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         bool wakeup = false;
  44
  45         do_gettimeofday(&start);
  46
  47         end_time = jiffies + TIMEOUT;
  48
  49         if (!sig_only)
  50                 freeze_workqueues_begin();
  51
  52         while (true) {
  53                 todo = 0;
  54                 read_lock(&tasklist_lock);
  55                 do_each_thread(g, p) {
  56                         if (frozen(p) || !freezeable(p))
  57                                 continue;
  58
  59                         if (!freeze_task(p, sig_only))
  60                                 continue;
  61
  62                         /*
  63                          * Now that we've done set_freeze_flag, don't
  64                          * perturb a task in TASK_STOPPED or TASK_TRACED.
  65                          * It is "frozen enough".  If the task does wake
  66                          * up, it will immediately call try_to_freeze.
  67                          */
  68                         if (!task_is_stopped_or_traced(p) &&
  69                             !freezer_should_skip(p))
  70                                 todo++;
  71                 } while_each_thread(g, p);
  72                 read_unlock(&tasklist_lock);
  73
  74                 if (!sig_only) {
  75                         wq_busy = freeze_workqueues_busy();
  76                         todo += wq_busy;
  77                 }
  78
  79                 if (!todo || time_after(jiffies, end_time))
  80                         break;
  81
  82                 if (!pm_check_wakeup_events()) {
  83                         wakeup = true;
  84                         break;
  85                 }
  86
  87                 /*
  88                  * We need to retry, but first give the freezing tasks some
  89                  * time to enter the regrigerator.
  90                  */
  91                 msleep(10);
  92         }
  93
  94         do_gettimeofday(&end);
  95         elapsed_csecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
  96         do_div(elapsed_csecs64, NSEC_PER_SEC / 100);
  97         elapsed_csecs = elapsed_csecs64;
  98
  99         if (todo) {
 100                 /* This does not unfreeze processes that are already frozen
 101                  * (we have slightly ugly calling convention in that respect,
 102                  * and caller must call thaw_processes() if something fails),
 103                  * but it cleans up leftover PF_FREEZE requests.
 104                  */
 105                 printk("\n");
 106                 printk(KERN_ERR "Freezing of tasks %s after %d.%02d seconds "
 107                        "(%d tasks refusing to freeze, wq_busy=%d):\n",
 108                        wakeup ? "aborted" : "failed",
 109                        elapsed_csecs / 100, elapsed_csecs % 100,
 110                        todo - wq_busy, wq_busy);
 111
 112                 thaw_workqueues();
 113
 114                 read_lock(&tasklist_lock);
 115                 do_each_thread(g, p) {
 116                         task_lock(p);
 117                         if (!wakeup && freezing(p) && !freezer_should_skip(p))
 118                                 sched_show_task(p);
 119                         cancel_freezing(p);
 120                         task_unlock(p);
 121                 } while_each_thread(g, p);
 122                 read_unlock(&tasklist_lock);
 123         } else {
 124                 printk("(elapsed %d.%02d seconds) ", elapsed_csecs / 100,
 125                         elapsed_csecs % 100);
 126         }
 127
 128         return todo ? -EBUSY : 0;
 129 }
 130
 131 /**
 132  *      freeze_processes - tell processes to enter the refrigerator
 133  */
 134 int freeze_processes(void)
 135 {
 136         int error;
 137
 138         printk("Freezing user space processes ... ");
 139         error = try_to_freeze_tasks(true);
 140         if (error)
 141                 goto Exit;
 142         printk("done.\n");
 143
 144         printk("Freezing remaining freezable tasks ... ");
 145         error = try_to_freeze_tasks(false);
 146         if (error)
 147                 goto Exit;
 148         printk("done.");
 149
 150         oom_killer_disable();
 151  Exit:
 152         BUG_ON(in_atomic());
 153         printk("\n");
 154
 155         return error;
 156 }
 157
 158 static void thaw_tasks(bool nosig_only)
 159 {
 160         struct task_struct *g, *p;
 161
 162         read_lock(&tasklist_lock);
 163         do_each_thread(g, p) {
 164                 if (!freezeable(p))
 165                         continue;
 166
 167                 if (nosig_only && should_send_signal(p))
 168                         continue;
 169
 170                 if (cgroup_freezing_or_frozen(p))
 171                         continue;
 172
 173                 thaw_process(p);
 174         } while_each_thread(g, p);
 175         read_unlock(&tasklist_lock);
 176 }
 177
 178 void thaw_processes(void)
 179 {
 180         oom_killer_enable();
 181
 182         printk("Restarting tasks ... ");
 183         thaw_workqueues();
 184         thaw_tasks(true);
 185         thaw_tasks(false);
 186         schedule();
 187         printk("done.\n");
 188 }
 189