kernel/power/process.c

   1 /*
   2  * drivers/power/process.c - Functions for starting/stopping processes on
   3  *                           suspend transitions.
   4  *
   5  * Originally from swsusp.
   6  */
   7
   8
   9 #undef DEBUG
  10
  11 #include <linux/smp_lock.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/suspend.h>
  14 #include <linux/module.h>
  15
  16 /*
  17  * Timeout for stopping processes
  18  */
  19 #define TIMEOUT (6 * HZ)
  20
  21
  22 static inline int freezeable(struct task_struct * p)
  23 {
  24         if ((p == current) ||
  25             (p->flags & PF_NOFREEZE) ||
  26             (p->exit_state == EXIT_ZOMBIE) ||
  27             (p->exit_state == EXIT_DEAD) ||
  28             (p->state == TASK_STOPPED) ||
  29             (p->state == TASK_TRACED))
  30                 return 0;
  31         return 1;
  32 }
  33
  34 /* Refrigerator is place where frozen processes are stored :-). */
  35 void refrigerator(unsigned long flag)
  36 {
  37         /* Hmm, should we be allowed to suspend when there are realtime
  38            processes around? */
  39         long save;
  40         save = current->state;
  41         current->state = TASK_UNINTERRUPTIBLE;
  42         pr_debug("%s entered refrigerator\n", current->comm);
  43         printk("=");
  44         current->flags &= ~PF_FREEZE;
  45
  46         spin_lock_irq(&current->sighand->siglock);
  47         recalc_sigpending(); /* We sent fake signal, clean it up */
  48         spin_unlock_irq(&current->sighand->siglock);
  49
  50         current->flags |= PF_FROZEN;
  51         while (current->flags & PF_FROZEN)
  52                 schedule();
  53         pr_debug("%s left refrigerator\n", current->comm);
  54         current->state = save;
  55 }
  56
  57 /* 0 = success, else # of processes that we failed to stop */
  58 int freeze_processes(void)
  59 {
  60        int todo;
  61        unsigned long start_time;
  62         struct task_struct *g, *p;
  63
  64         printk( "Stopping tasks: " );
  65         start_time = jiffies;
  66         do {
  67                 todo = 0;
  68                 read_lock(&tasklist_lock);
  69                 do_each_thread(g, p) {
  70                         unsigned long flags;
  71                         if (!freezeable(p))
  72                                 continue;
  73                         if ((p->flags & PF_FROZEN) ||
  74                             (p->state == TASK_TRACED) ||
  75                             (p->state == TASK_STOPPED))
  76                                 continue;
  77
  78                         /* FIXME: smp problem here: we may not access other process' flags
  79                            without locking */
  80                         p->flags |= PF_FREEZE;
  81                         spin_lock_irqsave(&p->sighand->siglock, flags);
  82                         signal_wake_up(p, 0);
  83                         spin_unlock_irqrestore(&p->sighand->siglock, flags);
  84                         todo++;
  85                 } while_each_thread(g, p);
  86                 read_unlock(&tasklist_lock);
  87                 yield();                        /* Yield is okay here */
  88                 if (time_after(jiffies, start_time + TIMEOUT)) {
  89                         printk( "\n" );
  90                         printk(KERN_ERR " stopping tasks failed (%d tasks remaining)\n", todo );
  91                         return todo;
  92                 }
  93         } while(todo);
  94
  95         printk( "|\n" );
  96         BUG_ON(in_atomic());
  97         return 0;
  98 }
  99
 100 void thaw_processes(void)
 101 {
 102         struct task_struct *g, *p;
 103
 104         printk( "Restarting tasks..." );
 105         read_lock(&tasklist_lock);
 106         do_each_thread(g, p) {
 107                 if (!freezeable(p))
 108                         continue;
 109                 if (p->flags & PF_FROZEN) {
 110                         p->flags &= ~PF_FROZEN;
 111                         wake_up_process(p);
 112                 } else
 113                         printk(KERN_INFO " Strange, %s not stopped\n", p->comm );
 114         } while_each_thread(g, p);
 115
 116         read_unlock(&tasklist_lock);
 117         schedule();
 118         printk( " done\n" );
 119 }
 120
 121 EXPORT_SYMBOL(refrigerator);