include/linux/freezer.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /* Freezer declarations */
   3
   4 #ifndef FREEZER_H_INCLUDED
   5 #define FREEZER_H_INCLUDED
   6
   7 #include <linux/debug_locks.h>
   8 #include <linux/sched.h>
   9 #include <linux/wait.h>
  10 #include <linux/atomic.h>
  11
  12 #ifdef CONFIG_FREEZER
  13 extern atomic_t system_freezing_cnt;    /* nr of freezing conds in effect */
  14 extern bool pm_freezing;                /* PM freezing in effect */
  15 extern bool pm_nosig_freezing;          /* PM nosig freezing in effect */
  16
  17 /*
  18  * Timeout for stopping processes
  19  */
  20 extern unsigned int freeze_timeout_msecs;
  21
  22 /*
  23  * Check if a process has been frozen
  24  */
  25 static inline bool frozen(struct task_struct *p)
  26 {
  27         return p->flags & PF_FROZEN;
  28 }
  29
  30 extern bool freezing_slow_path(struct task_struct *p);
  31
  32 /*
  33  * Check if there is a request to freeze a process
  34  */
  35 static inline bool freezing(struct task_struct *p)
  36 {
  37         if (likely(!atomic_read(&system_freezing_cnt)))
  38                 return false;
  39         return freezing_slow_path(p);
  40 }
  41
  42 /* Takes and releases task alloc lock using task_lock() */
  43 extern void __thaw_task(struct task_struct *t);
  44
  45 extern bool __refrigerator(bool check_kthr_stop);
  46 extern int freeze_processes(void);
  47 extern int freeze_kernel_threads(void);
  48 extern void thaw_processes(void);
  49 extern void thaw_kernel_threads(void);
  50
  51 /*
  52  * DO NOT ADD ANY NEW CALLERS OF THIS FUNCTION
  53  * If try_to_freeze causes a lockdep warning it means the caller may deadlock
  54  */
  55 static inline bool try_to_freeze_unsafe(void)
  56 {
  57         might_sleep();
  58         if (likely(!freezing(current)))
  59                 return false;
  60         return __refrigerator(false);
  61 }
  62
  63 static inline bool try_to_freeze(void)
  64 {
  65         if (!(current->flags & PF_NOFREEZE))
  66                 debug_check_no_locks_held();
  67         return try_to_freeze_unsafe();
  68 }
  69
  70 extern bool freeze_task(struct task_struct *p);
  71 extern bool set_freezable(void);
  72
  73 #ifdef CONFIG_CGROUP_FREEZER
  74 extern bool cgroup_freezing(struct task_struct *task);
  75 #else /* !CONFIG_CGROUP_FREEZER */
  76 static inline bool cgroup_freezing(struct task_struct *task)
  77 {
  78         return false;
  79 }
  80 #endif /* !CONFIG_CGROUP_FREEZER */
  81
  82 /*
  83  * The PF_FREEZER_SKIP flag should be set by a vfork parent right before it
  84  * calls wait_for_completion(&vfork) and reset right after it returns from this
  85  * function.  Next, the parent should call try_to_freeze() to freeze itself
  86  * appropriately in case the child has exited before the freezing of tasks is
  87  * complete.  However, we don't want kernel threads to be frozen in unexpected
  88  * places, so we allow them to block freeze_processes() instead or to set
  89  * PF_NOFREEZE if needed. Fortunately, in the ____call_usermodehelper() case the
  90  * parent won't really block freeze_processes(), since ____call_usermodehelper()
  91  * (the child) does a little before exec/exit and it can't be frozen before
  92  * waking up the parent.
  93  */
  94
  95
  96 /**
  97  * freezer_do_not_count - tell freezer to ignore %current
  98  *
  99  * Tell freezers to ignore the current task when determining whether the
 100  * target frozen state is reached.  IOW, the current task will be
 101  * considered frozen enough by freezers.
 102  *
 103  * The caller shouldn't do anything which isn't allowed for a frozen task
 104  * until freezer_cont() is called.  Usually, freezer[_do_not]_count() pair
 105  * wrap a scheduling operation and nothing much else.
 106  */
 107 static inline void freezer_do_not_count(void)
 108 {
 109         current->flags |= PF_FREEZER_SKIP;
 110 }
 111
 112 /**
 113  * freezer_count - tell freezer to stop ignoring %current
 114  *
 115  * Undo freezer_do_not_count().  It tells freezers that %current should be
 116  * considered again and tries to freeze if freezing condition is already in
 117  * effect.
 118  */
 119 static inline void freezer_count(void)
 120 {
 121         current->flags &= ~PF_FREEZER_SKIP;
 122         /*
 123          * If freezing is in progress, the following paired with smp_mb()
 124          * in freezer_should_skip() ensures that either we see %true
 125          * freezing() or freezer_should_skip() sees !PF_FREEZER_SKIP.
 126          */
 127         smp_mb();
 128         try_to_freeze();
 129 }
 130
 131 /* DO NOT ADD ANY NEW CALLERS OF THIS FUNCTION */
 132 static inline void freezer_count_unsafe(void)
 133 {
 134         current->flags &= ~PF_FREEZER_SKIP;
 135         smp_mb();
 136         try_to_freeze_unsafe();
 137 }
 138
 139 /**
 140  * freezer_should_skip - whether to skip a task when determining frozen
 141  *                       state is reached
 142  * @p: task in quesion
 143  *
 144  * This function is used by freezers after establishing %true freezing() to
 145  * test whether a task should be skipped when determining the target frozen
 146  * state is reached.  IOW, if this function returns %true, @p is considered
 147  * frozen enough.
 148  */
 149 static inline bool freezer_should_skip(struct task_struct *p)
 150 {
 151         /*
 152          * The following smp_mb() paired with the one in freezer_count()
 153          * ensures that either freezer_count() sees %true freezing() or we
 154          * see cleared %PF_FREEZER_SKIP and return %false.  This makes it
 155          * impossible for a task to slip frozen state testing after
 156          * clearing %PF_FREEZER_SKIP.
 157          */
 158         smp_mb();
 159         return p->flags & PF_FREEZER_SKIP;
 160 }
 161
 162 /*
 163  * These functions are intended to be used whenever you want allow a sleeping
 164  * task to be frozen. Note that neither return any clear indication of
 165  * whether a freeze event happened while in this function.
 166  */
 167
 168 /* Like schedule(), but should not block the freezer. */
 169 static inline void freezable_schedule(void)
 170 {
 171         freezer_do_not_count();
 172         schedule();
 173         freezer_count();
 174 }
 175
 176 /* DO NOT ADD ANY NEW CALLERS OF THIS FUNCTION */
 177 static inline void freezable_schedule_unsafe(void)
 178 {
 179         freezer_do_not_count();
 180         schedule();
 181         freezer_count_unsafe();
 182 }
 183
 184 /*
 185  * Like schedule_timeout(), but should not block the freezer.  Do not
 186  * call this with locks held.
 187  */
 188 static inline long freezable_schedule_timeout(long timeout)
 189 {
 190         long __retval;
 191         freezer_do_not_count();
 192         __retval = schedule_timeout(timeout);
 193         freezer_count();
 194         return __retval;
 195 }
 196
 197 /*
 198  * Like schedule_timeout_interruptible(), but should not block the freezer.  Do not
 199  * call this with locks held.
 200  */
 201 static inline long freezable_schedule_timeout_interruptible(long timeout)
 202 {
 203         long __retval;
 204         freezer_do_not_count();
 205         __retval = schedule_timeout_interruptible(timeout);
 206         freezer_count();
 207         return __retval;
 208 }
 209
 210 /* Like schedule_timeout_killable(), but should not block the freezer. */
 211 static inline long freezable_schedule_timeout_killable(long timeout)
 212 {
 213         long __retval;
 214         freezer_do_not_count();
 215         __retval = schedule_timeout_killable(timeout);
 216         freezer_count();
 217         return __retval;
 218 }
 219
 220 /* DO NOT ADD ANY NEW CALLERS OF THIS FUNCTION */
 221 static inline long freezable_schedule_timeout_killable_unsafe(long timeout)
 222 {
 223         long __retval;
 224         freezer_do_not_count();
 225         __retval = schedule_timeout_killable(timeout);
 226         freezer_count_unsafe();
 227         return __retval;
 228 }
 229
 230 /*
 231  * Like schedule_hrtimeout_range(), but should not block the freezer.  Do not
 232  * call this with locks held.
 233  */
 234 static inline int freezable_schedule_hrtimeout_range(ktime_t *expires,
 235                 u64 delta, const enum hrtimer_mode mode)
 236 {
 237         int __retval;
 238         freezer_do_not_count();
 239         __retval = schedule_hrtimeout_range(expires, delta, mode);
 240         freezer_count();
 241         return __retval;
 242 }
 243
 244 /*
 245  * Freezer-friendly wrappers around wait_event_interruptible(),
 246  * wait_event_killable() and wait_event_interruptible_timeout(), originally
 247  * defined in <linux/wait.h>
 248  */
 249
 250 /* DO NOT ADD ANY NEW CALLERS OF THIS FUNCTION */
 251 #define wait_event_freezekillable_unsafe(wq, condition)                 \
 252 ({                                                                      \
 253         int __retval;                                                   \
 254         freezer_do_not_count();                                         \
 255         __retval = wait_event_killable(wq, (condition));                \
 256         freezer_count_unsafe();                                         \
 257         __retval;                                                       \
 258 })
 259
 260 #else /* !CONFIG_FREEZER */
 261 static inline bool frozen(struct task_struct *p) { return false; }
 262 static inline bool freezing(struct task_struct *p) { return false; }
 263 static inline void __thaw_task(struct task_struct *t) {}
 264
 265 static inline bool __refrigerator(bool check_kthr_stop) { return false; }
 266 static inline int freeze_processes(void) { return -ENOSYS; }
 267 static inline int freeze_kernel_threads(void) { return -ENOSYS; }
 268 static inline void thaw_processes(void) {}
 269 static inline void thaw_kernel_threads(void) {}
 270
 271 static inline bool try_to_freeze_nowarn(void) { return false; }
 272 static inline bool try_to_freeze(void) { return false; }
 273
 274 static inline void freezer_do_not_count(void) {}
 275 static inline void freezer_count(void) {}
 276 static inline int freezer_should_skip(struct task_struct *p) { return 0; }
 277 static inline void set_freezable(void) {}
 278
 279 #define freezable_schedule()  schedule()
 280
 281 #define freezable_schedule_unsafe()  schedule()
 282
 283 #define freezable_schedule_timeout(timeout)  schedule_timeout(timeout)
 284
 285 #define freezable_schedule_timeout_interruptible(timeout)               \
 286         schedule_timeout_interruptible(timeout)
 287
 288 #define freezable_schedule_timeout_killable(timeout)                    \
 289         schedule_timeout_killable(timeout)
 290
 291 #define freezable_schedule_timeout_killable_unsafe(timeout)             \
 292         schedule_timeout_killable(timeout)
 293
 294 #define freezable_schedule_hrtimeout_range(expires, delta, mode)        \
 295         schedule_hrtimeout_range(expires, delta, mode)
 296
 297 #define wait_event_freezekillable_unsafe(wq, condition)                 \
 298                 wait_event_killable(wq, condition)
 299
 300 #endif /* !CONFIG_FREEZER */
 301
 302 #endif  /* FREEZER_H_INCLUDED */