1 // SPDX-License-Identifier: GPL-2.0
3 * drivers/power/process.c - Functions for starting/stopping processes on
6 * Originally from swsusp.
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>
24 * Timeout for stopping processes
26 unsigned int __read_mostly freeze_timeout_msecs = 20 * MSEC_PER_SEC;
28 static int try_to_freeze_tasks(bool user_only)
30 struct task_struct *g, *p;
31 unsigned long end_time;
34 ktime_t start, end, elapsed;
35 unsigned int elapsed_msecs;
37 int sleep_usecs = USEC_PER_MSEC;
39 start = ktime_get_boottime();
41 end_time = jiffies + msecs_to_jiffies(freeze_timeout_msecs);
44 freeze_workqueues_begin();
48 read_lock(&tasklist_lock);
49 for_each_process_thread(g, p) {
50 if (p == current || !freeze_task(p))
53 if (!freezer_should_skip(p))
56 read_unlock(&tasklist_lock);
59 wq_busy = freeze_workqueues_busy();
63 if (!todo || time_after(jiffies, end_time))
66 if (pm_wakeup_pending()) {
72 * We need to retry, but first give the freezing tasks some
73 * time to enter the refrigerator. Start with an initial
74 * 1 ms sleep followed by exponential backoff until 8 ms.
76 usleep_range(sleep_usecs / 2, sleep_usecs);
77 if (sleep_usecs < 8 * USEC_PER_MSEC)
81 end = ktime_get_boottime();
82 elapsed = ktime_sub(end, start);
83 elapsed_msecs = ktime_to_ms(elapsed);
87 pr_err("Freezing of tasks %s after %d.%03d seconds "
88 "(%d tasks refusing to freeze, wq_busy=%d):\n",
89 wakeup ? "aborted" : "failed",
90 elapsed_msecs / 1000, elapsed_msecs % 1000,
91 todo - wq_busy, wq_busy);
94 show_all_workqueues();
96 if (!wakeup || pm_debug_messages_on) {
97 read_lock(&tasklist_lock);
98 for_each_process_thread(g, p) {
99 if (p != current && !freezer_should_skip(p)
100 && freezing(p) && !frozen(p))
103 read_unlock(&tasklist_lock);
106 pr_cont("(elapsed %d.%03d seconds) ", elapsed_msecs / 1000,
107 elapsed_msecs % 1000);
110 return todo ? -EBUSY : 0;
114 * freeze_processes - Signal user space processes to enter the refrigerator.
115 * The current thread will not be frozen. The same process that calls
116 * freeze_processes must later call thaw_processes.
118 * On success, returns 0. On failure, -errno and system is fully thawed.
120 int freeze_processes(void)
124 error = __usermodehelper_disable(UMH_FREEZING);
128 /* Make sure this task doesn't get frozen */
129 current->flags |= PF_SUSPEND_TASK;
132 atomic_inc(&system_freezing_cnt);
135 pr_info("Freezing user space processes ... ");
137 error = try_to_freeze_tasks(true);
139 __usermodehelper_set_disable_depth(UMH_DISABLED);
146 * Now that the whole userspace is frozen we need to disable
147 * the OOM killer to disallow any further interference with
148 * killable tasks. There is no guarantee oom victims will
149 * ever reach a point they go away we have to wait with a timeout.
151 if (!error && !oom_killer_disable(msecs_to_jiffies(freeze_timeout_msecs)))
160 * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
162 * On success, returns 0. On failure, -errno and only the kernel threads are
163 * thawed, so as to give a chance to the caller to do additional cleanups
164 * (if any) before thawing the userspace tasks. So, it is the responsibility
165 * of the caller to thaw the userspace tasks, when the time is right.
167 int freeze_kernel_threads(void)
171 pr_info("Freezing remaining freezable tasks ... ");
173 pm_nosig_freezing = true;
174 error = try_to_freeze_tasks(false);
182 thaw_kernel_threads();
186 void thaw_processes(void)
188 struct task_struct *g, *p;
189 struct task_struct *curr = current;
191 trace_suspend_resume(TPS("thaw_processes"), 0, true);
193 atomic_dec(&system_freezing_cnt);
195 pm_nosig_freezing = false;
199 pr_info("Restarting tasks ... ");
201 __usermodehelper_set_disable_depth(UMH_FREEZING);
204 cpuset_wait_for_hotplug();
206 read_lock(&tasklist_lock);
207 for_each_process_thread(g, p) {
208 /* No other threads should have PF_SUSPEND_TASK set */
209 WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK));
212 read_unlock(&tasklist_lock);
214 WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
215 curr->flags &= ~PF_SUSPEND_TASK;
217 usermodehelper_enable();
221 trace_suspend_resume(TPS("thaw_processes"), 0, false);
224 void thaw_kernel_threads(void)
226 struct task_struct *g, *p;
228 pm_nosig_freezing = false;
229 pr_info("Restarting kernel threads ... ");
233 read_lock(&tasklist_lock);
234 for_each_process_thread(g, p) {
235 if (p->flags & PF_KTHREAD)
238 read_unlock(&tasklist_lock);