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