2 * drivers/power/process.c - Functions for starting/stopping processes on
5 * Originally from swsusp.
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 #include <linux/cpuset.h>
26 * Timeout for stopping processes
28 unsigned int __read_mostly freeze_timeout_msecs = 20 * MSEC_PER_SEC;
30 static int try_to_freeze_tasks(bool user_only)
32 struct task_struct *g, *p;
33 unsigned long end_time;
36 ktime_t start, end, elapsed;
37 unsigned int elapsed_msecs;
39 int sleep_usecs = USEC_PER_MSEC;
41 start = ktime_get_boottime();
43 end_time = jiffies + msecs_to_jiffies(freeze_timeout_msecs);
46 freeze_workqueues_begin();
50 read_lock(&tasklist_lock);
51 for_each_process_thread(g, p) {
52 if (p == current || !freeze_task(p))
55 if (!freezer_should_skip(p))
58 read_unlock(&tasklist_lock);
61 wq_busy = freeze_workqueues_busy();
65 if (!todo || time_after(jiffies, end_time))
68 if (pm_wakeup_pending()) {
74 * We need to retry, but first give the freezing tasks some
75 * time to enter the refrigerator. Start with an initial
76 * 1 ms sleep followed by exponential backoff until 8 ms.
78 usleep_range(sleep_usecs / 2, sleep_usecs);
79 if (sleep_usecs < 8 * USEC_PER_MSEC)
83 end = ktime_get_boottime();
84 elapsed = ktime_sub(end, start);
85 elapsed_msecs = ktime_to_ms(elapsed);
89 pr_err("Freezing of tasks %s after %d.%03d seconds "
90 "(%d tasks refusing to freeze, wq_busy=%d):\n",
91 wakeup ? "aborted" : "failed",
92 elapsed_msecs / 1000, elapsed_msecs % 1000,
93 todo - wq_busy, wq_busy);
96 show_workqueue_state();
99 read_lock(&tasklist_lock);
100 for_each_process_thread(g, p) {
101 if (p != current && !freezer_should_skip(p)
102 && freezing(p) && !frozen(p))
105 read_unlock(&tasklist_lock);
108 pr_cont("(elapsed %d.%03d seconds) ", elapsed_msecs / 1000,
109 elapsed_msecs % 1000);
112 return todo ? -EBUSY : 0;
116 * freeze_processes - Signal user space processes to enter the refrigerator.
117 * The current thread will not be frozen. The same process that calls
118 * freeze_processes must later call thaw_processes.
120 * On success, returns 0. On failure, -errno and system is fully thawed.
122 int freeze_processes(void)
126 error = __usermodehelper_disable(UMH_FREEZING);
130 /* Make sure this task doesn't get frozen */
131 current->flags |= PF_SUSPEND_TASK;
134 atomic_inc(&system_freezing_cnt);
136 pm_wakeup_clear(true);
137 pr_info("Freezing user space processes ... ");
139 error = try_to_freeze_tasks(true);
141 __usermodehelper_set_disable_depth(UMH_DISABLED);
148 * Now that the whole userspace is frozen we need to disbale
149 * the OOM killer to disallow any further interference with
150 * killable tasks. There is no guarantee oom victims will
151 * ever reach a point they go away we have to wait with a timeout.
153 if (!error && !oom_killer_disable(msecs_to_jiffies(freeze_timeout_msecs)))
162 * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
164 * On success, returns 0. On failure, -errno and only the kernel threads are
165 * thawed, so as to give a chance to the caller to do additional cleanups
166 * (if any) before thawing the userspace tasks. So, it is the responsibility
167 * of the caller to thaw the userspace tasks, when the time is right.
169 int freeze_kernel_threads(void)
173 pr_info("Freezing remaining freezable tasks ... ");
175 pm_nosig_freezing = true;
176 error = try_to_freeze_tasks(false);
184 thaw_kernel_threads();
188 void thaw_processes(void)
190 struct task_struct *g, *p;
191 struct task_struct *curr = current;
193 trace_suspend_resume(TPS("thaw_processes"), 0, true);
195 atomic_dec(&system_freezing_cnt);
197 pm_nosig_freezing = false;
201 pr_info("Restarting tasks ... ");
203 __usermodehelper_set_disable_depth(UMH_FREEZING);
206 cpuset_wait_for_hotplug();
208 read_lock(&tasklist_lock);
209 for_each_process_thread(g, p) {
210 /* No other threads should have PF_SUSPEND_TASK set */
211 WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK));
214 read_unlock(&tasklist_lock);
216 WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
217 curr->flags &= ~PF_SUSPEND_TASK;
219 usermodehelper_enable();
223 trace_suspend_resume(TPS("thaw_processes"), 0, false);
226 void thaw_kernel_threads(void)
228 struct task_struct *g, *p;
230 pm_nosig_freezing = false;
231 pr_info("Restarting kernel threads ... ");
235 read_lock(&tasklist_lock);
236 for_each_process_thread(g, p) {
237 if (p->flags & (PF_KTHREAD | PF_WQ_WORKER))
240 read_unlock(&tasklist_lock);