projects/linux·blob v6.0 · refs

242 lines · 5.5 KiB

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 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 if (!freezer_should_skip(p))
54 todo++;
55 }
56 read_unlock(&tasklist_lock);
57
58 if (!user_only) {
59 wq_busy = freeze_workqueues_busy();
60 todo += wq_busy;
61 }
62
63 if (!todo || time_after(jiffies, end_time))
64 break;
65
66 if (pm_wakeup_pending()) {
67 wakeup = true;
68 break;
69 }
70
71 /*
72 * We need to retry, but first give the freezing tasks some
73 * time to enter the refrigerator. Start with an initial
74 * 1 ms sleep followed by exponential backoff until 8 ms.
75 */
76 usleep_range(sleep_usecs / 2, sleep_usecs);
77 if (sleep_usecs < 8 * USEC_PER_MSEC)
78 sleep_usecs *= 2;
79 }
80
81 end = ktime_get_boottime();
82 elapsed = ktime_sub(end, start);
83 elapsed_msecs = ktime_to_ms(elapsed);
84
85 if (todo) {
86 pr_cont("\n");
87 pr_err("Freezing of tasks %s after %d.%03d seconds "
88 "(%d tasks refusing to freeze, wq_busy=%d):\n",
89 wakeup ? "aborted" : "failed",
90 elapsed_msecs / 1000, elapsed_msecs % 1000,
91 todo - wq_busy, wq_busy);
92
93 if (wq_busy)
94 show_all_workqueues();
95
96 if (!wakeup || pm_debug_messages_on) {
97 read_lock(&tasklist_lock);
98 for_each_process_thread(g, p) {
99 if (p != current && !freezer_should_skip(p)
100 && freezing(p) && !frozen(p))
101 sched_show_task(p);
102 }
103 read_unlock(&tasklist_lock);
104 }
105 } else {
106 pr_cont("(elapsed %d.%03d seconds) ", elapsed_msecs / 1000,
107 elapsed_msecs % 1000);
108 }
109
110 return todo ? -EBUSY : 0;
111}
112
113/**
114 * freeze_processes - Signal user space processes to enter the refrigerator.
115 * The current thread will not be frozen. The same process that calls
116 * freeze_processes must later call thaw_processes.
117 *
118 * On success, returns 0. On failure, -errno and system is fully thawed.
119 */
120int freeze_processes(void)
121{
122 int error;
123
124 error = __usermodehelper_disable(UMH_FREEZING);
125 if (error)
126 return error;
127
128 /* Make sure this task doesn't get frozen */
129 current->flags |= PF_SUSPEND_TASK;
130
131 if (!pm_freezing)
132 atomic_inc(&system_freezing_cnt);
133
134 pm_wakeup_clear(0);
135 pr_info("Freezing user space processes ... ");
136 pm_freezing = true;
137 error = try_to_freeze_tasks(true);
138 if (!error) {
139 __usermodehelper_set_disable_depth(UMH_DISABLED);
140 pr_cont("done.");
141 }
142 pr_cont("\n");
143 BUG_ON(in_atomic());
144
145 /*
146 * Now that the whole userspace is frozen we need to disable
147 * the OOM killer to disallow any further interference with
148 * killable tasks. There is no guarantee oom victims will
149 * ever reach a point they go away we have to wait with a timeout.
150 */
151 if (!error && !oom_killer_disable(msecs_to_jiffies(freeze_timeout_msecs)))
152 error = -EBUSY;
153
154 if (error)
155 thaw_processes();
156 return error;
157}
158
159/**
160 * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
161 *
162 * On success, returns 0. On failure, -errno and only the kernel threads are
163 * thawed, so as to give a chance to the caller to do additional cleanups
164 * (if any) before thawing the userspace tasks. So, it is the responsibility
165 * of the caller to thaw the userspace tasks, when the time is right.
166 */
167int freeze_kernel_threads(void)
168{
169 int error;
170
171 pr_info("Freezing remaining freezable tasks ... ");
172
173 pm_nosig_freezing = true;
174 error = try_to_freeze_tasks(false);
175 if (!error)
176 pr_cont("done.");
177
178 pr_cont("\n");
179 BUG_ON(in_atomic());
180
181 if (error)
182 thaw_kernel_threads();
183 return error;
184}
185
186void thaw_processes(void)
187{
188 struct task_struct *g, *p;
189 struct task_struct *curr = current;
190
191 trace_suspend_resume(TPS("thaw_processes"), 0, true);
192 if (pm_freezing)
193 atomic_dec(&system_freezing_cnt);
194 pm_freezing = false;
195 pm_nosig_freezing = false;
196
197 oom_killer_enable();
198
199 pr_info("Restarting tasks ... ");
200
201 __usermodehelper_set_disable_depth(UMH_FREEZING);
202 thaw_workqueues();
203
204 cpuset_wait_for_hotplug();
205
206 read_lock(&tasklist_lock);
207 for_each_process_thread(g, p) {
208 /* No other threads should have PF_SUSPEND_TASK set */
209 WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK));
210 __thaw_task(p);
211 }
212 read_unlock(&tasklist_lock);
213
214 WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
215 curr->flags &= ~PF_SUSPEND_TASK;
216
217 usermodehelper_enable();
218
219 schedule();
220 pr_cont("done.\n");
221 trace_suspend_resume(TPS("thaw_processes"), 0, false);
222}
223
224void thaw_kernel_threads(void)
225{
226 struct task_struct *g, *p;
227
228 pm_nosig_freezing = false;
229 pr_info("Restarting kernel threads ... ");
230
231 thaw_workqueues();
232
233 read_lock(&tasklist_lock);
234 for_each_process_thread(g, p) {
235 if (p->flags & PF_KTHREAD)
236 __thaw_task(p);
237 }
238 read_unlock(&tasklist_lock);
239
240 schedule();
241 pr_cont("done.\n");
242}