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 #include <linux/workqueue.h>
  19
  20 /*
  21  * Timeout for stopping processes
  22  */
  23 #define TIMEOUT (20 * HZ)
  24
  25 static inline int freezeable(struct task_struct * p)
  26 {
  27         if ((p == current) ||
  28             (p->flags & PF_NOFREEZE) ||
  29             (p->exit_state != 0))
  30                 return 0;
  31         return 1;
  32 }
  33
  34 static int try_to_freeze_tasks(bool sig_only)
  35 {
  36         struct task_struct *g, *p;
  37         unsigned long end_time;
  38         unsigned int todo;
  39         bool wq_busy = false;
  40         struct timeval start, end;
  41         u64 elapsed_csecs64;
  42         unsigned int elapsed_csecs;
  43
  44         do_gettimeofday(&start);
  45
  46         end_time = jiffies + TIMEOUT;
  47
  48         if (!sig_only)
  49                 freeze_workqueues_begin();
  50
  51         while (true) {
  52                 todo = 0;
  53                 read_lock(&tasklist_lock);
  54                 do_each_thread(g, p) {
  55                         if (frozen(p) || !freezeable(p))
  56                                 continue;
  57
  58                         if (!freeze_task(p, sig_only))
  59                                 continue;
  60
  61                         /*
  62                          * Now that we've done set_freeze_flag, don't
  63                          * perturb a task in TASK_STOPPED or TASK_TRACED.
  64                          * It is "frozen enough".  If the task does wake
  65                          * up, it will immediately call try_to_freeze.
  66                          */
  67                         if (!task_is_stopped_or_traced(p) &&
  68                             !freezer_should_skip(p))
  69                                 todo++;
  70                 } while_each_thread(g, p);
  71                 read_unlock(&tasklist_lock);
  72
  73                 if (!sig_only) {
  74                         wq_busy = freeze_workqueues_busy();
  75                         todo += wq_busy;
  76                 }
  77
  78                 if (!todo || time_after(jiffies, end_time))
  79                         break;
  80
  81                 /*
  82                  * We need to retry, but first give the freezing tasks some
  83                  * time to enter the regrigerator.
  84                  */
  85                 msleep(10);
  86         }
  87
  88         do_gettimeofday(&end);
  89         elapsed_csecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
  90         do_div(elapsed_csecs64, NSEC_PER_SEC / 100);
  91         elapsed_csecs = elapsed_csecs64;
  92
  93         if (todo) {
  94                 /* This does not unfreeze processes that are already frozen
  95                  * (we have slightly ugly calling convention in that respect,
  96                  * and caller must call thaw_processes() if something fails),
  97                  * but it cleans up leftover PF_FREEZE requests.
  98                  */
  99                 printk("\n");
 100                 printk(KERN_ERR "Freezing of tasks failed after %d.%02d seconds "
 101                        "(%d tasks refusing to freeze, wq_busy=%d):\n",
 102                        elapsed_csecs / 100, elapsed_csecs % 100,
 103                        todo - wq_busy, wq_busy);
 104
 105                 thaw_workqueues();
 106
 107                 read_lock(&tasklist_lock);
 108                 do_each_thread(g, p) {
 109                         task_lock(p);
 110                         if (freezing(p) && !freezer_should_skip(p))
 111                                 sched_show_task(p);
 112                         cancel_freezing(p);
 113                         task_unlock(p);
 114                 } while_each_thread(g, p);
 115                 read_unlock(&tasklist_lock);
 116         } else {
 117                 printk("(elapsed %d.%02d seconds) ", elapsed_csecs / 100,
 118                         elapsed_csecs % 100);
 119         }
 120
 121         return todo ? -EBUSY : 0;
 122 }
 123
 124 /**
 125  *      freeze_processes - tell processes to enter the refrigerator
 126  */
 127 int freeze_processes(void)
 128 {
 129         int error;
 130
 131         printk("Freezing user space processes ... ");
 132         error = try_to_freeze_tasks(true);
 133         if (error)
 134                 goto Exit;
 135         printk("done.\n");
 136
 137         printk("Freezing remaining freezable tasks ... ");
 138         error = try_to_freeze_tasks(false);
 139         if (error)
 140                 goto Exit;
 141         printk("done.");
 142
 143         oom_killer_disable();
 144  Exit:
 145         BUG_ON(in_atomic());
 146         printk("\n");
 147
 148         return error;
 149 }
 150
 151 static void thaw_tasks(bool nosig_only)
 152 {
 153         struct task_struct *g, *p;
 154
 155         read_lock(&tasklist_lock);
 156         do_each_thread(g, p) {
 157                 if (!freezeable(p))
 158                         continue;
 159
 160                 if (nosig_only && should_send_signal(p))
 161                         continue;
 162
 163                 if (cgroup_freezing_or_frozen(p))
 164                         continue;
 165
 166                 thaw_process(p);
 167         } while_each_thread(g, p);
 168         read_unlock(&tasklist_lock);
 169 }
 170
 171 void thaw_processes(void)
 172 {
 173         oom_killer_enable();
 174
 175         printk("Restarting tasks ... ");
 176         thaw_workqueues();
 177         thaw_tasks(true);
 178         thaw_tasks(false);
 179         schedule();
 180         printk("done.\n");
 181 }
 182