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 #include <linux/wakelock.h>
  20
  21 /*
  22  * Timeout for stopping processes
  23  */
  24 #define TIMEOUT (20 * HZ)
  25
  26 static inline int freezable(struct task_struct * p)
  27 {
  28         if ((p == current) ||
  29             (p->flags & PF_NOFREEZE) ||
  30             (p->exit_state != 0))
  31                 return 0;
  32         return 1;
  33 }
  34
  35 static int try_to_freeze_tasks(bool sig_only)
  36 {
  37         struct task_struct *g, *p;
  38         unsigned long end_time;
  39         unsigned int todo;
  40         bool wq_busy = false;
  41         struct timeval start, end;
  42         u64 elapsed_csecs64;
  43         unsigned int elapsed_csecs;
  44         bool wakeup = false;
  45
  46         do_gettimeofday(&start);
  47
  48         end_time = jiffies + TIMEOUT;
  49
  50         if (!sig_only)
  51                 freeze_workqueues_begin();
  52
  53         while (true) {
  54                 todo = 0;
  55                 read_lock(&tasklist_lock);
  56                 do_each_thread(g, p) {
  57                         if (frozen(p) || !freezable(p))
  58                                 continue;
  59
  60                         if (!freeze_task(p, sig_only))
  61                                 continue;
  62
  63                         /*
  64                          * Now that we've done set_freeze_flag, don't
  65                          * perturb a task in TASK_STOPPED or TASK_TRACED.
  66                          * It is "frozen enough".  If the task does wake
  67                          * up, it will immediately call try_to_freeze.
  68                          *
  69                          * Because freeze_task() goes through p's
  70                          * scheduler lock after setting TIF_FREEZE, it's
  71                          * guaranteed that either we see TASK_RUNNING or
  72                          * try_to_stop() after schedule() in ptrace/signal
  73                          * stop sees TIF_FREEZE.
  74                          */
  75                         if (!task_is_stopped_or_traced(p) &&
  76                             !freezer_should_skip(p))
  77                                 todo++;
  78                 } while_each_thread(g, p);
  79                 read_unlock(&tasklist_lock);
  80
  81                 if (!sig_only) {
  82                         wq_busy = freeze_workqueues_busy();
  83                         todo += wq_busy;
  84                 }
  85
  86                 if (todo && has_wake_lock(WAKE_LOCK_SUSPEND)) {
  87                         wakeup = 1;
  88                         break;
  89                 }
  90                 if (!todo || time_after(jiffies, end_time))
  91                         break;
  92
  93                 if (pm_wakeup_pending()) {
  94                         wakeup = true;
  95                         break;
  96                 }
  97
  98                 /*
  99                  * We need to retry, but first give the freezing tasks some
 100                  * time to enter the regrigerator.
 101                  */
 102                 msleep(10);
 103         }
 104
 105         do_gettimeofday(&end);
 106         elapsed_csecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
 107         do_div(elapsed_csecs64, NSEC_PER_SEC / 100);
 108         elapsed_csecs = elapsed_csecs64;
 109
 110         if (todo) {
 111                 /* This does not unfreeze processes that are already frozen
 112                  * (we have slightly ugly calling convention in that respect,
 113                  * and caller must call thaw_processes() if something fails),
 114                  * but it cleans up leftover PF_FREEZE requests.
 115                  */
 116                 if(wakeup) {
 117                         printk("\n");
 118                         printk(KERN_ERR "Freezing of %s aborted\n",
 119                                         sig_only ? "user space " : "tasks ");
 120                 }
 121                 else {
 122                         printk("\n");
 123                         printk(KERN_ERR "Freezing of tasks failed after %d.%02d seconds "
 124                                "(%d tasks refusing to freeze, wq_busy=%d):\n",
 125                                elapsed_csecs / 100, elapsed_csecs % 100,
 126                                todo - wq_busy, wq_busy);
 127                 }
 128                 thaw_workqueues();
 129
 130                 read_lock(&tasklist_lock);
 131                 do_each_thread(g, p) {
 132                         task_lock(p);
 133                         if (freezing(p) && !freezer_should_skip(p) &&
 134                                 elapsed_csecs > 100)
 135                                 sched_show_task(p);
 136                         cancel_freezing(p);
 137                         task_unlock(p);
 138                 } while_each_thread(g, p);
 139                 read_unlock(&tasklist_lock);
 140         } else {
 141                 printk("(elapsed %d.%02d seconds) ", elapsed_csecs / 100,
 142                         elapsed_csecs % 100);
 143         }
 144
 145         return todo ? -EBUSY : 0;
 146 }
 147
 148 /**
 149  *      freeze_processes - tell processes to enter the refrigerator
 150  */
 151 int freeze_processes(void)
 152 {
 153         int error;
 154
 155         printk("Freezing user space processes ... ");
 156         error = try_to_freeze_tasks(true);
 157         if (error)
 158                 goto Exit;
 159         printk("done.\n");
 160
 161         printk("Freezing remaining freezable tasks ... ");
 162         error = try_to_freeze_tasks(false);
 163         if (error)
 164                 goto Exit;
 165         printk("done.");
 166
 167         oom_killer_disable();
 168  Exit:
 169         BUG_ON(in_atomic());
 170         printk("\n");
 171
 172         return error;
 173 }
 174
 175 static void thaw_tasks(bool nosig_only)
 176 {
 177         struct task_struct *g, *p;
 178
 179         read_lock(&tasklist_lock);
 180         do_each_thread(g, p) {
 181                 if (!freezable(p))
 182                         continue;
 183
 184                 if (nosig_only && should_send_signal(p))
 185                         continue;
 186
 187                 if (cgroup_freezing_or_frozen(p))
 188                         continue;
 189
 190                 thaw_process(p);
 191         } while_each_thread(g, p);
 192         read_unlock(&tasklist_lock);
 193 }
 194
 195 void thaw_processes(void)
 196 {
 197         oom_killer_enable();
 198
 199         printk("Restarting tasks ... ");
 200         thaw_workqueues();
 201         thaw_tasks(true);
 202         thaw_tasks(false);
 203         schedule();
 204         printk("done.\n");
 205 }
 206