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 static inline int freezeable(struct task_struct * p)
  23 {
  24         if ((p == current) ||
  25             (p->flags & PF_NOFREEZE) ||
  26             (p->exit_state != 0))
  27                 return 0;
  28         return 1;
  29 }
  30
  31 /*
  32  * freezing is complete, mark current process as frozen
  33  */
  34 static inline void frozen_process(void)
  35 {
  36         if (!unlikely(current->flags & PF_NOFREEZE)) {
  37                 current->flags |= PF_FROZEN;
  38                 wmb();
  39         }
  40         clear_freeze_flag(current);
  41 }
  42
  43 /* Refrigerator is place where frozen processes are stored :-). */
  44 void refrigerator(void)
  45 {
  46         /* Hmm, should we be allowed to suspend when there are realtime
  47            processes around? */
  48         long save;
  49
  50         task_lock(current);
  51         if (freezing(current)) {
  52                 frozen_process();
  53                 task_unlock(current);
  54         } else {
  55                 task_unlock(current);
  56                 return;
  57         }
  58         save = current->state;
  59         pr_debug("%s entered refrigerator\n", current->comm);
  60
  61         spin_lock_irq(&current->sighand->siglock);
  62         recalc_sigpending(); /* We sent fake signal, clean it up */
  63         spin_unlock_irq(&current->sighand->siglock);
  64
  65         for (;;) {
  66                 set_current_state(TASK_UNINTERRUPTIBLE);
  67                 if (!frozen(current))
  68                         break;
  69                 schedule();
  70         }
  71         pr_debug("%s left refrigerator\n", current->comm);
  72         __set_current_state(save);
  73 }
  74
  75 static void fake_signal_wake_up(struct task_struct *p)
  76 {
  77         unsigned long flags;
  78
  79         spin_lock_irqsave(&p->sighand->siglock, flags);
  80         signal_wake_up(p, 0);
  81         spin_unlock_irqrestore(&p->sighand->siglock, flags);
  82 }
  83
  84 static inline bool should_send_signal(struct task_struct *p)
  85 {
  86         return !(p->flags & PF_FREEZER_NOSIG);
  87 }
  88
  89 /**
  90  *      freeze_task - send a freeze request to given task
  91  *      @p: task to send the request to
  92  *      @sig_only: if set, the request will only be sent if the task has the
  93  *              PF_FREEZER_NOSIG flag unset
  94  *      Return value: 'false', if @sig_only is set and the task has
  95  *              PF_FREEZER_NOSIG set or the task is frozen, 'true', otherwise
  96  *
  97  *      The freeze request is sent by setting the tasks's TIF_FREEZE flag and
  98  *      either sending a fake signal to it or waking it up, depending on whether
  99  *      or not it has PF_FREEZER_NOSIG set.  If @sig_only is set and the task
 100  *      has PF_FREEZER_NOSIG set (ie. it is a typical kernel thread), its
 101  *      TIF_FREEZE flag will not be set.
 102  */
 103 static bool freeze_task(struct task_struct *p, bool sig_only)
 104 {
 105         /*
 106          * We first check if the task is freezing and next if it has already
 107          * been frozen to avoid the race with frozen_process() which first marks
 108          * the task as frozen and next clears its TIF_FREEZE.
 109          */
 110         if (!freezing(p)) {
 111                 rmb();
 112                 if (frozen(p))
 113                         return false;
 114
 115                 if (!sig_only || should_send_signal(p))
 116                         set_freeze_flag(p);
 117                 else
 118                         return false;
 119         }
 120
 121         if (should_send_signal(p)) {
 122                 if (!signal_pending(p))
 123                         fake_signal_wake_up(p);
 124         } else if (sig_only) {
 125                 return false;
 126         } else {
 127                 wake_up_state(p, TASK_INTERRUPTIBLE);
 128         }
 129
 130         return true;
 131 }
 132
 133 static void cancel_freezing(struct task_struct *p)
 134 {
 135         unsigned long flags;
 136
 137         if (freezing(p)) {
 138                 pr_debug("  clean up: %s\n", p->comm);
 139                 clear_freeze_flag(p);
 140                 spin_lock_irqsave(&p->sighand->siglock, flags);
 141                 recalc_sigpending_and_wake(p);
 142                 spin_unlock_irqrestore(&p->sighand->siglock, flags);
 143         }
 144 }
 145
 146 static int try_to_freeze_tasks(bool sig_only)
 147 {
 148         struct task_struct *g, *p;
 149         unsigned long end_time;
 150         unsigned int todo;
 151         struct timeval start, end;
 152         s64 elapsed_csecs64;
 153         unsigned int elapsed_csecs;
 154
 155         do_gettimeofday(&start);
 156
 157         end_time = jiffies + TIMEOUT;
 158         do {
 159                 todo = 0;
 160                 read_lock(&tasklist_lock);
 161                 do_each_thread(g, p) {
 162                         if (frozen(p) || !freezeable(p))
 163                                 continue;
 164
 165                         if (!freeze_task(p, sig_only))
 166                                 continue;
 167
 168                         /*
 169                          * Now that we've done set_freeze_flag, don't
 170                          * perturb a task in TASK_STOPPED or TASK_TRACED.
 171                          * It is "frozen enough".  If the task does wake
 172                          * up, it will immediately call try_to_freeze.
 173                          */
 174                         if (!task_is_stopped_or_traced(p) &&
 175                             !freezer_should_skip(p))
 176                                 todo++;
 177                 } while_each_thread(g, p);
 178                 read_unlock(&tasklist_lock);
 179                 yield();                        /* Yield is okay here */
 180                 if (time_after(jiffies, end_time))
 181                         break;
 182         } while (todo);
 183
 184         do_gettimeofday(&end);
 185         elapsed_csecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
 186         do_div(elapsed_csecs64, NSEC_PER_SEC / 100);
 187         elapsed_csecs = elapsed_csecs64;
 188
 189         if (todo) {
 190                 /* This does not unfreeze processes that are already frozen
 191                  * (we have slightly ugly calling convention in that respect,
 192                  * and caller must call thaw_processes() if something fails),
 193                  * but it cleans up leftover PF_FREEZE requests.
 194                  */
 195                 printk("\n");
 196                 printk(KERN_ERR "Freezing of tasks failed after %d.%02d seconds "
 197                                 "(%d tasks refusing to freeze):\n",
 198                                 elapsed_csecs / 100, elapsed_csecs % 100, todo);
 199                 show_state();
 200                 read_lock(&tasklist_lock);
 201                 do_each_thread(g, p) {
 202                         task_lock(p);
 203                         if (freezing(p) && !freezer_should_skip(p))
 204                                 printk(KERN_ERR " %s\n", p->comm);
 205                         cancel_freezing(p);
 206                         task_unlock(p);
 207                 } while_each_thread(g, p);
 208                 read_unlock(&tasklist_lock);
 209         } else {
 210                 printk("(elapsed %d.%02d seconds) ", elapsed_csecs / 100,
 211                         elapsed_csecs % 100);
 212         }
 213
 214         return todo ? -EBUSY : 0;
 215 }
 216
 217 /**
 218  *      freeze_processes - tell processes to enter the refrigerator
 219  */
 220 int freeze_processes(void)
 221 {
 222         int error;
 223
 224         printk("Freezing user space processes ... ");
 225         error = try_to_freeze_tasks(true);
 226         if (error)
 227                 goto Exit;
 228         printk("done.\n");
 229
 230         printk("Freezing remaining freezable tasks ... ");
 231         error = try_to_freeze_tasks(false);
 232         if (error)
 233                 goto Exit;
 234         printk("done.");
 235  Exit:
 236         BUG_ON(in_atomic());
 237         printk("\n");
 238         return error;
 239 }
 240
 241 static void thaw_tasks(bool nosig_only)
 242 {
 243         struct task_struct *g, *p;
 244
 245         read_lock(&tasklist_lock);
 246         do_each_thread(g, p) {
 247                 if (!freezeable(p))
 248                         continue;
 249
 250                 if (nosig_only && should_send_signal(p))
 251                         continue;
 252
 253                 thaw_process(p);
 254         } while_each_thread(g, p);
 255         read_unlock(&tasklist_lock);
 256 }
 257
 258 void thaw_processes(void)
 259 {
 260         printk("Restarting tasks ... ");
 261         thaw_tasks(true);
 262         thaw_tasks(false);
 263         schedule();
 264         printk("done.\n");
 265 }
 266
 267 EXPORT_SYMBOL(refrigerator);