// SPDX-License-Identifier: GPL-2.0
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/*
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* drivers/power/process.c - Functions for starting/stopping processes on
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* suspend transitions.
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*
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* Originally from swsusp.
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*/
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#undef DEBUG
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#include <linux/interrupt.h>
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#include <linux/oom.h>
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#include <linux/suspend.h>
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#include <linux/module.h>
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#include <linux/sched/debug.h>
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#include <linux/sched/task.h>
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#include <linux/syscalls.h>
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#include <linux/freezer.h>
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#include <linux/delay.h>
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#include <linux/workqueue.h>
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#include <linux/kmod.h>
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#include <trace/events/power.h>
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#include <linux/cpuset.h>
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/*
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* Timeout for stopping processes
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*/
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unsigned int __read_mostly freeze_timeout_msecs = 20 * MSEC_PER_SEC;
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static int try_to_freeze_tasks(bool user_only)
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{
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struct task_struct *g, *p;
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unsigned long end_time;
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unsigned int todo;
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bool wq_busy = false;
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ktime_t start, end, elapsed;
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unsigned int elapsed_msecs;
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bool wakeup = false;
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int sleep_usecs = USEC_PER_MSEC;
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start = ktime_get_boottime();
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end_time = jiffies + msecs_to_jiffies(freeze_timeout_msecs);
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if (!user_only)
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freeze_workqueues_begin();
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while (true) {
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todo = 0;
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read_lock(&tasklist_lock);
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for_each_process_thread(g, p) {
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if (p == current || !freeze_task(p))
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continue;
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if (!freezer_should_skip(p))
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todo++;
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}
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read_unlock(&tasklist_lock);
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if (!user_only) {
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wq_busy = freeze_workqueues_busy();
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todo += wq_busy;
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}
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if (!todo || time_after(jiffies, end_time))
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break;
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if (pm_wakeup_pending()) {
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wakeup = true;
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break;
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}
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/*
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* We need to retry, but first give the freezing tasks some
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* time to enter the refrigerator. Start with an initial
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* 1 ms sleep followed by exponential backoff until 8 ms.
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*/
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usleep_range(sleep_usecs / 2, sleep_usecs);
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if (sleep_usecs < 8 * USEC_PER_MSEC)
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sleep_usecs *= 2;
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}
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end = ktime_get_boottime();
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elapsed = ktime_sub(end, start);
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elapsed_msecs = ktime_to_ms(elapsed);
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if (wakeup) {
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pr_cont("\n");
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pr_err("Freezing of tasks aborted after %d.%03d seconds",
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elapsed_msecs / 1000, elapsed_msecs % 1000);
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} else if (todo) {
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pr_cont("\n");
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pr_err("Freezing of tasks failed after %d.%03d seconds"
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" (%d tasks refusing to freeze, wq_busy=%d):\n",
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elapsed_msecs / 1000, elapsed_msecs % 1000,
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todo - wq_busy, wq_busy);
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if (wq_busy)
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show_workqueue_state();
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read_lock(&tasklist_lock);
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for_each_process_thread(g, p) {
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if (p != current && !freezer_should_skip(p)
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&& freezing(p) && !frozen(p))
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sched_show_task(p);
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}
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read_unlock(&tasklist_lock);
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} else {
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pr_cont("(elapsed %d.%03d seconds) ", elapsed_msecs / 1000,
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elapsed_msecs % 1000);
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}
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return todo ? -EBUSY : 0;
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}
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/**
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* freeze_processes - Signal user space processes to enter the refrigerator.
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* The current thread will not be frozen. The same process that calls
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* freeze_processes must later call thaw_processes.
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*
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* On success, returns 0. On failure, -errno and system is fully thawed.
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*/
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int freeze_processes(void)
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{
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int error;
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error = __usermodehelper_disable(UMH_FREEZING);
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if (error)
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return error;
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/* Make sure this task doesn't get frozen */
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current->flags |= PF_SUSPEND_TASK;
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if (!pm_freezing)
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atomic_inc(&system_freezing_cnt);
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pm_wakeup_clear(true);
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pr_info("Freezing user space processes ... ");
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pm_freezing = true;
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error = try_to_freeze_tasks(true);
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if (!error) {
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__usermodehelper_set_disable_depth(UMH_DISABLED);
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pr_cont("done.");
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}
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pr_cont("\n");
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BUG_ON(in_atomic());
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/*
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* Now that the whole userspace is frozen we need to disbale
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* the OOM killer to disallow any further interference with
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* killable tasks. There is no guarantee oom victims will
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* ever reach a point they go away we have to wait with a timeout.
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*/
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if (!error && !oom_killer_disable(msecs_to_jiffies(freeze_timeout_msecs)))
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error = -EBUSY;
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if (error)
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thaw_processes();
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return error;
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}
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/**
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* freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
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*
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* On success, returns 0. On failure, -errno and only the kernel threads are
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* thawed, so as to give a chance to the caller to do additional cleanups
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* (if any) before thawing the userspace tasks. So, it is the responsibility
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* of the caller to thaw the userspace tasks, when the time is right.
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*/
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int freeze_kernel_threads(void)
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{
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int error;
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pr_info("Freezing remaining freezable tasks ... ");
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pm_nosig_freezing = true;
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error = try_to_freeze_tasks(false);
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if (!error)
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pr_cont("done.");
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pr_cont("\n");
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BUG_ON(in_atomic());
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if (error)
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thaw_kernel_threads();
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return error;
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}
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void thaw_processes(void)
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{
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struct task_struct *g, *p;
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struct task_struct *curr = current;
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trace_suspend_resume(TPS("thaw_processes"), 0, true);
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if (pm_freezing)
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atomic_dec(&system_freezing_cnt);
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pm_freezing = false;
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pm_nosig_freezing = false;
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oom_killer_enable();
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pr_info("Restarting tasks ... ");
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__usermodehelper_set_disable_depth(UMH_FREEZING);
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thaw_workqueues();
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cpuset_wait_for_hotplug();
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read_lock(&tasklist_lock);
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for_each_process_thread(g, p) {
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/* No other threads should have PF_SUSPEND_TASK set */
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WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK));
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__thaw_task(p);
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}
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read_unlock(&tasklist_lock);
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WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
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curr->flags &= ~PF_SUSPEND_TASK;
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usermodehelper_enable();
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schedule();
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pr_cont("done.\n");
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trace_suspend_resume(TPS("thaw_processes"), 0, false);
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}
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void thaw_kernel_threads(void)
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{
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struct task_struct *g, *p;
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pm_nosig_freezing = false;
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pr_info("Restarting kernel threads ... ");
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thaw_workqueues();
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read_lock(&tasklist_lock);
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for_each_process_thread(g, p) {
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if (p->flags & (PF_KTHREAD | PF_WQ_WORKER))
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__thaw_task(p);
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}
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read_unlock(&tasklist_lock);
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schedule();
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pr_cont("done.\n");
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}
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