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 */
26 unsigned int __read_mostly freeze_timeout_msecs = 20 * MSEC_PER_SEC;
27
try_to_freeze_tasks(bool user_only)28 static int try_to_freeze_tasks(bool user_only)
29 {
30 struct task_struct *g, *p;
31 unsigned long end_time;
32 unsigned int todo;
33 bool wq_busy = false;
34 ktime_t start, end, elapsed;
35 unsigned int elapsed_msecs;
36 bool wakeup = false;
37 int sleep_usecs = USEC_PER_MSEC;
38
39 start = ktime_get_boottime();
40
41 end_time = jiffies + msecs_to_jiffies(freeze_timeout_msecs);
42
43 if (!user_only)
44 freeze_workqueues_begin();
45
46 while (true) {
47 todo = 0;
48 read_lock(&tasklist_lock);
49 for_each_process_thread(g, p) {
50 if (p == current || !freeze_task(p))
51 continue;
52
53 todo++;
54 }
55 read_unlock(&tasklist_lock);
56
57 if (!user_only) {
58 wq_busy = freeze_workqueues_busy();
59 todo += wq_busy;
60 }
61
62 if (!todo || time_after(jiffies, end_time))
63 break;
64
65 if (pm_wakeup_pending()) {
66 wakeup = true;
67 break;
68 }
69
70 /*
71 * We need to retry, but first give the freezing tasks some
72 * time to enter the refrigerator. Start with an initial
73 * 1 ms sleep followed by exponential backoff until 8 ms.
74 */
75 usleep_range(sleep_usecs / 2, sleep_usecs);
76 if (sleep_usecs < 8 * USEC_PER_MSEC)
77 sleep_usecs *= 2;
78 }
79
80 end = ktime_get_boottime();
81 elapsed = ktime_sub(end, start);
82 elapsed_msecs = ktime_to_ms(elapsed);
83
84 if (todo) {
85 pr_cont("\n");
86 pr_err("Freezing of tasks %s after %d.%03d seconds "
87 "(%d tasks refusing to freeze, wq_busy=%d):\n",
88 wakeup ? "aborted" : "failed",
89 elapsed_msecs / 1000, elapsed_msecs % 1000,
90 todo - wq_busy, wq_busy);
91
92 if (wq_busy)
93 show_all_workqueues();
94
95 if (!wakeup || pm_debug_messages_on) {
96 read_lock(&tasklist_lock);
97 for_each_process_thread(g, p) {
98 if (p != current && freezing(p) && !frozen(p))
99 sched_show_task(p);
100 }
101 read_unlock(&tasklist_lock);
102 }
103 } else {
104 pr_cont("(elapsed %d.%03d seconds) ", elapsed_msecs / 1000,
105 elapsed_msecs % 1000);
106 }
107
108 return todo ? -EBUSY : 0;
109 }
110
111 /**
112 * freeze_processes - Signal user space processes to enter the refrigerator.
113 * The current thread will not be frozen. The same process that calls
114 * freeze_processes must later call thaw_processes.
115 *
116 * On success, returns 0. On failure, -errno and system is fully thawed.
117 */
freeze_processes(void)118 int freeze_processes(void)
119 {
120 int error;
121
122 error = __usermodehelper_disable(UMH_FREEZING);
123 if (error)
124 return error;
125
126 /* Make sure this task doesn't get frozen */
127 current->flags |= PF_SUSPEND_TASK;
128
129 if (!pm_freezing)
130 static_branch_inc(&freezer_active);
131
132 pm_wakeup_clear(0);
133 pr_info("Freezing user space processes ... ");
134 pm_freezing = true;
135 error = try_to_freeze_tasks(true);
136 if (!error) {
137 __usermodehelper_set_disable_depth(UMH_DISABLED);
138 pr_cont("done.");
139 }
140 pr_cont("\n");
141 BUG_ON(in_atomic());
142
143 /*
144 * Now that the whole userspace is frozen we need to disable
145 * the OOM killer to disallow any further interference with
146 * killable tasks. There is no guarantee oom victims will
147 * ever reach a point they go away we have to wait with a timeout.
148 */
149 if (!error && !oom_killer_disable(msecs_to_jiffies(freeze_timeout_msecs)))
150 error = -EBUSY;
151
152 if (error)
153 thaw_processes();
154 return error;
155 }
156
157 /**
158 * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
159 *
160 * On success, returns 0. On failure, -errno and only the kernel threads are
161 * thawed, so as to give a chance to the caller to do additional cleanups
162 * (if any) before thawing the userspace tasks. So, it is the responsibility
163 * of the caller to thaw the userspace tasks, when the time is right.
164 */
freeze_kernel_threads(void)165 int freeze_kernel_threads(void)
166 {
167 int error;
168
169 pr_info("Freezing remaining freezable tasks ... ");
170
171 pm_nosig_freezing = true;
172 error = try_to_freeze_tasks(false);
173 if (!error)
174 pr_cont("done.");
175
176 pr_cont("\n");
177 BUG_ON(in_atomic());
178
179 if (error)
180 thaw_kernel_threads();
181 return error;
182 }
183
thaw_processes(void)184 void thaw_processes(void)
185 {
186 struct task_struct *g, *p;
187 struct task_struct *curr = current;
188
189 trace_suspend_resume(TPS("thaw_processes"), 0, true);
190 if (pm_freezing)
191 static_branch_dec(&freezer_active);
192 pm_freezing = false;
193 pm_nosig_freezing = false;
194
195 oom_killer_enable();
196
197 pr_info("Restarting tasks ... ");
198
199 __usermodehelper_set_disable_depth(UMH_FREEZING);
200 thaw_workqueues();
201
202 cpuset_wait_for_hotplug();
203
204 read_lock(&tasklist_lock);
205 for_each_process_thread(g, p) {
206 /* No other threads should have PF_SUSPEND_TASK set */
207 WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK));
208 __thaw_task(p);
209 }
210 read_unlock(&tasklist_lock);
211
212 WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
213 curr->flags &= ~PF_SUSPEND_TASK;
214
215 usermodehelper_enable();
216
217 schedule();
218 pr_cont("done.\n");
219 trace_suspend_resume(TPS("thaw_processes"), 0, false);
220 }
221
thaw_kernel_threads(void)222 void thaw_kernel_threads(void)
223 {
224 struct task_struct *g, *p;
225
226 pm_nosig_freezing = false;
227 pr_info("Restarting kernel threads ... ");
228
229 thaw_workqueues();
230
231 read_lock(&tasklist_lock);
232 for_each_process_thread(g, p) {
233 if (p->flags & PF_KTHREAD)
234 __thaw_task(p);
235 }
236 read_unlock(&tasklist_lock);
237
238 schedule();
239 pr_cont("done.\n");
240 }
241
