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 */ 303