sched/isolation: Handle the nohz_full= parameter

We want to centralize the isolation management, done by the housekeeping
subsystem. Therefore we need to handle the nohz_full= parameter from
there.

Since nohz_full= so far has involved unbound timers, watchdog, RCU
and tilegx NAPI isolation, we keep that default behaviour.

nohz_full= will be deprecated in the future. We want to control
the isolation features from the isolcpus= parameter.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
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: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Link: http://lkml.kernel.org/r/1509072159-31808-10-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

5 files changed, 36 insertions, 23 deletions

diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h
index 9bb753eece3b..e53cfa96e91e 100644
--- a/include/linux/sched/isolation.h
+++ b/include/linux/sched/isolation.h
@@ -10,6 +10,7 @@ enum hk_flags {
         HK_FLAG_RCU             = (1 << 1),
         HK_FLAG_MISC            = (1 << 2),
         HK_FLAG_SCHED           = (1 << 3),
+        HK_FLAG_TICK            = (1 << 4),
 };
 
 #ifdef CONFIG_CPU_ISOLATION
diff --git a/include/linux/tick.h b/include/linux/tick.h
index 68afc09aa8ac..e2a163a9f96c 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -228,6 +228,7 @@ static inline void tick_dep_clear_signal(struct signal_struct *signal,
 
 extern void tick_nohz_full_kick_cpu(int cpu);
 extern void __tick_nohz_task_switch(void);
+extern void __init tick_nohz_full_setup(cpumask_var_t cpumask);
 #else
 static inline bool tick_nohz_full_enabled(void) { return false; }
 static inline bool tick_nohz_full_cpu(int cpu) { return false; }
@@ -248,6 +249,7 @@ static inline void tick_dep_clear_signal(struct signal_struct *signal,
 
 static inline void tick_nohz_full_kick_cpu(int cpu) { }
 static inline void __tick_nohz_task_switch(void) { }
+static inline void tick_nohz_full_setup(cpumask_var_t cpumask) { }
 #endif
 
 static inline void tick_nohz_task_switch(void)
diff --git a/init/Kconfig b/init/Kconfig
index 6f52e6f4bd9d..f8564df58d0a 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -474,7 +474,6 @@ endmenu # "CPU/Task time and stats accounting"
 
 config CPU_ISOLATION
         bool "CPU isolation"
-        depends on NO_HZ_FULL
         help
           Make sure that CPUs running critical tasks are not disturbed by
           any source of "noise" such as unbound workqueues, timers, kthreads...
diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index 37a138a780ff..1f61e440358d 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -54,23 +54,41 @@ EXPORT_SYMBOL_GPL(housekeeping_test_cpu);
 
 void __init housekeeping_init(void)
 {
-        if (!tick_nohz_full_enabled())
+        if (!housekeeping_flags)
                 return;
 
-        if (!alloc_cpumask_var(&housekeeping_mask, GFP_KERNEL)) {
-                WARN(1, "NO_HZ: Can't allocate not-full dynticks cpumask\n");
-                cpumask_clear(tick_nohz_full_mask);
-                tick_nohz_full_running = false;
-                return;
+        static_branch_enable(&housekeeping_overriden);
+
+        /* We need at least one CPU to handle housekeeping work */
+        WARN_ON_ONCE(cpumask_empty(housekeeping_mask));
+}
+
+#ifdef CONFIG_NO_HZ_FULL
+static int __init housekeeping_nohz_full_setup(char *str)
+{
+        cpumask_var_t non_housekeeping_mask;
+
+        alloc_bootmem_cpumask_var(&non_housekeeping_mask);
+        if (cpulist_parse(str, non_housekeeping_mask) < 0) {
+                pr_warn("Housekeeping: Incorrect nohz_full cpumask\n");
+                free_bootmem_cpumask_var(non_housekeeping_mask);
+                return 0;
         }
 
-        cpumask_andnot(housekeeping_mask,
-                       cpu_possible_mask, tick_nohz_full_mask);
+        alloc_bootmem_cpumask_var(&housekeeping_mask);
+        cpumask_andnot(housekeeping_mask, cpu_possible_mask, non_housekeeping_mask);
 
-        housekeeping_flags = HK_FLAG_TIMER | HK_FLAG_RCU | HK_FLAG_MISC;
+        if (cpumask_empty(housekeeping_mask))
+                cpumask_set_cpu(smp_processor_id(), housekeeping_mask);
 
-        static_branch_enable(&housekeeping_overriden);
+        housekeeping_flags = HK_FLAG_TICK | HK_FLAG_TIMER |
+                                HK_FLAG_RCU | HK_FLAG_MISC;
 
-        /* We need at least one CPU to handle housekeeping work */
-        WARN_ON_ONCE(cpumask_empty(housekeeping_mask));
+        tick_nohz_full_setup(non_housekeeping_mask);
+
+        free_bootmem_cpumask_var(non_housekeeping_mask);
+
+        return 1;
 }
+__setup("nohz_full=", housekeeping_nohz_full_setup);
+#endif
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 27d7d522ac4e..69f3dbe38984 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -385,20 +385,13 @@ out:
         local_irq_restore(flags);
 }
 
-/* Parse the boot-time nohz CPU list from the kernel parameters. */
-static int __init tick_nohz_full_setup(char *str)
+/* Get the boot-time nohz CPU list from the kernel parameters. */
+void __init tick_nohz_full_setup(cpumask_var_t cpumask)
 {
         alloc_bootmem_cpumask_var(&tick_nohz_full_mask);
-        if (cpulist_parse(str, tick_nohz_full_mask) < 0) {
-                pr_warn("NO_HZ: Incorrect nohz_full cpumask\n");
-                free_bootmem_cpumask_var(tick_nohz_full_mask);
-                return 1;
-        }
+        cpumask_copy(tick_nohz_full_mask, cpumask);
         tick_nohz_full_running = true;
-
-        return 1;
 }
-__setup("nohz_full=", tick_nohz_full_setup);
 
 static int tick_nohz_cpu_down(unsigned int cpu)
 {