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
  41         do_gettimeofday(&start);
  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         do_gettimeofday(&end);
  84         elapsed_msecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
  85         do_div(elapsed_msecs64, NSEC_PER_MSEC);
  86         elapsed_msecs = elapsed_msecs64;
  87
  88         if (wakeup) {
  89                 pr_cont("\n");
  90                 pr_err("Freezing of tasks aborted after %d.%03d seconds",
  91                        elapsed_msecs / 1000, elapsed_msecs % 1000);
  92         } else if (todo) {
  93                 pr_cont("\n");
  94                 pr_err("Freezing of tasks failed after %d.%03d seconds"
  95                        " (%d tasks refusing to freeze, wq_busy=%d):\n",
  96                        elapsed_msecs / 1000, elapsed_msecs % 1000,
  97                        todo - wq_busy, wq_busy);
  98
  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         } 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();
 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.
 150          */
 151         if (!error && !oom_killer_disable())
 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 }