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   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                 read_lock(&tasklist_lock);
  92                 do_each_thread(g, p) {
  93                         task_lock(p);
  94                         if (freezing(p) && !freezer_should_skip(p))
  95                                 sched_show_task(p);
  96                         cancel_freezing(p);
  97                         task_unlock(p);
  98                 } while_each_thread(g, p);
  99                 read_unlock(&tasklist_lock);
 100         } else {
 101                 printk("(elapsed %d.%02d seconds) ", elapsed_csecs / 100,
 102                         elapsed_csecs % 100);
 103         }
 104
 105         return todo ? -EBUSY : 0;
 106 }
 107
 108 /**
 109  *      freeze_processes - tell processes to enter the refrigerator
 110  */
 111 int freeze_processes(void)
 112 {
 113         int error;
 114
 115         printk("Freezing user space processes ... ");
 116         error = try_to_freeze_tasks(true);
 117         if (error)
 118                 goto Exit;
 119         printk("done.\n");
 120
 121         printk("Freezing remaining freezable tasks ... ");
 122         error = try_to_freeze_tasks(false);
 123         if (error)
 124                 goto Exit;
 125         printk("done.");
 126
 127         oom_killer_disable();
 128  Exit:
 129         BUG_ON(in_atomic());
 130         printk("\n");
 131
 132         return error;
 133 }
 134
 135 static void thaw_tasks(bool nosig_only)
 136 {
 137         struct task_struct *g, *p;
 138
 139         read_lock(&tasklist_lock);
 140         do_each_thread(g, p) {
 141                 if (!freezeable(p))
 142                         continue;
 143
 144                 if (nosig_only && should_send_signal(p))
 145                         continue;
 146
 147                 if (cgroup_freezing_or_frozen(p))
 148                         continue;
 149
 150                 thaw_process(p);
 151         } while_each_thread(g, p);
 152         read_unlock(&tasklist_lock);
 153 }
 154
 155 void thaw_processes(void)
 156 {
 157         oom_killer_enable();
 158
 159         printk("Restarting tasks ... ");
 160         thaw_tasks(true);
 161         thaw_tasks(false);
 162         schedule();
 163         printk("done.\n");
 164 }
 165