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 #include <linux/atomic.h>
   9
  10 #ifdef CONFIG_FREEZER
  11 extern atomic_t system_freezing_cnt;    /* nr of freezing conds in effect */
  12 extern bool pm_freezing;                /* PM freezing in effect */
  13 extern bool pm_nosig_freezing;          /* PM nosig freezing in effect */
  14
  15 /*
  16  * Timeout for stopping processes
  17  */
  18 extern unsigned int freeze_timeout_msecs;
  19
  20 /*
  21  * Check if a process has been frozen
  22  */
  23 static inline bool frozen(struct task_struct *p)
  24 {
  25         return p->flags & PF_FROZEN;
  26 }
  27
  28 extern bool freezing_slow_path(struct task_struct *p);
  29
  30 /*
  31  * Check if there is a request to freeze a process
  32  */
  33 static inline bool freezing(struct task_struct *p)
  34 {
  35         if (likely(!atomic_read(&system_freezing_cnt)))
  36                 return false;
  37         return freezing_slow_path(p);
  38 }
  39
  40 /* Takes and releases task alloc lock using task_lock() */
  41 extern void __thaw_task(struct task_struct *t);
  42
  43 extern bool __refrigerator(bool check_kthr_stop);
  44 extern int freeze_processes(void);
  45 extern int freeze_kernel_threads(void);
  46 extern void thaw_processes(void);
  47 extern void thaw_kernel_threads(void);
  48
  49 static inline bool try_to_freeze(void)
  50 {
  51         might_sleep();
  52         if (likely(!freezing(current)))
  53                 return false;
  54         return __refrigerator(false);
  55 }
  56
  57 extern bool freeze_task(struct task_struct *p);
  58 extern bool set_freezable(void);
  59
  60 #ifdef CONFIG_CGROUP_FREEZER
  61 extern bool cgroup_freezing(struct task_struct *task);
  62 #else /* !CONFIG_CGROUP_FREEZER */
  63 static inline bool cgroup_freezing(struct task_struct *task)
  64 {
  65         return false;
  66 }
  67 #endif /* !CONFIG_CGROUP_FREEZER */
  68
  69 /*
  70  * The PF_FREEZER_SKIP flag should be set by a vfork parent right before it
  71  * calls wait_for_completion(&vfork) and reset right after it returns from this
  72  * function.  Next, the parent should call try_to_freeze() to freeze itself
  73  * appropriately in case the child has exited before the freezing of tasks is
  74  * complete.  However, we don't want kernel threads to be frozen in unexpected
  75  * places, so we allow them to block freeze_processes() instead or to set
  76  * PF_NOFREEZE if needed. Fortunately, in the ____call_usermodehelper() case the
  77  * parent won't really block freeze_processes(), since ____call_usermodehelper()
  78  * (the child) does a little before exec/exit and it can't be frozen before
  79  * waking up the parent.
  80  */
  81
  82
  83 /**
  84  * freezer_do_not_count - tell freezer to ignore %current
  85  *
  86  * Tell freezers to ignore the current task when determining whether the
  87  * target frozen state is reached.  IOW, the current task will be
  88  * considered frozen enough by freezers.
  89  *
  90  * The caller shouldn't do anything which isn't allowed for a frozen task
  91  * until freezer_cont() is called.  Usually, freezer[_do_not]_count() pair
  92  * wrap a scheduling operation and nothing much else.
  93  */
  94 static inline void freezer_do_not_count(void)
  95 {
  96         current->flags |= PF_FREEZER_SKIP;
  97 }
  98
  99 /**
 100  * freezer_count - tell freezer to stop ignoring %current
 101  *
 102  * Undo freezer_do_not_count().  It tells freezers that %current should be
 103  * considered again and tries to freeze if freezing condition is already in
 104  * effect.
 105  */
 106 static inline void freezer_count(void)
 107 {
 108         current->flags &= ~PF_FREEZER_SKIP;
 109         /*
 110          * If freezing is in progress, the following paired with smp_mb()
 111          * in freezer_should_skip() ensures that either we see %true
 112          * freezing() or freezer_should_skip() sees !PF_FREEZER_SKIP.
 113          */
 114         smp_mb();
 115         try_to_freeze();
 116 }
 117
 118 /**
 119  * freezer_should_skip - whether to skip a task when determining frozen
 120  *                       state is reached
 121  * @p: task in quesion
 122  *
 123  * This function is used by freezers after establishing %true freezing() to
 124  * test whether a task should be skipped when determining the target frozen
 125  * state is reached.  IOW, if this function returns %true, @p is considered
 126  * frozen enough.
 127  */
 128 static inline bool freezer_should_skip(struct task_struct *p)
 129 {
 130         /*
 131          * The following smp_mb() paired with the one in freezer_count()
 132          * ensures that either freezer_count() sees %true freezing() or we
 133          * see cleared %PF_FREEZER_SKIP and return %false.  This makes it
 134          * impossible for a task to slip frozen state testing after
 135          * clearing %PF_FREEZER_SKIP.
 136          */
 137         smp_mb();
 138         return p->flags & PF_FREEZER_SKIP;
 139 }
 140
 141 /*
 142  * These macros are intended to be used whenever you want allow a sleeping
 143  * task to be frozen. Note that neither return any clear indication of
 144  * whether a freeze event happened while in this function.
 145  */
 146
 147 /* Like schedule(), but should not block the freezer. */
 148 #define freezable_schedule()                                            \
 149 ({                                                                      \
 150         freezer_do_not_count();                                         \
 151         schedule();                                                     \
 152         freezer_count();                                                \
 153 })
 154
 155 /* Like schedule_timeout_killable(), but should not block the freezer. */
 156 #define freezable_schedule_timeout_killable(timeout)                    \
 157 ({                                                                      \
 158         long __retval;                                                  \
 159         freezer_do_not_count();                                         \
 160         __retval = schedule_timeout_killable(timeout);                  \
 161         freezer_count();                                                \
 162         __retval;                                                       \
 163 })
 164
 165 /*
 166  * Freezer-friendly wrappers around wait_event_interruptible(),
 167  * wait_event_killable() and wait_event_interruptible_timeout(), originally
 168  * defined in <linux/wait.h>
 169  */
 170
 171 #define wait_event_freezekillable(wq, condition)                        \
 172 ({                                                                      \
 173         int __retval;                                                   \
 174         freezer_do_not_count();                                         \
 175         __retval = wait_event_killable(wq, (condition));                \
 176         freezer_count();                                                \
 177         __retval;                                                       \
 178 })
 179
 180 #define wait_event_freezable(wq, condition)                             \
 181 ({                                                                      \
 182         int __retval;                                                   \
 183         for (;;) {                                                      \
 184                 __retval = wait_event_interruptible(wq,                 \
 185                                 (condition) || freezing(current));      \
 186                 if (__retval || (condition))                            \
 187                         break;                                          \
 188                 try_to_freeze();                                        \
 189         }                                                               \
 190         __retval;                                                       \
 191 })
 192
 193 #define wait_event_freezable_timeout(wq, condition, timeout)            \
 194 ({                                                                      \
 195         long __retval = timeout;                                        \
 196         for (;;) {                                                      \
 197                 __retval = wait_event_interruptible_timeout(wq,         \
 198                                 (condition) || freezing(current),       \
 199                                 __retval);                              \
 200                 if (__retval <= 0 || (condition))                       \
 201                         break;                                          \
 202                 try_to_freeze();                                        \
 203         }                                                               \
 204         __retval;                                                       \
 205 })
 206
 207 #else /* !CONFIG_FREEZER */
 208 static inline bool frozen(struct task_struct *p) { return false; }
 209 static inline bool freezing(struct task_struct *p) { return false; }
 210 static inline void __thaw_task(struct task_struct *t) {}
 211
 212 static inline bool __refrigerator(bool check_kthr_stop) { return false; }
 213 static inline int freeze_processes(void) { return -ENOSYS; }
 214 static inline int freeze_kernel_threads(void) { return -ENOSYS; }
 215 static inline void thaw_processes(void) {}
 216 static inline void thaw_kernel_threads(void) {}
 217
 218 static inline bool try_to_freeze_nowarn(void) { return false; }
 219 static inline bool try_to_freeze(void) { return false; }
 220
 221 static inline void freezer_do_not_count(void) {}
 222 static inline void freezer_count(void) {}
 223 static inline int freezer_should_skip(struct task_struct *p) { return 0; }
 224 static inline void set_freezable(void) {}
 225
 226 #define freezable_schedule()  schedule()
 227
 228 #define freezable_schedule_timeout_killable(timeout)                    \
 229         schedule_timeout_killable(timeout)
 230
 231 #define wait_event_freezable(wq, condition)                             \
 232                 wait_event_interruptible(wq, condition)
 233
 234 #define wait_event_freezable_timeout(wq, condition, timeout)            \
 235                 wait_event_interruptible_timeout(wq, condition, timeout)
 236
 237 #define wait_event_freezekillable(wq, condition)                \
 238                 wait_event_killable(wq, condition)
 239
 240 #endif /* !CONFIG_FREEZER */
 241
 242 #endif  /* FREEZER_H_INCLUDED */