projects/linux·blob v4.4 · refs

237 lines · 5.3 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/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
22/*
23 * Timeout for stopping processes
24 */
25unsigned int __read_mostly freeze_timeout_msecs = 20 * MSEC_PER_SEC;
26
27static int try_to_freeze_tasks(bool user_only)
28{
29 struct task_struct *g, *p;
30 unsigned long end_time;
31 unsigned int todo;
32 bool wq_busy = false;
33 struct timeval start, end;
34 u64 elapsed_msecs64;
35 unsigned int elapsed_msecs;
36 bool wakeup = false;
37 int sleep_usecs = USEC_PER_MSEC;
38
39 do_gettimeofday(&start);
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 do_gettimeofday(&end);
82 elapsed_msecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
83 do_div(elapsed_msecs64, NSEC_PER_MSEC);
84 elapsed_msecs = elapsed_msecs64;
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 (!wakeup) {
95 read_lock(&tasklist_lock);
96 for_each_process_thread(g, p) {
97 if (p != current && !freezer_should_skip(p)
98 && 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 */
118int 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 atomic_inc(&system_freezing_cnt);
131
132 pm_wakeup_clear();
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 disbale
145 * the OOM killer to disallow any further interference with
146 * killable tasks.
147 */
148 if (!error && !oom_killer_disable())
149 error = -EBUSY;
150
151 if (error)
152 thaw_processes();
153 return error;
154}
155
156/**
157 * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
158 *
159 * On success, returns 0. On failure, -errno and only the kernel threads are
160 * thawed, so as to give a chance to the caller to do additional cleanups
161 * (if any) before thawing the userspace tasks. So, it is the responsibility
162 * of the caller to thaw the userspace tasks, when the time is right.
163 */
164int freeze_kernel_threads(void)
165{
166 int error;
167
168 pr_info("Freezing remaining freezable tasks ... ");
169
170 pm_nosig_freezing = true;
171 error = try_to_freeze_tasks(false);
172 if (!error)
173 pr_cont("done.");
174
175 pr_cont("\n");
176 BUG_ON(in_atomic());
177
178 if (error)
179 thaw_kernel_threads();
180 return error;
181}
182
183void thaw_processes(void)
184{
185 struct task_struct *g, *p;
186 struct task_struct *curr = current;
187
188 trace_suspend_resume(TPS("thaw_processes"), 0, true);
189 if (pm_freezing)
190 atomic_dec(&system_freezing_cnt);
191 pm_freezing = false;
192 pm_nosig_freezing = false;
193
194 oom_killer_enable();
195
196 pr_info("Restarting tasks ... ");
197
198 __usermodehelper_set_disable_depth(UMH_FREEZING);
199 thaw_workqueues();
200
201 read_lock(&tasklist_lock);
202 for_each_process_thread(g, p) {
203 /* No other threads should have PF_SUSPEND_TASK set */
204 WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK));
205 __thaw_task(p);
206 }
207 read_unlock(&tasklist_lock);
208
209 WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
210 curr->flags &= ~PF_SUSPEND_TASK;
211
212 usermodehelper_enable();
213
214 schedule();
215 pr_cont("done.\n");
216 trace_suspend_resume(TPS("thaw_processes"), 0, false);
217}
218
219void thaw_kernel_threads(void)
220{
221 struct task_struct *g, *p;
222
223 pm_nosig_freezing = false;
224 pr_info("Restarting kernel threads ... ");
225
226 thaw_workqueues();
227
228 read_lock(&tasklist_lock);
229 for_each_process_thread(g, p) {
230 if (p->flags & (PF_KTHREAD | PF_WQ_WORKER))
231 __thaw_task(p);
232 }
233 read_unlock(&tasklist_lock);
234
235 schedule();
236 pr_cont("done.\n");
237}