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         struct timeval start, end;
  34         u64 elapsed_msecs64;
  35         unsigned int elapsed_msecs;
  36         bool wakeup = false;
  37         int sleep_usecs = USEC_PER_MSEC;
  38
  39         do_gettimeofday(&start);
  40
  41         end_time = jiffies + msecs_to_jiffies(freeze_timeout_msecs);
  42
  43         if (!user_only)
  44                 freeze_workqueues_begin();
  45
  46         while (true) {
  47                 todo = 0;
  48                 read_lock(&tasklist_lock);
  49                 for_each_process_thread(g, p) {
  50                         if (p == current || !freeze_task(p))
  51                                 continue;
  52
  53                         if (!freezer_should_skip(p))
  54                                 todo++;
  55                 }
  56                 read_unlock(&tasklist_lock);
  57
  58                 if (!user_only) {
  59                         wq_busy = freeze_workqueues_busy();
  60                         todo += wq_busy;
  61                 }
  62
  63                 if (!todo || time_after(jiffies, end_time))
  64                         break;
  65
  66                 if (pm_wakeup_pending()) {
  67                         wakeup = true;
  68                         break;
  69                 }
  70
  71                 /*
  72                  * We need to retry, but first give the freezing tasks some
  73                  * time to enter the refrigerator.  Start with an initial
  74                  * 1 ms sleep followed by exponential backoff until 8 ms.
  75                  */
  76                 usleep_range(sleep_usecs / 2, sleep_usecs);
  77                 if (sleep_usecs < 8 * USEC_PER_MSEC)
  78                         sleep_usecs *= 2;
  79         }
  80
  81         do_gettimeofday(&end);
  82         elapsed_msecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
  83         do_div(elapsed_msecs64, NSEC_PER_MSEC);
  84         elapsed_msecs = elapsed_msecs64;
  85
  86         if (todo) {
  87                 pr_cont("\n");
  88                 pr_err("Freezing of tasks %s after %d.%03d seconds "
  89                        "(%d tasks refusing to freeze, wq_busy=%d):\n",
  90                        wakeup ? "aborted" : "failed",
  91                        elapsed_msecs / 1000, elapsed_msecs % 1000,
  92                        todo - wq_busy, wq_busy);
  93
  94                 if (!wakeup) {
  95                         read_lock(&tasklist_lock);
  96                         for_each_process_thread(g, p) {
  97                                 if (p != current && !freezer_should_skip(p)
  98                                     && freezing(p) && !frozen(p))
  99                                         sched_show_task(p);
 100                         }
 101                         read_unlock(&tasklist_lock);
 102                 }
 103         } else {
 104                 pr_cont("(elapsed %d.%03d seconds) ", elapsed_msecs / 1000,
 105                         elapsed_msecs % 1000);
 106         }
 107
 108         return todo ? -EBUSY : 0;
 109 }
 110
 111 /**
 112  * freeze_processes - Signal user space processes to enter the refrigerator.
 113  * The current thread will not be frozen.  The same process that calls
 114  * freeze_processes must later call thaw_processes.
 115  *
 116  * On success, returns 0.  On failure, -errno and system is fully thawed.
 117  */
 118 int freeze_processes(void)
 119 {
 120         int error;
 121
 122         error = __usermodehelper_disable(UMH_FREEZING);
 123         if (error)
 124                 return error;
 125
 126         /* Make sure this task doesn't get frozen */
 127         current->flags |= PF_SUSPEND_TASK;
 128
 129         if (!pm_freezing)
 130                 atomic_inc(&system_freezing_cnt);
 131
 132         pm_wakeup_clear();
 133         pr_info("Freezing user space processes ... ");
 134         pm_freezing = true;
 135         error = try_to_freeze_tasks(true);
 136         if (!error) {
 137                 __usermodehelper_set_disable_depth(UMH_DISABLED);
 138                 pr_cont("done.");
 139         }
 140         pr_cont("\n");
 141         BUG_ON(in_atomic());
 142
 143         /*
 144          * Now that the whole userspace is frozen we need to disbale
 145          * the OOM killer to disallow any further interference with
 146          * killable tasks.
 147          */
 148         if (!error && !oom_killer_disable())
 149                 error = -EBUSY;
 150
 151         if (error)
 152                 thaw_processes();
 153         return error;
 154 }
 155
 156 /**
 157  * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
 158  *
 159  * On success, returns 0.  On failure, -errno and only the kernel threads are
 160  * thawed, so as to give a chance to the caller to do additional cleanups
 161  * (if any) before thawing the userspace tasks. So, it is the responsibility
 162  * of the caller to thaw the userspace tasks, when the time is right.
 163  */
 164 int freeze_kernel_threads(void)
 165 {
 166         int error;
 167
 168         pr_info("Freezing remaining freezable tasks ... ");
 169
 170         pm_nosig_freezing = true;
 171         error = try_to_freeze_tasks(false);
 172         if (!error)
 173                 pr_cont("done.");
 174
 175         pr_cont("\n");
 176         BUG_ON(in_atomic());
 177
 178         if (error)
 179                 thaw_kernel_threads();
 180         return error;
 181 }
 182
 183 void thaw_processes(void)
 184 {
 185         struct task_struct *g, *p;
 186         struct task_struct *curr = current;
 187
 188         trace_suspend_resume(TPS("thaw_processes"), 0, true);
 189         if (pm_freezing)
 190                 atomic_dec(&system_freezing_cnt);
 191         pm_freezing = false;
 192         pm_nosig_freezing = false;
 193
 194         oom_killer_enable();
 195
 196         pr_info("Restarting tasks ... ");
 197
 198         __usermodehelper_set_disable_depth(UMH_FREEZING);
 199         thaw_workqueues();
 200
 201         read_lock(&tasklist_lock);
 202         for_each_process_thread(g, p) {
 203                 /* No other threads should have PF_SUSPEND_TASK set */
 204                 WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK));
 205                 __thaw_task(p);
 206         }
 207         read_unlock(&tasklist_lock);
 208
 209         WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
 210         curr->flags &= ~PF_SUSPEND_TASK;
 211
 212         usermodehelper_enable();
 213
 214         schedule();
 215         pr_cont("done.\n");
 216         trace_suspend_resume(TPS("thaw_processes"), 0, false);
 217 }
 218
 219 void thaw_kernel_threads(void)
 220 {
 221         struct task_struct *g, *p;
 222
 223         pm_nosig_freezing = false;
 224         pr_info("Restarting kernel threads ... ");
 225
 226         thaw_workqueues();
 227
 228         read_lock(&tasklist_lock);
 229         for_each_process_thread(g, p) {
 230                 if (p->flags & (PF_KTHREAD | PF_WQ_WORKER))
 231                         __thaw_task(p);
 232         }
 233         read_unlock(&tasklist_lock);
 234
 235         schedule();
 236         pr_cont("done.\n");
 237 }