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

Pull scheduler updates from Ingo Molnar:

 - Clean up SCHED_DEBUG: move the decades old mess of sysctl, procfs and
   debugfs interfaces to a unified debugfs interface.

 - Signals: Allow caching one sigqueue object per task, to improve
   performance & latencies.

 - Improve newidle_balance() irq-off latencies on systems with a large
   number of CPU cgroups.

 - Improve energy-aware scheduling

 - Improve the PELT metrics for certain workloads

 - Reintroduce select_idle_smt() to improve load-balancing locality -
   but without the previous regressions

 - Add 'scheduler latency debugging': warn after long periods of pending
   need_resched. This is an opt-in feature that requires the enabling of
   the LATENCY_WARN scheduler feature, or the use of the
   resched_latency_warn_ms=xx boot parameter.

 - CPU hotplug fixes for HP-rollback, and for the 'fail' interface. Fix
   remaining balance_push() vs. hotplug holes/races

 - PSI fixes, plus allow /proc/pressure/ files to be written by
   CAP_SYS_RESOURCE tasks as well

 - Fix/improve various load-balancing corner cases vs. capacity margins

 - Fix sched topology on systems with NUMA diameter of 3 or above

 - Fix PF_KTHREAD vs to_kthread() race

 - Minor rseq optimizations

 - Misc cleanups, optimizations, fixes and smaller updates

* tag 'sched-core-2021-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (61 commits)
  cpumask/hotplug: Fix cpu_dying() state tracking
  kthread: Fix PF_KTHREAD vs to_kthread() race
  sched/debug: Fix cgroup_path[] serialization
  sched,psi: Handle potential task count underflow bugs more gracefully
  sched: Warn on long periods of pending need_resched
  sched/fair: Move update_nohz_stats() to the CONFIG_NO_HZ_COMMON block to simplify the code & fix an unused function warning
  sched/debug: Rename the sched_debug parameter to sched_verbose
  sched,fair: Alternative sched_slice()
  sched: Move /proc/sched_debug to debugfs
  sched,debug: Convert sysctl sched_domains to debugfs
  debugfs: Implement debugfs_create_str()
  sched,preempt: Move preempt_dynamic to debug.c
  sched: Move SCHED_DEBUG sysctl to debugfs
  sched: Don't make LATENCYTOP select SCHED_DEBUG
  sched: Remove sched_schedstats sysctl out from under SCHED_DEBUG
  sched/numa: Allow runtime enabling/disabling of NUMA balance without SCHED_DEBUG
  sched: Use cpu_dying() to fix balance_push vs hotplug-rollback
  cpumask: Introduce DYING mask
  cpumask: Make cpu_{online,possible,present,active}() inline
  rseq: Optimise rseq_get_rseq_cs() and clear_rseq_cs()
  ...

1 files changed, 86 insertions, 31 deletions

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 383684e30f12..e6b948a6000d 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -91,44 +91,15 @@ extern struct cpumask __cpu_possible_mask;
 extern struct cpumask __cpu_online_mask;
 extern struct cpumask __cpu_present_mask;
 extern struct cpumask __cpu_active_mask;
+extern struct cpumask __cpu_dying_mask;
 #define cpu_possible_mask ((const struct cpumask *)&__cpu_possible_mask)
 #define cpu_online_mask   ((const struct cpumask *)&__cpu_online_mask)
 #define cpu_present_mask  ((const struct cpumask *)&__cpu_present_mask)
 #define cpu_active_mask   ((const struct cpumask *)&__cpu_active_mask)
+#define cpu_dying_mask    ((const struct cpumask *)&__cpu_dying_mask)
 
 extern atomic_t __num_online_cpus;
 
-#if NR_CPUS > 1
-/**
- * num_online_cpus() - Read the number of online CPUs
- *
- * Despite the fact that __num_online_cpus is of type atomic_t, this
- * interface gives only a momentary snapshot and is not protected against
- * concurrent CPU hotplug operations unless invoked from a cpuhp_lock held
- * region.
- */
-static inline unsigned int num_online_cpus(void)
-{
-	return atomic_read(&__num_online_cpus);
-}
-#define num_possible_cpus()	cpumask_weight(cpu_possible_mask)
-#define num_present_cpus()	cpumask_weight(cpu_present_mask)
-#define num_active_cpus()	cpumask_weight(cpu_active_mask)
-#define cpu_online(cpu)		cpumask_test_cpu((cpu), cpu_online_mask)
-#define cpu_possible(cpu)	cpumask_test_cpu((cpu), cpu_possible_mask)
-#define cpu_present(cpu)	cpumask_test_cpu((cpu), cpu_present_mask)
-#define cpu_active(cpu)		cpumask_test_cpu((cpu), cpu_active_mask)
-#else
-#define num_online_cpus()	1U
-#define num_possible_cpus()	1U
-#define num_present_cpus()	1U
-#define num_active_cpus()	1U
-#define cpu_online(cpu)		((cpu) == 0)
-#define cpu_possible(cpu)	((cpu) == 0)
-#define cpu_present(cpu)	((cpu) == 0)
-#define cpu_active(cpu)		((cpu) == 0)
-#endif
-
 extern cpumask_t cpus_booted_once_mask;
 
 static inline void cpu_max_bits_warn(unsigned int cpu, unsigned int bits)
@@ -857,6 +828,14 @@ set_cpu_active(unsigned int cpu, bool active)
 		cpumask_clear_cpu(cpu, &__cpu_active_mask);
 }
 
+static inline void
+set_cpu_dying(unsigned int cpu, bool dying)
+{
+	if (dying)
+		cpumask_set_cpu(cpu, &__cpu_dying_mask);
+	else
+		cpumask_clear_cpu(cpu, &__cpu_dying_mask);
+}
 
 /**
  * to_cpumask - convert an NR_CPUS bitmap to a struct cpumask *
@@ -894,6 +873,82 @@ static inline const struct cpumask *get_cpu_mask(unsigned int cpu)
 	return to_cpumask(p);
 }
 
+#if NR_CPUS > 1
+/**
+ * num_online_cpus() - Read the number of online CPUs
+ *
+ * Despite the fact that __num_online_cpus is of type atomic_t, this
+ * interface gives only a momentary snapshot and is not protected against
+ * concurrent CPU hotplug operations unless invoked from a cpuhp_lock held
+ * region.
+ */
+static inline unsigned int num_online_cpus(void)
+{
+	return atomic_read(&__num_online_cpus);
+}
+#define num_possible_cpus()	cpumask_weight(cpu_possible_mask)
+#define num_present_cpus()	cpumask_weight(cpu_present_mask)
+#define num_active_cpus()	cpumask_weight(cpu_active_mask)
+
+static inline bool cpu_online(unsigned int cpu)
+{
+	return cpumask_test_cpu(cpu, cpu_online_mask);
+}
+
+static inline bool cpu_possible(unsigned int cpu)
+{
+	return cpumask_test_cpu(cpu, cpu_possible_mask);
+}
+
+static inline bool cpu_present(unsigned int cpu)
+{
+	return cpumask_test_cpu(cpu, cpu_present_mask);
+}
+
+static inline bool cpu_active(unsigned int cpu)
+{
+	return cpumask_test_cpu(cpu, cpu_active_mask);
+}
+
+static inline bool cpu_dying(unsigned int cpu)
+{
+	return cpumask_test_cpu(cpu, cpu_dying_mask);
+}
+
+#else
+
+#define num_online_cpus()	1U
+#define num_possible_cpus()	1U
+#define num_present_cpus()	1U
+#define num_active_cpus()	1U
+
+static inline bool cpu_online(unsigned int cpu)
+{
+	return cpu == 0;
+}
+
+static inline bool cpu_possible(unsigned int cpu)
+{
+	return cpu == 0;
+}
+
+static inline bool cpu_present(unsigned int cpu)
+{
+	return cpu == 0;
+}
+
+static inline bool cpu_active(unsigned int cpu)
+{
+	return cpu == 0;
+}
+
+static inline bool cpu_dying(unsigned int cpu)
+{
+	return false;
+}
+
+#endif /* NR_CPUS > 1 */
+
 #define cpu_is_offline(cpu)	unlikely(!cpu_online(cpu))
 
 #if NR_CPUS <= BITS_PER_LONG