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 fake_signal_wake_up(struct task_struct *p)
  79 {
  80         unsigned long flags;
  81
  82         spin_lock_irqsave(&p->sighand->siglock, flags);
  83         signal_wake_up(p, 0);
  84         spin_unlock_irqrestore(&p->sighand->siglock, flags);
  85 }
  86
  87 static int has_mm(struct task_struct *p)
  88 {
  89         return (p->mm && !(p->flags & PF_BORROWED_MM));
  90 }
  91
  92 /**
  93  *      freeze_task - send a freeze request to given task
  94  *      @p: task to send the request to
  95  *      @with_mm_only: if set, the request will only be sent if the task has its
  96  *              own mm
  97  *      Return value: 0, if @with_mm_only is set and the task has no mm of its
  98  *              own or the task is frozen, 1, otherwise
  99  *
 100  *      The freeze request is sent by seting the tasks's TIF_FREEZE flag and
 101  *      either sending a fake signal to it or waking it up, depending on whether
 102  *      or not it has its own mm (ie. it is a user land task).  If @with_mm_only
 103  *      is set and the task has no mm of its own (ie. it is a kernel thread),
 104  *      its TIF_FREEZE flag should not be set.
 105  *
 106  *      The task_lock() is necessary to prevent races with exit_mm() or
 107  *      use_mm()/unuse_mm() from occuring.
 108  */
 109 static int freeze_task(struct task_struct *p, int with_mm_only)
 110 {
 111         int ret = 1;
 112
 113         task_lock(p);
 114         if (freezing(p)) {
 115                 if (has_mm(p)) {
 116                         if (!signal_pending(p))
 117                                 fake_signal_wake_up(p);
 118                 } else {
 119                         if (with_mm_only)
 120                                 ret = 0;
 121                         else
 122                                 wake_up_state(p, TASK_INTERRUPTIBLE);
 123                 }
 124         } else {
 125                 rmb();
 126                 if (frozen(p)) {
 127                         ret = 0;
 128                 } else {
 129                         if (has_mm(p)) {
 130                                 set_freeze_flag(p);
 131                                 fake_signal_wake_up(p);
 132                         } else {
 133                                 if (with_mm_only) {
 134                                         ret = 0;
 135                                 } else {
 136                                         set_freeze_flag(p);
 137                                         wake_up_state(p, TASK_INTERRUPTIBLE);
 138                                 }
 139                         }
 140                 }
 141         }
 142         task_unlock(p);
 143         return ret;
 144 }
 145
 146 static void cancel_freezing(struct task_struct *p)
 147 {
 148         unsigned long flags;
 149
 150         if (freezing(p)) {
 151                 pr_debug("  clean up: %s\n", p->comm);
 152                 clear_freeze_flag(p);
 153                 spin_lock_irqsave(&p->sighand->siglock, flags);
 154                 recalc_sigpending_and_wake(p);
 155                 spin_unlock_irqrestore(&p->sighand->siglock, flags);
 156         }
 157 }
 158
 159 static int try_to_freeze_tasks(int freeze_user_space)
 160 {
 161         struct task_struct *g, *p;
 162         unsigned long end_time;
 163         unsigned int todo;
 164         struct timeval start, end;
 165         s64 elapsed_csecs64;
 166         unsigned int elapsed_csecs;
 167
 168         do_gettimeofday(&start);
 169
 170         end_time = jiffies + TIMEOUT;
 171         do {
 172                 todo = 0;
 173                 read_lock(&tasklist_lock);
 174                 do_each_thread(g, p) {
 175                         if (frozen(p) || !freezeable(p))
 176                                 continue;
 177
 178                         if (!freeze_task(p, freeze_user_space))
 179                                 continue;
 180
 181                         /*
 182                          * Now that we've done set_freeze_flag, don't
 183                          * perturb a task in TASK_STOPPED or TASK_TRACED.
 184                          * It is "frozen enough".  If the task does wake
 185                          * up, it will immediately call try_to_freeze.
 186                          */
 187                         if (!task_is_stopped_or_traced(p) &&
 188                             !freezer_should_skip(p))
 189                                 todo++;
 190                 } while_each_thread(g, p);
 191                 read_unlock(&tasklist_lock);
 192                 yield();                        /* Yield is okay here */
 193                 if (time_after(jiffies, end_time))
 194                         break;
 195         } while (todo);
 196
 197         do_gettimeofday(&end);
 198         elapsed_csecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
 199         do_div(elapsed_csecs64, NSEC_PER_SEC / 100);
 200         elapsed_csecs = elapsed_csecs64;
 201
 202         if (todo) {
 203                 /* This does not unfreeze processes that are already frozen
 204                  * (we have slightly ugly calling convention in that respect,
 205                  * and caller must call thaw_processes() if something fails),
 206                  * but it cleans up leftover PF_FREEZE requests.
 207                  */
 208                 printk("\n");
 209                 printk(KERN_ERR "Freezing of tasks failed after %d.%02d seconds "
 210                                 "(%d tasks refusing to freeze):\n",
 211                                 elapsed_csecs / 100, elapsed_csecs % 100, todo);
 212                 show_state();
 213                 read_lock(&tasklist_lock);
 214                 do_each_thread(g, p) {
 215                         task_lock(p);
 216                         if (freezing(p) && !freezer_should_skip(p))
 217                                 printk(KERN_ERR " %s\n", p->comm);
 218                         cancel_freezing(p);
 219                         task_unlock(p);
 220                 } while_each_thread(g, p);
 221                 read_unlock(&tasklist_lock);
 222         } else {
 223                 printk("(elapsed %d.%02d seconds) ", elapsed_csecs / 100,
 224                         elapsed_csecs % 100);
 225         }
 226
 227         return todo ? -EBUSY : 0;
 228 }
 229
 230 /**
 231  *      freeze_processes - tell processes to enter the refrigerator
 232  */
 233 int freeze_processes(void)
 234 {
 235         int error;
 236
 237         printk("Freezing user space processes ... ");
 238         error = try_to_freeze_tasks(FREEZER_USER_SPACE);
 239         if (error)
 240                 goto Exit;
 241         printk("done.\n");
 242
 243         printk("Freezing remaining freezable tasks ... ");
 244         error = try_to_freeze_tasks(FREEZER_KERNEL_THREADS);
 245         if (error)
 246                 goto Exit;
 247         printk("done.");
 248  Exit:
 249         BUG_ON(in_atomic());
 250         printk("\n");
 251         return error;
 252 }
 253
 254 static void thaw_tasks(int thaw_user_space)
 255 {
 256         struct task_struct *g, *p;
 257
 258         read_lock(&tasklist_lock);
 259         do_each_thread(g, p) {
 260                 if (!freezeable(p))
 261                         continue;
 262
 263                 if (!p->mm == thaw_user_space)
 264                         continue;
 265
 266                 thaw_process(p);
 267         } while_each_thread(g, p);
 268         read_unlock(&tasklist_lock);
 269 }
 270
 271 void thaw_processes(void)
 272 {
 273         printk("Restarting tasks ... ");
 274         thaw_tasks(FREEZER_KERNEL_THREADS);
 275         thaw_tasks(FREEZER_USER_SPACE);
 276         schedule();
 277         printk("done.\n");
 278 }
 279
 280 EXPORT_SYMBOL(refrigerator);