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()
  ...

1 files changed, 10 insertions, 3 deletions

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 303cb0591b4b..69e92ddef5dd 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1380,7 +1380,14 @@ static int takedown_cpu(unsigned int cpu)
 	cpuhp_bp_sync_dead(cpu);
 
 	tick_cleanup_dead_cpu(cpu);
+
+	/*
+	 * Callbacks must be re-integrated right away to the RCU state machine.
+	 * Otherwise an RCU callback could block a further teardown function
+	 * waiting for its completion.
+	 */
 	rcutree_migrate_callbacks(cpu);
+
 	return 0;
 }
 
@@ -1396,10 +1403,10 @@ void cpuhp_report_idle_dead(void)
 	struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
 
 	BUG_ON(st->state != CPUHP_AP_OFFLINE);
-	rcu_report_dead(smp_processor_id());
+	rcutree_report_cpu_dead();
 	st->state = CPUHP_AP_IDLE_DEAD;
 	/*
-	 * We cannot call complete after rcu_report_dead() so we delegate it
+	 * We cannot call complete after rcutree_report_cpu_dead() so we delegate it
 	 * to an online cpu.
 	 */
 	smp_call_function_single(cpumask_first(cpu_online_mask),
@@ -1628,7 +1635,7 @@ void notify_cpu_starting(unsigned int cpu)
 	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
 	enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
 
-	rcu_cpu_starting(cpu);	/* Enables RCU usage on this CPU. */
+	rcutree_report_cpu_starting(cpu);	/* Enables RCU usage on this CPU. */
 	cpumask_set_cpu(cpu, &cpus_booted_once_mask);
 
 	/*