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         for (;;) {
  51                 set_current_state(TASK_UNINTERRUPTIBLE);
  52                 if (!frozen(current))
  53                         break;
  54                 schedule();
  55         }
  56         pr_debug("%s left refrigerator\n", current->comm);
  57         current->state = save;
  58 }
  59
  60 static inline void freeze_process(struct task_struct *p)
  61 {
  62         unsigned long flags;
  63
  64         if (!freezing(p)) {
  65                 rmb();
  66                 if (!frozen(p)) {
  67                         if (p->state == TASK_STOPPED)
  68                                 force_sig_specific(SIGSTOP, p);
  69
  70                         freeze(p);
  71                         spin_lock_irqsave(&p->sighand->siglock, flags);
  72                         signal_wake_up(p, p->state == TASK_STOPPED);
  73                         spin_unlock_irqrestore(&p->sighand->siglock, flags);
  74                 }
  75         }
  76 }
  77
  78 static void cancel_freezing(struct task_struct *p)
  79 {
  80         unsigned long flags;
  81
  82         if (freezing(p)) {
  83                 pr_debug("  clean up: %s\n", p->comm);
  84                 do_not_freeze(p);
  85                 spin_lock_irqsave(&p->sighand->siglock, flags);
  86                 recalc_sigpending_tsk(p);
  87                 spin_unlock_irqrestore(&p->sighand->siglock, flags);
  88         }
  89 }
  90
  91 static inline int is_user_space(struct task_struct *p)
  92 {
  93         return p->mm && !(p->flags & PF_BORROWED_MM);
  94 }
  95
  96 static unsigned int try_to_freeze_tasks(int freeze_user_space)
  97 {
  98         struct task_struct *g, *p;
  99         unsigned long end_time;
 100         unsigned int todo;
 101
 102         end_time = jiffies + TIMEOUT;
 103         do {
 104                 todo = 0;
 105                 read_lock(&tasklist_lock);
 106                 do_each_thread(g, p) {
 107                         if (!freezeable(p))
 108                                 continue;
 109
 110                         if (frozen(p))
 111                                 continue;
 112
 113                         if (p->state == TASK_TRACED && frozen(p->parent)) {
 114                                 cancel_freezing(p);
 115                                 continue;
 116                         }
 117                         if (is_user_space(p)) {
 118                                 if (!freeze_user_space)
 119                                         continue;
 120
 121                                 /* Freeze the task unless there is a vfork
 122                                  * completion pending
 123                                  */
 124                                 if (!p->vfork_done)
 125                                         freeze_process(p);
 126                         } else {
 127                                 if (freeze_user_space)
 128                                         continue;
 129
 130                                 freeze_process(p);
 131                         }
 132                         todo++;
 133                 } while_each_thread(g, p);
 134                 read_unlock(&tasklist_lock);
 135                 yield();                        /* Yield is okay here */
 136                 if (todo && time_after(jiffies, end_time))
 137                         break;
 138         } while (todo);
 139
 140         if (todo) {
 141                 /* This does not unfreeze processes that are already frozen
 142                  * (we have slightly ugly calling convention in that respect,
 143                  * and caller must call thaw_processes() if something fails),
 144                  * but it cleans up leftover PF_FREEZE requests.
 145                  */
 146                 printk("\n");
 147                 printk(KERN_ERR "Stopping %s timed out after %d seconds "
 148                                 "(%d tasks refusing to freeze):\n",
 149                                 freeze_user_space ? "user space processes" :
 150                                         "kernel threads",
 151                                 TIMEOUT / HZ, todo);
 152                 read_lock(&tasklist_lock);
 153                 do_each_thread(g, p) {
 154                         if (is_user_space(p) == !freeze_user_space)
 155                                 continue;
 156
 157                         if (freezeable(p) && !frozen(p))
 158                                 printk(KERN_ERR " %s\n", p->comm);
 159
 160                         cancel_freezing(p);
 161                 } while_each_thread(g, p);
 162                 read_unlock(&tasklist_lock);
 163         }
 164
 165         return todo;
 166 }
 167
 168 /**
 169  *      freeze_processes - tell processes to enter the refrigerator
 170  *
 171  *      Returns 0 on success, or the number of processes that didn't freeze,
 172  *      although they were told to.
 173  */
 174 int freeze_processes(void)
 175 {
 176         unsigned int nr_unfrozen;
 177
 178         printk("Stopping tasks ... ");
 179         nr_unfrozen = try_to_freeze_tasks(FREEZER_USER_SPACE);
 180         if (nr_unfrozen)
 181                 return nr_unfrozen;
 182
 183         sys_sync();
 184         nr_unfrozen = try_to_freeze_tasks(FREEZER_KERNEL_THREADS);
 185         if (nr_unfrozen)
 186                 return nr_unfrozen;
 187
 188         printk("done.\n");
 189         BUG_ON(in_atomic());
 190         return 0;
 191 }
 192
 193 static void thaw_tasks(int thaw_user_space)
 194 {
 195         struct task_struct *g, *p;
 196
 197         read_lock(&tasklist_lock);
 198         do_each_thread(g, p) {
 199                 if (!freezeable(p))
 200                         continue;
 201
 202                 if (is_user_space(p) == !thaw_user_space)
 203                         continue;
 204
 205                 if (!thaw_process(p))
 206                         printk(KERN_WARNING " Strange, %s not stopped\n",
 207                                 p->comm );
 208         } while_each_thread(g, p);
 209         read_unlock(&tasklist_lock);
 210 }
 211
 212 void thaw_processes(void)
 213 {
 214         printk("Restarting tasks ... ");
 215         thaw_tasks(FREEZER_KERNEL_THREADS);
 216         thaw_tasks(FREEZER_USER_SPACE);
 217         schedule();
 218         printk("done.\n");
 219 }
 220
 221 EXPORT_SYMBOL(refrigerator);