1// SPDX-License-Identifier: GPL-2.0
2/*
3 * drivers/power/process.c - Functions for starting/stopping processes on
4 * suspend transitions.
5 *
6 * Originally from swsusp.
7 */
8
9#include <linux/interrupt.h>
10#include <linux/oom.h>
11#include <linux/suspend.h>
12#include <linux/module.h>
13#include <linux/sched/debug.h>
14#include <linux/sched/task.h>
15#include <linux/syscalls.h>
16#include <linux/freezer.h>
17#include <linux/delay.h>
18#include <linux/workqueue.h>
19#include <linux/kmod.h>
20#include <trace/events/power.h>
21#include <linux/cpuset.h>
22
23/*
24 * Timeout for stopping processes
25 */
26unsigned int __read_mostly freeze_timeout_msecs = 20 * MSEC_PER_SEC;
27
28static int try_to_freeze_tasks(bool user_only)
29{
30 const char *what = user_only ? "user space processes" :
31 "remaining freezable tasks";
32 struct task_struct *g, *p;
33 unsigned long end_time;
34 unsigned int todo;
35 bool wq_busy = false;
36 ktime_t start, end, elapsed;
37 unsigned int elapsed_msecs;
38 bool wakeup = false;
39 int sleep_usecs = USEC_PER_MSEC;
40
41 pr_info("Freezing %s\n", what);
42
43 start = ktime_get_boottime();
44
45 end_time = jiffies + msecs_to_jiffies(m: freeze_timeout_msecs);
46
47 if (!user_only)
48 freeze_workqueues_begin();
49
50 while (true) {
51 todo = 0;
52 read_lock(&tasklist_lock);
53 for_each_process_thread(g, p) {
54 if (p == current || !freeze_task(p))
55 continue;
56
57 todo++;
58 }
59 read_unlock(&tasklist_lock);
60
61 if (!user_only) {
62 wq_busy = freeze_workqueues_busy();
63 todo += wq_busy;
64 }
65
66 if (!todo || time_after(jiffies, end_time))
67 break;
68
69 if (pm_wakeup_pending()) {
70 wakeup = true;
71 break;
72 }
73
74 /*
75 * We need to retry, but first give the freezing tasks some
76 * time to enter the refrigerator. Start with an initial
77 * 1 ms sleep followed by exponential backoff until 8 ms.
78 */
79 usleep_range(min: sleep_usecs / 2, max: sleep_usecs);
80 if (sleep_usecs < 8 * USEC_PER_MSEC)
81 sleep_usecs *= 2;
82 }
83
84 end = ktime_get_boottime();
85 elapsed = ktime_sub(end, start);
86 elapsed_msecs = ktime_to_ms(kt: elapsed);
87
88 if (todo) {
89 pr_err("Freezing %s %s after %d.%03d seconds "
90 "(%d tasks refusing to freeze, wq_busy=%d):\n", what,
91 wakeup ? "aborted" : "failed",
92 elapsed_msecs / 1000, elapsed_msecs % 1000,
93 todo - wq_busy, wq_busy);
94
95 if (wq_busy)
96 show_freezable_workqueues();
97
98 if (!wakeup || pm_debug_messages_on) {
99 read_lock(&tasklist_lock);
100 for_each_process_thread(g, p) {
101 if (p != current && freezing(p) && !frozen(p))
102 sched_show_task(p);
103 }
104 read_unlock(&tasklist_lock);
105 }
106 } else {
107 pr_info("Freezing %s completed (elapsed %d.%03d seconds)\n",
108 what, elapsed_msecs / 1000, elapsed_msecs % 1000);
109 }
110
111 return todo ? -EBUSY : 0;
112}
113
114/**
115 * freeze_processes - Signal user space processes to enter the refrigerator.
116 * The current thread will not be frozen. The same process that calls
117 * freeze_processes must later call thaw_processes.
118 *
119 * On success, returns 0. On failure, -errno and system is fully thawed.
120 */
121int freeze_processes(void)
122{
123 int error;
124
125 error = __usermodehelper_disable(depth: UMH_FREEZING);
126 if (error)
127 return error;
128
129 /* Make sure this task doesn't get frozen */
130 current->flags |= PF_SUSPEND_TASK;
131
132 if (!pm_freezing)
133 static_branch_inc(&freezer_active);
134
135 pm_freezing = true;
136 error = try_to_freeze_tasks(user_only: true);
137 if (!error)
138 __usermodehelper_set_disable_depth(depth: UMH_DISABLED);
139
140 BUG_ON(in_atomic());
141
142 /*
143 * Now that the whole userspace is frozen we need to disable
144 * the OOM killer to disallow any further interference with
145 * killable tasks. There is no guarantee oom victims will
146 * ever reach a point they go away we have to wait with a timeout.
147 */
148 if (!error && !oom_killer_disable(timeout: msecs_to_jiffies(m: freeze_timeout_msecs)))
149 error = -EBUSY;
150
151 if (error)
152 thaw_processes();
153 return error;
154}
155
156/**
157 * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
158 *
159 * On success, returns 0. On failure, -errno and only the kernel threads are
160 * thawed, so as to give a chance to the caller to do additional cleanups
161 * (if any) before thawing the userspace tasks. So, it is the responsibility
162 * of the caller to thaw the userspace tasks, when the time is right.
163 */
164int freeze_kernel_threads(void)
165{
166 int error;
167
168 pm_nosig_freezing = true;
169 error = try_to_freeze_tasks(user_only: false);
170
171 BUG_ON(in_atomic());
172
173 if (error)
174 thaw_kernel_threads();
175 return error;
176}
177
178void thaw_processes(void)
179{
180 struct task_struct *g, *p;
181 struct task_struct *curr = current;
182
183 trace_suspend_resume(TPS("thaw_processes"), val: 0, start: true);
184 if (pm_freezing)
185 static_branch_dec(&freezer_active);
186 pm_freezing = false;
187 pm_nosig_freezing = false;
188
189 oom_killer_enable();
190
191 pr_info("Restarting tasks: Starting\n");
192
193 __usermodehelper_set_disable_depth(depth: UMH_FREEZING);
194 thaw_workqueues();
195
196 read_lock(&tasklist_lock);
197 for_each_process_thread(g, p) {
198 /* No other threads should have PF_SUSPEND_TASK set */
199 WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK));
200 __thaw_task(t: p);
201 }
202 read_unlock(&tasklist_lock);
203
204 WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
205 curr->flags &= ~PF_SUSPEND_TASK;
206
207 usermodehelper_enable();
208
209 schedule();
210 pr_info("Restarting tasks: Done\n");
211 trace_suspend_resume(TPS("thaw_processes"), val: 0, start: false);
212}
213
214void thaw_kernel_threads(void)
215{
216 struct task_struct *g, *p;
217
218 pm_nosig_freezing = false;
219 pr_info("Restarting kernel threads ...\n");
220
221 thaw_workqueues();
222
223 read_lock(&tasklist_lock);
224 for_each_process_thread(g, p) {
225 if (p->flags & PF_KTHREAD)
226 __thaw_task(t: p);
227 }
228 read_unlock(&tasklist_lock);
229
230 schedule();
231 pr_info("Done restarting kernel threads.\n");
232}
233