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 static int try_to_freeze_tasks(bool sig_only)
  32 {
  33         struct task_struct *g, *p;
  34         unsigned long end_time;
  35         unsigned int todo;
  36         struct timeval start, end;
  37         u64 elapsed_csecs64;
  38         unsigned int elapsed_csecs;
  39
  40         do_gettimeofday(&start);
  41
  42         end_time = jiffies + TIMEOUT;
  43         do {
  44                 todo = 0;
  45                 read_lock(&tasklist_lock);
  46                 do_each_thread(g, p) {
  47                         if (frozen(p) || !freezeable(p))
  48                                 continue;
  49
  50                         if (!freeze_task(p, sig_only))
  51                                 continue;
  52
  53                         /*
  54                          * Now that we've done set_freeze_flag, don't
  55                          * perturb a task in TASK_STOPPED or TASK_TRACED.
  56                          * It is "frozen enough".  If the task does wake
  57                          * up, it will immediately call try_to_freeze.
  58                          */
  59                         if (!task_is_stopped_or_traced(p) &&
  60                             !freezer_should_skip(p))
  61                                 todo++;
  62                 } while_each_thread(g, p);
  63                 read_unlock(&tasklist_lock);
  64                 yield();                        /* Yield is okay here */
  65                 if (time_after(jiffies, end_time))
  66                         break;
  67         } while (todo);
  68
  69         do_gettimeofday(&end);
  70         elapsed_csecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
  71         do_div(elapsed_csecs64, NSEC_PER_SEC / 100);
  72         elapsed_csecs = elapsed_csecs64;
  73
  74         if (todo) {
  75                 /* This does not unfreeze processes that are already frozen
  76                  * (we have slightly ugly calling convention in that respect,
  77                  * and caller must call thaw_processes() if something fails),
  78                  * but it cleans up leftover PF_FREEZE requests.
  79                  */
  80                 printk("\n");
  81                 printk(KERN_ERR "Freezing of tasks failed after %d.%02d seconds "
  82                                 "(%d tasks refusing to freeze):\n",
  83                                 elapsed_csecs / 100, elapsed_csecs % 100, todo);
  84                 show_state();
  85                 read_lock(&tasklist_lock);
  86                 do_each_thread(g, p) {
  87                         task_lock(p);
  88                         if (freezing(p) && !freezer_should_skip(p))
  89                                 printk(KERN_ERR " %s\n", p->comm);
  90                         cancel_freezing(p);
  91                         task_unlock(p);
  92                 } while_each_thread(g, p);
  93                 read_unlock(&tasklist_lock);
  94         } else {
  95                 printk("(elapsed %d.%02d seconds) ", elapsed_csecs / 100,
  96                         elapsed_csecs % 100);
  97         }
  98
  99         return todo ? -EBUSY : 0;
 100 }
 101
 102 /**
 103  *      freeze_processes - tell processes to enter the refrigerator
 104  */
 105 int freeze_processes(void)
 106 {
 107         int error;
 108
 109         printk("Freezing user space processes ... ");
 110         error = try_to_freeze_tasks(true);
 111         if (error)
 112                 goto Exit;
 113         printk("done.\n");
 114
 115         printk("Freezing remaining freezable tasks ... ");
 116         error = try_to_freeze_tasks(false);
 117         if (error)
 118                 goto Exit;
 119         printk("done.");
 120
 121         oom_killer_disable();
 122  Exit:
 123         BUG_ON(in_atomic());
 124         printk("\n");
 125
 126         return error;
 127 }
 128
 129 static void thaw_tasks(bool nosig_only)
 130 {
 131         struct task_struct *g, *p;
 132
 133         read_lock(&tasklist_lock);
 134         do_each_thread(g, p) {
 135                 if (!freezeable(p))
 136                         continue;
 137
 138                 if (nosig_only && should_send_signal(p))
 139                         continue;
 140
 141                 if (cgroup_frozen(p))
 142                         continue;
 143
 144                 thaw_process(p);
 145         } while_each_thread(g, p);
 146         read_unlock(&tasklist_lock);
 147 }
 148
 149 void thaw_processes(void)
 150 {
 151         oom_killer_enable();
 152
 153         printk("Restarting tasks ... ");
 154         thaw_tasks(true);
 155         thaw_tasks(false);
 156         schedule();
 157         printk("done.\n");
 158 }
 159