Re: [PATCH v9 04/13] task_isolation: add initial support

diff --git a/kernel/isolation.c b/kernel/isolation.c
new file mode 100644
index 000000000000..68a9f7457bc0
--- /dev/null
+++ b/kernel/isolation.c

@@ -0,0 +1,105 @@
+/*
+ *  linux/kernel/isolation.c
+ *
+ *  Implementation for task isolation.
+ *
+ *  Distributed under GPLv2.
+ */
+
+#include <linux/mm.h>
+#include <linux/swap.h>
+#include <linux/vmstat.h>
+#include <linux/isolation.h>
+#include <linux/syscalls.h>
+#include "time/tick-sched.h"
+
+cpumask_var_t task_isolation_map;
+
+/*
+ * Isolation requires both nohz and isolcpus support from the scheduler.
+ * We provide a boot flag that enables both for now, and which we can
+ * add other functionality to over time if needed.  Note that just
+ * specifying "nohz_full=... isolcpus=..." does not enable task isolation.
+ */
+static int __init task_isolation_setup(char *str)
+{
+	alloc_bootmem_cpumask_var(&task_isolation_map);
+	if (cpulist_parse(str, task_isolation_map) < 0) {
+		pr_warn("task_isolation: Incorrect cpumask '%s'\n", str);
+		return 1;
+	}
+
+	alloc_bootmem_cpumask_var(&cpu_isolated_map);
+	cpumask_copy(cpu_isolated_map, task_isolation_map);
+
+	alloc_bootmem_cpumask_var(&tick_nohz_full_mask);
+	cpumask_copy(tick_nohz_full_mask, task_isolation_map);
+	tick_nohz_full_running = true;

+
+	return 1;
+}
+__setup("task_isolation=", task_isolation_setup);
+
+/*
+ * This routine controls whether we can enable task-isolation mode.
+ * The task must be affinitized to a single task_isolation core or we will
+ * return EINVAL.  Although the application could later re-affinitize
+ * to a housekeeping core and lose task isolation semantics, this
+ * initial test should catch 99% of bugs with task placement prior to
+ * enabling task isolation.
+ */
+int task_isolation_set(unsigned int flags)
+{
+	if (cpumask_weight(tsk_cpus_allowed(current)) != 1 ||
+	    !task_isolation_possible(smp_processor_id()))
+		return -EINVAL;
+
+	current->task_isolation_flags = flags;
+	return 0;
+}

+
+/*
+ * In task isolation mode we try to return to userspace only after
+ * attempting to make sure we won't be interrupted again.  To handle
+ * the periodic scheduler tick, we test to make sure that the tick is
+ * stopped, and if it isn't yet, we request a reschedule so that if
+ * another task needs to run to completion first, it can do so.
+ * Similarly, if any other subsystems require quiescing, we will need
+ * to do that before we return to userspace.
+ */
+bool _task_isolation_ready(void)
+{
+	WARN_ON_ONCE(!irqs_disabled());
+
+	/* If we need to drain the LRU cache, we're not ready. */
+	if (lru_add_drain_needed(smp_processor_id()))
+		return false;
+
+	/* If vmstats need updating, we're not ready. */
+	if (!vmstat_idle())
+		return false;
+
+	/* Request rescheduling unless we are in full dynticks mode. */
+	if (!tick_nohz_tick_stopped()) {
+		set_tsk_need_resched(current);

+		return false;
+	}
+
+	return true;
+}