Merge tag 'kthread-for-7.0' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks

Pull kthread updates from Frederic Weisbecker:
 "The kthread code provides an infrastructure which manages the
  preferred affinity of unbound kthreads (node or custom cpumask)
  against housekeeping (CPU isolation) constraints and CPU hotplug
  events.

  One crucial missing piece is the handling of cpuset: when an isolated
  partition is created, deleted, or its CPUs updated, all the unbound
  kthreads in the top cpuset become indifferently affine to _all_ the
  non-isolated CPUs, possibly breaking their preferred affinity along
  the way.

  Solve this with performing the kthreads affinity update from cpuset to
  the kthreads consolidated relevant code instead so that preferred
  affinities are honoured and applied against the updated cpuset
  isolated partitions.

  The dispatch of the new isolated cpumasks to timers, workqueues and
  kthreads is performed by housekeeping, as per the nice Tejun's
  suggestion.

  As a welcome side effect, HK_TYPE_DOMAIN then integrates both the set
  from boot defined domain isolation (through isolcpus=) and cpuset
  isolated partitions. Housekeeping cpumasks are now modifiable with a
  specific RCU based synchronization. A big step toward making
  nohz_full= also mutable through cpuset in the future"

* tag 'kthread-for-7.0' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks: (33 commits)
  doc: Add housekeeping documentation
  kthread: Document kthread_affine_preferred()
  kthread: Comment on the purpose and placement of kthread_affine_node() call
  kthread: Honour kthreads preferred affinity after cpuset changes
  sched/arm64: Move fallback task cpumask to HK_TYPE_DOMAIN
  sched: Switch the fallback task allowed cpumask to HK_TYPE_DOMAIN
  kthread: Rely on HK_TYPE_DOMAIN for preferred affinity management
  kthread: Include kthreadd to the managed affinity list
  kthread: Include unbound kthreads in the managed affinity list
  kthread: Refine naming of affinity related fields
  PCI: Remove superfluous HK_TYPE_WQ check
  sched/isolation: Remove HK_TYPE_TICK test from cpu_is_isolated()
  cpuset: Remove cpuset_cpu_is_isolated()
  timers/migration: Remove superfluous cpuset isolation test
  cpuset: Propagate cpuset isolation update to timers through housekeeping
  cpuset: Propagate cpuset isolation update to workqueue through housekeeping
  PCI: Flush PCI probe workqueue on cpuset isolated partition change
  sched/isolation: Flush vmstat workqueues on cpuset isolated partition change
  sched/isolation: Flush memcg workqueues on cpuset isolated partition change
  cpuset: Update HK_TYPE_DOMAIN cpumask from cpuset
  ...

1 files changed, 17 insertions, 8 deletions

diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c
index 18dda1aa782d..6da9cd562b20 100644
--- a/kernel/time/timer_migration.c
+++ b/kernel/time/timer_migration.c
@@ -466,9 +466,8 @@ static inline bool tmigr_is_isolated(int cpu)
 {
 	if (!static_branch_unlikely(&tmigr_exclude_isolated))
 		return false;
-	return (!housekeeping_cpu(cpu, HK_TYPE_DOMAIN) ||
-		cpuset_cpu_is_isolated(cpu)) &&
-	       housekeeping_cpu(cpu, HK_TYPE_KERNEL_NOISE);
+	return (!housekeeping_cpu(cpu, HK_TYPE_DOMAIN) &&
+		housekeeping_cpu(cpu, HK_TYPE_KERNEL_NOISE));
 }
 
 /*
@@ -1497,7 +1496,7 @@ static int tmigr_clear_cpu_available(unsigned int cpu)
 	return 0;
 }
 
-static int tmigr_set_cpu_available(unsigned int cpu)
+static int __tmigr_set_cpu_available(unsigned int cpu)
 {
 	struct tmigr_cpu *tmc = this_cpu_ptr(&tmigr_cpu);
 
@@ -1505,9 +1504,6 @@ static int tmigr_set_cpu_available(unsigned int cpu)
 	if (WARN_ON_ONCE(!tmc->tmgroup))
 		return -EINVAL;
 
-	if (tmigr_is_isolated(cpu))
-		return 0;
-
 	guard(mutex)(&tmigr_available_mutex);
 
 	cpumask_set_cpu(cpu, tmigr_available_cpumask);
@@ -1523,6 +1519,14 @@ static int tmigr_set_cpu_available(unsigned int cpu)
 	return 0;
 }
 
+static int tmigr_set_cpu_available(unsigned int cpu)
+{
+	if (tmigr_is_isolated(cpu))
+		return 0;
+
+	return __tmigr_set_cpu_available(cpu);
+}
+
 static void tmigr_cpu_isolate(struct work_struct *ignored)
 {
 	tmigr_clear_cpu_available(smp_processor_id());
@@ -1530,7 +1534,12 @@ static void tmigr_cpu_isolate(struct work_struct *ignored)
 
 static void tmigr_cpu_unisolate(struct work_struct *ignored)
 {
-	tmigr_set_cpu_available(smp_processor_id());
+	/*
+	 * Don't call tmigr_is_isolated() ->housekeeping_cpu() directly because
+	 * the cpuset mutex is correctly held by the workqueue caller but lockdep
+	 * doesn't know that.
+	 */
+	__tmigr_set_cpu_available(smp_processor_id());
 }
 
 /**