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_tsk_thread_flag(current, TIF_FREEZE);
  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         current->state = save;
  76 }
  77
  78 static inline void freeze_process(struct task_struct *p)
  79 {
  80         unsigned long flags;
  81
  82         if (!freezing(p)) {
  83                 rmb();
  84                 if (!frozen(p)) {
  85                         if (p->state == TASK_STOPPED)
  86                                 force_sig_specific(SIGSTOP, p);
  87
  88                         freeze(p);
  89                         spin_lock_irqsave(&p->sighand->siglock, flags);
  90                         signal_wake_up(p, p->state == TASK_STOPPED);
  91                         spin_unlock_irqrestore(&p->sighand->siglock, flags);
  92                 }
  93         }
  94 }
  95
  96 static void cancel_freezing(struct task_struct *p)
  97 {
  98         unsigned long flags;
  99
 100         if (freezing(p)) {
 101                 pr_debug("  clean up: %s\n", p->comm);
 102                 do_not_freeze(p);
 103                 spin_lock_irqsave(&p->sighand->siglock, flags);
 104                 recalc_sigpending_and_wake(p);
 105                 spin_unlock_irqrestore(&p->sighand->siglock, flags);
 106         }
 107 }
 108
 109 static inline int is_user_space(struct task_struct *p)
 110 {
 111         return p->mm && !(p->flags & PF_BORROWED_MM);
 112 }
 113
 114 static unsigned int try_to_freeze_tasks(int freeze_user_space)
 115 {
 116         struct task_struct *g, *p;
 117         unsigned long end_time;
 118         unsigned int todo;
 119
 120         end_time = jiffies + TIMEOUT;
 121         do {
 122                 todo = 0;
 123                 read_lock(&tasklist_lock);
 124                 do_each_thread(g, p) {
 125                         if (!freezeable(p))
 126                                 continue;
 127
 128                         if (frozen(p))
 129                                 continue;
 130
 131                         if (p->state == TASK_TRACED && frozen(p->parent)) {
 132                                 cancel_freezing(p);
 133                                 continue;
 134                         }
 135                         if (freeze_user_space && !is_user_space(p))
 136                                 continue;
 137
 138                         freeze_process(p);
 139                         if (!freezer_should_skip(p))
 140                                 todo++;
 141                 } while_each_thread(g, p);
 142                 read_unlock(&tasklist_lock);
 143                 yield();                        /* Yield is okay here */
 144                 if (todo && time_after(jiffies, end_time))
 145                         break;
 146         } while (todo);
 147
 148         if (todo) {
 149                 /* This does not unfreeze processes that are already frozen
 150                  * (we have slightly ugly calling convention in that respect,
 151                  * and caller must call thaw_processes() if something fails),
 152                  * but it cleans up leftover PF_FREEZE requests.
 153                  */
 154                 printk("\n");
 155                 printk(KERN_ERR "Stopping %s timed out after %d seconds "
 156                                 "(%d tasks refusing to freeze):\n",
 157                                 freeze_user_space ? "user space processes" :
 158                                         "kernel threads",
 159                                 TIMEOUT / HZ, todo);
 160                 show_state();
 161                 read_lock(&tasklist_lock);
 162                 do_each_thread(g, p) {
 163                         if (freeze_user_space && !is_user_space(p))
 164                                 continue;
 165
 166                         task_lock(p);
 167                         if (freezeable(p) && !frozen(p) &&
 168                             !freezer_should_skip(p))
 169                                 printk(KERN_ERR " %s\n", p->comm);
 170
 171                         cancel_freezing(p);
 172                         task_unlock(p);
 173                 } while_each_thread(g, p);
 174                 read_unlock(&tasklist_lock);
 175         }
 176
 177         return todo;
 178 }
 179
 180 /**
 181  *      freeze_processes - tell processes to enter the refrigerator
 182  *
 183  *      Returns 0 on success, or the number of processes that didn't freeze,
 184  *      although they were told to.
 185  */
 186 int freeze_processes(void)
 187 {
 188         unsigned int nr_unfrozen;
 189
 190         printk("Stopping tasks ... ");
 191         nr_unfrozen = try_to_freeze_tasks(FREEZER_USER_SPACE);
 192         if (nr_unfrozen)
 193                 return nr_unfrozen;
 194
 195         sys_sync();
 196         nr_unfrozen = try_to_freeze_tasks(FREEZER_KERNEL_THREADS);
 197         if (nr_unfrozen)
 198                 return nr_unfrozen;
 199
 200         printk("done.\n");
 201         BUG_ON(in_atomic());
 202         return 0;
 203 }
 204
 205 static void thaw_tasks(int thaw_user_space)
 206 {
 207         struct task_struct *g, *p;
 208
 209         read_lock(&tasklist_lock);
 210         do_each_thread(g, p) {
 211                 if (!freezeable(p))
 212                         continue;
 213
 214                 if (is_user_space(p) == !thaw_user_space)
 215                         continue;
 216
 217                 thaw_process(p);
 218         } while_each_thread(g, p);
 219         read_unlock(&tasklist_lock);
 220 }
 221
 222 void thaw_processes(void)
 223 {
 224         printk("Restarting tasks ... ");
 225         thaw_tasks(FREEZER_KERNEL_THREADS);
 226         thaw_tasks(FREEZER_USER_SPACE);
 227         schedule();
 228         printk("done.\n");
 229 }
 230
 231 EXPORT_SYMBOL(refrigerator);