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/smp_lock.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/suspend.h>
  14 #include <linux/module.h>
  15 #include <linux/syscalls.h>
  16 #include <linux/freezer.h>
  17
  18 /*
  19  * Timeout for stopping processes
  20  */
  21 #define TIMEOUT (20 * HZ)
  22
  23 #define FREEZER_KERNEL_THREADS 0
  24 #define FREEZER_USER_SPACE 1
  25
  26 static inline int freezeable(struct task_struct * p)
  27 {
  28         if ((p == current) ||
  29             (p->flags & PF_NOFREEZE) ||
  30             (p->exit_state == EXIT_ZOMBIE) ||
  31             (p->exit_state == EXIT_DEAD) ||
  32             (p->state == TASK_STOPPED))
  33                 return 0;
  34         return 1;
  35 }
  36
  37 /* Refrigerator is place where frozen processes are stored :-). */
  38 void refrigerator(void)
  39 {
  40         /* Hmm, should we be allowed to suspend when there are realtime
  41            processes around? */
  42         long save;
  43         save = current->state;
  44         pr_debug("%s entered refrigerator\n", current->comm);
  45
  46         frozen_process(current);
  47         spin_lock_irq(&current->sighand->siglock);
  48         recalc_sigpending(); /* We sent fake signal, clean it up */
  49         spin_unlock_irq(&current->sighand->siglock);
  50
  51         while (frozen(current)) {
  52                 current->state = TASK_UNINTERRUPTIBLE;
  53                 schedule();
  54         }
  55         pr_debug("%s left refrigerator\n", current->comm);
  56         current->state = save;
  57 }
  58
  59 static inline void freeze_process(struct task_struct *p)
  60 {
  61         unsigned long flags;
  62
  63         if (!freezing(p)) {
  64                 freeze(p);
  65                 spin_lock_irqsave(&p->sighand->siglock, flags);
  66                 signal_wake_up(p, 0);
  67                 spin_unlock_irqrestore(&p->sighand->siglock, flags);
  68         }
  69 }
  70
  71 static void cancel_freezing(struct task_struct *p)
  72 {
  73         unsigned long flags;
  74
  75         if (freezing(p)) {
  76                 pr_debug("  clean up: %s\n", p->comm);
  77                 do_not_freeze(p);
  78                 spin_lock_irqsave(&p->sighand->siglock, flags);
  79                 recalc_sigpending_tsk(p);
  80                 spin_unlock_irqrestore(&p->sighand->siglock, flags);
  81         }
  82 }
  83
  84 static inline int is_user_space(struct task_struct *p)
  85 {
  86         return p->mm && !(p->flags & PF_BORROWED_MM);
  87 }
  88
  89 /* 0 = success, else # of processes that we failed to stop */
  90 int freeze_processes(void)
  91 {
  92         int todo, nr_user, user_frozen;
  93         unsigned long start_time;
  94         struct task_struct *g, *p;
  95
  96         printk("Stopping tasks... ");
  97         start_time = jiffies;
  98         user_frozen = 0;
  99         do {
 100                 nr_user = todo = 0;
 101                 read_lock(&tasklist_lock);
 102                 do_each_thread(g, p) {
 103                         if (!freezeable(p))
 104                                 continue;
 105                         if (frozen(p))
 106                                 continue;
 107                         if (p->state == TASK_TRACED &&
 108                             (frozen(p->parent) ||
 109                              p->parent->state == TASK_STOPPED)) {
 110                                 cancel_freezing(p);
 111                                 continue;
 112                         }
 113                         if (is_user_space(p)) {
 114                                 /* Freeze the task unless there is a vfork
 115                                  * completion pending
 116                                  */
 117                                 if (!p->vfork_done)
 118                                         freeze_process(p);
 119                                 nr_user++;
 120                         } else {
 121                                 /* Freeze only if the user space is frozen */
 122                                 if (user_frozen)
 123                                         freeze_process(p);
 124                                 todo++;
 125                         }
 126                 } while_each_thread(g, p);
 127                 read_unlock(&tasklist_lock);
 128                 todo += nr_user;
 129                 if (!user_frozen && !nr_user) {
 130                         sys_sync();
 131                         start_time = jiffies;
 132                 }
 133                 user_frozen = !nr_user;
 134                 yield();                        /* Yield is okay here */
 135                 if (todo && time_after(jiffies, start_time + TIMEOUT))
 136                         break;
 137         } while(todo);
 138
 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         if (todo) {
 145                 printk("\n");
 146                 printk(KERN_ERR "Stopping tasks timed out "
 147                         "after %d seconds (%d tasks remaining):\n",
 148                         TIMEOUT / HZ, todo);
 149                 read_lock(&tasklist_lock);
 150                 do_each_thread(g, p) {
 151                         if (freezeable(p) && !frozen(p))
 152                                 printk(KERN_ERR " %s\n", p->comm);
 153                         cancel_freezing(p);
 154                 } while_each_thread(g, p);
 155                 read_unlock(&tasklist_lock);
 156                 return todo;
 157         }
 158
 159         printk("done.\n");
 160         BUG_ON(in_atomic());
 161         return 0;
 162 }
 163
 164 static void thaw_tasks(int thaw_user_space)
 165 {
 166         struct task_struct *g, *p;
 167
 168         read_lock(&tasklist_lock);
 169         do_each_thread(g, p) {
 170                 if (!freezeable(p))
 171                         continue;
 172
 173                 if (is_user_space(p) == !thaw_user_space)
 174                         continue;
 175
 176                 if (!thaw_process(p))
 177                         printk(KERN_WARNING " Strange, %s not stopped\n",
 178                                 p->comm );
 179         } while_each_thread(g, p);
 180         read_unlock(&tasklist_lock);
 181 }
 182
 183 void thaw_processes(void)
 184 {
 185         printk("Restarting tasks ... ");
 186         thaw_tasks(FREEZER_KERNEL_THREADS);
 187         thaw_tasks(FREEZER_USER_SPACE);
 188         schedule();
 189         printk("done.\n");
 190 }
 191
 192 EXPORT_SYMBOL(refrigerator);