Merge tag 'rcu.6.4.april5.2023.3' of git://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux

Pull RCU updates from Joel Fernandes:

 - Updates and additions to MAINTAINERS files, with Boqun being added to
   the RCU entry and Zqiang being added as an RCU reviewer.

   I have also transitioned from reviewer to maintainer; however, Paul
   will be taking over sending RCU pull-requests for the next merge
   window.

 - Resolution of hotplug warning in nohz code, achieved by fixing
   cpu_is_hotpluggable() through interaction with the nohz subsystem.

   Tick dependency modifications by Zqiang, focusing on fixing usage of
   the TICK_DEP_BIT_RCU_EXP bitmask.

 - Avoid needless calls to the rcu-lazy shrinker for CONFIG_RCU_LAZY=n
   kernels, fixed by Zqiang.

 - Improvements to rcu-tasks stall reporting by Neeraj.

 - Initial renaming of k[v]free_rcu() to k[v]free_rcu_mightsleep() for
   increased robustness, affecting several components like mac802154,
   drbd, vmw_vmci, tracing, and more.

   A report by Eric Dumazet showed that the API could be unknowingly
   used in an atomic context, so we'd rather make sure they know what
   they're asking for by being explicit:

      https://lore.kernel.org/all/20221202052847.2623997-1-edumazet@google.com/

 - Documentation updates, including corrections to spelling,
   clarifications in comments, and improvements to the srcu_size_state
   comments.

 - Better srcu_struct cache locality for readers, by adjusting the size
   of srcu_struct in support of SRCU usage by Christoph Hellwig.

 - Teach lockdep to detect deadlocks between srcu_read_lock() vs
   synchronize_srcu() contributed by Boqun.

   Previously lockdep could not detect such deadlocks, now it can.

 - Integration of rcutorture and rcu-related tools, targeted for v6.4
   from Boqun's tree, featuring new SRCU deadlock scenarios, test_nmis
   module parameter, and more

 - Miscellaneous changes, various code cleanups and comment improvements

* tag 'rcu.6.4.april5.2023.3' of git://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux: (71 commits)
  checkpatch: Error out if deprecated RCU API used
  mac802154: Rename kfree_rcu() to kvfree_rcu_mightsleep()
  rcuscale: Rename kfree_rcu() to kfree_rcu_mightsleep()
  ext4/super: Rename kfree_rcu() to kfree_rcu_mightsleep()
  net/mlx5: Rename kfree_rcu() to kfree_rcu_mightsleep()
  net/sysctl: Rename kvfree_rcu() to kvfree_rcu_mightsleep()
  lib/test_vmalloc.c: Rename kvfree_rcu() to kvfree_rcu_mightsleep()
  tracing: Rename kvfree_rcu() to kvfree_rcu_mightsleep()
  misc: vmw_vmci: Rename kvfree_rcu() to kvfree_rcu_mightsleep()
  drbd: Rename kvfree_rcu() to kvfree_rcu_mightsleep()
  rcu: Protect rcu_print_task_exp_stall() ->exp_tasks access
  rcu: Avoid stack overflow due to __rcu_irq_enter_check_tick() being kprobe-ed
  rcu-tasks: Report stalls during synchronize_srcu() in rcu_tasks_postscan()
  rcu: Permit start_poll_synchronize_rcu_expedited() to be invoked early
  rcu: Remove never-set needwake assignment from rcu_report_qs_rdp()
  rcu: Register rcu-lazy shrinker only for CONFIG_RCU_LAZY=y kernels
  rcu: Fix missing TICK_DEP_MASK_RCU_EXP dependency check
  rcu: Fix set/clear TICK_DEP_BIT_RCU_EXP bitmask race
  rcu/trace: use strscpy() to instead of strncpy()
  tick/nohz: Fix cpu_is_hotpluggable() by checking with nohz subsystem
  ...

2 files changed, 58 insertions, 8 deletions

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 50d4863974e7..dcd1d5bfc1e0 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1881,6 +1881,8 @@ print_circular_lock_scenario(struct held_lock *src,
 	struct lock_class *source = hlock_class(src);
 	struct lock_class *target = hlock_class(tgt);
 	struct lock_class *parent = prt->class;
+	int src_read = src->read;
+	int tgt_read = tgt->read;
 
 	/*
 	 * A direct locking problem where unsafe_class lock is taken
@@ -1908,7 +1910,10 @@ print_circular_lock_scenario(struct held_lock *src,
 	printk(" Possible unsafe locking scenario:\n\n");
 	printk("       CPU0                    CPU1\n");
 	printk("       ----                    ----\n");
-	printk("  lock(");
+	if (tgt_read != 0)
+		printk("  rlock(");
+	else
+		printk("  lock(");
 	__print_lock_name(target);
 	printk(KERN_CONT ");\n");
 	printk("                               lock(");
@@ -1917,7 +1922,12 @@ print_circular_lock_scenario(struct held_lock *src,
 	printk("                               lock(");
 	__print_lock_name(target);
 	printk(KERN_CONT ");\n");
-	printk("  lock(");
+	if (src_read != 0)
+		printk("  rlock(");
+	else if (src->sync)
+		printk("  sync(");
+	else
+		printk("  lock(");
 	__print_lock_name(source);
 	printk(KERN_CONT ");\n");
 	printk("\n *** DEADLOCK ***\n\n");
@@ -4531,7 +4541,13 @@ mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
 					return 0;
 		}
 	}
-	if (!hlock->hardirqs_off) {
+
+	/*
+	 * For lock_sync(), don't mark the ENABLED usage, since lock_sync()
+	 * creates no critical section and no extra dependency can be introduced
+	 * by interrupts
+	 */
+	if (!hlock->hardirqs_off && !hlock->sync) {
 		if (hlock->read) {
 			if (!mark_lock(curr, hlock,
 					LOCK_ENABLED_HARDIRQ_READ))
@@ -4910,7 +4926,7 @@ static int __lock_is_held(const struct lockdep_map *lock, int read);
 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 			  int trylock, int read, int check, int hardirqs_off,
 			  struct lockdep_map *nest_lock, unsigned long ip,
-			  int references, int pin_count)
+			  int references, int pin_count, int sync)
 {
 	struct task_struct *curr = current;
 	struct lock_class *class = NULL;
@@ -4961,7 +4977,8 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 
 	class_idx = class - lock_classes;
 
-	if (depth) { /* we're holding locks */
+	if (depth && !sync) {
+		/* we're holding locks and the new held lock is not a sync */
 		hlock = curr->held_locks + depth - 1;
 		if (hlock->class_idx == class_idx && nest_lock) {
 			if (!references)
@@ -4995,6 +5012,7 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 	hlock->trylock = trylock;
 	hlock->read = read;
 	hlock->check = check;
+	hlock->sync = !!sync;
 	hlock->hardirqs_off = !!hardirqs_off;
 	hlock->references = references;
 #ifdef CONFIG_LOCK_STAT
@@ -5056,6 +5074,10 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 	if (!validate_chain(curr, hlock, chain_head, chain_key))
 		return 0;
 
+	/* For lock_sync(), we are done here since no actual critical section */
+	if (hlock->sync)
+		return 1;
+
 	curr->curr_chain_key = chain_key;
 	curr->lockdep_depth++;
 	check_chain_key(curr);
@@ -5197,7 +5219,7 @@ static int reacquire_held_locks(struct task_struct *curr, unsigned int depth,
 				    hlock->read, hlock->check,
 				    hlock->hardirqs_off,
 				    hlock->nest_lock, hlock->acquire_ip,
-				    hlock->references, hlock->pin_count)) {
+				    hlock->references, hlock->pin_count, 0)) {
 		case 0:
 			return 1;
 		case 1:
@@ -5667,7 +5689,7 @@ void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 
 	lockdep_recursion_inc();
 	__lock_acquire(lock, subclass, trylock, read, check,
-		       irqs_disabled_flags(flags), nest_lock, ip, 0, 0);
+		       irqs_disabled_flags(flags), nest_lock, ip, 0, 0, 0);
 	lockdep_recursion_finish();
 	raw_local_irq_restore(flags);
 }
@@ -5693,6 +5715,34 @@ void lock_release(struct lockdep_map *lock, unsigned long ip)
 }
 EXPORT_SYMBOL_GPL(lock_release);
 
+/*
+ * lock_sync() - A special annotation for synchronize_{s,}rcu()-like API.
+ *
+ * No actual critical section is created by the APIs annotated with this: these
+ * APIs are used to wait for one or multiple critical sections (on other CPUs
+ * or threads), and it means that calling these APIs inside these critical
+ * sections is potential deadlock.
+ */
+void lock_sync(struct lockdep_map *lock, unsigned subclass, int read,
+	       int check, struct lockdep_map *nest_lock, unsigned long ip)
+{
+	unsigned long flags;
+
+	if (unlikely(!lockdep_enabled()))
+		return;
+
+	raw_local_irq_save(flags);
+	check_flags(flags);
+
+	lockdep_recursion_inc();
+	__lock_acquire(lock, subclass, 0, read, check,
+		       irqs_disabled_flags(flags), nest_lock, ip, 0, 0, 1);
+	check_chain_key(current);
+	lockdep_recursion_finish();
+	raw_local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(lock_sync);
+
 noinstr int lock_is_held_type(const struct lockdep_map *lock, int read)
 {
 	unsigned long flags;
diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c
index 29dc253d03af..93cca6e69860 100644
--- a/kernel/locking/test-ww_mutex.c
+++ b/kernel/locking/test-ww_mutex.c
@@ -659,7 +659,7 @@ static int __init test_ww_mutex_init(void)
 	if (ret)
 		return ret;
 
-	ret = stress(4095, hweight32(STRESS_ALL)*ncpus, STRESS_ALL);
+	ret = stress(2047, hweight32(STRESS_ALL)*ncpus, STRESS_ALL);
 	if (ret)
 		return ret;