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