Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu

Pull v4.20 RCU changes from Paul E. McKenney:

- Documentation updates, including some good-eye catches from
  Joel Fernandes.

- SRCU updates, most notably changes enabling call_srcu() to be
  invoked very early in the boot sequence.

- Torture-test updates, including some preliminary work towards
  making rcutorture better able to find problems that result in
  insufficient grace-period forward progress.

- Consolidate the RCU-bh, RCU-preempt, and RCU-sched flavors into
  a single flavor similar to RCU-sched in !PREEMPT kernels and
  into a single flavor similar to RCU-preempt (but also waiting
  on preempt-disabled sequences of code) in PREEMPT kernels.  This
  branch also includes a refactoring of rcu_{nmi,irq}_{enter,exit}()
  from Byungchul Park.

- Now that there is only one RCU flavor in any given running kernel,
  the many "rsp" pointers are no longer required, and this cleanup
  series removes them.

- This branch carries out additional cleanups made possible by
  the RCU flavor consolidation, including inlining how-trivial
  functions, updating comments and definitions, and removing
  now-unneeded rcutorture scenarios.

- Initial changes to RCU to better promote forward progress of
  grace periods, including fixing a bug found by Marius Hillenbrand
  and David Woodhouse, with the fix suggested by Peter Zijlstra.

- Now that there is only one flavor of RCU in any running kernel,
  there is also only on rcu_data structure per CPU.  This means
  that the rcu_dynticks structure can be merged into the rcu_data
  structure, a task taken on by this branch.  This branch also
  contains a -rt-related fix from Mike Galbraith.

Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 16 insertions, 15 deletions

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 92eb1f42240d..e9054fd1d0d0 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3540,14 +3540,14 @@
 
 			In kernels built with CONFIG_RCU_NOCB_CPU=y, set
 			the specified list of CPUs to be no-callback CPUs.
-			Invocation of these CPUs' RCU callbacks will
-			be offloaded to "rcuox/N" kthreads created for
-			that purpose, where "x" is "b" for RCU-bh, "p"
-			for RCU-preempt, and "s" for RCU-sched, and "N"
-			is the CPU number.  This reduces OS jitter on the
-			offloaded CPUs, which can be useful for HPC and
-			real-time workloads.  It can also improve energy
-			efficiency for asymmetric multiprocessors.
+			Invocation of these CPUs' RCU callbacks will be
+			offloaded to "rcuox/N" kthreads created for that
+			purpose, where "x" is "p" for RCU-preempt, and
+			"s" for RCU-sched, and "N" is the CPU number.
+			This reduces OS jitter on the offloaded CPUs,
+			which can be useful for HPC and real-time
+			workloads.  It can also improve energy efficiency
+			for asymmetric multiprocessors.
 
 	rcu_nocb_poll	[KNL]
 			Rather than requiring that offloaded CPUs
@@ -3601,7 +3601,14 @@
 			Set required age in jiffies for a
 			given grace period before RCU starts
 			soliciting quiescent-state help from
-			rcu_note_context_switch().
+			rcu_note_context_switch().  If not specified, the
+			kernel will calculate a value based on the most
+			recent settings of rcutree.jiffies_till_first_fqs
+			and rcutree.jiffies_till_next_fqs.
+			This calculated value may be viewed in
+			rcutree.jiffies_to_sched_qs.  Any attempt to
+			set rcutree.jiffies_to_sched_qs will be
+			cheerfully overwritten.
 
 	rcutree.jiffies_till_first_fqs= [KNL]
 			Set delay from grace-period initialization to
@@ -3869,12 +3876,6 @@
 	rcupdate.rcu_self_test= [KNL]
 			Run the RCU early boot self tests
 
-	rcupdate.rcu_self_test_bh= [KNL]
-			Run the RCU bh early boot self tests
-
-	rcupdate.rcu_self_test_sched= [KNL]
-			Run the RCU sched early boot self tests
-
 	rdinit=		[KNL]
 			Format: <full_path>
 			Run specified binary instead of /init from the ramdisk,