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/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>
23 * Timeout for stopping processes
25 unsigned int __read_mostly freeze_timeout_msecs = 20 * MSEC_PER_SEC;
27 static int try_to_freeze_tasks(bool user_only)
29 struct task_struct *g, *p;
30 unsigned long end_time;
33 ktime_t start, end, elapsed;
34 unsigned int elapsed_msecs;
36 int sleep_usecs = USEC_PER_MSEC;
38 start = ktime_get_boottime();
40 end_time = jiffies + msecs_to_jiffies(freeze_timeout_msecs);
43 freeze_workqueues_begin();
47 read_lock(&tasklist_lock);
48 for_each_process_thread(g, p) {
49 if (p == current || !freeze_task(p))
52 if (!freezer_should_skip(p))
55 read_unlock(&tasklist_lock);
58 wq_busy = freeze_workqueues_busy();
62 if (!todo || time_after(jiffies, end_time))
65 if (pm_wakeup_pending()) {
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.
75 usleep_range(sleep_usecs / 2, sleep_usecs);
76 if (sleep_usecs < 8 * USEC_PER_MSEC)
80 end = ktime_get_boottime();
81 elapsed = ktime_sub(end, start);
82 elapsed_msecs = ktime_to_ms(elapsed);
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);
93 show_workqueue_state();
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))
102 read_unlock(&tasklist_lock);
105 pr_cont("(elapsed %d.%03d seconds) ", elapsed_msecs / 1000,
106 elapsed_msecs % 1000);
109 return todo ? -EBUSY : 0;
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.
117 * On success, returns 0. On failure, -errno and system is fully thawed.
119 int freeze_processes(void)
123 error = __usermodehelper_disable(UMH_FREEZING);
127 /* Make sure this task doesn't get frozen */
128 current->flags |= PF_SUSPEND_TASK;
131 atomic_inc(&system_freezing_cnt);
134 pr_info("Freezing user space processes ... ");
136 error = try_to_freeze_tasks(true);
138 __usermodehelper_set_disable_depth(UMH_DISABLED);
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.
150 if (!error && !oom_killer_disable(msecs_to_jiffies(freeze_timeout_msecs)))
159 * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
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.
166 int freeze_kernel_threads(void)
170 pr_info("Freezing remaining freezable tasks ... ");
172 pm_nosig_freezing = true;
173 error = try_to_freeze_tasks(false);
181 thaw_kernel_threads();
185 void thaw_processes(void)
187 struct task_struct *g, *p;
188 struct task_struct *curr = current;
190 trace_suspend_resume(TPS("thaw_processes"), 0, true);
192 atomic_dec(&system_freezing_cnt);
194 pm_nosig_freezing = false;
198 pr_info("Restarting tasks ... ");
200 __usermodehelper_set_disable_depth(UMH_FREEZING);
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));
209 read_unlock(&tasklist_lock);
211 WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
212 curr->flags &= ~PF_SUSPEND_TASK;
214 usermodehelper_enable();
218 trace_suspend_resume(TPS("thaw_processes"), 0, false);
221 void thaw_kernel_threads(void)
223 struct task_struct *g, *p;
225 pm_nosig_freezing = false;
226 pr_info("Restarting kernel threads ... ");
230 read_lock(&tasklist_lock);
231 for_each_process_thread(g, p) {
232 if (p->flags & (PF_KTHREAD | PF_WQ_WORKER))
235 read_unlock(&tasklist_lock);