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 #include <linux/cpuset.h>
  24
  25 /*
  26  * Timeout for stopping processes
  27  */
  28 unsigned int __read_mostly freeze_timeout_msecs = 20 * MSEC_PER_SEC;
  29
  30 static int try_to_freeze_tasks(bool user_only)
  31 {
  32         struct task_struct *g, *p;
  33         unsigned long end_time;
  34         unsigned int todo;
  35         bool wq_busy = false;
  36         ktime_t start, end, elapsed;
  37         unsigned int elapsed_msecs;
  38         bool wakeup = false;
  39         int sleep_usecs = USEC_PER_MSEC;
  40
  41         start = ktime_get_boottime();
  42
  43         end_time = jiffies + msecs_to_jiffies(freeze_timeout_msecs);
  44
  45         if (!user_only)
  46                 freeze_workqueues_begin();
  47
  48         while (true) {
  49                 todo = 0;
  50                 read_lock(&tasklist_lock);
  51                 for_each_process_thread(g, p) {
  52                         if (p == current || !freeze_task(p))
  53                                 continue;
  54
  55                         if (!freezer_should_skip(p))
  56                                 todo++;
  57                 }
  58                 read_unlock(&tasklist_lock);
  59
  60                 if (!user_only) {
  61                         wq_busy = freeze_workqueues_busy();
  62                         todo += wq_busy;
  63                 }
  64
  65                 if (!todo || time_after(jiffies, end_time))
  66                         break;
  67
  68                 if (pm_wakeup_pending()) {
  69                         wakeup = true;
  70                         break;
  71                 }
  72
  73                 /*
  74                  * We need to retry, but first give the freezing tasks some
  75                  * time to enter the refrigerator.  Start with an initial
  76                  * 1 ms sleep followed by exponential backoff until 8 ms.
  77                  */
  78                 usleep_range(sleep_usecs / 2, sleep_usecs);
  79                 if (sleep_usecs < 8 * USEC_PER_MSEC)
  80                         sleep_usecs *= 2;
  81         }
  82
  83         end = ktime_get_boottime();
  84         elapsed = ktime_sub(end, start);
  85         elapsed_msecs = ktime_to_ms(elapsed);
  86
  87         if (todo) {
  88                 pr_cont("\n");
  89                 pr_err("Freezing of tasks %s after %d.%03d seconds "
  90                        "(%d tasks refusing to freeze, wq_busy=%d):\n",
  91                        wakeup ? "aborted" : "failed",
  92                        elapsed_msecs / 1000, elapsed_msecs % 1000,
  93                        todo - wq_busy, wq_busy);
  94
  95                 if (wq_busy)
  96                         show_workqueue_state();
  97
  98                 if (!wakeup) {
  99                         read_lock(&tasklist_lock);
 100                         for_each_process_thread(g, p) {
 101                                 if (p != current && !freezer_should_skip(p)
 102                                     && freezing(p) && !frozen(p))
 103                                         sched_show_task(p);
 104                         }
 105                         read_unlock(&tasklist_lock);
 106                 }
 107         } else {
 108                 pr_cont("(elapsed %d.%03d seconds) ", elapsed_msecs / 1000,
 109                         elapsed_msecs % 1000);
 110         }
 111
 112         return todo ? -EBUSY : 0;
 113 }
 114
 115 /**
 116  * freeze_processes - Signal user space processes to enter the refrigerator.
 117  * The current thread will not be frozen.  The same process that calls
 118  * freeze_processes must later call thaw_processes.
 119  *
 120  * On success, returns 0.  On failure, -errno and system is fully thawed.
 121  */
 122 int freeze_processes(void)
 123 {
 124         int error;
 125
 126         error = __usermodehelper_disable(UMH_FREEZING);
 127         if (error)
 128                 return error;
 129
 130         /* Make sure this task doesn't get frozen */
 131         current->flags |= PF_SUSPEND_TASK;
 132
 133         if (!pm_freezing)
 134                 atomic_inc(&system_freezing_cnt);
 135
 136         pm_wakeup_clear(true);
 137         pr_info("Freezing user space processes ... ");
 138         pm_freezing = true;
 139         error = try_to_freeze_tasks(true);
 140         if (!error) {
 141                 __usermodehelper_set_disable_depth(UMH_DISABLED);
 142                 pr_cont("done.");
 143         }
 144         pr_cont("\n");
 145         BUG_ON(in_atomic());
 146
 147         /*
 148          * Now that the whole userspace is frozen we need to disbale
 149          * the OOM killer to disallow any further interference with
 150          * killable tasks. There is no guarantee oom victims will
 151          * ever reach a point they go away we have to wait with a timeout.
 152          */
 153         if (!error && !oom_killer_disable(msecs_to_jiffies(freeze_timeout_msecs)))
 154                 error = -EBUSY;
 155
 156         if (error)
 157                 thaw_processes();
 158         return error;
 159 }
 160
 161 /**
 162  * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
 163  *
 164  * On success, returns 0.  On failure, -errno and only the kernel threads are
 165  * thawed, so as to give a chance to the caller to do additional cleanups
 166  * (if any) before thawing the userspace tasks. So, it is the responsibility
 167  * of the caller to thaw the userspace tasks, when the time is right.
 168  */
 169 int freeze_kernel_threads(void)
 170 {
 171         int error;
 172
 173         pr_info("Freezing remaining freezable tasks ... ");
 174
 175         pm_nosig_freezing = true;
 176         error = try_to_freeze_tasks(false);
 177         if (!error)
 178                 pr_cont("done.");
 179
 180         pr_cont("\n");
 181         BUG_ON(in_atomic());
 182
 183         if (error)
 184                 thaw_kernel_threads();
 185         return error;
 186 }
 187
 188 void thaw_processes(void)
 189 {
 190         struct task_struct *g, *p;
 191         struct task_struct *curr = current;
 192
 193         trace_suspend_resume(TPS("thaw_processes"), 0, true);
 194         if (pm_freezing)
 195                 atomic_dec(&system_freezing_cnt);
 196         pm_freezing = false;
 197         pm_nosig_freezing = false;
 198
 199         oom_killer_enable();
 200
 201         pr_info("Restarting tasks ... ");
 202
 203         __usermodehelper_set_disable_depth(UMH_FREEZING);
 204         thaw_workqueues();
 205
 206         cpuset_wait_for_hotplug();
 207
 208         read_lock(&tasklist_lock);
 209         for_each_process_thread(g, p) {
 210                 /* No other threads should have PF_SUSPEND_TASK set */
 211                 WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK));
 212                 __thaw_task(p);
 213         }
 214         read_unlock(&tasklist_lock);
 215
 216         WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
 217         curr->flags &= ~PF_SUSPEND_TASK;
 218
 219         usermodehelper_enable();
 220
 221         schedule();
 222         pr_cont("done.\n");
 223         trace_suspend_resume(TPS("thaw_processes"), 0, false);
 224 }
 225
 226 void thaw_kernel_threads(void)
 227 {
 228         struct task_struct *g, *p;
 229
 230         pm_nosig_freezing = false;
 231         pr_info("Restarting kernel threads ... ");
 232
 233         thaw_workqueues();
 234
 235         read_lock(&tasklist_lock);
 236         for_each_process_thread(g, p) {
 237                 if (p->flags & (PF_KTHREAD | PF_WQ_WORKER))
 238                         __thaw_task(p);
 239         }
 240         read_unlock(&tasklist_lock);
 241
 242         schedule();
 243         pr_cont("done.\n");
 244 }