v4.19.13 snapshot.
diff --git a/kernel/power/process.c b/kernel/power/process.c
new file mode 100644
index 0000000..7381d49
--- /dev/null
+++ b/kernel/power/process.c
@@ -0,0 +1,245 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * drivers/power/process.c - Functions for starting/stopping processes on
+ * suspend transitions.
+ *
+ * Originally from swsusp.
+ */
+
+
+#undef DEBUG
+
+#include <linux/interrupt.h>
+#include <linux/oom.h>
+#include <linux/suspend.h>
+#include <linux/module.h>
+#include <linux/sched/debug.h>
+#include <linux/sched/task.h>
+#include <linux/syscalls.h>
+#include <linux/freezer.h>
+#include <linux/delay.h>
+#include <linux/workqueue.h>
+#include <linux/kmod.h>
+#include <trace/events/power.h>
+#include <linux/cpuset.h>
+
+/*
+ * Timeout for stopping processes
+ */
+unsigned int __read_mostly freeze_timeout_msecs = 20 * MSEC_PER_SEC;
+
+static int try_to_freeze_tasks(bool user_only)
+{
+ struct task_struct *g, *p;
+ unsigned long end_time;
+ unsigned int todo;
+ bool wq_busy = false;
+ ktime_t start, end, elapsed;
+ unsigned int elapsed_msecs;
+ bool wakeup = false;
+ int sleep_usecs = USEC_PER_MSEC;
+
+ start = ktime_get_boottime();
+
+ end_time = jiffies + msecs_to_jiffies(freeze_timeout_msecs);
+
+ if (!user_only)
+ freeze_workqueues_begin();
+
+ while (true) {
+ todo = 0;
+ read_lock(&tasklist_lock);
+ for_each_process_thread(g, p) {
+ if (p == current || !freeze_task(p))
+ continue;
+
+ if (!freezer_should_skip(p))
+ todo++;
+ }
+ read_unlock(&tasklist_lock);
+
+ if (!user_only) {
+ wq_busy = freeze_workqueues_busy();
+ todo += wq_busy;
+ }
+
+ if (!todo || time_after(jiffies, end_time))
+ break;
+
+ if (pm_wakeup_pending()) {
+ wakeup = true;
+ break;
+ }
+
+ /*
+ * We need to retry, but first give the freezing tasks some
+ * time to enter the refrigerator. Start with an initial
+ * 1 ms sleep followed by exponential backoff until 8 ms.
+ */
+ usleep_range(sleep_usecs / 2, sleep_usecs);
+ if (sleep_usecs < 8 * USEC_PER_MSEC)
+ sleep_usecs *= 2;
+ }
+
+ end = ktime_get_boottime();
+ elapsed = ktime_sub(end, start);
+ elapsed_msecs = ktime_to_ms(elapsed);
+
+ if (todo) {
+ pr_cont("\n");
+ pr_err("Freezing of tasks %s after %d.%03d seconds "
+ "(%d tasks refusing to freeze, wq_busy=%d):\n",
+ wakeup ? "aborted" : "failed",
+ elapsed_msecs / 1000, elapsed_msecs % 1000,
+ todo - wq_busy, wq_busy);
+
+ if (wq_busy)
+ show_workqueue_state();
+
+ if (!wakeup) {
+ read_lock(&tasklist_lock);
+ for_each_process_thread(g, p) {
+ if (p != current && !freezer_should_skip(p)
+ && freezing(p) && !frozen(p))
+ sched_show_task(p);
+ }
+ read_unlock(&tasklist_lock);
+ }
+ } else {
+ pr_cont("(elapsed %d.%03d seconds) ", elapsed_msecs / 1000,
+ elapsed_msecs % 1000);
+ }
+
+ return todo ? -EBUSY : 0;
+}
+
+/**
+ * freeze_processes - Signal user space processes to enter the refrigerator.
+ * The current thread will not be frozen. The same process that calls
+ * freeze_processes must later call thaw_processes.
+ *
+ * On success, returns 0. On failure, -errno and system is fully thawed.
+ */
+int freeze_processes(void)
+{
+ int error;
+
+ error = __usermodehelper_disable(UMH_FREEZING);
+ if (error)
+ return error;
+
+ /* Make sure this task doesn't get frozen */
+ current->flags |= PF_SUSPEND_TASK;
+
+ if (!pm_freezing)
+ atomic_inc(&system_freezing_cnt);
+
+ pm_wakeup_clear(true);
+ pr_info("Freezing user space processes ... ");
+ pm_freezing = true;
+ error = try_to_freeze_tasks(true);
+ if (!error) {
+ __usermodehelper_set_disable_depth(UMH_DISABLED);
+ pr_cont("done.");
+ }
+ pr_cont("\n");
+ BUG_ON(in_atomic());
+
+ /*
+ * Now that the whole userspace is frozen we need to disbale
+ * the OOM killer to disallow any further interference with
+ * killable tasks. There is no guarantee oom victims will
+ * ever reach a point they go away we have to wait with a timeout.
+ */
+ if (!error && !oom_killer_disable(msecs_to_jiffies(freeze_timeout_msecs)))
+ error = -EBUSY;
+
+ if (error)
+ thaw_processes();
+ return error;
+}
+
+/**
+ * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
+ *
+ * On success, returns 0. On failure, -errno and only the kernel threads are
+ * thawed, so as to give a chance to the caller to do additional cleanups
+ * (if any) before thawing the userspace tasks. So, it is the responsibility
+ * of the caller to thaw the userspace tasks, when the time is right.
+ */
+int freeze_kernel_threads(void)
+{
+ int error;
+
+ pr_info("Freezing remaining freezable tasks ... ");
+
+ pm_nosig_freezing = true;
+ error = try_to_freeze_tasks(false);
+ if (!error)
+ pr_cont("done.");
+
+ pr_cont("\n");
+ BUG_ON(in_atomic());
+
+ if (error)
+ thaw_kernel_threads();
+ return error;
+}
+
+void thaw_processes(void)
+{
+ struct task_struct *g, *p;
+ struct task_struct *curr = current;
+
+ trace_suspend_resume(TPS("thaw_processes"), 0, true);
+ if (pm_freezing)
+ atomic_dec(&system_freezing_cnt);
+ pm_freezing = false;
+ pm_nosig_freezing = false;
+
+ oom_killer_enable();
+
+ pr_info("Restarting tasks ... ");
+
+ __usermodehelper_set_disable_depth(UMH_FREEZING);
+ thaw_workqueues();
+
+ cpuset_wait_for_hotplug();
+
+ read_lock(&tasklist_lock);
+ for_each_process_thread(g, p) {
+ /* No other threads should have PF_SUSPEND_TASK set */
+ WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK));
+ __thaw_task(p);
+ }
+ read_unlock(&tasklist_lock);
+
+ WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
+ curr->flags &= ~PF_SUSPEND_TASK;
+
+ usermodehelper_enable();
+
+ schedule();
+ pr_cont("done.\n");
+ trace_suspend_resume(TPS("thaw_processes"), 0, false);
+}
+
+void thaw_kernel_threads(void)
+{
+ struct task_struct *g, *p;
+
+ pm_nosig_freezing = false;
+ pr_info("Restarting kernel threads ... ");
+
+ thaw_workqueues();
+
+ read_lock(&tasklist_lock);
+ for_each_process_thread(g, p) {
+ if (p->flags & (PF_KTHREAD | PF_WQ_WORKER))
+ __thaw_task(p);
+ }
+ read_unlock(&tasklist_lock);
+
+ schedule();
+ pr_cont("done.\n");
+}