[PATCH 5.9 115/757] lockdep: Fix lockdep recursion

27 Oct 2020

From: Peter Zijlstra peterz@infradead.org
[ Upstream commit 4d004099a668c41522242aa146a38cc4eb59cb1e ]
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 rostedt@goodmis.org
Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org
Signed-off-by: Ingo Molnar mingo@kernel.org
Signed-off-by: Sasha Levin sashal@kernel.org
---
 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 6a584b3e5c74f..b1227be47496c 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 a430fbb01eb16..85d15f0362dc5 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 = &current->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);
-- 
2.25.1




    

2025

2024

2023

2022

2021

2020

2019

2018

2017

[PATCH 5.9 115/757] lockdep: Fix lockdep recursion