Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler fixes from Thomas Gleixner:
 "Three patches addressing the fallout of the CPU_ISOLATION changes
  especially with NO_HZ_FULL plus documentation of boot parameter
  dependency"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/isolation: Document boot parameters dependency on CONFIG_CPU_ISOLATION=y
  sched/isolation: Enable CONFIG_CPU_ISOLATION=y by default
  sched/isolation: Make CONFIG_NO_HZ_FULL select CONFIG_CPU_ISOLATION

4 files changed, 9 insertions, 3 deletions

diff --git a/Documentation/admin-guide/kernel-parameters.rst b/Documentation/admin-guide/kernel-parameters.rst
index b2598cc9834c..7242cbda15dd 100644
--- a/Documentation/admin-guide/kernel-parameters.rst
+++ b/Documentation/admin-guide/kernel-parameters.rst
@@ -109,6 +109,7 @@ parameter is applicable::
         IPV6    IPv6 support is enabled.
         ISAPNP  ISA PnP code is enabled.
         ISDN    Appropriate ISDN support is enabled.
+        ISOL    CPU Isolation is enabled.
         JOY     Appropriate joystick support is enabled.
         KGDB    Kernel debugger support is enabled.
         KVM     Kernel Virtual Machine support is enabled.
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index e49311d53504..7041c6710f22 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1737,7 +1737,7 @@
         isapnp=         [ISAPNP]
                         Format: <RDP>,<reset>,<pci_scan>,<verbosity>
 
-        isolcpus=       [KNL,SMP] Isolate a given set of CPUs from disturbance.
+        isolcpus=       [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
                         [Deprecated - use cpusets instead]
                         Format: [flag-list,]<cpu-list>
 
@@ -2662,7 +2662,7 @@
                         Valid arguments: on, off
                         Default: on
 
-        nohz_full=      [KNL,BOOT]
+        nohz_full=      [KNL,BOOT,SMP,ISOL]
                         The argument is a cpu list, as described above.
                         In kernels built with CONFIG_NO_HZ_FULL=y, set
                         the specified list of CPUs whose tick will be stopped
diff --git a/init/Kconfig b/init/Kconfig
index 2934249fba46..690a381adee0 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -461,10 +461,14 @@ endmenu # "CPU/Task time and stats accounting"
 
 config CPU_ISOLATION
         bool "CPU isolation"
+        default y
         help
           Make sure that CPUs running critical tasks are not disturbed by
           any source of "noise" such as unbound workqueues, timers, kthreads...
-          Unbound jobs get offloaded to housekeeping CPUs.
+          Unbound jobs get offloaded to housekeeping CPUs. This is driven by
+          the "isolcpus=" boot parameter.
+
+          Say Y if unsure.
 
 source "kernel/rcu/Kconfig"
 
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
index e776fc8cc1df..f6b5f19223d6 100644
--- a/kernel/time/Kconfig
+++ b/kernel/time/Kconfig
@@ -95,6 +95,7 @@ config NO_HZ_FULL
         select RCU_NOCB_CPU
         select VIRT_CPU_ACCOUNTING_GEN
         select IRQ_WORK
+        select CPU_ISOLATION
         help
          Adaptively try to shutdown the tick whenever possible, even when
          the CPU is running tasks. Typically this requires running a single