[PATCH v13 11/12] task_isolation: support CONFIG_TASK_ISOLATION_ALL

[Chris Metcalf <cmetcalf@mellanox.com>]

This option, similar to NO_HZ_FULL_ALL, simplifies configuring
a system to boot by default with all cores except the boot core
running in task isolation mode.

Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com>
---
 init/Kconfig       | 10 ++++++++++
 kernel/isolation.c |  6 ++++++
 2 files changed, 16 insertions(+)

diff --git a/init/Kconfig b/init/Kconfig
index fc71444f9c30..0b8384c76571 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -810,6 +810,16 @@ config TASK_ISOLATION
 	 You should say "N" unless you are intending to run a
 	 high-performance userspace driver or similar task.
 
+config TASK_ISOLATION_ALL
+	bool "Provide task isolation on all CPUs by default (except CPU 0)"
+	depends on TASK_ISOLATION
+	help
+	 If the user doesn't pass the task_isolation boot option to
+	 define the range of task isolation CPUs, consider that all
+	 CPUs in the system are task isolation by default.
+	 Note the boot CPU will still be kept outside the range to
+	 handle timekeeping duty, etc.
+
 config BUILD_BIN2C
 	bool
 	default n
diff --git a/kernel/isolation.c b/kernel/isolation.c
index a9fd4709825a..5e6cd67dfb0c 100644
--- a/kernel/isolation.c
+++ b/kernel/isolation.c
@@ -43,8 +43,14 @@ int __init task_isolation_init(void)
 {
 	/* For offstack cpumask, ensure we allocate an empty cpumask early. */
 	if (!saw_boot_arg) {
+#ifdef CONFIG_TASK_ISOLATION_ALL
+		alloc_cpumask_var(&task_isolation_map, GFP_KERNEL);
+		cpumask_copy(task_isolation_map, cpu_possible_mask);
+		cpumask_clear_cpu(smp_processor_id(), task_isolation_map);
+#else
 		zalloc_cpumask_var(&task_isolation_map, GFP_KERNEL);
 		return 0;
+#endif
 	}
 
 	/*
-- 
2.7.2