Commit b4c5c57c authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'locking-urgent-2025-03-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull misc locking fixes and updates from Ingo Molnar:

 - Fix a locking self-test FAIL on PREEMPT_RT kernels

 - Fix nr_unused_locks accounting bug

 - Simplify the split-lock debugging feature's fast-path

* tag 'locking-urgent-2025-03-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking/lockdep: Decrease nr_unused_locks if lock unused in zap_class()
  lockdep: Fix wait context check on softirq for PREEMPT_RT
  x86/split_lock: Simplify reenabling
parents aa918db7 495f53d5

arch/x86/kernel/cpu/bus_lock.c

+24 −11
Original line number Diff line number Diff line
@@ -200,6 +200,26 @@ static void __split_lock_reenable(struct work_struct *work) 
 */

static DEFINE_PER_CPU(struct delayed_work, sl_reenable);



/*

 * Per-CPU delayed_work can't be statically initialized properly because

 * the struct address is unknown. Thus per-CPU delayed_work structures

 * have to be initialized during kernel initialization and after calling

 * setup_per_cpu_areas().

 */

static int __init setup_split_lock_delayed_work(void)

{

	unsigned int cpu;



	for_each_possible_cpu(cpu) {

		struct delayed_work *work = per_cpu_ptr(&sl_reenable, cpu);



		INIT_DELAYED_WORK(work, __split_lock_reenable);

	}



	return 0;

}

pure_initcall(setup_split_lock_delayed_work);



/*

 * If a CPU goes offline with pending delayed work to re-enable split lock

 * detection then the delayed work will be executed on some other CPU. That
@@ -219,15 +239,16 @@ static int splitlock_cpu_offline(unsigned int cpu) 


static void split_lock_warn(unsigned long ip)

{

	struct delayed_work *work = NULL;

	struct delayed_work *work;

	int cpu;

	unsigned int saved_sld_mitigate = READ_ONCE(sysctl_sld_mitigate);



	if (!current->reported_split_lock)

		pr_warn_ratelimited("#AC: %s/%d took a split_lock trap at address: 0x%lx\n",

				    current->comm, current->pid, ip);

	current->reported_split_lock = 1;



	if (sysctl_sld_mitigate) {

	if (saved_sld_mitigate) {

		/*

		 * misery factor #1:

		 * sleep 10ms before trying to execute split lock.
@@ -240,18 +261,10 @@ static void split_lock_warn(unsigned long ip) 
		 */

		if (down_interruptible(&buslock_sem) == -EINTR)

			return;

		work = &sl_reenable_unlock;

	}



	cpu = get_cpu();



	if (!work) {

		work = this_cpu_ptr(&sl_reenable);

		/* Deferred initialization of per-CPU struct */

		if (!work->work.func)

			INIT_DELAYED_WORK(work, __split_lock_reenable);

	}



	work = saved_sld_mitigate ? &sl_reenable_unlock : per_cpu_ptr(&sl_reenable, cpu);

	schedule_delayed_work_on(cpu, work, 2);



	/* Disable split lock detection on this CPU to make progress */

kernel/locking/lockdep.c

+3 −0
Original line number Diff line number Diff line
@@ -6264,6 +6264,9 @@ static void zap_class(struct pending_free *pf, struct lock_class *class) 
		hlist_del_rcu(&class->hash_entry);

		WRITE_ONCE(class->key, NULL);

		WRITE_ONCE(class->name, NULL);

		/* Class allocated but not used, -1 in nr_unused_locks */

		if (class->usage_mask == 0)

			debug_atomic_dec(nr_unused_locks);

		nr_lock_classes--;

		__clear_bit(class - lock_classes, lock_classes_in_use);

		if (class - lock_classes == max_lock_class_idx)

kernel/softirq.c

+18 −0
Original line number Diff line number Diff line
@@ -126,6 +126,18 @@ static DEFINE_PER_CPU(struct softirq_ctrl, softirq_ctrl) = { 
	.lock	= INIT_LOCAL_LOCK(softirq_ctrl.lock),

};



#ifdef CONFIG_DEBUG_LOCK_ALLOC

static struct lock_class_key bh_lock_key;

struct lockdep_map bh_lock_map = {

	.name			= "local_bh",

	.key			= &bh_lock_key,

	.wait_type_outer	= LD_WAIT_FREE,

	.wait_type_inner	= LD_WAIT_CONFIG, /* PREEMPT_RT makes BH preemptible. */

	.lock_type		= LD_LOCK_PERCPU,

};

EXPORT_SYMBOL_GPL(bh_lock_map);

#endif



/**

 * local_bh_blocked() - Check for idle whether BH processing is blocked

 *
@@ -148,6 +160,8 @@ void __local_bh_disable_ip(unsigned long ip, unsigned int cnt) 


	WARN_ON_ONCE(in_hardirq());



	lock_map_acquire_read(&bh_lock_map);



	/* First entry of a task into a BH disabled section? */

	if (!current->softirq_disable_cnt) {

		if (preemptible()) {
@@ -211,6 +225,8 @@ void __local_bh_enable_ip(unsigned long ip, unsigned int cnt) 
	WARN_ON_ONCE(in_hardirq());

	lockdep_assert_irqs_enabled();



	lock_map_release(&bh_lock_map);



	local_irq_save(flags);

	curcnt = __this_cpu_read(softirq_ctrl.cnt);
@@ -261,6 +277,8 @@ static inline void ksoftirqd_run_begin(void) 
/* Counterpart to ksoftirqd_run_begin() */

static inline void ksoftirqd_run_end(void)

{

	/* pairs with the lock_map_acquire_read() in ksoftirqd_run_begin() */

	lock_map_release(&bh_lock_map);

	__local_bh_enable(SOFTIRQ_OFFSET, true);

	WARN_ON_ONCE(in_interrupt());

	local_irq_enable();