include/linux/freezer.h

   1 /* Freezer declarations */
   2
   3 #ifndef FREEZER_H_INCLUDED
   4 #define FREEZER_H_INCLUDED
   5
   6 #include <linux/sched.h>
   7 #include <linux/wait.h>
   8
   9 #ifdef CONFIG_PM_SLEEP
  10 /*
  11  * Check if a process has been frozen
  12  */
  13 static inline int frozen(struct task_struct *p)
  14 {
  15         return p->flags & PF_FROZEN;
  16 }
  17
  18 /*
  19  * Check if there is a request to freeze a process
  20  */
  21 static inline int freezing(struct task_struct *p)
  22 {
  23         return test_tsk_thread_flag(p, TIF_FREEZE);
  24 }
  25
  26 /*
  27  * Request that a process be frozen
  28  */
  29 static inline void set_freeze_flag(struct task_struct *p)
  30 {
  31         set_tsk_thread_flag(p, TIF_FREEZE);
  32 }
  33
  34 /*
  35  * Sometimes we may need to cancel the previous 'freeze' request
  36  */
  37 static inline void clear_freeze_flag(struct task_struct *p)
  38 {
  39         clear_tsk_thread_flag(p, TIF_FREEZE);
  40 }
  41
  42 /*
  43  * Wake up a frozen process
  44  *
  45  * task_lock() is taken to prevent the race with refrigerator() which may
  46  * occur if the freezing of tasks fails.  Namely, without the lock, if the
  47  * freezing of tasks failed, thaw_tasks() might have run before a task in
  48  * refrigerator() could call frozen_process(), in which case the task would be
  49  * frozen and no one would thaw it.
  50  */
  51 static inline int thaw_process(struct task_struct *p)
  52 {
  53         task_lock(p);
  54         if (frozen(p)) {
  55                 p->flags &= ~PF_FROZEN;
  56                 task_unlock(p);
  57                 wake_up_process(p);
  58                 return 1;
  59         }
  60         clear_freeze_flag(p);
  61         task_unlock(p);
  62         return 0;
  63 }
  64
  65 extern void refrigerator(void);
  66 extern int freeze_processes(void);
  67 extern void thaw_processes(void);
  68
  69 static inline int try_to_freeze(void)
  70 {
  71         if (freezing(current)) {
  72                 refrigerator();
  73                 return 1;
  74         } else
  75                 return 0;
  76 }
  77
  78 /*
  79  * The PF_FREEZER_SKIP flag should be set by a vfork parent right before it
  80  * calls wait_for_completion(&vfork) and reset right after it returns from this
  81  * function.  Next, the parent should call try_to_freeze() to freeze itself
  82  * appropriately in case the child has exited before the freezing of tasks is
  83  * complete.  However, we don't want kernel threads to be frozen in unexpected
  84  * places, so we allow them to block freeze_processes() instead or to set
  85  * PF_NOFREEZE if needed and PF_FREEZER_SKIP is only set for userland vfork
  86  * parents.  Fortunately, in the ____call_usermodehelper() case the parent won't
  87  * really block freeze_processes(), since ____call_usermodehelper() (the child)
  88  * does a little before exec/exit and it can't be frozen before waking up the
  89  * parent.
  90  */
  91
  92 /*
  93  * If the current task is a user space one, tell the freezer not to count it as
  94  * freezable.
  95  */
  96 static inline void freezer_do_not_count(void)
  97 {
  98         if (current->mm)
  99                 current->flags |= PF_FREEZER_SKIP;
 100 }
 101
 102 /*
 103  * If the current task is a user space one, tell the freezer to count it as
 104  * freezable again and try to freeze it.
 105  */
 106 static inline void freezer_count(void)
 107 {
 108         if (current->mm) {
 109                 current->flags &= ~PF_FREEZER_SKIP;
 110                 try_to_freeze();
 111         }
 112 }
 113
 114 /*
 115  * Check if the task should be counted as freezeable by the freezer
 116  */
 117 static inline int freezer_should_skip(struct task_struct *p)
 118 {
 119         return !!(p->flags & PF_FREEZER_SKIP);
 120 }
 121
 122 /*
 123  * Tell the freezer that the current task should be frozen by it
 124  */
 125 static inline void set_freezable(void)
 126 {
 127         current->flags &= ~PF_NOFREEZE;
 128 }
 129
 130 /*
 131  * Freezer-friendly wrappers around wait_event_interruptible() and
 132  * wait_event_interruptible_timeout(), originally defined in <linux/wait.h>
 133  */
 134
 135 #define wait_event_freezable(wq, condition)                             \
 136 ({                                                                      \
 137         int __retval;                                                   \
 138         do {                                                            \
 139                 __retval = wait_event_interruptible(wq,                 \
 140                                 (condition) || freezing(current));      \
 141                 if (__retval && !freezing(current))                     \
 142                         break;                                          \
 143                 else if (!(condition))                                  \
 144                         __retval = -ERESTARTSYS;                        \
 145         } while (try_to_freeze());                                      \
 146         __retval;                                                       \
 147 })
 148
 149
 150 #define wait_event_freezable_timeout(wq, condition, timeout)            \
 151 ({                                                                      \
 152         long __retval = timeout;                                        \
 153         do {                                                            \
 154                 __retval = wait_event_interruptible_timeout(wq,         \
 155                                 (condition) || freezing(current),       \
 156                                 __retval);                              \
 157         } while (try_to_freeze());                                      \
 158         __retval;                                                       \
 159 })
 160 #else /* !CONFIG_PM_SLEEP */
 161 static inline int frozen(struct task_struct *p) { return 0; }
 162 static inline int freezing(struct task_struct *p) { return 0; }
 163 static inline void set_freeze_flag(struct task_struct *p) {}
 164 static inline void clear_freeze_flag(struct task_struct *p) {}
 165 static inline int thaw_process(struct task_struct *p) { return 1; }
 166
 167 static inline void refrigerator(void) {}
 168 static inline int freeze_processes(void) { BUG(); return 0; }
 169 static inline void thaw_processes(void) {}
 170
 171 static inline int try_to_freeze(void) { return 0; }
 172
 173 static inline void freezer_do_not_count(void) {}
 174 static inline void freezer_count(void) {}
 175 static inline int freezer_should_skip(struct task_struct *p) { return 0; }
 176 static inline void set_freezable(void) {}
 177
 178 #define wait_event_freezable(wq, condition)                             \
 179                 wait_event_interruptible(wq, condition)
 180
 181 #define wait_event_freezable_timeout(wq, condition, timeout)            \
 182                 wait_event_interruptible_timeout(wq, condition, timeout)
 183
 184 #endif /* !CONFIG_PM_SLEEP */
 185
 186 #endif  /* FREEZER_H_INCLUDED */