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 extern void refrigerator(void);
  62 extern int freeze_processes(void);
  63 extern void thaw_processes(void);
  64
  65 static inline int try_to_freeze(void)
  66 {
  67         if (freezing(current)) {
  68                 refrigerator();
  69                 return 1;
  70         } else
  71                 return 0;
  72 }
  73
  74 /*
  75  * The PF_FREEZER_SKIP flag should be set by a vfork parent right before it
  76  * calls wait_for_completion(&vfork) and reset right after it returns from this
  77  * function.  Next, the parent should call try_to_freeze() to freeze itself
  78  * appropriately in case the child has exited before the freezing of tasks is
  79  * complete.  However, we don't want kernel threads to be frozen in unexpected
  80  * places, so we allow them to block freeze_processes() instead or to set
  81  * PF_NOFREEZE if needed and PF_FREEZER_SKIP is only set for userland vfork
  82  * parents.  Fortunately, in the ____call_usermodehelper() case the parent won't
  83  * really block freeze_processes(), since ____call_usermodehelper() (the child)
  84  * does a little before exec/exit and it can't be frozen before waking up the
  85  * parent.
  86  */
  87
  88 /*
  89  * If the current task is a user space one, tell the freezer not to count it as
  90  * freezable.
  91  */
  92 static inline void freezer_do_not_count(void)
  93 {
  94         if (current->mm)
  95                 current->flags |= PF_FREEZER_SKIP;
  96 }
  97
  98 /*
  99  * If the current task is a user space one, tell the freezer to count it as
 100  * freezable again and try to freeze it.
 101  */
 102 static inline void freezer_count(void)
 103 {
 104         if (current->mm) {
 105                 current->flags &= ~PF_FREEZER_SKIP;
 106                 try_to_freeze();
 107         }
 108 }
 109
 110 /*
 111  * Check if the task should be counted as freezeable by the freezer
 112  */
 113 static inline int freezer_should_skip(struct task_struct *p)
 114 {
 115         return !!(p->flags & PF_FREEZER_SKIP);
 116 }
 117
 118 #else
 119 static inline int frozen(struct task_struct *p) { return 0; }
 120 static inline int freezing(struct task_struct *p) { return 0; }
 121 static inline void freeze(struct task_struct *p) { BUG(); }
 122 static inline int thaw_process(struct task_struct *p) { return 1; }
 123
 124 static inline void refrigerator(void) {}
 125 static inline int freeze_processes(void) { BUG(); return 0; }
 126 static inline void thaw_processes(void) {}
 127
 128 static inline int try_to_freeze(void) { return 0; }
 129
 130 static inline void freezer_do_not_count(void) {}
 131 static inline void freezer_count(void) {}
 132 static inline int freezer_should_skip(struct task_struct *p) { return 0; }
 133 #endif