/* * 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/syscalls.h>#include <linux/freezer.h>#include <linux/delay.h>#include <linux/workqueue.h>#include <linux/kmod.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;	struct timeval start, end;	u64 elapsed_msecs64;	unsigned int elapsed_msecs;	bool wakeup = false;	int sleep_usecs = USEC_PER_MSEC; 	do_gettimeofday(&start); 	end_time = jiffies + msecs_to_jiffies(freeze_timeout_msecs); 	if (!user_only)		freeze_workqueues_begin(); 	while (true) {		todo = 0;		read_lock(&tasklist_lock);		do_each_thread(g, p) {			if (p == current || !freeze_task(p))				continue; 			if (!freezer_should_skip(p))				todo++;		} while_each_thread(g, p);		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;	} 	do_gettimeofday(&end);	elapsed_msecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);	do_div(elapsed_msecs64, NSEC_PER_MSEC);	elapsed_msecs = elapsed_msecs64; 	if (todo) {		printk("\n");		printk(KERN_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 (!wakeup) {			read_lock(&tasklist_lock);			do_each_thread(g, p) {				if (p != current && !freezer_should_skip(p)				    && freezing(p) && !frozen(p))					sched_show_task(p);			} while_each_thread(g, p);			read_unlock(&tasklist_lock);		}	} else {		printk("(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); 	printk("Freezing user space processes ... ");	pm_freezing = true;	error = try_to_freeze_tasks(true);	if (!error) {		printk("done.");		__usermodehelper_set_disable_depth(UMH_DISABLED);		oom_killer_disable();	}	printk("\n");	BUG_ON(in_atomic()); 	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; 	printk("Freezing remaining freezable tasks ... ");	pm_nosig_freezing = true;	error = try_to_freeze_tasks(false);	if (!error)		printk("done."); 	printk("\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; 	if (pm_freezing)		atomic_dec(&system_freezing_cnt);	pm_freezing = false;	pm_nosig_freezing = false; 	oom_killer_enable(); 	printk("Restarting tasks ... "); 	thaw_workqueues(); 	read_lock(&tasklist_lock);	do_each_thread(g, p) {		/* No other threads should have PF_SUSPEND_TASK set */		WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK));		__thaw_task(p);	} while_each_thread(g, p);	read_unlock(&tasklist_lock); 	WARN_ON(!(curr->flags & PF_SUSPEND_TASK));	curr->flags &= ~PF_SUSPEND_TASK; 	usermodehelper_enable(); 	schedule();	printk("done.\n");} void thaw_kernel_threads(void){	struct task_struct *g, *p; 	pm_nosig_freezing = false;	printk("Restarting kernel threads ... "); 	thaw_workqueues(); 	read_lock(&tasklist_lock);	do_each_thread(g, p) {		if (p->flags & (PF_KTHREAD | PF_WQ_WORKER))			__thaw_task(p);	} while_each_thread(g, p);	read_unlock(&tasklist_lock); 	schedule();	printk("done.\n");}