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 #include <trace/events/power.h>
  21
  22 /*
  23  * Timeout for stopping processes
  24  */
  25 unsigned int __read_mostly freeze_timeout_msecs = 20 * MSEC_PER_SEC;
  26
  27 static int try_to_freeze_tasks(bool user_only)
  28 {
  29         struct task_struct *g, *p;
  30         unsigned long end_time;
  31         unsigned int todo;
  32         bool wq_busy = false;
  33         ktime_t start, end, elapsed;
  34         unsigned int elapsed_msecs;
  35         bool wakeup = false;
  36         int sleep_usecs = USEC_PER_MSEC;
  37
  38         start = ktime_get_boottime();
  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                 for_each_process_thread(g, p) {
  49                         if (p == current || !freeze_task(p))
  50                                 continue;
  51
  52                         if (!freezer_should_skip(p))
  53                                 todo++;
  54                 }
  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         end = ktime_get_boottime();
  81         elapsed = ktime_sub(end, start);
  82         elapsed_msecs = ktime_to_ms(elapsed);
  83
  84         if (todo) {
  85                 pr_cont("\n");
  86                 pr_err("Freezing of tasks %s after %d.%03d seconds "
  87                        "(%d tasks refusing to freeze, wq_busy=%d):\n",
  88                        wakeup ? "aborted" : "failed",
  89                        elapsed_msecs / 1000, elapsed_msecs % 1000,
  90                        todo - wq_busy, wq_busy);
  91
  92                 if (!wakeup) {
  93                         read_lock(&tasklist_lock);
  94                         for_each_process_thread(g, p) {
  95                                 if (p != current && !freezer_should_skip(p)
  96                                     && freezing(p) && !frozen(p))
  97                                         sched_show_task(p);
  98                         }
  99                         read_unlock(&tasklist_lock);
 100                 }
 101         } else {
 102                 pr_cont("(elapsed %d.%03d seconds) ", elapsed_msecs / 1000,
 103                         elapsed_msecs % 1000);
 104         }
 105
 106         return todo ? -EBUSY : 0;
 107 }
 108
 109 /**
 110  * freeze_processes - Signal user space processes to enter the refrigerator.
 111  * The current thread will not be frozen.  The same process that calls
 112  * freeze_processes must later call thaw_processes.
 113  *
 114  * On success, returns 0.  On failure, -errno and system is fully thawed.
 115  */
 116 int freeze_processes(void)
 117 {
 118         int error;
 119
 120         error = __usermodehelper_disable(UMH_FREEZING);
 121         if (error)
 122                 return error;
 123
 124         /* Make sure this task doesn't get frozen */
 125         current->flags |= PF_SUSPEND_TASK;
 126
 127         if (!pm_freezing)
 128                 atomic_inc(&system_freezing_cnt);
 129
 130         pm_wakeup_clear();
 131         pr_info("Freezing user space processes ... ");
 132         pm_freezing = true;
 133         error = try_to_freeze_tasks(true);
 134         if (!error) {
 135                 __usermodehelper_set_disable_depth(UMH_DISABLED);
 136                 pr_cont("done.");
 137         }
 138         pr_cont("\n");
 139         BUG_ON(in_atomic());
 140
 141         /*
 142          * Now that the whole userspace is frozen we need to disbale
 143          * the OOM killer to disallow any further interference with
 144          * killable tasks.
 145          */
 146         if (!error && !oom_killer_disable())
 147                 error = -EBUSY;
 148
 149         /*
 150          * There is a hard to fix race between oom_reaper kernel thread
 151          * and oom_killer_disable. oom_reaper calls exit_oom_victim
 152          * before the victim reaches exit_mm so try to freeze all the tasks
 153          * again and catch such a left over task.
 154          */
 155         if (!error) {
 156                 pr_info("Double checking all user space processes after OOM killer disable... ");
 157                 error = try_to_freeze_tasks(true);
 158                 pr_cont("\n");
 159         }
 160
 161         if (error)
 162                 thaw_processes();
 163         return error;
 164 }
 165
 166 /**
 167  * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
 168  *
 169  * On success, returns 0.  On failure, -errno and only the kernel threads are
 170  * thawed, so as to give a chance to the caller to do additional cleanups
 171  * (if any) before thawing the userspace tasks. So, it is the responsibility
 172  * of the caller to thaw the userspace tasks, when the time is right.
 173  */
 174 int freeze_kernel_threads(void)
 175 {
 176         int error;
 177
 178         pr_info("Freezing remaining freezable tasks ... ");
 179
 180         pm_nosig_freezing = true;
 181         error = try_to_freeze_tasks(false);
 182         if (!error)
 183                 pr_cont("done.");
 184
 185         pr_cont("\n");
 186         BUG_ON(in_atomic());
 187
 188         if (error)
 189                 thaw_kernel_threads();
 190         return error;
 191 }
 192
 193 void thaw_processes(void)
 194 {
 195         struct task_struct *g, *p;
 196         struct task_struct *curr = current;
 197
 198         trace_suspend_resume(TPS("thaw_processes"), 0, true);
 199         if (pm_freezing)
 200                 atomic_dec(&system_freezing_cnt);
 201         pm_freezing = false;
 202         pm_nosig_freezing = false;
 203
 204         oom_killer_enable();
 205
 206         pr_info("Restarting tasks ... ");
 207
 208         __usermodehelper_set_disable_depth(UMH_FREEZING);
 209         thaw_workqueues();
 210
 211         read_lock(&tasklist_lock);
 212         for_each_process_thread(g, p) {
 213                 /* No other threads should have PF_SUSPEND_TASK set */
 214                 WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK));
 215                 __thaw_task(p);
 216         }
 217         read_unlock(&tasklist_lock);
 218
 219         WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
 220         curr->flags &= ~PF_SUSPEND_TASK;
 221
 222         usermodehelper_enable();
 223
 224         schedule();
 225         pr_cont("done.\n");
 226         trace_suspend_resume(TPS("thaw_processes"), 0, false);
 227 }
 228
 229 void thaw_kernel_threads(void)
 230 {
 231         struct task_struct *g, *p;
 232
 233         pm_nosig_freezing = false;
 234         pr_info("Restarting kernel threads ... ");
 235
 236         thaw_workqueues();
 237
 238         read_lock(&tasklist_lock);
 239         for_each_process_thread(g, p) {
 240                 if (p->flags & (PF_KTHREAD | PF_WQ_WORKER))
 241                         __thaw_task(p);
 242         }
 243         read_unlock(&tasklist_lock);
 244
 245         schedule();
 246         pr_cont("done.\n");
 247 }