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 freezable(struct task_struct * p)
  26 {
  27         if ((p == current) ||
  28             (p->flags & PF_NOFREEZE))
  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         bool wq_busy = false;
  39         struct timeval start, end;
  40         u64 elapsed_csecs64;
  41         unsigned int elapsed_csecs;
  42         bool wakeup = false;
  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) || !freezable(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                          * Because freeze_task() goes through p's
  68                          * scheduler lock after setting TIF_FREEZE, it's
  69                          * guaranteed that either we see TASK_RUNNING or
  70                          * try_to_stop() after schedule() in ptrace/signal
  71                          * stop sees TIF_FREEZE.
  72                          */
  73                         if (!task_is_stopped_or_traced(p) &&
  74                             !freezer_should_skip(p))
  75                                 todo++;
  76                 } while_each_thread(g, p);
  77                 read_unlock(&tasklist_lock);
  78
  79                 if (!sig_only) {
  80                         wq_busy = freeze_workqueues_busy();
  81                         todo += wq_busy;
  82                 }
  83
  84                 if (!todo || time_after(jiffies, end_time))
  85                         break;
  86
  87                 if (pm_wakeup_pending()) {
  88                         wakeup = true;
  89                         break;
  90                 }
  91
  92                 /*
  93                  * We need to retry, but first give the freezing tasks some
  94                  * time to enter the regrigerator.
  95                  */
  96                 msleep(10);
  97         }
  98
  99         do_gettimeofday(&end);
 100         elapsed_csecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
 101         do_div(elapsed_csecs64, NSEC_PER_SEC / 100);
 102         elapsed_csecs = elapsed_csecs64;
 103
 104         if (todo) {
 105                 /* This does not unfreeze processes that are already frozen
 106                  * (we have slightly ugly calling convention in that respect,
 107                  * and caller must call thaw_processes() if something fails),
 108                  * but it cleans up leftover PF_FREEZE requests.
 109                  */
 110                 printk("\n");
 111                 printk(KERN_ERR "Freezing of tasks %s after %d.%02d seconds "
 112                        "(%d tasks refusing to freeze, wq_busy=%d):\n",
 113                        wakeup ? "aborted" : "failed",
 114                        elapsed_csecs / 100, elapsed_csecs % 100,
 115                        todo - wq_busy, wq_busy);
 116
 117                 thaw_workqueues();
 118
 119                 read_lock(&tasklist_lock);
 120                 do_each_thread(g, p) {
 121                         if (!wakeup && !freezer_should_skip(p) &&
 122                             freezing(p) && !frozen(p))
 123                                 sched_show_task(p);
 124                         cancel_freezing(p);
 125                 } while_each_thread(g, p);
 126                 read_unlock(&tasklist_lock);
 127         } else {
 128                 printk("(elapsed %d.%02d seconds) ", elapsed_csecs / 100,
 129                         elapsed_csecs % 100);
 130         }
 131
 132         return todo ? -EBUSY : 0;
 133 }
 134
 135 /**
 136  * freeze_processes - Signal user space processes to enter the refrigerator.
 137  */
 138 int freeze_processes(void)
 139 {
 140         int error;
 141
 142         printk("Freezing user space processes ... ");
 143         error = try_to_freeze_tasks(true);
 144         if (!error) {
 145                 printk("done.");
 146                 oom_killer_disable();
 147         }
 148         printk("\n");
 149         BUG_ON(in_atomic());
 150
 151         return error;
 152 }
 153
 154 /**
 155  * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
 156  */
 157 int freeze_kernel_threads(void)
 158 {
 159         int error;
 160
 161         printk("Freezing remaining freezable tasks ... ");
 162         error = try_to_freeze_tasks(false);
 163         if (!error)
 164                 printk("done.");
 165
 166         printk("\n");
 167         BUG_ON(in_atomic());
 168
 169         return error;
 170 }
 171
 172 void thaw_processes(void)
 173 {
 174         struct task_struct *g, *p;
 175
 176         oom_killer_enable();
 177
 178         printk("Restarting tasks ... ");
 179
 180         thaw_workqueues();
 181
 182         read_lock(&tasklist_lock);
 183         do_each_thread(g, p) {
 184                 if (!freezable(p))
 185                         continue;
 186
 187                 if (cgroup_freezing_or_frozen(p))
 188                         continue;
 189
 190                 __thaw_task(p);
 191         } while_each_thread(g, p);
 192         read_unlock(&tasklist_lock);
 193
 194         schedule();
 195         printk("done.\n");
 196 }
 197