1 files changed, 62 insertions, 0 deletions
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index a19a39952c1b..79c275f08b7d 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -142,6 +142,68 @@ static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs)
 	profile_tick(CPU_PROFILING);
 }
 
+#ifdef CONFIG_NO_HZ_EXTENDED
+static cpumask_var_t nohz_extended_mask;
+bool have_nohz_extended_mask;
+
+int tick_nohz_extended_cpu(int cpu)
+{
+	if (!have_nohz_extended_mask)
+		return 0;
+
+	return cpumask_test_cpu(cpu, nohz_extended_mask);
+}
+
+/* Parse the boot-time nohz CPU list from the kernel parameters. */
+static int __init tick_nohz_extended_setup(char *str)
+{
+	alloc_bootmem_cpumask_var(&nohz_extended_mask);
+	if (cpulist_parse(str, nohz_extended_mask) < 0)
+		pr_warning("NOHZ: Incorrect nohz_extended cpumask\n");
+	else
+		have_nohz_extended_mask = true;
+	return 1;
+}
+__setup("nohz_extended=", tick_nohz_extended_setup);
+
+static int __init init_tick_nohz_extended(void)
+{
+	cpumask_var_t online_nohz;
+	int cpu;
+
+	if (!have_nohz_extended_mask)
+		return 0;
+
+	if (!zalloc_cpumask_var(&online_nohz, GFP_KERNEL)) {
+		pr_warning("NO_HZ: Not enough memory to check extended nohz mask\n");
+		return -ENOMEM;
+	}
+
+	/*
+	 * CPUs can probably not be concurrently offlined on initcall time.
+	 * But we are paranoid, aren't we?
+	 */
+	get_online_cpus();
+
+	/* Ensure we keep a CPU outside the dynticks range for timekeeping */
+	cpumask_and(online_nohz, cpu_online_mask, nohz_extended_mask);
+	if (cpumask_equal(online_nohz, cpu_online_mask)) {
+		cpu = cpumask_any(cpu_online_mask);
+		pr_warning("NO_HZ: Must keep at least one online CPU "
+			   "out of nohz_extended range\n");
+		pr_warning("NO_HZ: Clearing %d from nohz_extended range\n", cpu);
+		cpumask_clear_cpu(cpu, nohz_extended_mask);
+	}
+	put_online_cpus();
+	free_cpumask_var(online_nohz);
+
+	return 0;
+}
+core_initcall(init_tick_nohz_extended);
+#else
+#define have_nohz_extended_mask (0)
+#endif
+
 /*
  * NOHZ - aka dynamic tick functionality
  */