Line data Source code
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 0 : static int try_to_freeze_tasks(bool user_only)
29 : {
30 0 : 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 0 : bool wq_busy = false;
36 : ktime_t start, end, elapsed;
37 : unsigned int elapsed_msecs;
38 0 : bool wakeup = false;
39 0 : int sleep_usecs = USEC_PER_MSEC;
40 :
41 0 : pr_info("Freezing %s\n", what);
42 :
43 0 : start = ktime_get_boottime();
44 :
45 0 : end_time = jiffies + msecs_to_jiffies(freeze_timeout_msecs);
46 :
47 0 : if (!user_only)
48 0 : freeze_workqueues_begin();
49 :
50 : while (true) {
51 0 : todo = 0;
52 0 : read_lock(&tasklist_lock);
53 0 : for_each_process_thread(g, p) {
54 0 : if (p == current || !freeze_task(p))
55 0 : continue;
56 :
57 0 : todo++;
58 : }
59 0 : read_unlock(&tasklist_lock);
60 :
61 0 : if (!user_only) {
62 0 : wq_busy = freeze_workqueues_busy();
63 0 : todo += wq_busy;
64 : }
65 :
66 0 : if (!todo || time_after(jiffies, end_time))
67 : break;
68 :
69 0 : 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 0 : usleep_range(sleep_usecs / 2, sleep_usecs);
80 0 : if (sleep_usecs < 8 * USEC_PER_MSEC)
81 0 : sleep_usecs *= 2;
82 : }
83 :
84 0 : end = ktime_get_boottime();
85 0 : elapsed = ktime_sub(end, start);
86 0 : elapsed_msecs = ktime_to_ms(elapsed);
87 :
88 0 : if (todo) {
89 0 : 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 0 : if (wq_busy)
96 0 : show_freezable_workqueues();
97 :
98 0 : if (!wakeup || pm_debug_messages_on) {
99 0 : read_lock(&tasklist_lock);
100 0 : for_each_process_thread(g, p) {
101 0 : if (p != current && freezing(p) && !frozen(p))
102 0 : sched_show_task(p);
103 : }
104 0 : read_unlock(&tasklist_lock);
105 : }
106 : } else {
107 0 : pr_info("Freezing %s completed (elapsed %d.%03d seconds)\n",
108 : what, elapsed_msecs / 1000, elapsed_msecs % 1000);
109 : }
110 :
111 0 : 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 0 : int freeze_processes(void)
122 : {
123 : int error;
124 :
125 0 : error = __usermodehelper_disable(UMH_FREEZING);
126 0 : if (error)
127 : return error;
128 :
129 : /* Make sure this task doesn't get frozen */
130 0 : current->flags |= PF_SUSPEND_TASK;
131 :
132 0 : if (!pm_freezing)
133 0 : static_branch_inc(&freezer_active);
134 :
135 0 : pm_wakeup_clear(0);
136 0 : pm_freezing = true;
137 0 : error = try_to_freeze_tasks(true);
138 0 : if (!error)
139 0 : __usermodehelper_set_disable_depth(UMH_DISABLED);
140 :
141 0 : 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 0 : if (!error && !oom_killer_disable(msecs_to_jiffies(freeze_timeout_msecs)))
150 0 : error = -EBUSY;
151 :
152 0 : if (error)
153 0 : 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 0 : int freeze_kernel_threads(void)
166 : {
167 : int error;
168 :
169 0 : pm_nosig_freezing = true;
170 0 : error = try_to_freeze_tasks(false);
171 :
172 0 : BUG_ON(in_atomic());
173 :
174 0 : if (error)
175 0 : thaw_kernel_threads();
176 0 : return error;
177 : }
178 :
179 0 : void thaw_processes(void)
180 : {
181 : struct task_struct *g, *p;
182 0 : struct task_struct *curr = current;
183 :
184 0 : trace_suspend_resume(TPS("thaw_processes"), 0, true);
185 0 : if (pm_freezing)
186 0 : static_branch_dec(&freezer_active);
187 0 : pm_freezing = false;
188 0 : pm_nosig_freezing = false;
189 :
190 0 : oom_killer_enable();
191 :
192 0 : pr_info("Restarting tasks ... ");
193 :
194 0 : __usermodehelper_set_disable_depth(UMH_FREEZING);
195 0 : thaw_workqueues();
196 :
197 : cpuset_wait_for_hotplug();
198 :
199 0 : read_lock(&tasklist_lock);
200 0 : for_each_process_thread(g, p) {
201 : /* No other threads should have PF_SUSPEND_TASK set */
202 0 : WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK));
203 0 : __thaw_task(p);
204 : }
205 0 : read_unlock(&tasklist_lock);
206 :
207 0 : WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
208 0 : curr->flags &= ~PF_SUSPEND_TASK;
209 :
210 : usermodehelper_enable();
211 :
212 0 : schedule();
213 0 : pr_cont("done.\n");
214 0 : trace_suspend_resume(TPS("thaw_processes"), 0, false);
215 0 : }
216 :
217 0 : void thaw_kernel_threads(void)
218 : {
219 : struct task_struct *g, *p;
220 :
221 0 : pm_nosig_freezing = false;
222 0 : pr_info("Restarting kernel threads ... ");
223 :
224 0 : thaw_workqueues();
225 :
226 0 : read_lock(&tasklist_lock);
227 0 : for_each_process_thread(g, p) {
228 0 : if (p->flags & PF_KTHREAD)
229 0 : __thaw_task(p);
230 : }
231 0 : read_unlock(&tasklist_lock);
232 :
233 0 : schedule();
234 0 : pr_cont("done.\n");
235 0 : }
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