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 unsigned int __read_mostly freeze_timeout_msecs = 20 * MSEC_PER_SEC;
  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_msecs64;
  34         unsigned int elapsed_msecs;
  35         bool wakeup = false;
  36         int sleep_usecs = USEC_PER_MSEC;
  37
  38         do_gettimeofday(&start);
  39
  40         end_time = jiffies + msecs_to_jiffies(freeze_timeout_msecs);
  41
  42         if (!user_only)
  43                 freeze_workqueues_begin();
  44
  45         while (true) {
  46                 todo = 0;
  47                 read_lock(&tasklist_lock);
  48                 do_each_thread(g, p) {
  49                         if (p == current || !freeze_task(p))
  50                                 continue;
  51
  52                         if (!freezer_should_skip(p))
  53                                 todo++;
  54                 } while_each_thread(g, p);
  55                 read_unlock(&tasklist_lock);
  56
  57                 if (!user_only) {
  58                         wq_busy = freeze_workqueues_busy();
  59                         todo += wq_busy;
  60                 }
  61
  62                 if (!todo || time_after(jiffies, end_time))
  63                         break;
  64
  65                 if (pm_wakeup_pending()) {
  66                         wakeup = true;
  67                         break;
  68                 }
  69
  70                 /*
  71                  * We need to retry, but first give the freezing tasks some
  72                  * time to enter the refrigerator.  Start with an initial
  73                  * 1 ms sleep followed by exponential backoff until 8 ms.
  74                  */
  75                 usleep_range(sleep_usecs / 2, sleep_usecs);
  76                 if (sleep_usecs < 8 * USEC_PER_MSEC)
  77                         sleep_usecs *= 2;
  78         }
  79
  80         do_gettimeofday(&end);
  81         elapsed_msecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
  82         do_div(elapsed_msecs64, NSEC_PER_MSEC);
  83         elapsed_msecs = elapsed_msecs64;
  84
  85         if (todo) {
  86                 printk("\n");
  87                 printk(KERN_ERR "Freezing of tasks %s after %d.%03d seconds "
  88                        "(%d tasks refusing to freeze, wq_busy=%d):\n",
  89                        wakeup ? "aborted" : "failed",
  90                        elapsed_msecs / 1000, elapsed_msecs % 1000,
  91                        todo - wq_busy, wq_busy);
  92
  93                 if (!wakeup) {
  94                         read_lock(&tasklist_lock);
  95                         do_each_thread(g, p) {
  96                                 if (p != current && !freezer_should_skip(p)
  97                                     && freezing(p) && !frozen(p))
  98                                         sched_show_task(p);
  99                         } while_each_thread(g, p);
 100                         read_unlock(&tasklist_lock);
 101                 }
 102         } else {
 103                 printk("(elapsed %d.%03d seconds) ", elapsed_msecs / 1000,
 104                         elapsed_msecs % 1000);
 105         }
 106
 107         return todo ? -EBUSY : 0;
 108 }
 109
 110 /*
 111  * Returns true if all freezable tasks (except for current) are frozen already
 112  */
 113 static bool check_frozen_processes(void)
 114 {
 115         struct task_struct *g, *p;
 116         bool ret = true;
 117
 118         read_lock(&tasklist_lock);
 119         for_each_process_thread(g, p) {
 120                 if (p != current && !freezer_should_skip(p) &&
 121                     !frozen(p)) {
 122                         ret = false;
 123                         goto done;
 124                 }
 125         }
 126 done:
 127         read_unlock(&tasklist_lock);
 128
 129         return ret;
 130 }
 131
 132 /**
 133  * freeze_processes - Signal user space processes to enter the refrigerator.
 134  *
 135  * On success, returns 0.  On failure, -errno and system is fully thawed.
 136  */
 137 int freeze_processes(void)
 138 {
 139         int error;
 140         int oom_kills_saved;
 141
 142         error = __usermodehelper_disable(UMH_FREEZING);
 143         if (error)
 144                 return error;
 145
 146         if (!pm_freezing)
 147                 atomic_inc(&system_freezing_cnt);
 148
 149         printk("Freezing user space processes ... ");
 150         pm_freezing = true;
 151         oom_kills_saved = oom_kills_count();
 152         error = try_to_freeze_tasks(true);
 153         if (!error) {
 154                 __usermodehelper_set_disable_depth(UMH_DISABLED);
 155                 oom_killer_disable();
 156
 157                 /*
 158                  * There might have been an OOM kill while we were
 159                  * freezing tasks and the killed task might be still
 160                  * on the way out so we have to double check for race.
 161                  */
 162                 if (oom_kills_count() != oom_kills_saved &&
 163                                 !check_frozen_processes()) {
 164                         __usermodehelper_set_disable_depth(UMH_ENABLED);
 165                         printk("OOM in progress.");
 166                         error = -EBUSY;
 167                         goto done;
 168                 }
 169                 printk("done.");
 170         }
 171 done:
 172         printk("\n");
 173         BUG_ON(in_atomic());
 174
 175         if (error)
 176                 thaw_processes();
 177         return error;
 178 }
 179 EXPORT_SYMBOL_GPL(freeze_processes);
 180
 181 /**
 182  * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
 183  *
 184  * On success, returns 0.  On failure, -errno and only the kernel threads are
 185  * thawed, so as to give a chance to the caller to do additional cleanups
 186  * (if any) before thawing the userspace tasks. So, it is the responsibility
 187  * of the caller to thaw the userspace tasks, when the time is right.
 188  */
 189 int freeze_kernel_threads(void)
 190 {
 191         int error;
 192
 193         printk("Freezing remaining freezable tasks ... ");
 194         pm_nosig_freezing = true;
 195         error = try_to_freeze_tasks(false);
 196         if (!error)
 197                 printk("done.");
 198
 199         printk("\n");
 200         BUG_ON(in_atomic());
 201
 202         if (error)
 203                 thaw_kernel_threads();
 204         return error;
 205 }
 206 EXPORT_SYMBOL_GPL(freeze_kernel_threads);
 207
 208 void thaw_processes(void)
 209 {
 210         struct task_struct *g, *p;
 211
 212         if (pm_freezing)
 213                 atomic_dec(&system_freezing_cnt);
 214         pm_freezing = false;
 215         pm_nosig_freezing = false;
 216
 217         oom_killer_enable();
 218
 219         printk("Restarting tasks ... ");
 220
 221         __usermodehelper_set_disable_depth(UMH_FREEZING);
 222         thaw_workqueues();
 223
 224         read_lock(&tasklist_lock);
 225         do_each_thread(g, p) {
 226                 BUG_ON(!virt_addr_valid(next_task(g)));
 227                 __thaw_task(p);
 228         } while_each_thread(g, p);
 229         read_unlock(&tasklist_lock);
 230
 231         usermodehelper_enable();
 232
 233         schedule();
 234         printk("done.\n");
 235 }
 236 EXPORT_SYMBOL_GPL(thaw_processes);
 237
 238 void thaw_kernel_threads(void)
 239 {
 240         struct task_struct *g, *p;
 241
 242         pm_nosig_freezing = false;
 243         printk("Restarting kernel threads ... ");
 244
 245         thaw_workqueues();
 246
 247         read_lock(&tasklist_lock);
 248         do_each_thread(g, p) {
 249                 if (p->flags & (PF_KTHREAD | PF_WQ_WORKER))
 250                         __thaw_task(p);
 251         } while_each_thread(g, p);
 252         read_unlock(&tasklist_lock);
 253
 254         schedule();
 255         printk("done.\n");
 256 }
 257 EXPORT_SYMBOL_GPL(thaw_kernel_threads);