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
  ...

1 files changed, 65 insertions, 29 deletions

diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
index 558057b517b7..8f3f72480e78 100644
--- a/include/linux/srcutree.h
+++ b/include/linux/srcutree.h
@@ -58,9 +58,9 @@ struct srcu_node {
 };
 
 /*
- * Per-SRCU-domain structure, similar in function to rcu_state.
+ * Per-SRCU-domain structure, update-side data linked from srcu_struct.
  */
-struct srcu_struct {
+struct srcu_usage {
 	struct srcu_node *node;			/* Combining tree. */
 	struct srcu_node *level[RCU_NUM_LVLS + 1];
 						/* First node at each level. */
@@ -68,7 +68,6 @@ struct srcu_struct {
 	struct mutex srcu_cb_mutex;		/* Serialize CB preparation. */
 	spinlock_t __private lock;		/* Protect counters and size state. */
 	struct mutex srcu_gp_mutex;		/* Serialize GP work. */
-	unsigned int srcu_idx;			/* Current rdr array element. */
 	unsigned long srcu_gp_seq;		/* Grace-period seq #. */
 	unsigned long srcu_gp_seq_needed;	/* Latest gp_seq needed. */
 	unsigned long srcu_gp_seq_needed_exp;	/* Furthest future exp GP. */
@@ -77,7 +76,6 @@ struct srcu_struct {
 	unsigned long srcu_size_jiffies;	/* Current contention-measurement interval. */
 	unsigned long srcu_n_lock_retries;	/* Contention events in current interval. */
 	unsigned long srcu_n_exp_nodelay;	/* # expedited no-delays in current GP phase. */
-	struct srcu_data __percpu *sda;		/* Per-CPU srcu_data array. */
 	bool sda_is_static;			/* May ->sda be passed to free_percpu()? */
 	unsigned long srcu_barrier_seq;		/* srcu_barrier seq #. */
 	struct mutex srcu_barrier_mutex;	/* Serialize barrier ops. */
@@ -89,32 +87,68 @@ struct srcu_struct {
 	unsigned long reschedule_jiffies;
 	unsigned long reschedule_count;
 	struct delayed_work work;
+	struct srcu_struct *srcu_ssp;
+};
+
+/*
+ * Per-SRCU-domain structure, similar in function to rcu_state.
+ */
+struct srcu_struct {
+	unsigned int srcu_idx;			/* Current rdr array element. */
+	struct srcu_data __percpu *sda;		/* Per-CPU srcu_data array. */
 	struct lockdep_map dep_map;
+	struct srcu_usage *srcu_sup;		/* Update-side data. */
 };
 
-/* Values for size state variable (->srcu_size_state). */
-#define SRCU_SIZE_SMALL		0
-#define SRCU_SIZE_ALLOC		1
-#define SRCU_SIZE_WAIT_BARRIER	2
-#define SRCU_SIZE_WAIT_CALL	3
-#define SRCU_SIZE_WAIT_CBS1	4
-#define SRCU_SIZE_WAIT_CBS2	5
-#define SRCU_SIZE_WAIT_CBS3	6
-#define SRCU_SIZE_WAIT_CBS4	7
-#define SRCU_SIZE_BIG		8
+// Values for size state variable (->srcu_size_state).  Once the state
+// has been set to SRCU_SIZE_ALLOC, the grace-period code advances through
+// this state machine one step per grace period until the SRCU_SIZE_BIG state
+// is reached.  Otherwise, the state machine remains in the SRCU_SIZE_SMALL
+// state indefinitely.
+#define SRCU_SIZE_SMALL		0	// No srcu_node combining tree, ->node == NULL
+#define SRCU_SIZE_ALLOC		1	// An srcu_node tree is being allocated, initialized,
+					//  and then referenced by ->node.  It will not be used.
+#define SRCU_SIZE_WAIT_BARRIER	2	// The srcu_node tree starts being used by everything
+					//  except call_srcu(), especially by srcu_barrier().
+					//  By the end of this state, all CPUs and threads
+					//  are aware of this tree's existence.
+#define SRCU_SIZE_WAIT_CALL	3	// The srcu_node tree starts being used by call_srcu().
+					//  By the end of this state, all of the call_srcu()
+					//  invocations that were running on a non-boot CPU
+					//  and using the boot CPU's callback queue will have
+					//  completed.
+#define SRCU_SIZE_WAIT_CBS1	4	// Don't trust the ->srcu_have_cbs[] grace-period
+#define SRCU_SIZE_WAIT_CBS2	5	//  sequence elements or the ->srcu_data_have_cbs[]
+#define SRCU_SIZE_WAIT_CBS3	6	//  CPU-bitmask elements until all four elements of
+#define SRCU_SIZE_WAIT_CBS4	7	//  each array have been initialized.
+#define SRCU_SIZE_BIG		8	// The srcu_node combining tree is fully initialized
+					//  and all aspects of it are being put to use.
 
 /* Values for state variable (bottom bits of ->srcu_gp_seq). */
 #define SRCU_STATE_IDLE		0
 #define SRCU_STATE_SCAN1	1
 #define SRCU_STATE_SCAN2	2
 
-#define __SRCU_STRUCT_INIT(name, pcpu_name)				\
-{									\
-	.sda = &pcpu_name,						\
-	.lock = __SPIN_LOCK_UNLOCKED(name.lock),			\
-	.srcu_gp_seq_needed = -1UL,					\
-	.work = __DELAYED_WORK_INITIALIZER(name.work, NULL, 0),		\
-	__SRCU_DEP_MAP_INIT(name)					\
+#define __SRCU_USAGE_INIT(name)									\
+{												\
+	.lock = __SPIN_LOCK_UNLOCKED(name.lock),						\
+	.srcu_gp_seq_needed = -1UL,								\
+	.work = __DELAYED_WORK_INITIALIZER(name.work, NULL, 0),					\
+}
+
+#define __SRCU_STRUCT_INIT_COMMON(name, usage_name)						\
+	.srcu_sup = &usage_name,								\
+	__SRCU_DEP_MAP_INIT(name)
+
+#define __SRCU_STRUCT_INIT_MODULE(name, usage_name)						\
+{												\
+	__SRCU_STRUCT_INIT_COMMON(name, usage_name)						\
+}
+
+#define __SRCU_STRUCT_INIT(name, usage_name, pcpu_name)						\
+{												\
+	.sda = &pcpu_name,									\
+	__SRCU_STRUCT_INIT_COMMON(name, usage_name)						\
 }
 
 /*
@@ -137,16 +171,18 @@ struct srcu_struct {
  * See include/linux/percpu-defs.h for the rules on per-CPU variables.
  */
 #ifdef MODULE
-# define __DEFINE_SRCU(name, is_static)					\
-	is_static struct srcu_struct name;				\
-	extern struct srcu_struct * const __srcu_struct_##name;		\
-	struct srcu_struct * const __srcu_struct_##name			\
+# define __DEFINE_SRCU(name, is_static)								\
+	static struct srcu_usage name##_srcu_usage = __SRCU_USAGE_INIT(name##_srcu_usage);	\
+	is_static struct srcu_struct name = __SRCU_STRUCT_INIT_MODULE(name, name##_srcu_usage);	\
+	extern struct srcu_struct * const __srcu_struct_##name;					\
+	struct srcu_struct * const __srcu_struct_##name						\
 		__section("___srcu_struct_ptrs") = &name
 #else
-# define __DEFINE_SRCU(name, is_static)					\
-	static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data);	\
-	is_static struct srcu_struct name =				\
-		__SRCU_STRUCT_INIT(name, name##_srcu_data)
+# define __DEFINE_SRCU(name, is_static)								\
+	static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data);				\
+	static struct srcu_usage name##_srcu_usage = __SRCU_USAGE_INIT(name##_srcu_usage);	\
+	is_static struct srcu_struct name =							\
+		__SRCU_STRUCT_INIT(name, name##_srcu_usage, name##_srcu_data)
 #endif
 #define DEFINE_SRCU(name)		__DEFINE_SRCU(name, /* not static */)
 #define DEFINE_STATIC_SRCU(name)	__DEFINE_SRCU(name, static)