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