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             (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) || !freezable(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                          * Because freeze_task() goes through p's
  69                          * scheduler lock after setting TIF_FREEZE, it's
  70                          * guaranteed that either we see TASK_RUNNING or
  71                          * try_to_stop() after schedule() in ptrace/signal
  72                          * stop sees TIF_FREEZE.
  73                          */
  74                         if (!task_is_stopped_or_traced(p) &&
  75                             !freezer_should_skip(p))
  76                                 todo++;
  77                 } while_each_thread(g, p);
  78                 read_unlock(&tasklist_lock);
  79
  80                 if (!sig_only) {
  81                         wq_busy = freeze_workqueues_busy();
  82                         todo += wq_busy;
  83                 }
  84
  85                 if (!todo || time_after(jiffies, end_time))
  86                         break;
  87
  88                 if (pm_wakeup_pending()) {
  89                         wakeup = true;
  90                         break;
  91                 }
  92
  93                 /*
  94                  * We need to retry, but first give the freezing tasks some
  95                  * time to enter the regrigerator.
  96                  */
  97                 msleep(10);
  98         }
  99
 100         do_gettimeofday(&end);
 101         elapsed_csecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
 102         do_div(elapsed_csecs64, NSEC_PER_SEC / 100);
 103         elapsed_csecs = elapsed_csecs64;
 104
 105         if (todo) {
 106                 /* This does not unfreeze processes that are already frozen
 107                  * (we have slightly ugly calling convention in that respect,
 108                  * and caller must call thaw_processes() if something fails),
 109                  * but it cleans up leftover PF_FREEZE requests.
 110                  */
 111                 printk("\n");
 112                 printk(KERN_ERR "Freezing of tasks %s after %d.%02d seconds "
 113                        "(%d tasks refusing to freeze, wq_busy=%d):\n",
 114                        wakeup ? "aborted" : "failed",
 115                        elapsed_csecs / 100, elapsed_csecs % 100,
 116                        todo - wq_busy, wq_busy);
 117
 118                 thaw_workqueues();
 119
 120                 read_lock(&tasklist_lock);
 121                 do_each_thread(g, p) {
 122                         task_lock(p);
 123                         if (!wakeup && freezing(p) && !freezer_should_skip(p))
 124                                 sched_show_task(p);
 125                         cancel_freezing(p);
 126                         task_unlock(p);
 127                 } while_each_thread(g, p);
 128                 read_unlock(&tasklist_lock);
 129         } else {
 130                 printk("(elapsed %d.%02d seconds) ", elapsed_csecs / 100,
 131                         elapsed_csecs % 100);
 132         }
 133
 134         return todo ? -EBUSY : 0;
 135 }
 136
 137 /**
 138  * freeze_processes - Signal user space processes to enter the refrigerator.
 139  */
 140 int freeze_processes(void)
 141 {
 142         int error;
 143
 144         printk("Freezing user space processes ... ");
 145         error = try_to_freeze_tasks(true);
 146         if (!error) {
 147                 printk("done.");
 148                 oom_killer_disable();
 149         }
 150         printk("\n");
 151         BUG_ON(in_atomic());
 152
 153         return error;
 154 }
 155
 156 /**
 157  * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
 158  */
 159 int freeze_kernel_threads(void)
 160 {
 161         int error;
 162
 163         printk("Freezing remaining freezable tasks ... ");
 164         error = try_to_freeze_tasks(false);
 165         if (!error)
 166                 printk("done.");
 167
 168         printk("\n");
 169         BUG_ON(in_atomic());
 170
 171         return error;
 172 }
 173
 174 static void thaw_tasks(bool nosig_only)
 175 {
 176         struct task_struct *g, *p;
 177
 178         read_lock(&tasklist_lock);
 179         do_each_thread(g, p) {
 180                 if (!freezable(p))
 181                         continue;
 182
 183                 if (nosig_only && should_send_signal(p))
 184                         continue;
 185
 186                 if (cgroup_freezing_or_frozen(p))
 187                         continue;
 188
 189                 thaw_process(p);
 190         } while_each_thread(g, p);
 191         read_unlock(&tasklist_lock);
 192 }
 193
 194 void thaw_processes(void)
 195 {
 196         oom_killer_enable();
 197
 198         printk("Restarting tasks ... ");
 199         thaw_workqueues();
 200         thaw_tasks(true);
 201         thaw_tasks(false);
 202         schedule();
 203         printk("done.\n");
 204 }
 205