Re: [PATCH v7 02/11] task_isolation: add initial support

diff --git a/include/linux/isolation.h b/include/linux/isolation.h
new file mode 100644
index 000000000000..fd04011b1c1e
--- /dev/null
+++ b/include/linux/isolation.h

@@ -0,0 +1,24 @@
+/*
+ * Task isolation related global functions
+ */
+#ifndef _LINUX_ISOLATION_H
+#define _LINUX_ISOLATION_H
+
+#include <linux/tick.h>
+#include <linux/prctl.h>
+
+#ifdef CONFIG_TASK_ISOLATION
+static inline bool task_isolation_enabled(void)
+{
+	return tick_nohz_full_cpu(smp_processor_id()) &&
+		(current->task_isolation_flags & PR_TASK_ISOLATION_ENABLE);

diff --git a/kernel/isolation.c b/kernel/isolation.c
new file mode 100644
index 000000000000..6ace866c69f6
--- /dev/null
+++ b/kernel/isolation.c

@@ -0,0 +1,77 @@
+/*
+ *  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 "time/tick-sched.h"
+
+/*
+ * Rather than continuously polling for the next_event in the
+ * tick_cpu_device, architectures can provide a method to save power
+ * by sleeping until an interrupt arrives.
+ *
+ * Note that it must be guaranteed for a particular architecture
+ * that if next_event is not KTIME_MAX, then a timer interrupt will
+ * occur, otherwise the sleep may never awaken.
+ */
+void __weak task_isolation_wait(void)
+{
+	cpu_relax();
+}
+
+/*
+ * We normally return immediately to userspace.
+ *
+ * In task_isolation mode we wait until no more interrupts are
+ * pending.  Otherwise we nap with interrupts enabled and wait for the
+ * next interrupt to fire, then loop back and retry.
+ *
+ * Note that if you schedule two task_isolation processes on the same
+ * core, neither will ever leave the kernel, and one will have to be
+ * killed manually.  Otherwise in situations where another process is
+ * in the runqueue on this cpu, this task will just wait for that
+ * other task to go idle before returning to user space.
+ */
+void task_isolation_enter(void)
+{
+	struct clock_event_device *dev =
+		__this_cpu_read(tick_cpu_device.evtdev);
+	struct task_struct *task = current;
+	unsigned long start = jiffies;
+	bool warned = false;
+
+	if (WARN_ON(irqs_disabled()))
+		local_irq_enable();
+
+	/* Drain the pagevecs to avoid unnecessary IPI flushes later. */
+	lru_add_drain();
+
+	/* Quieten the vmstat worker so it won't interrupt us. */
+	quiet_vmstat();
+
+	while (READ_ONCE(dev->next_event.tv64) != KTIME_MAX) {