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  * The current thread will not be frozen.  The same process that calls
 135  * freeze_processes must later call thaw_processes.
 136  *
 137  * On success, returns 0.  On failure, -errno and system is fully thawed.
 138  */
 139 int freeze_processes(void)
 140 {
 141         int error;
 142         int oom_kills_saved;
 143
 144         error = __usermodehelper_disable(UMH_FREEZING);
 145         if (error)
 146                 return error;
 147
 148         /* Make sure this task doesn't get frozen */
 149         current->flags |= PF_SUSPEND_TASK;
 150
 151         if (!pm_freezing)
 152                 atomic_inc(&system_freezing_cnt);
 153
 154         printk("Freezing user space processes ... ");
 155         pm_freezing = true;
 156         oom_kills_saved = oom_kills_count();
 157         error = try_to_freeze_tasks(true);
 158         if (!error) {
 159                 __usermodehelper_set_disable_depth(UMH_DISABLED);
 160                 oom_killer_disable();
 161
 162                 /*
 163                  * There might have been an OOM kill while we were
 164                  * freezing tasks and the killed task might be still
 165                  * on the way out so we have to double check for race.
 166                  */
 167                 if (oom_kills_count() != oom_kills_saved &&
 168                                 !check_frozen_processes()) {
 169                         __usermodehelper_set_disable_depth(UMH_ENABLED);
 170                         printk("OOM in progress.");
 171                         error = -EBUSY;
 172                         goto done;
 173                 }
 174                 printk("done.");
 175         }
 176 done:
 177         printk("\n");
 178         BUG_ON(in_atomic());
 179
 180         if (error)
 181                 thaw_processes();
 182         return error;
 183 }
 184
 185 /**
 186  * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
 187  *
 188  * On success, returns 0.  On failure, -errno and only the kernel threads are
 189  * thawed, so as to give a chance to the caller to do additional cleanups
 190  * (if any) before thawing the userspace tasks. So, it is the responsibility
 191  * of the caller to thaw the userspace tasks, when the time is right.
 192  */
 193 int freeze_kernel_threads(void)
 194 {
 195         int error;
 196
 197         printk("Freezing remaining freezable tasks ... ");
 198         pm_nosig_freezing = true;
 199         error = try_to_freeze_tasks(false);
 200         if (!error)
 201                 printk("done.");
 202
 203         printk("\n");
 204         BUG_ON(in_atomic());
 205
 206         if (error)
 207                 thaw_kernel_threads();
 208         return error;
 209 }
 210
 211 void thaw_processes(void)
 212 {
 213         struct task_struct *g, *p;
 214         struct task_struct *curr = current;
 215
 216         if (pm_freezing)
 217                 atomic_dec(&system_freezing_cnt);
 218         pm_freezing = false;
 219         pm_nosig_freezing = false;
 220
 221         oom_killer_enable();
 222
 223         printk("Restarting tasks ... ");
 224
 225         __usermodehelper_set_disable_depth(UMH_FREEZING);
 226         thaw_workqueues();
 227
 228         read_lock(&tasklist_lock);
 229         do_each_thread(g, p) {
 230                 /* No other threads should have PF_SUSPEND_TASK set */
 231                 WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK));
 232                 __thaw_task(p);
 233         } while_each_thread(g, p);
 234         read_unlock(&tasklist_lock);
 235
 236         WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
 237         curr->flags &= ~PF_SUSPEND_TASK;
 238
 239         usermodehelper_enable();
 240
 241         schedule();
 242         printk("done.\n");
 243 }
 244
 245 void thaw_kernel_threads(void)
 246 {
 247         struct task_struct *g, *p;
 248
 249         pm_nosig_freezing = false;
 250         printk("Restarting kernel threads ... ");
 251
 252         thaw_workqueues();
 253
 254         read_lock(&tasklist_lock);
 255         do_each_thread(g, p) {
 256                 if (p->flags & (PF_KTHREAD | PF_WQ_WORKER))
 257                         __thaw_task(p);
 258         } while_each_thread(g, p);
 259         read_unlock(&tasklist_lock);
 260
 261         schedule();
 262         printk("done.\n");
 263 }