sched/isolation: Isolate workqueues when "nohz_full=" is set

As we prepare for offloading the residual 1hz scheduler ticks to
workqueue, let's affine those to housekeepers so that they don't
interrupt the CPUs that don't want to be disturbed.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Link: http://lkml.kernel.org/r/1519186649-3242-5-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

3 files changed, 5 insertions, 2 deletions

diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h
index d849431c8060..4a6582c27dea 100644
--- a/include/linux/sched/isolation.h
+++ b/include/linux/sched/isolation.h
@@ -12,6 +12,7 @@ enum hk_flags {
         HK_FLAG_SCHED           = (1 << 3),
         HK_FLAG_TICK            = (1 << 4),
         HK_FLAG_DOMAIN          = (1 << 5),
+        HK_FLAG_WQ              = (1 << 6),
 };
 
 #ifdef CONFIG_CPU_ISOLATION
diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index b71b436f59f2..a2500c459617 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -3,6 +3,7 @@
  *  any CPU: unbound workqueues, timers, kthreads and any offloadable work.
  *
  * Copyright (C) 2017 Red Hat, Inc., Frederic Weisbecker
+ * Copyright (C) 2017-2018 SUSE, Frederic Weisbecker
  *
  */
 
@@ -119,7 +120,7 @@ static int __init housekeeping_nohz_full_setup(char *str)
 {
         unsigned int flags;
 
-        flags = HK_FLAG_TICK | HK_FLAG_TIMER | HK_FLAG_RCU | HK_FLAG_MISC;
+        flags = HK_FLAG_TICK | HK_FLAG_WQ | HK_FLAG_TIMER | HK_FLAG_RCU | HK_FLAG_MISC;
 
         return housekeeping_setup(str, flags);
 }
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 017044c26233..593dbe749174 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -5565,12 +5565,13 @@ static void __init wq_numa_init(void)
 int __init workqueue_init_early(void)
 {
         int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
+        int hk_flags = HK_FLAG_DOMAIN | HK_FLAG_WQ;
         int i, cpu;
 
         WARN_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
 
         BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
-        cpumask_copy(wq_unbound_cpumask, housekeeping_cpumask(HK_FLAG_DOMAIN));
+        cpumask_copy(wq_unbound_cpumask, housekeeping_cpumask(hk_flags));
 
         pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);