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                 return 0;
  33         return 1;
  34 }
  35
  36 /* Refrigerator is place where frozen processes are stored :-). */
  37 void refrigerator(void)
  38 {
  39         /* Hmm, should we be allowed to suspend when there are realtime
  40            processes around? */
  41         long save;
  42         save = current->state;
  43         pr_debug("%s entered refrigerator\n", current->comm);
  44
  45         frozen_process(current);
  46         spin_lock_irq(&current->sighand->siglock);
  47         recalc_sigpending(); /* We sent fake signal, clean it up */
  48         spin_unlock_irq(&current->sighand->siglock);
  49
  50         while (frozen(current)) {
  51                 current->state = TASK_UNINTERRUPTIBLE;
  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                 if (p->state == TASK_STOPPED)
  64                         force_sig_specific(SIGSTOP, p);
  65
  66                 freeze(p);
  67                 spin_lock_irqsave(&p->sighand->siglock, flags);
  68                 signal_wake_up(p, p->state == TASK_STOPPED);
  69                 spin_unlock_irqrestore(&p->sighand->siglock, flags);
  70         }
  71 }
  72
  73 static void cancel_freezing(struct task_struct *p)
  74 {
  75         unsigned long flags;
  76
  77         if (freezing(p)) {
  78                 pr_debug("  clean up: %s\n", p->comm);
  79                 do_not_freeze(p);
  80                 spin_lock_irqsave(&p->sighand->siglock, flags);
  81                 recalc_sigpending_tsk(p);
  82                 spin_unlock_irqrestore(&p->sighand->siglock, flags);
  83         }
  84 }
  85
  86 static inline int is_user_space(struct task_struct *p)
  87 {
  88         return p->mm && !(p->flags & PF_BORROWED_MM);
  89 }
  90
  91 static unsigned int try_to_freeze_tasks(int freeze_user_space)
  92 {
  93         struct task_struct *g, *p;
  94         unsigned long end_time;
  95         unsigned int todo;
  96
  97         end_time = jiffies + TIMEOUT;
  98         do {
  99                 todo = 0;
 100                 read_lock(&tasklist_lock);
 101                 do_each_thread(g, p) {
 102                         if (!freezeable(p))
 103                                 continue;
 104
 105                         if (frozen(p))
 106                                 continue;
 107
 108                         if (p->state == TASK_TRACED && frozen(p->parent)) {
 109                                 cancel_freezing(p);
 110                                 continue;
 111                         }
 112                         if (is_user_space(p)) {
 113                                 if (!freeze_user_space)
 114                                         continue;
 115
 116                                 /* Freeze the task unless there is a vfork
 117                                  * completion pending
 118                                  */
 119                                 if (!p->vfork_done)
 120                                         freeze_process(p);
 121                         } else {
 122                                 if (freeze_user_space)
 123                                         continue;
 124
 125                                 freeze_process(p);
 126                         }
 127                         todo++;
 128                 } while_each_thread(g, p);
 129                 read_unlock(&tasklist_lock);
 130                 yield();                        /* Yield is okay here */
 131                 if (todo && time_after(jiffies, end_time))
 132                         break;
 133         } while (todo);
 134
 135         if (todo) {
 136                 /* This does not unfreeze processes that are already frozen
 137                  * (we have slightly ugly calling convention in that respect,
 138                  * and caller must call thaw_processes() if something fails),
 139                  * but it cleans up leftover PF_FREEZE requests.
 140                  */
 141                 printk("\n");
 142                 printk(KERN_ERR "Stopping %s timed out after %d seconds "
 143                                 "(%d tasks refusing to freeze):\n",
 144                                 freeze_user_space ? "user space processes" :
 145                                         "kernel threads",
 146                                 TIMEOUT / HZ, todo);
 147                 read_lock(&tasklist_lock);
 148                 do_each_thread(g, p) {
 149                         if (is_user_space(p) == !freeze_user_space)
 150                                 continue;
 151
 152                         if (freezeable(p) && !frozen(p))
 153                                 printk(KERN_ERR " %s\n", p->comm);
 154
 155                         cancel_freezing(p);
 156                 } while_each_thread(g, p);
 157                 read_unlock(&tasklist_lock);
 158         }
 159
 160         return todo;
 161 }
 162
 163 /**
 164  *      freeze_processes - tell processes to enter the refrigerator
 165  *
 166  *      Returns 0 on success, or the number of processes that didn't freeze,
 167  *      although they were told to.
 168  */
 169 int freeze_processes(void)
 170 {
 171         unsigned int nr_unfrozen;
 172
 173         printk("Stopping tasks ... ");
 174         nr_unfrozen = try_to_freeze_tasks(FREEZER_USER_SPACE);
 175         if (nr_unfrozen)
 176                 return nr_unfrozen;
 177
 178         sys_sync();
 179         nr_unfrozen = try_to_freeze_tasks(FREEZER_KERNEL_THREADS);
 180         if (nr_unfrozen)
 181                 return nr_unfrozen;
 182
 183         printk("done.\n");
 184         BUG_ON(in_atomic());
 185         return 0;
 186 }
 187
 188 static void thaw_tasks(int thaw_user_space)
 189 {
 190         struct task_struct *g, *p;
 191
 192         read_lock(&tasklist_lock);
 193         do_each_thread(g, p) {
 194                 if (!freezeable(p))
 195                         continue;
 196
 197                 if (is_user_space(p) == !thaw_user_space)
 198                         continue;
 199
 200                 if (!thaw_process(p))
 201                         printk(KERN_WARNING " Strange, %s not stopped\n",
 202                                 p->comm );
 203         } while_each_thread(g, p);
 204         read_unlock(&tasklist_lock);
 205 }
 206
 207 void thaw_processes(void)
 208 {
 209         printk("Restarting tasks ... ");
 210         thaw_tasks(FREEZER_KERNEL_THREADS);
 211         thaw_tasks(FREEZER_USER_SPACE);
 212         schedule();
 213         printk("done.\n");
 214 }
 215
 216 EXPORT_SYMBOL(refrigerator);