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/interrupt.h>
  12 #include <linux/suspend.h>
  13 #include <linux/module.h>
  14 #include <linux/syscalls.h>
  15 #include <linux/freezer.h>
  16
  17 /*
  18  * Timeout for stopping processes
  19  */
  20 #define TIMEOUT (20 * HZ)
  21
  22 #define FREEZER_KERNEL_THREADS 0
  23 #define FREEZER_USER_SPACE 1
  24
  25 static inline int freezeable(struct task_struct * p)
  26 {
  27         if ((p == current) ||
  28             (p->flags & PF_NOFREEZE) ||
  29             (p->exit_state != 0))
  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
  41         task_lock(current);
  42         if (freezing(current)) {
  43                 frozen_process(current);
  44                 task_unlock(current);
  45         } else {
  46                 task_unlock(current);
  47                 return;
  48         }
  49         save = current->state;
  50         pr_debug("%s entered refrigerator\n", current->comm);
  51
  52         spin_lock_irq(&current->sighand->siglock);
  53         recalc_sigpending(); /* We sent fake signal, clean it up */
  54         spin_unlock_irq(&current->sighand->siglock);
  55
  56         for (;;) {
  57                 set_current_state(TASK_UNINTERRUPTIBLE);
  58                 if (!frozen(current))
  59                         break;
  60                 schedule();
  61         }
  62         pr_debug("%s left refrigerator\n", current->comm);
  63         current->state = save;
  64 }
  65
  66 static inline void freeze_process(struct task_struct *p)
  67 {
  68         unsigned long flags;
  69
  70         if (!freezing(p)) {
  71                 rmb();
  72                 if (!frozen(p)) {
  73                         if (p->state == TASK_STOPPED)
  74                                 force_sig_specific(SIGSTOP, p);
  75
  76                         freeze(p);
  77                         spin_lock_irqsave(&p->sighand->siglock, flags);
  78                         signal_wake_up(p, p->state == TASK_STOPPED);
  79                         spin_unlock_irqrestore(&p->sighand->siglock, flags);
  80                 }
  81         }
  82 }
  83
  84 static void cancel_freezing(struct task_struct *p)
  85 {
  86         unsigned long flags;
  87
  88         if (freezing(p)) {
  89                 pr_debug("  clean up: %s\n", p->comm);
  90                 do_not_freeze(p);
  91                 spin_lock_irqsave(&p->sighand->siglock, flags);
  92                 recalc_sigpending_tsk(p);
  93                 spin_unlock_irqrestore(&p->sighand->siglock, flags);
  94         }
  95 }
  96
  97 static inline int is_user_space(struct task_struct *p)
  98 {
  99         return p->mm && !(p->flags & PF_BORROWED_MM);
 100 }
 101
 102 static unsigned int try_to_freeze_tasks(int freeze_user_space)
 103 {
 104         struct task_struct *g, *p;
 105         unsigned long end_time;
 106         unsigned int todo;
 107
 108         end_time = jiffies + TIMEOUT;
 109         do {
 110                 todo = 0;
 111                 read_lock(&tasklist_lock);
 112                 do_each_thread(g, p) {
 113                         if (!freezeable(p))
 114                                 continue;
 115
 116                         if (frozen(p))
 117                                 continue;
 118
 119                         if (p->state == TASK_TRACED && frozen(p->parent)) {
 120                                 cancel_freezing(p);
 121                                 continue;
 122                         }
 123                         if (is_user_space(p) == !freeze_user_space)
 124                                 continue;
 125
 126                         freeze_process(p);
 127                         if (!freezer_should_skip(p))
 128                                 todo++;
 129                 } while_each_thread(g, p);
 130                 read_unlock(&tasklist_lock);
 131                 yield();                        /* Yield is okay here */
 132                 if (todo && time_after(jiffies, end_time))
 133                         break;
 134         } while (todo);
 135
 136         if (todo) {
 137                 /* This does not unfreeze processes that are already frozen
 138                  * (we have slightly ugly calling convention in that respect,
 139                  * and caller must call thaw_processes() if something fails),
 140                  * but it cleans up leftover PF_FREEZE requests.
 141                  */
 142                 printk("\n");
 143                 printk(KERN_ERR "Stopping %s timed out after %d seconds "
 144                                 "(%d tasks refusing to freeze):\n",
 145                                 freeze_user_space ? "user space processes" :
 146                                         "kernel threads",
 147                                 TIMEOUT / HZ, todo);
 148                 read_lock(&tasklist_lock);
 149                 do_each_thread(g, p) {
 150                         if (is_user_space(p) == !freeze_user_space)
 151                                 continue;
 152
 153                         task_lock(p);
 154                         if (freezeable(p) && !frozen(p) &&
 155                             !freezer_should_skip(p))
 156                                 printk(KERN_ERR " %s\n", p->comm);
 157
 158                         cancel_freezing(p);
 159                         task_unlock(p);
 160                 } while_each_thread(g, p);
 161                 read_unlock(&tasklist_lock);
 162         }
 163
 164         return todo;
 165 }
 166
 167 /**
 168  *      freeze_processes - tell processes to enter the refrigerator
 169  *
 170  *      Returns 0 on success, or the number of processes that didn't freeze,
 171  *      although they were told to.
 172  */
 173 int freeze_processes(void)
 174 {
 175         unsigned int nr_unfrozen;
 176
 177         printk("Stopping tasks ... ");
 178         nr_unfrozen = try_to_freeze_tasks(FREEZER_USER_SPACE);
 179         if (nr_unfrozen)
 180                 return nr_unfrozen;
 181
 182         sys_sync();
 183         nr_unfrozen = try_to_freeze_tasks(FREEZER_KERNEL_THREADS);
 184         if (nr_unfrozen)
 185                 return nr_unfrozen;
 186
 187         printk("done.\n");
 188         BUG_ON(in_atomic());
 189         return 0;
 190 }
 191
 192 static void thaw_tasks(int thaw_user_space)
 193 {
 194         struct task_struct *g, *p;
 195
 196         read_lock(&tasklist_lock);
 197         do_each_thread(g, p) {
 198                 if (!freezeable(p))
 199                         continue;
 200
 201                 if (is_user_space(p) == !thaw_user_space)
 202                         continue;
 203
 204                 thaw_process(p);
 205         } while_each_thread(g, p);
 206         read_unlock(&tasklist_lock);
 207 }
 208
 209 void thaw_processes(void)
 210 {
 211         printk("Restarting tasks ... ");
 212         thaw_tasks(FREEZER_KERNEL_THREADS);
 213         thaw_tasks(FREEZER_USER_SPACE);
 214         schedule();
 215         printk("done.\n");
 216 }
 217
 218 EXPORT_SYMBOL(refrigerator);