include/linux/freezer.h

   1 /* Freezer declarations */
   2
   3 #include <linux/sched.h>
   4
   5 #ifdef CONFIG_PM
   6 /*
   7  * Check if a process has been frozen
   8  */
   9 static inline int frozen(struct task_struct *p)
  10 {
  11         return p->flags & PF_FROZEN;
  12 }
  13
  14 /*
  15  * Check if there is a request to freeze a process
  16  */
  17 static inline int freezing(struct task_struct *p)
  18 {
  19         return test_tsk_thread_flag(p, TIF_FREEZE);
  20 }
  21
  22 /*
  23  * Request that a process be frozen
  24  */
  25 static inline void freeze(struct task_struct *p)
  26 {
  27         set_tsk_thread_flag(p, TIF_FREEZE);
  28 }
  29
  30 /*
  31  * Sometimes we may need to cancel the previous 'freeze' request
  32  */
  33 static inline void do_not_freeze(struct task_struct *p)
  34 {
  35         clear_tsk_thread_flag(p, TIF_FREEZE);
  36 }
  37
  38 /*
  39  * Wake up a frozen process
  40  *
  41  * task_lock() is taken to prevent the race with refrigerator() which may
  42  * occur if the freezing of tasks fails.  Namely, without the lock, if the
  43  * freezing of tasks failed, thaw_tasks() might have run before a task in
  44  * refrigerator() could call frozen_process(), in which case the task would be
  45  * frozen and no one would thaw it.
  46  */
  47 static inline int thaw_process(struct task_struct *p)
  48 {
  49         task_lock(p);
  50         if (frozen(p)) {
  51                 p->flags &= ~PF_FROZEN;
  52                 task_unlock(p);
  53                 wake_up_process(p);
  54                 return 1;
  55         }
  56         clear_tsk_thread_flag(p, TIF_FREEZE);
  57         task_unlock(p);
  58         return 0;
  59 }
  60
  61 /*
  62  * freezing is complete, mark process as frozen
  63  */
  64 static inline void frozen_process(struct task_struct *p)
  65 {
  66         if (!unlikely(p->flags & PF_NOFREEZE)) {
  67                 p->flags |= PF_FROZEN;
  68                 wmb();
  69         }
  70         clear_tsk_thread_flag(p, TIF_FREEZE);
  71 }
  72
  73 extern void refrigerator(void);
  74 extern int freeze_processes(void);
  75 extern void thaw_processes(void);
  76
  77 static inline int try_to_freeze(void)
  78 {
  79         if (freezing(current)) {
  80                 refrigerator();
  81                 return 1;
  82         } else
  83                 return 0;
  84 }
  85
  86 /*
  87  * The PF_FREEZER_SKIP flag should be set by a vfork parent right before it
  88  * calls wait_for_completion(&vfork) and reset right after it returns from this
  89  * function.  Next, the parent should call try_to_freeze() to freeze itself
  90  * appropriately in case the child has exited before the freezing of tasks is
  91  * complete.  However, we don't want kernel threads to be frozen in unexpected
  92  * places, so we allow them to block freeze_processes() instead or to set
  93  * PF_NOFREEZE if needed and PF_FREEZER_SKIP is only set for userland vfork
  94  * parents.  Fortunately, in the ____call_usermodehelper() case the parent won't
  95  * really block freeze_processes(), since ____call_usermodehelper() (the child)
  96  * does a little before exec/exit and it can't be frozen before waking up the
  97  * parent.
  98  */
  99
 100 /*
 101  * If the current task is a user space one, tell the freezer not to count it as
 102  * freezable.
 103  */
 104 static inline void freezer_do_not_count(void)
 105 {
 106         if (current->mm)
 107                 current->flags |= PF_FREEZER_SKIP;
 108 }
 109
 110 /*
 111  * If the current task is a user space one, tell the freezer to count it as
 112  * freezable again and try to freeze it.
 113  */
 114 static inline void freezer_count(void)
 115 {
 116         if (current->mm) {
 117                 current->flags &= ~PF_FREEZER_SKIP;
 118                 try_to_freeze();
 119         }
 120 }
 121
 122 /*
 123  * Check if the task should be counted as freezeable by the freezer
 124  */
 125 static inline int freezer_should_skip(struct task_struct *p)
 126 {
 127         return !!(p->flags & PF_FREEZER_SKIP);
 128 }
 129
 130 #else
 131 static inline int frozen(struct task_struct *p) { return 0; }
 132 static inline int freezing(struct task_struct *p) { return 0; }
 133 static inline void freeze(struct task_struct *p) { BUG(); }
 134 static inline int thaw_process(struct task_struct *p) { return 1; }
 135 static inline void frozen_process(struct task_struct *p) { BUG(); }
 136
 137 static inline void refrigerator(void) {}
 138 static inline int freeze_processes(void) { BUG(); return 0; }
 139 static inline void thaw_processes(void) {}
 140
 141 static inline int try_to_freeze(void) { return 0; }
 142
 143 static inline void freezer_do_not_count(void) {}
 144 static inline void freezer_count(void) {}
 145 static inline int freezer_should_skip(struct task_struct *p) { return 0; }
 146 #endif