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