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/wakeup_reason.h>
  22 #include <linux/cpuset.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         struct timeval start, end;
  36         u64 elapsed_msecs64;
  37         unsigned int elapsed_msecs;
  38         bool wakeup = false;
  39         int sleep_usecs = USEC_PER_MSEC;
  40 #ifdef CONFIG_PM_SLEEP
  41         char suspend_abort[MAX_SUSPEND_ABORT_LEN];
  42 #endif
  43
  44         do_gettimeofday(&start);
  45
  46         end_time = jiffies + msecs_to_jiffies(freeze_timeout_msecs);
  47
  48         if (!user_only)
  49                 freeze_workqueues_begin();
  50
  51         while (true) {
  52                 todo = 0;
  53                 read_lock(&tasklist_lock);
  54                 for_each_process_thread(g, p) {
  55                         if (p == current || !freeze_task(p))
  56                                 continue;
  57
  58                         if (!freezer_should_skip(p))
  59                                 todo++;
  60                 }
  61                 read_unlock(&tasklist_lock);
  62
  63                 if (!user_only) {
  64                         wq_busy = freeze_workqueues_busy();
  65                         todo += wq_busy;
  66                 }
  67
  68                 if (!todo || time_after(jiffies, end_time))
  69                         break;
  70
  71                 if (pm_wakeup_pending()) {
  72 #ifdef CONFIG_PM_SLEEP
  73                         pm_get_active_wakeup_sources(suspend_abort,
  74                                 MAX_SUSPEND_ABORT_LEN);
  75                         log_suspend_abort_reason(suspend_abort);
  76 #endif
  77                         wakeup = true;
  78                         break;
  79                 }
  80
  81                 /*
  82                  * We need to retry, but first give the freezing tasks some
  83                  * time to enter the refrigerator.  Start with an initial
  84                  * 1 ms sleep followed by exponential backoff until 8 ms.
  85                  */
  86                 usleep_range(sleep_usecs / 2, sleep_usecs);
  87                 if (sleep_usecs < 8 * USEC_PER_MSEC)
  88                         sleep_usecs *= 2;
  89         }
  90
  91         do_gettimeofday(&end);
  92         elapsed_msecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
  93         do_div(elapsed_msecs64, NSEC_PER_MSEC);
  94         elapsed_msecs = elapsed_msecs64;
  95
  96         if (wakeup) {
  97                 pr_cont("\n");
  98                 pr_err("Freezing of tasks aborted after %d.%03d seconds",
  99                        elapsed_msecs / 1000, elapsed_msecs % 1000);
 100         } else if (todo) {
 101                 pr_cont("\n");
 102                 pr_err("Freezing of tasks failed after %d.%03d seconds"
 103                        " (%d tasks refusing to freeze, wq_busy=%d):\n",
 104                        elapsed_msecs / 1000, elapsed_msecs % 1000,
 105                        todo - wq_busy, wq_busy);
 106
 107                         read_lock(&tasklist_lock);
 108                         for_each_process_thread(g, p) {
 109                                 if (p != current && !freezer_should_skip(p)
 110                                     && freezing(p) && !frozen(p))
 111                                         sched_show_task(p);
 112                         }
 113                         read_unlock(&tasklist_lock);
 114         } else {
 115                 pr_cont("(elapsed %d.%03d seconds) ", elapsed_msecs / 1000,
 116                         elapsed_msecs % 1000);
 117         }
 118
 119         return todo ? -EBUSY : 0;
 120 }
 121
 122 /**
 123  * freeze_processes - Signal user space processes to enter the refrigerator.
 124  * The current thread will not be frozen.  The same process that calls
 125  * freeze_processes must later call thaw_processes.
 126  *
 127  * On success, returns 0.  On failure, -errno and system is fully thawed.
 128  */
 129 int freeze_processes(void)
 130 {
 131         int error;
 132
 133         error = __usermodehelper_disable(UMH_FREEZING);
 134         if (error)
 135                 return error;
 136
 137         /* Make sure this task doesn't get frozen */
 138         current->flags |= PF_SUSPEND_TASK;
 139
 140         if (!pm_freezing)
 141                 atomic_inc(&system_freezing_cnt);
 142
 143         pm_wakeup_clear();
 144         pr_info("Freezing user space processes ... ");
 145         pm_freezing = true;
 146         error = try_to_freeze_tasks(true);
 147         if (!error) {
 148                 __usermodehelper_set_disable_depth(UMH_DISABLED);
 149                 pr_cont("done.");
 150         }
 151         pr_cont("\n");
 152         BUG_ON(in_atomic());
 153
 154         /*
 155          * Now that the whole userspace is frozen we need to disbale
 156          * the OOM killer to disallow any further interference with
 157          * killable tasks.
 158          */
 159         if (!error && !oom_killer_disable())
 160                 error = -EBUSY;
 161
 162         if (error)
 163                 thaw_processes();
 164         return error;
 165 }
 166
 167 /**
 168  * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
 169  *
 170  * On success, returns 0.  On failure, -errno and only the kernel threads are
 171  * thawed, so as to give a chance to the caller to do additional cleanups
 172  * (if any) before thawing the userspace tasks. So, it is the responsibility
 173  * of the caller to thaw the userspace tasks, when the time is right.
 174  */
 175 int freeze_kernel_threads(void)
 176 {
 177         int error;
 178
 179         pr_info("Freezing remaining freezable tasks ... ");
 180
 181         pm_nosig_freezing = true;
 182         error = try_to_freeze_tasks(false);
 183         if (!error)
 184                 pr_cont("done.");
 185
 186         pr_cont("\n");
 187         BUG_ON(in_atomic());
 188
 189         if (error)
 190                 thaw_kernel_threads();
 191         return error;
 192 }
 193
 194 void thaw_processes(void)
 195 {
 196         struct task_struct *g, *p;
 197         struct task_struct *curr = current;
 198
 199         trace_suspend_resume(TPS("thaw_processes"), 0, true);
 200         if (pm_freezing)
 201                 atomic_dec(&system_freezing_cnt);
 202         pm_freezing = false;
 203         pm_nosig_freezing = false;
 204
 205         oom_killer_enable();
 206
 207         pr_info("Restarting tasks ... ");
 208
 209         __usermodehelper_set_disable_depth(UMH_FREEZING);
 210         thaw_workqueues();
 211
 212         cpuset_wait_for_hotplug();
 213
 214         read_lock(&tasklist_lock);
 215         for_each_process_thread(g, p) {
 216                 /* No other threads should have PF_SUSPEND_TASK set */
 217                 WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK));
 218                 __thaw_task(p);
 219         }
 220         read_unlock(&tasklist_lock);
 221
 222         WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
 223         curr->flags &= ~PF_SUSPEND_TASK;
 224
 225         usermodehelper_enable();
 226
 227         schedule();
 228         pr_cont("done.\n");
 229         trace_suspend_resume(TPS("thaw_processes"), 0, false);
 230 }
 231
 232 void thaw_kernel_threads(void)
 233 {
 234         struct task_struct *g, *p;
 235
 236         pm_nosig_freezing = false;
 237         pr_info("Restarting kernel threads ... ");
 238
 239         thaw_workqueues();
 240
 241         read_lock(&tasklist_lock);
 242         for_each_process_thread(g, p) {
 243                 if (p->flags & (PF_KTHREAD | PF_WQ_WORKER))
 244                         __thaw_task(p);
 245         }
 246         read_unlock(&tasklist_lock);
 247
 248         schedule();
 249         pr_cont("done.\n");
 250 }