @@ -3659,7 +3681,7 @@ void lockdep_hardirqs_on_prepare(unsigned long ip) if (unlikely(in_nmi())) return; - if (unlikely(current->lockdep_recursion & LOCKDEP_RECURSION_MASK)) + if (unlikely(__this_cpu_read(lockdep_recursion))) return; if (unlikely(lockdep_hardirqs_enabled())) { @@ -3695,7 +3717,7 @@ void lockdep_hardirqs_on_prepare(unsigned long ip) current->hardirq_chain_key = current->curr_chain_key; - current->lockdep_recursion++; + lockdep_recursion_inc(); __trace_hardirqs_on_caller(); lockdep_recursion_finish(); } @@ -3728,7 +3750,7 @@ void noinstr lockdep_hardirqs_on(unsigned long ip) goto skip_checks; } - if (unlikely(current->lockdep_recursion & LOCKDEP_RECURSION_MASK)) + if (unlikely(__this_cpu_read(lockdep_recursion))) return; if (lockdep_hardirqs_enabled()) { @@ -3781,7 +3803,7 @@ void noinstr lockdep_hardirqs_off(unsigned long ip) if (in_nmi()) { if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI)) return; - } else if (current->lockdep_recursion & LOCKDEP_RECURSION_MASK) + } else if (__this_cpu_read(lockdep_recursion)) return; /* @@ -3814,7 +3836,7 @@ void lockdep_softirqs_on(unsigned long ip) { struct irqtrace_events *trace = ¤t->irqtrace; - if (unlikely(!debug_locks || current->lockdep_recursion)) + if (unlikely(!lockdep_enabled())) return; /* @@ -3829,7 +3851,7 @@ void lockdep_softirqs_on(unsigned long ip) return; } - current->lockdep_recursion++; + lockdep_recursion_inc(); /* * We'll do an OFF -> ON transition: */ @@ -3852,7 +3874,7 @@ void lockdep_softirqs_on(unsigned long ip) */ void lockdep_softirqs_off(unsigned long ip) { - if (unlikely(!debug_locks || current->lockdep_recursion)) + if (unlikely(!lockdep_enabled())) return; /* @@ -4233,11 +4255,11 @@ void lockdep_init_map_waits(struct lockdep_map *lock, const char *name, if (subclass) { unsigned long flags; - if (DEBUG_LOCKS_WARN_ON(current->lockdep_recursion)) + if (DEBUG_LOCKS_WARN_ON(!lockdep_enabled())) return; raw_local_irq_save(flags); - current->lockdep_recursion++; + lockdep_recursion_inc(); register_lock_class(lock, subclass, 1); lockdep_recursion_finish(); raw_local_irq_restore(flags); @@ -4920,11 +4942,11 @@ void lock_set_class(struct lockdep_map *lock, const char *name, { unsigned long flags; - if (unlikely(current->lockdep_recursion)) + if (unlikely(!lockdep_enabled())) return; raw_local_irq_save(flags); - current->lockdep_recursion++; + lockdep_recursion_inc(); check_flags(flags); if (__lock_set_class(lock, name, key, subclass, ip)) check_chain_key(current); @@ -4937,11 +4959,11 @@ void lock_downgrade(struct lockdep_map *lock, unsigned long ip) { unsigned long flags; - if (unlikely(current->lockdep_recursion)) + if (unlikely(!lockdep_enabled())) return; raw_local_irq_save(flags); - current->lockdep_recursion++; + lockdep_recursion_inc(); check_flags(flags); if (__lock_downgrade(lock, ip)) check_chain_key(current); @@ -4979,7 +5001,7 @@ static void verify_lock_unused(struct lockdep_map *lock, struct held_lock *hlock static bool lockdep_nmi(void) { - if (current->lockdep_recursion & LOCKDEP_RECURSION_MASK) + if (raw_cpu_read(lockdep_recursion)) return false; if (!in_nmi()) @@ -5000,7 +5022,10 @@ void lock_acquire(struct lockdep_map *lock, unsigned int subclass, trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip); - if (unlikely(current->lockdep_recursion)) { + if (!debug_locks) + return; + + if (unlikely(!lockdep_enabled())) { /* XXX allow trylock from NMI ?!? */ if (lockdep_nmi() && !trylock) { struct held_lock hlock; @@ -5023,7 +5048,7 @@ void lock_acquire(struct lockdep_map *lock, unsigned int subclass, raw_local_irq_save(flags); check_flags(flags); - current->lockdep_recursion++; + lockdep_recursion_inc(); __lock_acquire(lock, subclass, trylock, read, check, irqs_disabled_flags(flags), nest_lock, ip, 0, 0); lockdep_recursion_finish(); @@ -5037,13 +5062,13 @@ void lock_release(struct lockdep_map *lock, unsigned long ip) trace_lock_release(lock, ip); - if (unlikely(current->lockdep_recursion)) + if (unlikely(!lockdep_enabled())) return; raw_local_irq_save(flags); check_flags(flags); - current->lockdep_recursion++; + lockdep_recursion_inc(); if (__lock_release(lock, ip)) check_chain_key(current); lockdep_recursion_finish(); @@ -5056,13 +5081,13 @@ noinstr int lock_is_held_type(const struct lockdep_map *lock, int read) unsigned long flags; int ret = 0; - if (unlikely(current->lockdep_recursion)) + if (unlikely(!lockdep_enabled())) return 1; /* avoid false negative lockdep_assert_held() */ raw_local_irq_save(flags); check_flags(flags); - current->lockdep_recursion++; + lockdep_recursion_inc(); ret = __lock_is_held(lock, read); lockdep_recursion_finish(); raw_local_irq_restore(flags); @@ -5077,13 +5102,13 @@ struct pin_cookie lock_pin_lock(struct lockdep_map *lock) struct pin_cookie cookie = NIL_COOKIE; unsigned long flags; - if (unlikely(current->lockdep_recursion)) + if (unlikely(!lockdep_enabled())) return cookie; raw_local_irq_save(flags); check_flags(flags); - current->lockdep_recursion++; + lockdep_recursion_inc(); cookie = __lock_pin_lock(lock); lockdep_recursion_finish(); raw_local_irq_restore(flags); @@ -5096,13 +5121,13 @@ void lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie) { unsigned long flags; - if (unlikely(current->lockdep_recursion)) + if (unlikely(!lockdep_enabled())) return; raw_local_irq_save(flags); check_flags(flags); - current->lockdep_recursion++; + lockdep_recursion_inc(); __lock_repin_lock(lock, cookie); lockdep_recursion_finish(); raw_local_irq_restore(flags); @@ -5113,13 +5138,13 @@ void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie) { unsigned long flags; - if (unlikely(current->lockdep_recursion)) + if (unlikely(!lockdep_enabled())) return; raw_local_irq_save(flags); check_flags(flags); - current->lockdep_recursion++; + lockdep_recursion_inc(); __lock_unpin_lock(lock, cookie); lockdep_recursion_finish(); raw_local_irq_restore(flags); @@ -5249,15 +5274,12 @@ void lock_contended(struct lockdep_map *lock, unsigned long ip) trace_lock_acquired(lock, ip); - if (unlikely(!lock_stat || !debug_locks)) - return; - - if (unlikely(current->lockdep_recursion)) + if (unlikely(!lock_stat || !lockdep_enabled())) return; raw_local_irq_save(flags); check_flags(flags); - current->lockdep_recursion++; + lockdep_recursion_inc(); __lock_contended(lock, ip); lockdep_recursion_finish(); raw_local_irq_restore(flags); @@ -5270,15 +5292,12 @@ void lock_acquired(struct lockdep_map *lock, unsigned long ip) trace_lock_contended(lock, ip); - if (unlikely(!lock_stat || !debug_locks)) - return; - - if (unlikely(current->lockdep_recursion)) + if (unlikely(!lock_stat || !lockdep_enabled())) return; raw_local_irq_save(flags); check_flags(flags); - current->lockdep_recursion++; + lockdep_recursion_inc(); __lock_acquired(lock, ip); lockdep_recursion_finish(); raw_local_irq_restore(flags);