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
10 #undef DEBUG
11
12 #include <linux/interrupt.h>
13 #include <linux/oom.h>
14 #include <linux/suspend.h>
15 #include <linux/module.h>
16 #include <linux/sched/debug.h>
17 #include <linux/sched/task.h>
18 #include <linux/syscalls.h>
19 #include <linux/freezer.h>
20 #include <linux/delay.h>
21 #include <linux/workqueue.h>
22 #include <linux/kmod.h>
23 #include <trace/events/power.h>
24 #include <linux/cpuset.h>
25
26 /*
27 * Timeout for stopping processes
28 */
29 unsigned int __read_mostly freeze_timeout_msecs = 20 * MSEC_PER_SEC;
30
try_to_freeze_tasks(bool user_only)31 static int try_to_freeze_tasks(bool user_only)
32 {
33 struct task_struct *g, *p;
34 unsigned long end_time;
35 unsigned int todo;
36 bool wq_busy = false;
37 ktime_t start, end, elapsed;
38 unsigned int elapsed_msecs;
39 bool wakeup = false;
40 int sleep_usecs = USEC_PER_MSEC;
41
42 start = ktime_get_boottime();
43
44 end_time = jiffies + msecs_to_jiffies(freeze_timeout_msecs);
45
46 if (!user_only)
47 freeze_workqueues_begin();
48
49 while (true) {
50 todo = 0;
51 read_lock(&tasklist_lock);
52 for_each_process_thread(g, p) {
53 if (p == current || !freeze_task(p))
54 continue;
55
56 if (!freezer_should_skip(p))
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(sleep_usecs / 2, 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(elapsed);
87
88 if (wakeup) {
89 pr_cont("\n");
90 pr_err("Freezing of tasks aborted after %d.%03d seconds",
91 elapsed_msecs / 1000, elapsed_msecs % 1000);
92 } else if (todo) {
93 pr_cont("\n");
94 pr_err("Freezing of tasks failed after %d.%03d seconds"
95 " (%d tasks refusing to freeze, wq_busy=%d):\n",
96 elapsed_msecs / 1000, elapsed_msecs % 1000,
97 todo - wq_busy, wq_busy);
98
99 if (wq_busy)
100 show_workqueue_state();
101
102 if (pm_debug_messages_on) {
103 read_lock(&tasklist_lock);
104 for_each_process_thread(g, p) {
105 if (p != current && !freezer_should_skip(p)
106 && freezing(p) && !frozen(p))
107 sched_show_task(p);
108 }
109 read_unlock(&tasklist_lock);
110 }
111 } else {
112 pr_cont("(elapsed %d.%03d seconds) ", elapsed_msecs / 1000,
113 elapsed_msecs % 1000);
114 }
115
116 return todo ? -EBUSY : 0;
117 }
118
119 /**
120 * freeze_processes - Signal user space processes to enter the refrigerator.
121 * The current thread will not be frozen. The same process that calls
122 * freeze_processes must later call thaw_processes.
123 *
124 * On success, returns 0. On failure, -errno and system is fully thawed.
125 */
freeze_processes(void)126 int freeze_processes(void)
127 {
128 int error;
129
130 error = __usermodehelper_disable(UMH_FREEZING);
131 if (error)
132 return error;
133
134 /* Make sure this task doesn't get frozen */
135 current->flags |= PF_SUSPEND_TASK;
136
137 if (!pm_freezing)
138 atomic_inc(&system_freezing_cnt);
139
140 pm_wakeup_clear(0);
141 pr_info("Freezing user space processes ... ");
142 pm_freezing = true;
143 error = try_to_freeze_tasks(true);
144 if (!error) {
145 __usermodehelper_set_disable_depth(UMH_DISABLED);
146 pr_cont("done.");
147 }
148 pr_cont("\n");
149 BUG_ON(in_atomic());
150
151 /*
152 * Now that the whole userspace is frozen we need to disbale
153 * the OOM killer to disallow any further interference with
154 * killable tasks. There is no guarantee oom victims will
155 * ever reach a point they go away we have to wait with a timeout.
156 */
157 if (!error && !oom_killer_disable(msecs_to_jiffies(freeze_timeout_msecs)))
158 error = -EBUSY;
159
160 if (error)
161 thaw_processes();
162 return error;
163 }
164
165 /**
166 * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
167 *
168 * On success, returns 0. On failure, -errno and only the kernel threads are
169 * thawed, so as to give a chance to the caller to do additional cleanups
170 * (if any) before thawing the userspace tasks. So, it is the responsibility
171 * of the caller to thaw the userspace tasks, when the time is right.
172 */
freeze_kernel_threads(void)173 int freeze_kernel_threads(void)
174 {
175 int error;
176
177 pr_info("Freezing remaining freezable tasks ... ");
178
179 pm_nosig_freezing = true;
180 error = try_to_freeze_tasks(false);
181 if (!error)
182 pr_cont("done.");
183
184 pr_cont("\n");
185 BUG_ON(in_atomic());
186
187 if (error)
188 thaw_kernel_threads();
189 return error;
190 }
191
thaw_processes(void)192 void thaw_processes(void)
193 {
194 struct task_struct *g, *p;
195 struct task_struct *curr = current;
196
197 trace_suspend_resume(TPS("thaw_processes"), 0, true);
198 if (pm_freezing)
199 atomic_dec(&system_freezing_cnt);
200 pm_freezing = false;
201 pm_nosig_freezing = false;
202
203 oom_killer_enable();
204
205 pr_info("Restarting tasks ... ");
206
207 __usermodehelper_set_disable_depth(UMH_FREEZING);
208 thaw_workqueues();
209
210 cpuset_wait_for_hotplug();
211
212 read_lock(&tasklist_lock);
213 for_each_process_thread(g, p) {
214 /* No other threads should have PF_SUSPEND_TASK set */
215 WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK));
216 __thaw_task(p);
217 }
218 read_unlock(&tasklist_lock);
219
220 WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
221 curr->flags &= ~PF_SUSPEND_TASK;
222
223 usermodehelper_enable();
224
225 schedule();
226 pr_cont("done.\n");
227 trace_suspend_resume(TPS("thaw_processes"), 0, false);
228 }
229
thaw_kernel_threads(void)230 void thaw_kernel_threads(void)
231 {
232 struct task_struct *g, *p;
233
234 pm_nosig_freezing = false;
235 pr_info("Restarting kernel threads ... ");
236
237 thaw_workqueues();
238
239 read_lock(&tasklist_lock);
240 for_each_process_thread(g, p) {
241 if (p->flags & (PF_KTHREAD | PF_WQ_WORKER))
242 __thaw_task(p);
243 }
244 read_unlock(&tasklist_lock);
245
246 schedule();
247 pr_cont("done.\n");
248 }
249