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