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