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 #include <linux/syscalls.h>
  16
  17 /*
  18  * Timeout for stopping processes
  19  */
  20 #define TIMEOUT (20 * HZ)
  21
  22
  23 static inline int freezeable(struct task_struct * p)
  24 {
  25         if ((p == current) ||
  26             (p->flags & PF_NOFREEZE) ||
  27             (p->exit_state == EXIT_ZOMBIE) ||
  28             (p->exit_state == EXIT_DEAD) ||
  29             (p->state == TASK_STOPPED))
  30                 return 0;
  31         return 1;
  32 }
  33
  34 /* Refrigerator is place where frozen processes are stored :-). */
  35 void refrigerator(void)
  36 {
  37         /* Hmm, should we be allowed to suspend when there are realtime
  38            processes around? */
  39         long save;
  40         save = current->state;
  41         pr_debug("%s entered refrigerator\n", current->comm);
  42         printk("=");
  43
  44         frozen_process(current);
  45         spin_lock_irq(&current->sighand->siglock);
  46         recalc_sigpending(); /* We sent fake signal, clean it up */
  47         spin_unlock_irq(&current->sighand->siglock);
  48
  49         while (frozen(current)) {
  50                 current->state = TASK_UNINTERRUPTIBLE;
  51                 schedule();
  52         }
  53         pr_debug("%s left refrigerator\n", current->comm);
  54         current->state = save;
  55 }
  56
  57 static inline void freeze_process(struct task_struct *p)
  58 {
  59         unsigned long flags;
  60
  61         if (!freezing(p)) {
  62                 freeze(p);
  63                 spin_lock_irqsave(&p->sighand->siglock, flags);
  64                 signal_wake_up(p, 0);
  65                 spin_unlock_irqrestore(&p->sighand->siglock, flags);
  66         }
  67 }
  68
  69 static void cancel_freezing(struct task_struct *p)
  70 {
  71         unsigned long flags;
  72
  73         if (freezing(p)) {
  74                 pr_debug("  clean up: %s\n", p->comm);
  75                 do_not_freeze(p);
  76                 spin_lock_irqsave(&p->sighand->siglock, flags);
  77                 recalc_sigpending_tsk(p);
  78                 spin_unlock_irqrestore(&p->sighand->siglock, flags);
  79         }
  80 }
  81
  82 /* 0 = success, else # of processes that we failed to stop */
  83 int freeze_processes(void)
  84 {
  85         int todo, nr_user, user_frozen;
  86         unsigned long start_time;
  87         struct task_struct *g, *p;
  88
  89         printk( "Stopping tasks: " );
  90         start_time = jiffies;
  91         user_frozen = 0;
  92         do {
  93                 nr_user = todo = 0;
  94                 read_lock(&tasklist_lock);
  95                 do_each_thread(g, p) {
  96                         if (!freezeable(p))
  97                                 continue;
  98                         if (frozen(p))
  99                                 continue;
 100                         if (p->state == TASK_TRACED && frozen(p->parent)) {
 101                                 cancel_freezing(p);
 102                                 continue;
 103                         }
 104                         if (p->mm && !(p->flags & PF_BORROWED_MM)) {
 105                                 /* The task is a user-space one.
 106                                  * Freeze it unless there's a vfork completion
 107                                  * pending
 108                                  */
 109                                 if (!p->vfork_done)
 110                                         freeze_process(p);
 111                                 nr_user++;
 112                         } else {
 113                                 /* Freeze only if the user space is frozen */
 114                                 if (user_frozen)
 115                                         freeze_process(p);
 116                                 todo++;
 117                         }
 118                 } while_each_thread(g, p);
 119                 read_unlock(&tasklist_lock);
 120                 todo += nr_user;
 121                 if (!user_frozen && !nr_user) {
 122                         sys_sync();
 123                         start_time = jiffies;
 124                 }
 125                 user_frozen = !nr_user;
 126                 yield();                        /* Yield is okay here */
 127                 if (todo && time_after(jiffies, start_time + TIMEOUT))
 128                         break;
 129         } while(todo);
 130
 131         /* This does not unfreeze processes that are already frozen
 132          * (we have slightly ugly calling convention in that respect,
 133          * and caller must call thaw_processes() if something fails),
 134          * but it cleans up leftover PF_FREEZE requests.
 135          */
 136         if (todo) {
 137                 printk( "\n" );
 138                 printk(KERN_ERR " stopping tasks timed out "
 139                         "after %d seconds (%d tasks remaining):\n",
 140                         TIMEOUT / HZ, todo);
 141                 read_lock(&tasklist_lock);
 142                 do_each_thread(g, p) {
 143                         if (freezeable(p) && !frozen(p))
 144                                 printk(KERN_ERR "  %s\n", p->comm);
 145                         cancel_freezing(p);
 146                 } while_each_thread(g, p);
 147                 read_unlock(&tasklist_lock);
 148                 return todo;
 149         }
 150
 151         printk( "|\n" );
 152         BUG_ON(in_atomic());
 153         return 0;
 154 }
 155
 156 void thaw_processes(void)
 157 {
 158         struct task_struct *g, *p;
 159
 160         printk( "Restarting tasks..." );
 161         read_lock(&tasklist_lock);
 162         do_each_thread(g, p) {
 163                 if (!freezeable(p))
 164                         continue;
 165                 if (!thaw_process(p))
 166                         printk(KERN_INFO " Strange, %s not stopped\n", p->comm );
 167         } while_each_thread(g, p);
 168
 169         read_unlock(&tasklist_lock);
 170         schedule();
 171         printk( " done\n" );
 172 }
 173
 174 EXPORT_SYMBOL(refrigerator);