[RFC PATCH 08/12] housekeeping: Introduce housekeeping flags

[Frederic Weisbecker]

Before we implement isolcpus under housekeeping, we need the isolation
features to be more finegrained. For example some people want nohz_full
without the full scheduler isolation, others want full scheduler
isolation without nohz_full.

So let's cut all these isolation features piecewise, at the risk of
overcutting it right now. We can still merge some flags later if they
always make sense together.

Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Chris Metcalf <cmetcalf@xxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Wanpeng Li <kernellwp@xxxxxxxxx>
Cc: Luiz Capitulino <lcapitulino@xxxxxxxxxx>
---
 drivers/net/ethernet/tile/tilegx.c |  4 ++--
 include/linux/housekeeping.h       | 26 +++++++++++++++++---------
 kernel/housekeeping.c              | 26 +++++++++++++++-----------
 kernel/rcu/tree_plugin.h           |  2 +-
 kernel/rcu/update.c                |  2 +-
 kernel/sched/core.c                |  8 ++++----
 kernel/sched/fair.c                |  2 +-
 kernel/watchdog.c                  |  3 ++-
 8 files changed, 43 insertions(+), 30 deletions(-)

diff --git a/drivers/net/ethernet/tile/tilegx.c b/drivers/net/ethernet/tile/tilegx.c
index eb74e09..0bd765b 100644
--- a/drivers/net/ethernet/tile/tilegx.c
+++ b/drivers/net/ethernet/tile/tilegx.c
@@ -2270,8 +2270,8 @@ static int __init tile_net_init_module(void)
 		tile_net_dev_init(name, mac);
 
 	if (!network_cpus_init())
-		cpumask_and(&network_cpus_map, housekeeping_cpumask(),
-			    cpu_online_mask);
+		cpumask_and(&network_cpus_map,
+			    housekeeping_cpumask(HK_FLAG_MISC), cpu_online_mask);
 
 	return 0;
 }
diff --git a/include/linux/housekeeping.h b/include/linux/housekeeping.h
index dcbec47..b1a62544 100644
--- a/include/linux/housekeeping.h
+++ b/include/linux/housekeeping.h
@@ -5,35 +5,43 @@
 #include <linux/init.h>
 #include <linux/tick.h>
 
+enum hk_flags {
+	HK_FLAG_TIMER		= 1,
+	HK_FLAG_RCU		= (1 << 1),
+	HK_FLAG_MISC		= (1 << 2),
+	HK_FLAG_SCHED		= (1 << 3),
+};
+
 #ifdef CONFIG_CPU_ISOLATION
 DECLARE_STATIC_KEY_FALSE(housekeeping_overriden);
-extern int housekeeping_any_cpu(void);
-extern const struct cpumask *housekeeping_cpumask(void);
-extern void housekeeping_affine(struct task_struct *t);
-extern bool housekeeping_test_cpu(int cpu);
+extern int housekeeping_any_cpu(enum hk_flags flags);
+extern const struct cpumask *housekeeping_cpumask(enum hk_flags flags);
+extern void housekeeping_affine(struct task_struct *t, enum hk_flags flags);
+extern bool housekeeping_test_cpu(int cpu, enum hk_flags flags);
 extern void __init housekeeping_init(void);
 
 #else
 
-static inline int housekeeping_any_cpu(void)
+static inline int housekeeping_any_cpu(enum hk_flags flags)
 {
 	return smp_processor_id();
 }
 
-static inline const struct cpumask *housekeeping_cpumask(void)
+static inline const struct cpumask *housekeeping_cpumask(enum hk_flags flags)
 {
 	return cpu_possible_mask;
 }
 
-static inline void housekeeping_affine(struct task_struct *t) { }
+static inline void housekeeping_affine(struct task_struct *t,
+				       enum hk_flags flags) { }
 static inline void housekeeping_init(void) { }
 #endif /* CONFIG_CPU_ISOLATION */
 
-static inline bool housekeeping_cpu(int cpu)
+static inline bool housekeeping_cpu(int cpu, enum hk_flags flags)
 {
 #ifdef CONFIG_CPU_ISOLATION
 	if (static_branch_unlikely(&housekeeping_overriden))
-		return housekeeping_test_cpu(cpu);
+		return housekeeping_test_cpu(cpu, flags);
 #endif
 	return true;
 }
diff --git a/kernel/housekeeping.c b/kernel/housekeeping.c
index f8be7e6..e2196d1 100644
--- a/kernel/housekeeping.c
+++ b/kernel/housekeeping.c
@@ -14,34 +14,36 @@
 DEFINE_STATIC_KEY_FALSE(housekeeping_overriden);
 EXPORT_SYMBOL_GPL(housekeeping_overriden);
 static cpumask_var_t housekeeping_mask;
+static unsigned int housekeeping_flags;
 
-int housekeeping_any_cpu(void)
+int housekeeping_any_cpu(enum hk_flags flags)
 {
 	if (static_branch_unlikely(&housekeeping_overriden))
-		return cpumask_any_and(housekeeping_mask, cpu_online_mask);
-
+		if (housekeeping_flags & flags)
+			return cpumask_any_and(housekeeping_mask, cpu_online_mask);
 	return smp_processor_id();
 }
 
-const struct cpumask *housekeeping_cpumask(void)
+const struct cpumask *housekeeping_cpumask(enum hk_flags flags)
 {
 	if (static_branch_unlikely(&housekeeping_overriden))
-		return housekeeping_mask;
-
+		if (housekeeping_flags & flags)
+			return housekeeping_mask;
 	return cpu_possible_mask;
 }
 
-void housekeeping_affine(struct task_struct *t)
+void housekeeping_affine(struct task_struct *t, enum hk_flags flags)
 {
 	if (static_branch_unlikely(&housekeeping_overriden))
-		set_cpus_allowed_ptr(t, housekeeping_mask);
+		if (housekeeping_flags & flags)
+			set_cpus_allowed_ptr(t, housekeeping_mask);
 }
 
-bool housekeeping_test_cpu(int cpu)
+bool housekeeping_test_cpu(int cpu, enum hk_flags flags)
 {
 	if (static_branch_unlikely(&housekeeping_overriden))
-		return cpumask_test_cpu(cpu, housekeeping_mask);
-
+		if (housekeeping_flags & flags)
+			return cpumask_test_cpu(cpu, housekeeping_mask);
 	return true;
 }
 
@@ -60,6 +62,8 @@ void __init housekeeping_init(void)
 	cpumask_andnot(housekeeping_mask,
 		       cpu_possible_mask, tick_nohz_full_mask);
 
+	housekeeping_flags = HK_FLAG_TIMER | HK_FLAG_RCU | HK_FLAG_MISC;
+
 	static_branch_enable(&housekeeping_overriden);
 
 	/* We need at least one CPU to handle housekeeping work */
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index c66d162..47f2865 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -2542,7 +2542,7 @@ static void rcu_bind_gp_kthread(void)
 
 	if (!tick_nohz_full_enabled())
 		return;
-	housekeeping_affine(current);
+	housekeeping_affine(current, HK_FLAG_RCU);
 }
 
 /* Record the current task on dyntick-idle entry. */
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index bfe973d..7acfd74 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -719,7 +719,7 @@ static int __noreturn rcu_tasks_kthread(void *arg)
 	LIST_HEAD(rcu_tasks_holdouts);
 
 	/* Run on housekeeping CPUs by default.  Sysadm can move if desired. */
-	housekeeping_affine(current);
+	housekeeping_affine(current, HK_FLAG_RCU);
 
 	/*
 	 * Each pass through the following loop makes one check for
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index fd00ae3..877c85d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -527,7 +527,7 @@ int get_nohz_timer_target(void)
 	int i, cpu = smp_processor_id();
 	struct sched_domain *sd;
 
-	if (!idle_cpu(cpu) && housekeeping_cpu(cpu))
+	if (!idle_cpu(cpu) && housekeeping_cpu(cpu, HK_FLAG_TIMER))
 		return cpu;
 
 	rcu_read_lock();
@@ -536,15 +536,15 @@ int get_nohz_timer_target(void)
 			if (cpu == i)
 				continue;
 
-			if (!idle_cpu(i) && housekeeping_cpu(i)) {
+			if (!idle_cpu(i) && housekeeping_cpu(i, HK_FLAG_TIMER)) {
 				cpu = i;
 				goto unlock;
 			}
 		}
 	}
 
-	if (!housekeeping_cpu(cpu))
-		cpu = housekeeping_any_cpu();
+	if (!housekeeping_cpu(cpu, HK_FLAG_TIMER))
+		cpu = housekeeping_any_cpu(HK_FLAG_TIMER);
 unlock:
 	rcu_read_unlock();
 	return cpu;
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 0d8f7b1..74af955 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8739,7 +8739,7 @@ void nohz_balance_enter_idle(int cpu)
 		return;
 
 	/* Spare idle load balancing on CPUs that don't want to be disturbed: */
-	if (!housekeeping_cpu(cpu))
+	if (!housekeeping_cpu(cpu, HK_FLAG_SCHED))
 		return;
 
 	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index cdd0d11..631131c 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -944,7 +944,8 @@ void __init lockup_detector_init(void)
 	if (tick_nohz_full_enabled())
 		pr_info("Disabling watchdog on nohz_full cores by default\n");
 
-	cpumask_copy(&watchdog_cpumask, housekeeping_cpumask());
+	cpumask_copy(&watchdog_cpumask,
+		     housekeeping_cpumask(HK_FLAG_TIMER));
 
 	if (watchdog_enabled)
 		watchdog_enable_all_cpus();
-- 
2.7.4