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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
20/*
21 * Timeout for stopping processes
22 */
23#define TIMEOUT (20 * HZ)
24
25static inline int freezable(struct task_struct * p)
26{
27 if ((p == current) ||
28 (p->flags & PF_NOFREEZE) ||
29 (p->exit_state != 0))
30 return 0;
31 return 1;
32}
33
34static int try_to_freeze_tasks(bool sig_only)
35{
36 struct task_struct *g, *p;
37 unsigned long end_time;
38 unsigned int todo;
39 bool wq_busy = false;
40 struct timeval start, end;
41 u64 elapsed_csecs64;
42 unsigned int elapsed_csecs;
43 bool wakeup = false;
44
45 do_gettimeofday(&start);
46
47 end_time = jiffies + TIMEOUT;
48
49 if (!sig_only)
50 freeze_workqueues_begin();
51
52 while (true) {
53 todo = 0;
54 read_lock(&tasklist_lock);
55 do_each_thread(g, p) {
56 if (frozen(p) || !freezable(p))
57 continue;
58
59 if (!freeze_task(p, sig_only))
60 continue;
61
62 /*
63 * Now that we've done set_freeze_flag, don't
64 * perturb a task in TASK_STOPPED or TASK_TRACED.
65 * It is "frozen enough". If the task does wake
66 * up, it will immediately call try_to_freeze.
67 *
68 * Because freeze_task() goes through p's
69 * scheduler lock after setting TIF_FREEZE, it's
70 * guaranteed that either we see TASK_RUNNING or
71 * try_to_stop() after schedule() in ptrace/signal
72 * stop sees TIF_FREEZE.
73 */
74 if (!task_is_stopped_or_traced(p) &&
75 !freezer_should_skip(p))
76 todo++;
77 } while_each_thread(g, p);
78 read_unlock(&tasklist_lock);
79
80 if (!sig_only) {
81 wq_busy = freeze_workqueues_busy();
82 todo += wq_busy;
83 }
84
85 if (!todo || time_after(jiffies, end_time))
86 break;
87
88 if (pm_wakeup_pending()) {
89 wakeup = true;
90 break;
91 }
92
93 /*
94 * We need to retry, but first give the freezing tasks some
95 * time to enter the regrigerator.
96 */
97 msleep(10);
98 }
99
100 do_gettimeofday(&end);
101 elapsed_csecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
102 do_div(elapsed_csecs64, NSEC_PER_SEC / 100);
103 elapsed_csecs = elapsed_csecs64;
104
105 if (todo) {
106 /* This does not unfreeze processes that are already frozen
107 * (we have slightly ugly calling convention in that respect,
108 * and caller must call thaw_processes() if something fails),
109 * but it cleans up leftover PF_FREEZE requests.
110 */
111 printk("\n");
112 printk(KERN_ERR "Freezing of tasks %s after %d.%02d seconds "
113 "(%d tasks refusing to freeze, wq_busy=%d):\n",
114 wakeup ? "aborted" : "failed",
115 elapsed_csecs / 100, elapsed_csecs % 100,
116 todo - wq_busy, wq_busy);
117
118 thaw_workqueues();
119
120 read_lock(&tasklist_lock);
121 do_each_thread(g, p) {
122 task_lock(p);
123 if (!wakeup && freezing(p) && !freezer_should_skip(p))
124 sched_show_task(p);
125 cancel_freezing(p);
126 task_unlock(p);
127 } while_each_thread(g, p);
128 read_unlock(&tasklist_lock);
129 } else {
130 printk("(elapsed %d.%02d seconds) ", elapsed_csecs / 100,
131 elapsed_csecs % 100);
132 }
133
134 return todo ? -EBUSY : 0;
135}
136
137/**
138 * freeze_processes - tell processes to enter the refrigerator
139 */
140int freeze_processes(void)
141{
142 int error;
143
144 printk("Freezing user space processes ... ");
145 error = try_to_freeze_tasks(true);
146 if (error)
147 goto Exit;
148 printk("done.\n");
149
150 printk("Freezing remaining freezable tasks ... ");
151 error = try_to_freeze_tasks(false);
152 if (error)
153 goto Exit;
154 printk("done.");
155
156 oom_killer_disable();
157 Exit:
158 BUG_ON(in_atomic());
159 printk("\n");
160
161 return error;
162}
163
164static void thaw_tasks(bool nosig_only)
165{
166 struct task_struct *g, *p;
167
168 read_lock(&tasklist_lock);
169 do_each_thread(g, p) {
170 if (!freezable(p))
171 continue;
172
173 if (nosig_only && should_send_signal(p))
174 continue;
175
176 if (cgroup_freezing_or_frozen(p))
177 continue;
178
179 thaw_process(p);
180 } while_each_thread(g, p);
181 read_unlock(&tasklist_lock);
182}
183
184void thaw_processes(void)
185{
186 oom_killer_enable();
187
188 printk("Restarting tasks ... ");
189 thaw_workqueues();
190 thaw_tasks(true);
191 thaw_tasks(false);
192 schedule();
193 printk("done.\n");
194}
195
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 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 */
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 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 */
165int 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
179void 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
215void 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}