Merge tag 'rcu-next-v6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks

Pull RCU updates from Frederic Weisbecker:

 - RCU torture, locktorture and generic torture infrastructure updates
   that include various fixes, cleanups and consolidations.

   Among the user visible things, ftrace dumps can now be found into
   their own file, and module parameters get better documented and
   reported on dumps.

 - Generic and misc fixes all over the place. Some highlights:

     * Hotplug handling has seen some light cleanups and comments

     * An RCU barrier can now be triggered through sysfs to serialize
       memory stress testing and avoid OOM

     * Object information is now dumped in case of invalid callback
       invocation

     * Also various SRCU issues, too hard to trigger to deserve urgent
       pull requests, have been fixed

 - RCU documentation updates

 - RCU reference scalability test minor fixes and doc improvements.

 - RCU tasks minor fixes

 - Stall detection updates. Introduce RCU CPU Stall notifiers that
   allows a subsystem to provide informations to help debugging. Also
   cure some false positive stalls.

* tag 'rcu-next-v6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks: (56 commits)
  srcu: Only accelerate on enqueue time
  locktorture: Check the correct variable for allocation failure
  srcu: Fix callbacks acceleration mishandling
  rcu: Comment why callbacks migration can't wait for CPUHP_RCUTREE_PREP
  rcu: Standardize explicit CPU-hotplug calls
  rcu: Conditionally build CPU-hotplug teardown callbacks
  rcu: Remove references to rcu_migrate_callbacks() from diagrams
  rcu: Assume rcu_report_dead() is always called locally
  rcu: Assume IRQS disabled from rcu_report_dead()
  rcu: Use rcu_segcblist_segempty() instead of open coding it
  rcu: kmemleak: Ignore kmemleak false positives when RCU-freeing objects
  srcu: Fix srcu_struct node grpmask overflow on 64-bit systems
  torture: Convert parse-console.sh to mktemp
  rcutorture: Traverse possible cpu to set maxcpu in rcu_nocb_toggle()
  rcutorture: Replace schedule_timeout*() 1-jiffy waits with HZ/20
  torture: Add kvm.sh --debug-info argument
  locktorture: Rename readers_bind/writers_bind to bind_readers/bind_writers
  doc: Catch-up update for locktorture module parameters
  locktorture: Add call_rcu_chains module parameter
  locktorture: Add new module parameters to lock_torture_print_module_parms()
  ...

Author: torvalds

Documentation/RCU/Design/Expedited-Grace-Periods/Expedited-Grace-Periods.rst

@@ -181,7 +181,7 @@ operations is carried out at several levels:
    of this wait (or series of waits, as the case may be) is to permit a
    concurrent CPU-hotplug operation to complete.
 #. In the case of RCU-sched, one of the last acts of an outgoing CPU is
-   to invoke ``rcu_report_dead()``, which reports a quiescent state for
+   to invoke ``rcutree_report_cpu_dead()``, which reports a quiescent state for
    that CPU. However, this is likely paranoia-induced redundancy.
 
 +-----------------------------------------------------------------------+

Documentation/RCU/Design/Memory-Ordering/TreeRCU-callback-registry.svg

@@ -1955,12 +1955,12 @@ if offline CPUs block an RCU grace period for too long.
 
 An offline CPU's quiescent state will be reported either:
 
-1.  As the CPU goes offline using RCU's hotplug notifier (rcu_report_dead()).
+1.  As the CPU goes offline using RCU's hotplug notifier (rcutree_report_cpu_dead()).
 2.  When grace period initialization (rcu_gp_init()) detects a
     race either with CPU offlining or with a task unblocking on a leaf
     ``rcu_node`` structure whose CPUs are all offline.
 
-The CPU-online path (rcu_cpu_starting()) should never need to report
+The CPU-online path (rcutree_report_cpu_starting()) should never need to report
 a quiescent state for an offline CPU.  However, as a debugging measure,
 it does emit a warning if a quiescent state was not already reported
 for that CPU.

Documentation/RCU/Design/Memory-Ordering/TreeRCU-gp-fqs.svg

@@ -8,6 +8,15 @@ One of the most common uses of RCU is protecting read-mostly linked lists
 that all of the required memory ordering is provided by the list macros.
 This document describes several list-based RCU use cases.
 
+When iterating a list while holding the rcu_read_lock(), writers may
+modify the list.  The reader is guaranteed to see all of the elements
+which were added to the list before they acquired the rcu_read_lock()
+and are still on the list when they drop the rcu_read_unlock().
+Elements which are added to, or removed from the list may or may not
+be seen.  If the writer calls list_replace_rcu(), the reader may see
+either the old element or the new element; they will not see both,
+nor will they see neither.
+
 
 Example 1: Read-mostly list: Deferred Destruction
 -------------------------------------------------

Documentation/RCU/Design/Memory-Ordering/TreeRCU-gp.svg

@@ -59,8 +59,8 @@ experiment with should focus on Section 2.  People who prefer to start
 with example uses should focus on Sections 3 and 4.  People who need to
 understand the RCU implementation should focus on Section 5, then dive
 into the kernel source code.  People who reason best by analogy should
-focus on Section 6.  Section 7 serves as an index to the docbook API
-documentation, and Section 8 is the traditional answer key.
+focus on Section 6 and 7.  Section 8 serves as an index to the docbook
+API documentation, and Section 9 is the traditional answer key.
 
 So, start with the section that makes the most sense to you and your
 preferred method of learning.  If you need to know everything about

Documentation/RCU/Design/Memory-Ordering/TreeRCU-hotplug.svg

@@ -2919,6 +2919,38 @@
 			to extract confidential information from the kernel
 			are also disabled.
 
+	locktorture.acq_writer_lim= [KNL]
+			Set the time limit in jiffies for a lock
+			acquisition.  Acquisitions exceeding this limit
+			will result in a splat once they do complete.
+
+	locktorture.bind_readers= [KNL]
+			Specify the list of CPUs to which the readers are
+			to be bound.
+
+	locktorture.bind_writers= [KNL]
+			Specify the list of CPUs to which the writers are
+			to be bound.
+
+	locktorture.call_rcu_chains= [KNL]
+			Specify the number of self-propagating call_rcu()
+			chains to set up.  These are used to ensure that
+			there is a high probability of an RCU grace period
+			in progress at any given time.	Defaults to 0,
+			which disables these call_rcu() chains.
+
+	locktorture.long_hold= [KNL]
+			Specify the duration in milliseconds for the
+			occasional long-duration lock hold time.  Defaults
+			to 100 milliseconds.  Select 0 to disable.
+
+	locktorture.nested_locks= [KNL]
+			Specify the maximum lock nesting depth that
+			locktorture is to exercise, up to a limit of 8
+			(MAX_NESTED_LOCKS).  Specify zero to disable.
+			Note that this parameter is ineffective on types
+			of locks that do not support nested acquisition.
+
 	locktorture.nreaders_stress= [KNL]
 			Set the number of locking read-acquisition kthreads.
 			Defaults to being automatically set based on the
@@ -2934,6 +2966,25 @@
 			Set time (s) between CPU-hotplug operations, or
 			zero to disable CPU-hotplug testing.
 
+	locktorture.rt_boost= [KNL]
+			Do periodic testing of real-time lock priority
+			boosting.  Select 0 to disable, 1 to boost
+			only rt_mutex, and 2 to boost unconditionally.
+			Defaults to 2, which might seem to be an
+			odd choice, but which should be harmless for
+			non-real-time spinlocks, due to their disabling
+			of preemption.	Note that non-realtime mutexes
+			disable boosting.
+
+	locktorture.rt_boost_factor= [KNL]
+			Number that determines how often and for how
+			long priority boosting is exercised.  This is
+			scaled down by the number of writers, so that the
+			number of boosts per unit time remains roughly
+			constant as the number of writers increases.
+			On the other hand, the duration of each boost
+			increases with the number of writers.
+
 	locktorture.shuffle_interval= [KNL]
 			Set task-shuffle interval (jiffies).  Shuffling
 			tasks allows some CPUs to go into dyntick-idle
@@ -2956,13 +3007,13 @@
 	locktorture.torture_type= [KNL]
 			Specify the locking implementation to test.
 
+	locktorture.verbose= [KNL]
+			Enable additional printk() statements.
+
 	locktorture.writer_fifo= [KNL]
 			Run the write-side locktorture kthreads at
 			sched_set_fifo() real-time priority.
 
-	locktorture.verbose= [KNL]
-			Enable additional printk() statements.
-
 	logibm.irq=	[HW,MOUSE] Logitech Bus Mouse Driver
 			Format: <irq>
 
@@ -4775,6 +4826,13 @@
 			Set maximum number of finished RCU callbacks to
 			process in one batch.
 
+	rcutree.do_rcu_barrier=	[KNL]
+			Request a call to rcu_barrier().  This is
+			throttled so that userspace tests can safely
+			hammer on the sysfs variable if they so choose.
+			If triggered before the RCU grace-period machinery
+			is fully active, this will error out with EAGAIN.
+
 	rcutree.dump_tree=	[KNL]
 			Dump the structure of the rcu_node combining tree
 			out at early boot.  This is used for diagnostic
@@ -5428,6 +5486,12 @@
 			test until boot completes in order to avoid
 			interference.
 
+	refscale.lookup_instances= [KNL]
+			Number of data elements to use for the forms of
+			SLAB_TYPESAFE_BY_RCU testing.  A negative number
+			is negated and multiplied by nr_cpu_ids, while
+			zero specifies nr_cpu_ids.
+
 	refscale.loops= [KNL]
 			Set the number of loops over the synchronization
 			primitive under test.  Increasing this number

Documentation/RCU/Design/Requirements/Requirements.rst

@@ -215,7 +215,7 @@ asmlinkage notrace void secondary_start_kernel(void)
 	if (system_uses_irq_prio_masking())
 		init_gic_priority_masking();
 
-	rcu_cpu_starting(cpu);
+	rcutree_report_cpu_starting(cpu);
 	trace_hardirqs_off();
 
 	/*
@@ -401,7 +401,7 @@ void __noreturn cpu_die_early(void)
 
 	/* Mark this CPU absent */
 	set_cpu_present(cpu, 0);
-	rcu_report_dead(cpu);
+	rcutree_report_cpu_dead();
 
 	if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
 		update_cpu_boot_status(CPU_KILL_ME);