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