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/moduleparam.h>
  16 #include <linux/syscalls.h>
  17 #include <linux/freezer.h>
  18 #include <linux/delay.h>
  19 #include <linux/workqueue.h>
  20
  21 /*
  22  * Timeout for stopping processes
  23  */
  24 int freeze_task_timeout = 20;
  25 EXPORT_SYMBOL(freeze_task_timeout);
  26 module_param(freeze_task_timeout, int, S_IRUGO | S_IWUSR);
  27
  28 #define TIMEOUT (freeze_task_timeout * HZ)
  29
  30 static inline int freezeable(struct task_struct * p)
  31 {
  32         if ((p == current) ||
  33             (p->flags & PF_NOFREEZE) ||
  34             (p->exit_state != 0))
  35                 return 0;
  36         return 1;
  37 }
  38
  39 static int try_to_freeze_tasks(bool sig_only)
  40 {
  41         struct task_struct *g, *p;
  42         unsigned long end_time;
  43         unsigned int todo;
  44         bool wq_busy = false;
  45         struct timeval start, end;
  46         u64 elapsed_csecs64;
  47         unsigned int elapsed_csecs;
  48
  49         do_gettimeofday(&start);
  50
  51         end_time = jiffies + TIMEOUT;
  52
  53         if (!sig_only)
  54                 freeze_workqueues_begin();
  55
  56         while (true) {
  57                 todo = 0;
  58                 read_lock(&tasklist_lock);
  59                 do_each_thread(g, p) {
  60                         if (frozen(p) || !freezeable(p))
  61                                 continue;
  62
  63                         if (!freeze_task(p, sig_only))
  64                                 continue;
  65
  66                         /*
  67                          * Now that we've done set_freeze_flag, don't
  68                          * perturb a task in TASK_STOPPED or TASK_TRACED.
  69                          * It is "frozen enough".  If the task does wake
  70                          * up, it will immediately call try_to_freeze.
  71                          */
  72                         if (!task_is_stopped_or_traced(p) &&
  73                             !freezer_should_skip(p))
  74                                 todo++;
  75                 } while_each_thread(g, p);
  76                 read_unlock(&tasklist_lock);
  77
  78                 if (!sig_only) {
  79                         wq_busy = freeze_workqueues_busy();
  80                         todo += wq_busy;
  81                 }
  82
  83                 if (!todo || time_after(jiffies, end_time))
  84                         break;
  85
  86                 /*
  87                  * We need to retry, but first give the freezing tasks some
  88                  * time to enter the regrigerator.
  89                  */
  90                 msleep(10);
  91         }
  92
  93         do_gettimeofday(&end);
  94         elapsed_csecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
  95         do_div(elapsed_csecs64, NSEC_PER_SEC / 100);
  96         elapsed_csecs = elapsed_csecs64;
  97
  98         if (todo) {
  99                 /* This does not unfreeze processes that are already frozen
 100                  * (we have slightly ugly calling convention in that respect,
 101                  * and caller must call thaw_processes() if something fails),
 102                  * but it cleans up leftover PF_FREEZE requests.
 103                  */
 104                 printk("\n");
 105                 printk(KERN_ERR "Freezing of tasks failed after %d.%02d seconds "
 106                        "(%d tasks refusing to freeze, wq_busy=%d):\n",
 107                        elapsed_csecs / 100, elapsed_csecs % 100,
 108                        todo - wq_busy, wq_busy);
 109
 110                 thaw_workqueues();
 111
 112                 read_lock(&tasklist_lock);
 113                 do_each_thread(g, p) {
 114                         task_lock(p);
 115                         if (freezing(p) && !freezer_should_skip(p))
 116                                 sched_show_task(p);
 117                         cancel_freezing(p);
 118                         task_unlock(p);
 119                 } while_each_thread(g, p);
 120                 read_unlock(&tasklist_lock);
 121         } else {
 122                 printk("(elapsed %d.%02d seconds) ", elapsed_csecs / 100,
 123                         elapsed_csecs % 100);
 124         }
 125
 126         return todo ? -EBUSY : 0;
 127 }
 128
 129 /**
 130  *      freeze_processes - tell processes to enter the refrigerator
 131  */
 132 int freeze_processes(void)
 133 {
 134         int error;
 135
 136         printk("Freezing user space processes ... ");
 137         error = try_to_freeze_tasks(true);
 138         if (error)
 139                 goto Exit;
 140         printk("done.\n");
 141
 142         printk("Freezing remaining freezable tasks ... ");
 143         error = try_to_freeze_tasks(false);
 144         if (error)
 145                 goto Exit;
 146         printk("done.");
 147
 148         oom_killer_disable();
 149  Exit:
 150         BUG_ON(in_atomic());
 151         printk("\n");
 152
 153         return error;
 154 }
 155
 156 static void thaw_tasks(bool nosig_only)
 157 {
 158         struct task_struct *g, *p;
 159
 160         read_lock(&tasklist_lock);
 161         do_each_thread(g, p) {
 162                 if (!freezeable(p))
 163                         continue;
 164
 165                 if (nosig_only && should_send_signal(p))
 166                         continue;
 167
 168                 if (cgroup_freezing_or_frozen(p))
 169                         continue;
 170
 171                 thaw_process(p);
 172         } while_each_thread(g, p);
 173         read_unlock(&tasklist_lock);
 174 }
 175
 176 void thaw_processes(void)
 177 {
 178         oom_killer_enable();
 179
 180         printk("Restarting tasks ... ");
 181         thaw_workqueues();
 182         thaw_tasks(true);
 183         thaw_tasks(false);
 184         schedule();
 185         printk("done.\n");
 186 }
 187