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_csecs64;
  34         unsigned int elapsed_csecs;
  35         bool wakeup = false;
  36
  37         do_gettimeofday(&start);
  38
  39         end_time = jiffies + msecs_to_jiffies(freeze_timeout_msecs);
  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                         if (!freezer_should_skip(p))
  52                                 todo++;
  53                 } while_each_thread(g, p);
  54                 read_unlock(&tasklist_lock);
  55
  56                 if (!user_only) {
  57                         wq_busy = freeze_workqueues_busy();
  58                         todo += wq_busy;
  59                 }
  60
  61                 if (!todo || time_after(jiffies, end_time))
  62                         break;
  63
  64                 if (pm_wakeup_pending()) {
  65                         wakeup = true;
  66                         break;
  67                 }
  68
  69                 /*
  70                  * We need to retry, but first give the freezing tasks some
  71                  * time to enter the refrigerator.
  72                  */
  73                 msleep(10);
  74         }
  75
  76         do_gettimeofday(&end);
  77         elapsed_csecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
  78         do_div(elapsed_csecs64, NSEC_PER_SEC / 100);
  79         elapsed_csecs = elapsed_csecs64;
  80
  81         if (todo) {
  82                 printk("\n");
  83                 printk(KERN_ERR "Freezing of tasks %s after %d.%02d seconds "
  84                        "(%d tasks refusing to freeze, wq_busy=%d):\n",
  85                        wakeup ? "aborted" : "failed",
  86                        elapsed_csecs / 100, elapsed_csecs % 100,
  87                        todo - wq_busy, wq_busy);
  88
  89                 if (!wakeup) {
  90                         read_lock(&tasklist_lock);
  91                         do_each_thread(g, p) {
  92                                 if (p != current && !freezer_should_skip(p)
  93                                     && freezing(p) && !frozen(p))
  94                                         sched_show_task(p);
  95                         } while_each_thread(g, p);
  96                         read_unlock(&tasklist_lock);
  97                 }
  98         } else {
  99                 printk("(elapsed %d.%02d seconds) ", elapsed_csecs / 100,
 100                         elapsed_csecs % 100);
 101         }
 102
 103         return todo ? -EBUSY : 0;
 104 }
 105
 106 /*
 107  * Returns true if all freezable tasks (except for current) are frozen already
 108  */
 109 static bool check_frozen_processes(void)
 110 {
 111         struct task_struct *g, *p;
 112         bool ret = true;
 113
 114         read_lock(&tasklist_lock);
 115         for_each_process_thread(g, p) {
 116                 if (p != current && !freezer_should_skip(p) &&
 117                     !frozen(p)) {
 118                         ret = false;
 119                         goto done;
 120                 }
 121         }
 122 done:
 123         read_unlock(&tasklist_lock);
 124
 125         return ret;
 126 }
 127
 128 /**
 129  * freeze_processes - Signal user space processes to enter the refrigerator.
 130  *
 131  * On success, returns 0.  On failure, -errno and system is fully thawed.
 132  */
 133 int freeze_processes(void)
 134 {
 135         int error;
 136         int oom_kills_saved;
 137
 138         error = __usermodehelper_disable(UMH_FREEZING);
 139         if (error)
 140                 return error;
 141
 142         if (!pm_freezing)
 143                 atomic_inc(&system_freezing_cnt);
 144
 145         printk("Freezing user space processes ... ");
 146         pm_freezing = true;
 147         oom_kills_saved = oom_kills_count();
 148         error = try_to_freeze_tasks(true);
 149         if (!error) {
 150                 __usermodehelper_set_disable_depth(UMH_DISABLED);
 151                 oom_killer_disable();
 152
 153                 /*
 154                  * There might have been an OOM kill while we were
 155                  * freezing tasks and the killed task might be still
 156                  * on the way out so we have to double check for race.
 157                  */
 158                 if (oom_kills_count() != oom_kills_saved &&
 159                                 !check_frozen_processes()) {
 160                         __usermodehelper_set_disable_depth(UMH_ENABLED);
 161                         printk("OOM in progress.");
 162                         error = -EBUSY;
 163                         goto done;
 164                 }
 165                 printk("done.");
 166         }
 167 done:
 168         printk("\n");
 169         BUG_ON(in_atomic());
 170
 171         if (error)
 172                 thaw_processes();
 173         return error;
 174 }
 175
 176 /**
 177  * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
 178  *
 179  * On success, returns 0.  On failure, -errno and only the kernel threads are
 180  * thawed, so as to give a chance to the caller to do additional cleanups
 181  * (if any) before thawing the userspace tasks. So, it is the responsibility
 182  * of the caller to thaw the userspace tasks, when the time is right.
 183  */
 184 int freeze_kernel_threads(void)
 185 {
 186         int error;
 187
 188         printk("Freezing remaining freezable tasks ... ");
 189         pm_nosig_freezing = true;
 190         error = try_to_freeze_tasks(false);
 191         if (!error)
 192                 printk("done.");
 193
 194         printk("\n");
 195         BUG_ON(in_atomic());
 196
 197         if (error)
 198                 thaw_kernel_threads();
 199         return error;
 200 }
 201
 202 void thaw_processes(void)
 203 {
 204         struct task_struct *g, *p;
 205
 206         if (pm_freezing)
 207                 atomic_dec(&system_freezing_cnt);
 208         pm_freezing = false;
 209         pm_nosig_freezing = false;
 210
 211         oom_killer_enable();
 212
 213         printk("Restarting tasks ... ");
 214
 215         __usermodehelper_set_disable_depth(UMH_FREEZING);
 216         thaw_workqueues();
 217
 218         read_lock(&tasklist_lock);
 219         do_each_thread(g, p) {
 220                 __thaw_task(p);
 221         } while_each_thread(g, p);
 222         read_unlock(&tasklist_lock);
 223
 224         usermodehelper_enable();
 225
 226         schedule();
 227         printk("done.\n");
 228 }
 229
 230 void thaw_kernel_threads(void)
 231 {
 232         struct task_struct *g, *p;
 233
 234         pm_nosig_freezing = false;
 235         printk("Restarting kernel threads ... ");
 236
 237         thaw_workqueues();
 238
 239         read_lock(&tasklist_lock);
 240         do_each_thread(g, p) {
 241                 if (p->flags & (PF_KTHREAD | PF_WQ_WORKER))
 242                         __thaw_task(p);
 243         } while_each_thread(g, p);
 244         read_unlock(&tasklist_lock);
 245
 246         schedule();
 247         printk("done.\n");
 248 }