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/kmod.h>
  20
  21 /*
  22  * Timeout for stopping processes
  23  */
  24 #define TIMEOUT (20 * HZ)
  25
  26 static int try_to_freeze_tasks(bool user_only)
  27 {
  28         struct task_struct *g, *p;
  29         unsigned long end_time;
  30         unsigned int todo;
  31         bool wq_busy = false;
  32         struct timeval start, end;
  33         u64 elapsed_csecs64;
  34         unsigned int elapsed_csecs;
  35         bool wakeup = false;
  36
  37         do_gettimeofday(&start);
  38
  39         end_time = jiffies + TIMEOUT;
  40
  41         if (!user_only)
  42                 freeze_workqueues_begin();
  43
  44         while (true) {
  45                 todo = 0;
  46                 read_lock(&tasklist_lock);
  47                 do_each_thread(g, p) {
  48                         if (p == current || !freeze_task(p))
  49                                 continue;
  50
  51                         /*
  52                          * Now that we've done set_freeze_flag, don't
  53                          * perturb a task in TASK_STOPPED or TASK_TRACED.
  54                          * It is "frozen enough".  If the task does wake
  55                          * up, it will immediately call try_to_freeze.
  56                          *
  57                          * Because freeze_task() goes through p's
  58                          * scheduler lock after setting TIF_FREEZE, it's
  59                          * guaranteed that either we see TASK_RUNNING or
  60                          * try_to_stop() after schedule() in ptrace/signal
  61                          * stop sees TIF_FREEZE.
  62                          */
  63                         if (!task_is_stopped_or_traced(p) &&
  64                             !freezer_should_skip(p))
  65                                 todo++;
  66                 } while_each_thread(g, p);
  67                 read_unlock(&tasklist_lock);
  68
  69                 if (!user_only) {
  70                         wq_busy = freeze_workqueues_busy();
  71                         todo += wq_busy;
  72                 }
  73
  74                 if (!todo || time_after(jiffies, end_time))
  75                         break;
  76
  77                 if (pm_wakeup_pending()) {
  78                         wakeup = true;
  79                         break;
  80                 }
  81
  82                 /*
  83                  * We need to retry, but first give the freezing tasks some
  84                  * time to enter the regrigerator.
  85                  */
  86                 msleep(10);
  87         }
  88
  89         do_gettimeofday(&end);
  90         elapsed_csecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
  91         do_div(elapsed_csecs64, NSEC_PER_SEC / 100);
  92         elapsed_csecs = elapsed_csecs64;
  93
  94         if (todo) {
  95                 printk("\n");
  96                 printk(KERN_ERR "Freezing of tasks %s after %d.%02d seconds "
  97                        "(%d tasks refusing to freeze, wq_busy=%d):\n",
  98                        wakeup ? "aborted" : "failed",
  99                        elapsed_csecs / 100, elapsed_csecs % 100,
 100                        todo - wq_busy, wq_busy);
 101
 102                 read_lock(&tasklist_lock);
 103                 do_each_thread(g, p) {
 104                         if (!wakeup && !freezer_should_skip(p) &&
 105                             p != current && freezing(p) && !frozen(p))
 106                                 sched_show_task(p);
 107                 } while_each_thread(g, p);
 108                 read_unlock(&tasklist_lock);
 109         } else {
 110                 printk("(elapsed %d.%02d seconds) ", elapsed_csecs / 100,
 111                         elapsed_csecs % 100);
 112         }
 113
 114         return todo ? -EBUSY : 0;
 115 }
 116
 117 /**
 118  * freeze_processes - Signal user space processes to enter the refrigerator.
 119  *
 120  * On success, returns 0.  On failure, -errno and system is fully thawed.
 121  */
 122 int freeze_processes(void)
 123 {
 124         int error;
 125
 126         error = __usermodehelper_disable(UMH_FREEZING);
 127         if (error)
 128                 return error;
 129
 130         if (!pm_freezing)
 131                 atomic_inc(&system_freezing_cnt);
 132
 133         printk("Freezing user space processes ... ");
 134         pm_freezing = true;
 135         error = try_to_freeze_tasks(true);
 136         if (!error) {
 137                 printk("done.");
 138                 __usermodehelper_set_disable_depth(UMH_DISABLED);
 139                 oom_killer_disable();
 140         }
 141         printk("\n");
 142         BUG_ON(in_atomic());
 143
 144         if (error)
 145                 thaw_processes();
 146         return error;
 147 }
 148
 149 /**
 150  * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
 151  *
 152  * On success, returns 0.  On failure, -errno and only the kernel threads are
 153  * thawed, so as to give a chance to the caller to do additional cleanups
 154  * (if any) before thawing the userspace tasks. So, it is the responsibility
 155  * of the caller to thaw the userspace tasks, when the time is right.
 156  */
 157 int freeze_kernel_threads(void)
 158 {
 159         int error;
 160
 161         printk("Freezing remaining freezable tasks ... ");
 162         pm_nosig_freezing = true;
 163         error = try_to_freeze_tasks(false);
 164         if (!error)
 165                 printk("done.");
 166
 167         printk("\n");
 168         BUG_ON(in_atomic());
 169
 170         if (error)
 171                 thaw_kernel_threads();
 172         return error;
 173 }
 174
 175 void thaw_processes(void)
 176 {
 177         struct task_struct *g, *p;
 178
 179         if (pm_freezing)
 180                 atomic_dec(&system_freezing_cnt);
 181         pm_freezing = false;
 182         pm_nosig_freezing = false;
 183
 184         oom_killer_enable();
 185
 186         printk("Restarting tasks ... ");
 187
 188         thaw_workqueues();
 189
 190         read_lock(&tasklist_lock);
 191         do_each_thread(g, p) {
 192                 __thaw_task(p);
 193         } while_each_thread(g, p);
 194         read_unlock(&tasklist_lock);
 195
 196         usermodehelper_enable();
 197
 198         schedule();
 199         printk("done.\n");
 200 }
 201
 202 void thaw_kernel_threads(void)
 203 {
 204         struct task_struct *g, *p;
 205
 206         pm_nosig_freezing = false;
 207         printk("Restarting kernel threads ... ");
 208
 209         thaw_workqueues();
 210
 211         read_lock(&tasklist_lock);
 212         do_each_thread(g, p) {
 213                 if (p->flags & (PF_KTHREAD | PF_WQ_WORKER))
 214                         __thaw_task(p);
 215         } while_each_thread(g, p);
 216         read_unlock(&tasklist_lock);
 217
 218         schedule();
 219         printk("done.\n");
 220 }