xref: /openbmc/linux/kernel/power/process.c (revision de2bdb3d)
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  */
25 unsigned int __read_mostly freeze_timeout_msecs = 20 * MSEC_PER_SEC;
26 
27 static 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 	ktime_t start, end, elapsed;
34 	unsigned int elapsed_msecs;
35 	bool wakeup = false;
36 	int sleep_usecs = USEC_PER_MSEC;
37 
38 	start = ktime_get_boottime();
39 
40 	end_time = jiffies + msecs_to_jiffies(freeze_timeout_msecs);
41 
42 	if (!user_only)
43 		freeze_workqueues_begin();
44 
45 	while (true) {
46 		todo = 0;
47 		read_lock(&tasklist_lock);
48 		for_each_process_thread(g, p) {
49 			if (p == current || !freeze_task(p))
50 				continue;
51 
52 			if (!freezer_should_skip(p))
53 				todo++;
54 		}
55 		read_unlock(&tasklist_lock);
56 
57 		if (!user_only) {
58 			wq_busy = freeze_workqueues_busy();
59 			todo += wq_busy;
60 		}
61 
62 		if (!todo || time_after(jiffies, end_time))
63 			break;
64 
65 		if (pm_wakeup_pending()) {
66 			wakeup = true;
67 			break;
68 		}
69 
70 		/*
71 		 * We need to retry, but first give the freezing tasks some
72 		 * time to enter the refrigerator.  Start with an initial
73 		 * 1 ms sleep followed by exponential backoff until 8 ms.
74 		 */
75 		usleep_range(sleep_usecs / 2, sleep_usecs);
76 		if (sleep_usecs < 8 * USEC_PER_MSEC)
77 			sleep_usecs *= 2;
78 	}
79 
80 	end = ktime_get_boottime();
81 	elapsed = ktime_sub(end, start);
82 	elapsed_msecs = ktime_to_ms(elapsed);
83 
84 	if (todo) {
85 		pr_cont("\n");
86 		pr_err("Freezing of tasks %s after %d.%03d seconds "
87 		       "(%d tasks refusing to freeze, wq_busy=%d):\n",
88 		       wakeup ? "aborted" : "failed",
89 		       elapsed_msecs / 1000, elapsed_msecs % 1000,
90 		       todo - wq_busy, wq_busy);
91 
92 		if (wq_busy)
93 			show_workqueue_state();
94 
95 		if (!wakeup) {
96 			read_lock(&tasklist_lock);
97 			for_each_process_thread(g, p) {
98 				if (p != current && !freezer_should_skip(p)
99 				    && freezing(p) && !frozen(p))
100 					sched_show_task(p);
101 			}
102 			read_unlock(&tasklist_lock);
103 		}
104 	} else {
105 		pr_cont("(elapsed %d.%03d seconds) ", elapsed_msecs / 1000,
106 			elapsed_msecs % 1000);
107 	}
108 
109 	return todo ? -EBUSY : 0;
110 }
111 
112 /**
113  * freeze_processes - Signal user space processes to enter the refrigerator.
114  * The current thread will not be frozen.  The same process that calls
115  * freeze_processes must later call thaw_processes.
116  *
117  * On success, returns 0.  On failure, -errno and system is fully thawed.
118  */
119 int freeze_processes(void)
120 {
121 	int error;
122 
123 	error = __usermodehelper_disable(UMH_FREEZING);
124 	if (error)
125 		return error;
126 
127 	/* Make sure this task doesn't get frozen */
128 	current->flags |= PF_SUSPEND_TASK;
129 
130 	if (!pm_freezing)
131 		atomic_inc(&system_freezing_cnt);
132 
133 	pm_wakeup_clear();
134 	pr_info("Freezing user space processes ... ");
135 	pm_freezing = true;
136 	error = try_to_freeze_tasks(true);
137 	if (!error) {
138 		__usermodehelper_set_disable_depth(UMH_DISABLED);
139 		pr_cont("done.");
140 	}
141 	pr_cont("\n");
142 	BUG_ON(in_atomic());
143 
144 	/*
145 	 * Now that the whole userspace is frozen we need to disbale
146 	 * the OOM killer to disallow any further interference with
147 	 * killable tasks. There is no guarantee oom victims will
148 	 * ever reach a point they go away we have to wait with a timeout.
149 	 */
150 	if (!error && !oom_killer_disable(msecs_to_jiffies(freeze_timeout_msecs)))
151 		error = -EBUSY;
152 
153 	if (error)
154 		thaw_processes();
155 	return error;
156 }
157 
158 /**
159  * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
160  *
161  * On success, returns 0.  On failure, -errno and only the kernel threads are
162  * thawed, so as to give a chance to the caller to do additional cleanups
163  * (if any) before thawing the userspace tasks. So, it is the responsibility
164  * of the caller to thaw the userspace tasks, when the time is right.
165  */
166 int freeze_kernel_threads(void)
167 {
168 	int error;
169 
170 	pr_info("Freezing remaining freezable tasks ... ");
171 
172 	pm_nosig_freezing = true;
173 	error = try_to_freeze_tasks(false);
174 	if (!error)
175 		pr_cont("done.");
176 
177 	pr_cont("\n");
178 	BUG_ON(in_atomic());
179 
180 	if (error)
181 		thaw_kernel_threads();
182 	return error;
183 }
184 
185 void thaw_processes(void)
186 {
187 	struct task_struct *g, *p;
188 	struct task_struct *curr = current;
189 
190 	trace_suspend_resume(TPS("thaw_processes"), 0, true);
191 	if (pm_freezing)
192 		atomic_dec(&system_freezing_cnt);
193 	pm_freezing = false;
194 	pm_nosig_freezing = false;
195 
196 	oom_killer_enable();
197 
198 	pr_info("Restarting tasks ... ");
199 
200 	__usermodehelper_set_disable_depth(UMH_FREEZING);
201 	thaw_workqueues();
202 
203 	read_lock(&tasklist_lock);
204 	for_each_process_thread(g, p) {
205 		/* No other threads should have PF_SUSPEND_TASK set */
206 		WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK));
207 		__thaw_task(p);
208 	}
209 	read_unlock(&tasklist_lock);
210 
211 	WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
212 	curr->flags &= ~PF_SUSPEND_TASK;
213 
214 	usermodehelper_enable();
215 
216 	schedule();
217 	pr_cont("done.\n");
218 	trace_suspend_resume(TPS("thaw_processes"), 0, false);
219 }
220 
221 void thaw_kernel_threads(void)
222 {
223 	struct task_struct *g, *p;
224 
225 	pm_nosig_freezing = false;
226 	pr_info("Restarting kernel threads ... ");
227 
228 	thaw_workqueues();
229 
230 	read_lock(&tasklist_lock);
231 	for_each_process_thread(g, p) {
232 		if (p->flags & (PF_KTHREAD | PF_WQ_WORKER))
233 			__thaw_task(p);
234 	}
235 	read_unlock(&tasklist_lock);
236 
237 	schedule();
238 	pr_cont("done.\n");
239 }
240