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/sched/debug.h>
  16 #include <linux/sched/task.h>
  17 #include <linux/syscalls.h>
  18 #include <linux/freezer.h>
  19 #include <linux/delay.h>
  20 #include <linux/workqueue.h>
  21 #include <linux/kmod.h>
  22 #include <trace/events/power.h>
  23
  24 /*
  25  * Timeout for stopping processes
  26  */
  27 unsigned int __read_mostly freeze_timeout_msecs = 20 * MSEC_PER_SEC;
  28
  29 static int try_to_freeze_tasks(bool user_only)
  30 {
  31         struct task_struct *g, *p;
  32         unsigned long end_time;
  33         unsigned int todo;
  34         bool wq_busy = false;
  35         ktime_t start, end, elapsed;
  36         unsigned int elapsed_msecs;
  37         bool wakeup = false;
  38         int sleep_usecs = USEC_PER_MSEC;
  39
  40         start = ktime_get_boottime();
  41
  42         end_time = jiffies + msecs_to_jiffies(freeze_timeout_msecs);
  43
  44         if (!user_only)
  45                 freeze_workqueues_begin();
  46
  47         while (true) {
  48                 todo = 0;
  49                 read_lock(&tasklist_lock);
  50                 for_each_process_thread(g, p) {
  51                         if (p == current || !freeze_task(p))
  52                                 continue;
  53
  54                         if (!freezer_should_skip(p))
  55                                 todo++;
  56                 }
  57                 read_unlock(&tasklist_lock);
  58
  59                 if (!user_only) {
  60                         wq_busy = freeze_workqueues_busy();
  61                         todo += wq_busy;
  62                 }
  63
  64                 if (!todo || time_after(jiffies, end_time))
  65                         break;
  66
  67                 if (pm_wakeup_pending()) {
  68                         wakeup = true;
  69                         break;
  70                 }
  71
  72                 /*
  73                  * We need to retry, but first give the freezing tasks some
  74                  * time to enter the refrigerator.  Start with an initial
  75                  * 1 ms sleep followed by exponential backoff until 8 ms.
  76                  */
  77                 usleep_range(sleep_usecs / 2, sleep_usecs);
  78                 if (sleep_usecs < 8 * USEC_PER_MSEC)
  79                         sleep_usecs *= 2;
  80         }
  81
  82         end = ktime_get_boottime();
  83         elapsed = ktime_sub(end, start);
  84         elapsed_msecs = ktime_to_ms(elapsed);
  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 (wq_busy)
  95                         show_workqueue_state();
  96
  97                 if (!wakeup) {
  98                         read_lock(&tasklist_lock);
  99                         for_each_process_thread(g, p) {
 100                                 if (p != current && !freezer_should_skip(p)
 101                                     && freezing(p) && !frozen(p))
 102                                         sched_show_task(p);
 103                         }
 104                         read_unlock(&tasklist_lock);
 105                 }
 106         } else {
 107                 pr_cont("(elapsed %d.%03d seconds) ", elapsed_msecs / 1000,
 108                         elapsed_msecs % 1000);
 109         }
 110
 111         return todo ? -EBUSY : 0;
 112 }
 113
 114 /**
 115  * freeze_processes - Signal user space processes to enter the refrigerator.
 116  * The current thread will not be frozen.  The same process that calls
 117  * freeze_processes must later call thaw_processes.
 118  *
 119  * On success, returns 0.  On failure, -errno and system is fully thawed.
 120  */
 121 int freeze_processes(void)
 122 {
 123         int error;
 124
 125         error = __usermodehelper_disable(UMH_FREEZING);
 126         if (error)
 127                 return error;
 128
 129         /* Make sure this task doesn't get frozen */
 130         current->flags |= PF_SUSPEND_TASK;
 131
 132         if (!pm_freezing)
 133                 atomic_inc(&system_freezing_cnt);
 134
 135         pm_wakeup_clear(true);
 136         pr_info("Freezing user space processes ... ");
 137         pm_freezing = true;
 138         error = try_to_freeze_tasks(true);
 139         if (!error) {
 140                 __usermodehelper_set_disable_depth(UMH_DISABLED);
 141                 pr_cont("done.");
 142         }
 143         pr_cont("\n");
 144         BUG_ON(in_atomic());
 145
 146         /*
 147          * Now that the whole userspace is frozen we need to disbale
 148          * the OOM killer to disallow any further interference with
 149          * killable tasks. There is no guarantee oom victims will
 150          * ever reach a point they go away we have to wait with a timeout.
 151          */
 152         if (!error && !oom_killer_disable(msecs_to_jiffies(freeze_timeout_msecs)))
 153                 error = -EBUSY;
 154
 155         if (error)
 156                 thaw_processes();
 157         return error;
 158 }
 159
 160 /**
 161  * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
 162  *
 163  * On success, returns 0.  On failure, -errno and only the kernel threads are
 164  * thawed, so as to give a chance to the caller to do additional cleanups
 165  * (if any) before thawing the userspace tasks. So, it is the responsibility
 166  * of the caller to thaw the userspace tasks, when the time is right.
 167  */
 168 int freeze_kernel_threads(void)
 169 {
 170         int error;
 171
 172         pr_info("Freezing remaining freezable tasks ... ");
 173
 174         pm_nosig_freezing = true;
 175         error = try_to_freeze_tasks(false);
 176         if (!error)
 177                 pr_cont("done.");
 178
 179         pr_cont("\n");
 180         BUG_ON(in_atomic());
 181
 182         if (error)
 183                 thaw_kernel_threads();
 184         return error;
 185 }
 186
 187 void thaw_processes(void)
 188 {
 189         struct task_struct *g, *p;
 190         struct task_struct *curr = current;
 191
 192         trace_suspend_resume(TPS("thaw_processes"), 0, true);
 193         if (pm_freezing)
 194                 atomic_dec(&system_freezing_cnt);
 195         pm_freezing = false;
 196         pm_nosig_freezing = false;
 197
 198         oom_killer_enable();
 199
 200         pr_info("Restarting tasks ... ");
 201
 202         __usermodehelper_set_disable_depth(UMH_FREEZING);
 203         thaw_workqueues();
 204
 205         read_lock(&tasklist_lock);
 206         for_each_process_thread(g, p) {
 207                 /* No other threads should have PF_SUSPEND_TASK set */
 208                 WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK));
 209                 __thaw_task(p);
 210         }
 211         read_unlock(&tasklist_lock);
 212
 213         WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
 214         curr->flags &= ~PF_SUSPEND_TASK;
 215
 216         usermodehelper_enable();
 217
 218         schedule();
 219         pr_cont("done.\n");
 220         trace_suspend_resume(TPS("thaw_processes"), 0, false);
 221 }
 222
 223 void thaw_kernel_threads(void)
 224 {
 225         struct task_struct *g, *p;
 226
 227         pm_nosig_freezing = false;
 228         pr_info("Restarting kernel threads ... ");
 229
 230         thaw_workqueues();
 231
 232         read_lock(&tasklist_lock);
 233         for_each_process_thread(g, p) {
 234                 if (p->flags & (PF_KTHREAD | PF_WQ_WORKER))
 235                         __thaw_task(p);
 236         }
 237         read_unlock(&tasklist_lock);
 238
 239         schedule();
 240         pr_cont("done.\n");
 241 }