Release 4.15 kernel/power/process.c

// 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;
}

Contributors
Person
Tokens
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CommitProp
Rafael J. Wysocki
128
38.32%
11
42.31%
Patrick Mochel
56
16.77%
2
7.69%
Tejun Heo
54
16.17%
5
19.23%
Colin Cross
36
10.78%
1
3.85%
Pavel Machek
27
8.08%
1
3.85%
Abhilash Jindal
16
4.79%
1
3.85%
Roger Lu
7
2.10%
1
3.85%
Michal Hocko
5
1.50%
2
7.69%
Li Fei
4
1.20%
1
3.85%
Xiaotian Feng
1
0.30%
1
3.85%
Total
334
100.00%
26
100.00%

/**
 * 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;
}

Contributors
Person
Tokens
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Commits
CommitProp
Rafael J. Wysocki
65
53.72%
9
56.25%
Michal Hocko
27
22.31%
4
25.00%
Tejun Heo
22
18.18%
2
12.50%
Colin Cross
7
5.79%
1
6.25%
Total
121
100.00%
16
100.00%

/**
 * 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;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Rafael J. Wysocki
31
54.39%
6
54.55%
Patrick Mochel
12
21.05%
1
9.09%
Tejun Heo
10
17.54%
2
18.18%
Michal Hocko
3
5.26%
1
9.09%
Srivatsa S. Bhat
1
1.75%
1
9.09%
Total
57
100.00%
11
100.00%



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);
}

Contributors
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CommitProp
Colin Cross
44
28.21%
1
7.69%
Patrick Mochel
42
26.92%
2
15.38%
Tejun Heo
31
19.87%
3
23.08%
Todd E Brandt
24
15.38%
1
7.69%
Takashi Iwai
5
3.21%
1
7.69%
Michal Hocko
3
1.92%
2
15.38%
Rafael J. Wysocki
3
1.92%
1
7.69%
Peter Zijlstra
3
1.92%
1
7.69%
Nigel Cunningham
1
0.64%
1
7.69%
Total
156
100.00%
13
100.00%



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");
}
Contributors
Person
Tokens
Prop
Commits
CommitProp
Rafael J. Wysocki
69
95.83%
1
33.33%
Michal Hocko
3
4.17%
2
66.67%
Total
72
100.00%
3
100.00%

Overall Contributors
Person
Tokens
Prop
Commits
CommitProp
Rafael J. Wysocki
302
37.94%
19
36.54%
Patrick Mochel
123
15.45%
2
3.85%
Tejun Heo
123
15.45%
9
17.31%
Colin Cross
88
11.06%
2
3.85%
Michal Hocko
41
5.15%
5
9.62%
Pavel Machek
27
3.39%
1
1.92%
Todd E Brandt
27
3.39%
1
1.92%
Abhilash Jindal
16
2.01%
1
1.92%
Li Fei
13
1.63%
1
1.92%
Roger Lu
7
0.88%
1
1.92%
Peter Zijlstra
7
0.88%
1
1.92%
Ingo Molnar
6
0.75%
2
3.85%
Takashi Iwai
5
0.63%
1
1.92%
Nigel Cunningham
4
0.50%
2
3.85%
Alexey Dobriyan
3
0.38%
1
1.92%
Srivatsa S. Bhat
2
0.25%
1
1.92%
Xiaotian Feng
1
0.13%
1
1.92%
Greg Kroah-Hartman
1
0.13%
1
1.92%
Total
796
100.00%
52
100.00%
Directory: kernel/power

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