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 /*
  35  * freezing is complete, mark current process as frozen
  36  */
  37 static inline void frozen_process(void)
  38 {
  39         if (!unlikely(current->flags & PF_NOFREEZE)) {
  40                 current->flags |= PF_FROZEN;
  41                 wmb();
  42         }
  43         clear_freeze_flag(current);
  44 }
  45
  46 /* Refrigerator is place where frozen processes are stored :-). */
  47 void refrigerator(void)
  48 {
  49         /* Hmm, should we be allowed to suspend when there are realtime
  50            processes around? */
  51         long save;
  52
  53         task_lock(current);
  54         if (freezing(current)) {
  55                 frozen_process();
  56                 task_unlock(current);
  57         } else {
  58                 task_unlock(current);
  59                 return;
  60         }
  61         save = current->state;
  62         pr_debug("%s entered refrigerator\n", current->comm);
  63
  64         spin_lock_irq(&current->sighand->siglock);
  65         recalc_sigpending(); /* We sent fake signal, clean it up */
  66         spin_unlock_irq(&current->sighand->siglock);
  67
  68         for (;;) {
  69                 set_current_state(TASK_UNINTERRUPTIBLE);
  70                 if (!frozen(current))
  71                         break;
  72                 schedule();
  73         }
  74         pr_debug("%s left refrigerator\n", current->comm);
  75         __set_current_state(save);
  76 }
  77
  78 static void freeze_task(struct task_struct *p)
  79 {
  80         unsigned long flags;
  81
  82         if (!freezing(p)) {
  83                 rmb();
  84                 if (!frozen(p)) {
  85                         set_freeze_flag(p);
  86                         if (p->state == TASK_STOPPED)
  87                                 force_sig_specific(SIGSTOP, p);
  88                         spin_lock_irqsave(&p->sighand->siglock, flags);
  89                         signal_wake_up(p, p->state == TASK_STOPPED);
  90                         spin_unlock_irqrestore(&p->sighand->siglock, flags);
  91                 }
  92         }
  93 }
  94
  95 static void cancel_freezing(struct task_struct *p)
  96 {
  97         unsigned long flags;
  98
  99         if (freezing(p)) {
 100                 pr_debug("  clean up: %s\n", p->comm);
 101                 clear_freeze_flag(p);
 102                 spin_lock_irqsave(&p->sighand->siglock, flags);
 103                 recalc_sigpending_and_wake(p);
 104                 spin_unlock_irqrestore(&p->sighand->siglock, flags);
 105         }
 106 }
 107
 108 static int try_to_freeze_tasks(int freeze_user_space)
 109 {
 110         struct task_struct *g, *p;
 111         unsigned long end_time;
 112         unsigned int todo;
 113
 114         end_time = jiffies + TIMEOUT;
 115         do {
 116                 todo = 0;
 117                 read_lock(&tasklist_lock);
 118                 do_each_thread(g, p) {
 119                         if (frozen(p) || !freezeable(p))
 120                                 continue;
 121
 122                         if (freeze_user_space) {
 123                                 if (p->state == TASK_TRACED &&
 124                                     frozen(p->parent)) {
 125                                         cancel_freezing(p);
 126                                         continue;
 127                                 }
 128                                 /*
 129                                  * Kernel threads should not have TIF_FREEZE set
 130                                  * at this point, so we must ensure that either
 131                                  * p->mm is not NULL *and* PF_BORROWED_MM is
 132                                  * unset, or TIF_FRREZE is left unset.
 133                                  * The task_lock() is necessary to prevent races
 134                                  * with exit_mm() or use_mm()/unuse_mm() from
 135                                  * occuring.
 136                                  */
 137                                 task_lock(p);
 138                                 if (!p->mm || (p->flags & PF_BORROWED_MM)) {
 139                                         task_unlock(p);
 140                                         continue;
 141                                 }
 142                                 freeze_task(p);
 143                                 task_unlock(p);
 144                         } else {
 145                                 freeze_task(p);
 146                         }
 147                         if (!freezer_should_skip(p))
 148                                 todo++;
 149                 } while_each_thread(g, p);
 150                 read_unlock(&tasklist_lock);
 151                 yield();                        /* Yield is okay here */
 152                 if (time_after(jiffies, end_time))
 153                         break;
 154         } while (todo);
 155
 156         if (todo) {
 157                 /* This does not unfreeze processes that are already frozen
 158                  * (we have slightly ugly calling convention in that respect,
 159                  * and caller must call thaw_processes() if something fails),
 160                  * but it cleans up leftover PF_FREEZE requests.
 161                  */
 162                 printk("\n");
 163                 printk(KERN_ERR "Freezing of %s timed out after %d seconds "
 164                                 "(%d tasks refusing to freeze):\n",
 165                                 freeze_user_space ? "user space " : "tasks ",
 166                                 TIMEOUT / HZ, todo);
 167                 show_state();
 168                 read_lock(&tasklist_lock);
 169                 do_each_thread(g, p) {
 170                         task_lock(p);
 171                         if (freezing(p) && !freezer_should_skip(p))
 172                                 printk(KERN_ERR " %s\n", p->comm);
 173                         cancel_freezing(p);
 174                         task_unlock(p);
 175                 } while_each_thread(g, p);
 176                 read_unlock(&tasklist_lock);
 177         }
 178
 179         return todo ? -EBUSY : 0;
 180 }
 181
 182 /**
 183  *      freeze_processes - tell processes to enter the refrigerator
 184  */
 185 int freeze_processes(void)
 186 {
 187         int error;
 188
 189         printk("Stopping tasks ... ");
 190         error = try_to_freeze_tasks(FREEZER_USER_SPACE);
 191         if (error)
 192                 return error;
 193
 194         sys_sync();
 195         error = try_to_freeze_tasks(FREEZER_KERNEL_THREADS);
 196         if (error)
 197                 return error;
 198
 199         printk("done.\n");
 200         BUG_ON(in_atomic());
 201         return 0;
 202 }
 203
 204 static void thaw_tasks(int thaw_user_space)
 205 {
 206         struct task_struct *g, *p;
 207
 208         read_lock(&tasklist_lock);
 209         do_each_thread(g, p) {
 210                 if (!freezeable(p))
 211                         continue;
 212
 213                 if (!p->mm == thaw_user_space)
 214                         continue;
 215
 216                 thaw_process(p);
 217         } while_each_thread(g, p);
 218         read_unlock(&tasklist_lock);
 219 }
 220
 221 void thaw_processes(void)
 222 {
 223         printk("Restarting tasks ... ");
 224         thaw_tasks(FREEZER_KERNEL_THREADS);
 225         thaw_tasks(FREEZER_USER_SPACE);
 226         schedule();
 227         printk("done.\n");
 228 }
 229
 230 EXPORT_SYMBOL(refrigerator);