Merge tag 'core-rcu-2021-02-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull RCU updates from Ingo Molnar:
 "These are the latest RCU updates for v5.12:

   - Documentation updates.

   - Miscellaneous fixes.

   - kfree_rcu() updates: Addition of mem_dump_obj() to provide
     allocator return addresses to more easily locate bugs. This has a
     couple of RCU-related commits, but is mostly MM. Was pulled in with
     akpm's agreement.

   - Per-callback-batch tracking of numbers of callbacks, which enables
     better debugging information and smarter reactions to large numbers
     of callbacks.

   - The first round of changes to allow CPUs to be runtime switched
     from and to callback-offloaded state.

   - CONFIG_PREEMPT_RT-related changes.

   - RCU CPU stall warning updates.

   - Addition of polling grace-period APIs for SRCU.

   - Torture-test and torture-test scripting updates, including a
     "torture everything" script that runs rcutorture, locktorture,
     scftorture, rcuscale, and refscale. Plus does an allmodconfig
     build.

   - nolibc fixes for the torture tests"

* tag 'core-rcu-2021-02-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (130 commits)
  percpu_ref: Dump mem_dump_obj() info upon reference-count underflow
  rcu: Make call_rcu() print mem_dump_obj() info for double-freed callback
  mm: Make mem_obj_dump() vmalloc() dumps include start and length
  mm: Make mem_dump_obj() handle vmalloc() memory
  mm: Make mem_dump_obj() handle NULL and zero-sized pointers
  mm: Add mem_dump_obj() to print source of memory block
  tools/rcutorture: Fix position of -lgcc in mkinitrd.sh
  tools/nolibc: Fix position of -lgcc in the documented example
  tools/nolibc: Emit detailed error for missing alternate syscall number definitions
  tools/nolibc: Remove incorrect definitions of __ARCH_WANT_*
  tools/nolibc: Get timeval, timespec and timezone from linux/time.h
  tools/nolibc: Implement poll() based on ppoll()
  tools/nolibc: Implement fork() based on clone()
  tools/nolibc: Make getpgrp() fall back to getpgid(0)
  tools/nolibc: Make dup2() rely on dup3() when available
  tools/nolibc: Add the definition for dup()
  rcutorture: Add rcutree.use_softirq=0 to RUDE01 and TASKS01
  torture: Maintain torture-specific set of CPUs-online books
  torture: Clean up after torture-test CPU hotplugging
  rcutorture: Make object_debug also double call_rcu() heap object
  ...

1 files changed, 33 insertions, 6 deletions

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 85f31ca83864..a6c806557e25 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4078,6 +4078,10 @@
 			value, meaning that RCU_SOFTIRQ is used by default.
 			Specify rcutree.use_softirq=0 to use rcuc kthreads.
 
+			But note that CONFIG_PREEMPT_RT=y kernels disable
+			this kernel boot parameter, forcibly setting it
+			to zero.
+
 	rcutree.rcu_fanout_exact= [KNL]
 			Disable autobalancing of the rcu_node combining
 			tree.  This is used by rcutorture, and might
@@ -4165,12 +4169,6 @@
 			Set wakeup interval for idle CPUs that have
 			RCU callbacks (RCU_FAST_NO_HZ=y).
 
-	rcutree.rcu_idle_lazy_gp_delay= [KNL]
-			Set wakeup interval for idle CPUs that have
-			only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
-			Lazy RCU callbacks are those which RCU can
-			prove do nothing more than free memory.
-
 	rcutree.rcu_kick_kthreads= [KNL]
 			Cause the grace-period kthread to get an extra
 			wake_up() if it sleeps three times longer than
@@ -4324,6 +4322,14 @@
 			stress RCU, they don't participate in the actual
 			test, hence the "fake".
 
+	rcutorture.nocbs_nthreads= [KNL]
+			Set number of RCU callback-offload togglers.
+			Zero (the default) disables toggling.
+
+	rcutorture.nocbs_toggle= [KNL]
+			Set the delay in milliseconds between successive
+			callback-offload toggling attempts.
+
 	rcutorture.nreaders= [KNL]
 			Set number of RCU readers.  The value -1 selects
 			N-1, where N is the number of CPUs.  A value
@@ -4456,6 +4462,13 @@
 			only normal grace-period primitives.  No effect
 			on CONFIG_TINY_RCU kernels.
 
+			But note that CONFIG_PREEMPT_RT=y kernels enables
+			this kernel boot parameter, forcibly setting
+			it to the value one, that is, converting any
+			post-boot attempt at an expedited RCU grace
+			period to instead use normal non-expedited
+			grace-period processing.
+
 	rcupdate.rcu_task_ipi_delay= [KNL]
 			Set time in jiffies during which RCU tasks will
 			avoid sending IPIs, starting with the beginning
@@ -4543,6 +4556,12 @@
 	refscale.verbose= [KNL]
 			Enable additional printk() statements.
 
+	refscale.verbose_batched= [KNL]
+			Batch the additional printk() statements.  If zero
+			(the default) or negative, print everything.  Otherwise,
+			print every Nth verbose statement, where N is the value
+			specified.
+
 	relax_domain_level=
 			[KNL, SMP] Set scheduler's default relax_domain_level.
 			See Documentation/admin-guide/cgroup-v1/cpusets.rst.
@@ -5317,6 +5336,14 @@
 			are running concurrently, especially on systems
 			with rotating-rust storage.
 
+	torture.verbose_sleep_frequency= [KNL]
+			Specifies how many verbose printk()s should be
+			emitted between each sleep.  The default of zero
+			disables verbose-printk() sleeping.
+
+	torture.verbose_sleep_duration= [KNL]
+			Duration of each verbose-printk() sleep in jiffies.
+
 	tp720=		[HW,PS2]
 
 	tpm_suspend_pcr=[HW,TPM]