projects/linux·blob v4.13 · refs

241 lines · 5.5 KiB

1/*
2 * drivers/power/process.c - Functions for starting/stopping processes on
3 * suspend transitions.
4 *
5 * Originally from swsusp.
6 */
7
8
9#undef DEBUG
10
11#include <linux/interrupt.h>
12#include <linux/oom.h>
13#include <linux/suspend.h>
14#include <linux/module.h>
15#include <linux/sched/debug.h>
16#include <linux/sched/task.h>
17#include <linux/syscalls.h>
18#include <linux/freezer.h>
19#include <linux/delay.h>
20#include <linux/workqueue.h>
21#include <linux/kmod.h>
22#include <trace/events/power.h>
23
24/*
25 * Timeout for stopping processes
26 */
27unsigned int __read_mostly freeze_timeout_msecs = 20 * MSEC_PER_SEC;
28
29static int try_to_freeze_tasks(bool user_only)
30{
31 struct task_struct *g, *p;
32 unsigned long end_time;
33 unsigned int todo;
34 bool wq_busy = false;
35 ktime_t start, end, elapsed;
36 unsigned int elapsed_msecs;
37 bool wakeup = false;
38 int sleep_usecs = USEC_PER_MSEC;
39
40 start = ktime_get_boottime();
41
42 end_time = jiffies + msecs_to_jiffies(freeze_timeout_msecs);
43
44 if (!user_only)
45 freeze_workqueues_begin();
46
47 while (true) {
48 todo = 0;
49 read_lock(&tasklist_lock);
50 for_each_process_thread(g, p) {
51 if (p == current || !freeze_task(p))
52 continue;
53
54 if (!freezer_should_skip(p))
55 todo++;
56 }
57 read_unlock(&tasklist_lock);
58
59 if (!user_only) {
60 wq_busy = freeze_workqueues_busy();
61 todo += wq_busy;
62 }
63
64 if (!todo || time_after(jiffies, end_time))
65 break;
66
67 if (pm_wakeup_pending()) {
68 wakeup = true;
69 break;
70 }
71
72 /*
73 * We need to retry, but first give the freezing tasks some
74 * time to enter the refrigerator. Start with an initial
75 * 1 ms sleep followed by exponential backoff until 8 ms.
76 */
77 usleep_range(sleep_usecs / 2, sleep_usecs);
78 if (sleep_usecs < 8 * USEC_PER_MSEC)
79 sleep_usecs *= 2;
80 }
81
82 end = ktime_get_boottime();
83 elapsed = ktime_sub(end, start);
84 elapsed_msecs = ktime_to_ms(elapsed);
85
86 if (todo) {
87 pr_cont("\n");
88 pr_err("Freezing of tasks %s after %d.%03d seconds "
89 "(%d tasks refusing to freeze, wq_busy=%d):\n",
90 wakeup ? "aborted" : "failed",
91 elapsed_msecs / 1000, elapsed_msecs % 1000,
92 todo - wq_busy, wq_busy);
93
94 if (wq_busy)
95 show_workqueue_state();
96
97 if (!wakeup) {
98 read_lock(&tasklist_lock);
99 for_each_process_thread(g, p) {
100 if (p != current && !freezer_should_skip(p)
101 && freezing(p) && !frozen(p))
102 sched_show_task(p);
103 }
104 read_unlock(&tasklist_lock);
105 }
106 } else {
107 pr_cont("(elapsed %d.%03d seconds) ", elapsed_msecs / 1000,
108 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(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 atomic_inc(&system_freezing_cnt);
134
135 pm_wakeup_clear(true);
136 pr_info("Freezing user space processes ... ");
137 pm_freezing = true;
138 error = try_to_freeze_tasks(true);
139 if (!error) {
140 __usermodehelper_set_disable_depth(UMH_DISABLED);
141 pr_cont("done.");
142 }
143 pr_cont("\n");
144 BUG_ON(in_atomic());
145
146 /*
147 * Now that the whole userspace is frozen we need to disbale
148 * the OOM killer to disallow any further interference with
149 * killable tasks. There is no guarantee oom victims will
150 * ever reach a point they go away we have to wait with a timeout.
151 */
152 if (!error && !oom_killer_disable(msecs_to_jiffies(freeze_timeout_msecs)))
153 error = -EBUSY;
154
155 if (error)
156 thaw_processes();
157 return error;
158}
159
160/**
161 * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
162 *
163 * On success, returns 0. On failure, -errno and only the kernel threads are
164 * thawed, so as to give a chance to the caller to do additional cleanups
165 * (if any) before thawing the userspace tasks. So, it is the responsibility
166 * of the caller to thaw the userspace tasks, when the time is right.
167 */
168int freeze_kernel_threads(void)
169{
170 int error;
171
172 pr_info("Freezing remaining freezable tasks ... ");
173
174 pm_nosig_freezing = true;
175 error = try_to_freeze_tasks(false);
176 if (!error)
177 pr_cont("done.");
178
179 pr_cont("\n");
180 BUG_ON(in_atomic());
181
182 if (error)
183 thaw_kernel_threads();
184 return error;
185}
186
187void thaw_processes(void)
188{
189 struct task_struct *g, *p;
190 struct task_struct *curr = current;
191
192 trace_suspend_resume(TPS("thaw_processes"), 0, true);
193 if (pm_freezing)
194 atomic_dec(&system_freezing_cnt);
195 pm_freezing = false;
196 pm_nosig_freezing = false;
197
198 oom_killer_enable();
199
200 pr_info("Restarting tasks ... ");
201
202 __usermodehelper_set_disable_depth(UMH_FREEZING);
203 thaw_workqueues();
204
205 read_lock(&tasklist_lock);
206 for_each_process_thread(g, p) {
207 /* No other threads should have PF_SUSPEND_TASK set */
208 WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK));
209 __thaw_task(p);
210 }
211 read_unlock(&tasklist_lock);
212
213 WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
214 curr->flags &= ~PF_SUSPEND_TASK;
215
216 usermodehelper_enable();
217
218 schedule();
219 pr_cont("done.\n");
220 trace_suspend_resume(TPS("thaw_processes"), 0, false);
221}
222
223void thaw_kernel_threads(void)
224{
225 struct task_struct *g, *p;
226
227 pm_nosig_freezing = false;
228 pr_info("Restarting kernel threads ... ");
229
230 thaw_workqueues();
231
232 read_lock(&tasklist_lock);
233 for_each_process_thread(g, p) {
234 if (p->flags & (PF_KTHREAD | PF_WQ_WORKER))
235 __thaw_task(p);
236 }
237 read_unlock(&tasklist_lock);
238
239 schedule();
240 pr_cont("done.\n");
241}