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/oom.h>
  13 #include <linux/suspend.h>
  14 #include <linux/module.h>
  15 #include <linux/syscalls.h>
  16 #include <linux/freezer.h>
  17 #include <linux/delay.h>
  18
  19 /*
  20  * Timeout for stopping processes
  21  */
  22 #define TIMEOUT (20 * HZ)
  23
  24 static inline int freezeable(struct task_struct * p)
  25 {
  26         if ((p == current) ||
  27             (p->flags & PF_NOFREEZE) ||
  28             (p->exit_state != 0))
  29                 return 0;
  30         return 1;
  31 }
  32
  33 static int try_to_freeze_tasks(bool sig_only)
  34 {
  35         struct task_struct *g, *p;
  36         unsigned long end_time;
  37         unsigned int todo;
  38         struct timeval start, end;
  39         u64 elapsed_csecs64;
  40         unsigned int elapsed_csecs;
  41
  42         do_gettimeofday(&start);
  43
  44         end_time = jiffies + TIMEOUT;
  45         while (true) {
  46                 todo = 0;
  47                 read_lock(&tasklist_lock);
  48                 do_each_thread(g, p) {
  49                         if (frozen(p) || !freezeable(p))
  50                                 continue;
  51
  52                         if (!freeze_task(p, sig_only))
  53                                 continue;
  54
  55                         /*
  56                          * Now that we've done set_freeze_flag, don't
  57                          * perturb a task in TASK_STOPPED or TASK_TRACED.
  58                          * It is "frozen enough".  If the task does wake
  59                          * up, it will immediately call try_to_freeze.
  60                          */
  61                         if (!task_is_stopped_or_traced(p) &&
  62                             !freezer_should_skip(p))
  63                                 todo++;
  64                 } while_each_thread(g, p);
  65                 read_unlock(&tasklist_lock);
  66                 if (!todo || time_after(jiffies, end_time))
  67                         break;
  68
  69                 /*
  70                  * We need to retry, but first give the freezing tasks some
  71                  * time to enter the regrigerator.
  72                  */
  73                 msleep(10);
  74         }
  75
  76         do_gettimeofday(&end);
  77         elapsed_csecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
  78         do_div(elapsed_csecs64, NSEC_PER_SEC / 100);
  79         elapsed_csecs = elapsed_csecs64;
  80
  81         if (todo) {
  82                 /* This does not unfreeze processes that are already frozen
  83                  * (we have slightly ugly calling convention in that respect,
  84                  * and caller must call thaw_processes() if something fails),
  85                  * but it cleans up leftover PF_FREEZE requests.
  86                  */
  87                 printk("\n");
  88                 printk(KERN_ERR "Freezing of tasks failed after %d.%02d seconds "
  89                                 "(%d tasks refusing to freeze):\n",
  90                                 elapsed_csecs / 100, elapsed_csecs % 100, todo);
  91                 show_state();
  92                 read_lock(&tasklist_lock);
  93                 do_each_thread(g, p) {
  94                         task_lock(p);
  95                         if (freezing(p) && !freezer_should_skip(p))
  96                                 printk(KERN_ERR " %s\n", p->comm);
  97                         cancel_freezing(p);
  98                         task_unlock(p);
  99                 } while_each_thread(g, p);
 100                 read_unlock(&tasklist_lock);
 101         } else {
 102                 printk("(elapsed %d.%02d seconds) ", elapsed_csecs / 100,
 103                         elapsed_csecs % 100);
 104         }
 105
 106         return todo ? -EBUSY : 0;
 107 }
 108
 109 /**
 110  *      freeze_processes - tell processes to enter the refrigerator
 111  */
 112 int freeze_processes(void)
 113 {
 114         int error;
 115
 116         printk("Freezing user space processes ... ");
 117         error = try_to_freeze_tasks(true);
 118         if (error)
 119                 goto Exit;
 120         printk("done.\n");
 121
 122         printk("Freezing remaining freezable tasks ... ");
 123         error = try_to_freeze_tasks(false);
 124         if (error)
 125                 goto Exit;
 126         printk("done.");
 127
 128         oom_killer_disable();
 129  Exit:
 130         BUG_ON(in_atomic());
 131         printk("\n");
 132
 133         return error;
 134 }
 135
 136 static void thaw_tasks(bool nosig_only)
 137 {
 138         struct task_struct *g, *p;
 139
 140         read_lock(&tasklist_lock);
 141         do_each_thread(g, p) {
 142                 if (!freezeable(p))
 143                         continue;
 144
 145                 if (nosig_only && should_send_signal(p))
 146                         continue;
 147
 148                 if (cgroup_freezing_or_frozen(p))
 149                         continue;
 150
 151                 thaw_process(p);
 152         } while_each_thread(g, p);
 153         read_unlock(&tasklist_lock);
 154 }
 155
 156 void thaw_processes(void)
 157 {
 158         oom_killer_enable();
 159
 160         printk("Restarting tasks ... ");
 161         thaw_tasks(true);
 162         thaw_tasks(false);
 163         schedule();
 164         printk("done.\n");
 165 }
 166