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
28 static 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(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(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 (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 */
121 int freeze_processes(void)
122 {
123 int error;
124
125 error = __usermodehelper_disable(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_wakeup_clear(0);
136 pm_freezing = true;
137 error = try_to_freeze_tasks(true);
138 if (!error)
139 __usermodehelper_set_disable_depth(UMH_DISABLED);
140
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 */
165 int freeze_kernel_threads(void)
166 {
167 int error;
168
169 pm_nosig_freezing = true;
170 error = try_to_freeze_tasks(false);
171
172 BUG_ON(in_atomic());
173
174 if (error)
175 thaw_kernel_threads();
176 return error;
177 }
178
179 void thaw_processes(void)
180 {
181 struct task_struct *g, *p;
182 struct task_struct *curr = current;
183
184 trace_suspend_resume(TPS("thaw_processes"), 0, true);
185 if (pm_freezing)
186 static_branch_dec(&freezer_active);
187 pm_freezing = false;
188 pm_nosig_freezing = false;
189
190 oom_killer_enable();
191
192 pr_info("Restarting tasks ... ");
193
194 __usermodehelper_set_disable_depth(UMH_FREEZING);
195 thaw_workqueues();
196
197 read_lock(&tasklist_lock);
198 for_each_process_thread(g, p) {
199 /* No other threads should have PF_SUSPEND_TASK set */
200 WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK));
201 __thaw_task(p);
202 }
203 read_unlock(&tasklist_lock);
204
205 WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
206 curr->flags &= ~PF_SUSPEND_TASK;
207
208 usermodehelper_enable();
209
210 schedule();
211 pr_cont("done.\n");
212 trace_suspend_resume(TPS("thaw_processes"), 0, false);
213 }
214
215 void thaw_kernel_threads(void)
216 {
217 struct task_struct *g, *p;
218
219 pm_nosig_freezing = false;
220 pr_info("Restarting kernel threads ... ");
221
222 thaw_workqueues();
223
224 read_lock(&tasklist_lock);
225 for_each_process_thread(g, p) {
226 if (p->flags & PF_KTHREAD)
227 __thaw_task(p);
228 }
229 read_unlock(&tasklist_lock);
230
231 schedule();
232 pr_cont("done.\n");
233 }
234
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