Merge tag 'core-rcu-2021-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull RCU updates from Ingo Molnar:

 - Support for "N" as alias for last bit in bitmap parsing library (eg
   using syntax like "nohz_full=2-N")

 - kvfree_rcu updates

 - mm_dump_obj() updates. (One of these is to mm, but was suggested by
   Andrew Morton.)

 - RCU callback offloading update

 - Polling RCU grace-period interfaces

 - Realtime-related RCU updates

 - Tasks-RCU updates

 - Torture-test updates

 - Torture-test scripting updates

 - Miscellaneous fixes

* tag 'core-rcu-2021-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (77 commits)
  rcutorture: Test start_poll_synchronize_rcu() and poll_state_synchronize_rcu()
  rcu: Provide polling interfaces for Tiny RCU grace periods
  torture: Fix kvm.sh --datestamp regex check
  torture: Consolidate qemu-cmd duration editing into kvm-transform.sh
  torture: Print proper vmlinux path for kvm-again.sh runs
  torture: Make TORTURE_TRUST_MAKE available in kvm-again.sh environment
  torture: Make kvm-transform.sh update jitter commands
  torture: Add --duration argument to kvm-again.sh
  torture: Add kvm-again.sh to rerun a previous torture-test
  torture: Create a "batches" file for build reuse
  torture: De-capitalize TORTURE_SUITE
  torture: Make upper-case-only no-dot no-slash scenario names official
  torture: Rename SRCU-t and SRCU-u to avoid lowercase characters
  torture: Remove no-mpstat error message
  torture: Record kvm-test-1-run.sh and kvm-test-1-run-qemu.sh PIDs
  torture: Record jitter start/stop commands
  torture: Extract kvm-test-1-run-qemu.sh from kvm-test-1-run.sh
  torture: Record TORTURE_KCONFIG_GDB_ARG in qemu-cmd
  torture: Abstract jitter.sh start/stop into scripts
  rcu: Provide polling interfaces for Tree RCU grace periods
  ...

2 files changed, 20 insertions, 3 deletions

diff --git a/Documentation/admin-guide/kernel-parameters.rst b/Documentation/admin-guide/kernel-parameters.rst
index 24302cad174a..3996b54158bf 100644
--- a/Documentation/admin-guide/kernel-parameters.rst
+++ b/Documentation/admin-guide/kernel-parameters.rst
@@ -68,6 +68,13 @@ For example one can add to the command line following parameter:
 
 where the final item represents CPUs 100,101,125,126,150,151,...
 
+The value "N" can be used to represent the numerically last CPU on the system,
+i.e "foo_cpus=16-N" would be equivalent to "16-31" on a 32 core system.
+
+Keep in mind that "N" is dynamic, so if system changes cause the bitmap width
+to change, such as less cores in the CPU list, then N and any ranges using N
+will also change.  Use the same on a small 4 core system, and "16-N" becomes
+"16-3" and now the same boot input will be flagged as invalid (start > end).
 
 
 This document may not be entirely up to date and comprehensive. The command
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 70a30f65bfca..fa08ec0dfbe7 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4077,9 +4077,7 @@
 				see CONFIG_RAS_CEC help text.
 
 	rcu_nocbs=	[KNL]
-			The argument is a cpu list, as described above,
-			except that the string "all" can be used to
-			specify every CPU on the system.
+			The argument is a cpu list, as described above.
 
 			In kernels built with CONFIG_RCU_NOCB_CPU=y, set
 			the specified list of CPUs to be no-callback CPUs.
@@ -4268,6 +4266,18 @@
 	rcuscale.kfree_rcu_test= [KNL]
 			Set to measure performance of kfree_rcu() flooding.
 
+	rcuscale.kfree_rcu_test_double= [KNL]
+			Test the double-argument variant of kfree_rcu().
+			If this parameter has the same value as
+			rcuscale.kfree_rcu_test_single, both the single-
+			and double-argument variants are tested.
+
+	rcuscale.kfree_rcu_test_single= [KNL]
+			Test the single-argument variant of kfree_rcu().
+			If this parameter has the same value as
+			rcuscale.kfree_rcu_test_double, both the single-
+			and double-argument variants are tested.
+
 	rcuscale.kfree_nthreads= [KNL]
 			The number of threads running loops of kfree_rcu().