futex.h (8265B)
1/* SPDX-License-Identifier: GPL-2.0 */ 2#ifndef _FUTEX_H 3#define _FUTEX_H 4 5#include <linux/futex.h> 6#include <linux/rtmutex.h> 7#include <linux/sched/wake_q.h> 8 9#ifdef CONFIG_PREEMPT_RT 10#include <linux/rcuwait.h> 11#endif 12 13#include <asm/futex.h> 14 15/* 16 * Futex flags used to encode options to functions and preserve them across 17 * restarts. 18 */ 19#ifdef CONFIG_MMU 20# define FLAGS_SHARED 0x01 21#else 22/* 23 * NOMMU does not have per process address space. Let the compiler optimize 24 * code away. 25 */ 26# define FLAGS_SHARED 0x00 27#endif 28#define FLAGS_CLOCKRT 0x02 29#define FLAGS_HAS_TIMEOUT 0x04 30 31#ifdef CONFIG_FAIL_FUTEX 32extern bool should_fail_futex(bool fshared); 33#else 34static inline bool should_fail_futex(bool fshared) 35{ 36 return false; 37} 38#endif 39 40/* 41 * Hash buckets are shared by all the futex_keys that hash to the same 42 * location. Each key may have multiple futex_q structures, one for each task 43 * waiting on a futex. 44 */ 45struct futex_hash_bucket { 46 atomic_t waiters; 47 spinlock_t lock; 48 struct plist_head chain; 49} ____cacheline_aligned_in_smp; 50 51/* 52 * Priority Inheritance state: 53 */ 54struct futex_pi_state { 55 /* 56 * list of 'owned' pi_state instances - these have to be 57 * cleaned up in do_exit() if the task exits prematurely: 58 */ 59 struct list_head list; 60 61 /* 62 * The PI object: 63 */ 64 struct rt_mutex_base pi_mutex; 65 66 struct task_struct *owner; 67 refcount_t refcount; 68 69 union futex_key key; 70} __randomize_layout; 71 72/** 73 * struct futex_q - The hashed futex queue entry, one per waiting task 74 * @list: priority-sorted list of tasks waiting on this futex 75 * @task: the task waiting on the futex 76 * @lock_ptr: the hash bucket lock 77 * @key: the key the futex is hashed on 78 * @pi_state: optional priority inheritance state 79 * @rt_waiter: rt_waiter storage for use with requeue_pi 80 * @requeue_pi_key: the requeue_pi target futex key 81 * @bitset: bitset for the optional bitmasked wakeup 82 * @requeue_state: State field for futex_requeue_pi() 83 * @requeue_wait: RCU wait for futex_requeue_pi() (RT only) 84 * 85 * We use this hashed waitqueue, instead of a normal wait_queue_entry_t, so 86 * we can wake only the relevant ones (hashed queues may be shared). 87 * 88 * A futex_q has a woken state, just like tasks have TASK_RUNNING. 89 * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0. 90 * The order of wakeup is always to make the first condition true, then 91 * the second. 92 * 93 * PI futexes are typically woken before they are removed from the hash list via 94 * the rt_mutex code. See futex_unqueue_pi(). 95 */ 96struct futex_q { 97 struct plist_node list; 98 99 struct task_struct *task; 100 spinlock_t *lock_ptr; 101 union futex_key key; 102 struct futex_pi_state *pi_state; 103 struct rt_mutex_waiter *rt_waiter; 104 union futex_key *requeue_pi_key; 105 u32 bitset; 106 atomic_t requeue_state; 107#ifdef CONFIG_PREEMPT_RT 108 struct rcuwait requeue_wait; 109#endif 110} __randomize_layout; 111 112extern const struct futex_q futex_q_init; 113 114enum futex_access { 115 FUTEX_READ, 116 FUTEX_WRITE 117}; 118 119extern int get_futex_key(u32 __user *uaddr, bool fshared, union futex_key *key, 120 enum futex_access rw); 121 122extern struct hrtimer_sleeper * 123futex_setup_timer(ktime_t *time, struct hrtimer_sleeper *timeout, 124 int flags, u64 range_ns); 125 126extern struct futex_hash_bucket *futex_hash(union futex_key *key); 127 128/** 129 * futex_match - Check whether two futex keys are equal 130 * @key1: Pointer to key1 131 * @key2: Pointer to key2 132 * 133 * Return 1 if two futex_keys are equal, 0 otherwise. 134 */ 135static inline int futex_match(union futex_key *key1, union futex_key *key2) 136{ 137 return (key1 && key2 138 && key1->both.word == key2->both.word 139 && key1->both.ptr == key2->both.ptr 140 && key1->both.offset == key2->both.offset); 141} 142 143extern int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags, 144 struct futex_q *q, struct futex_hash_bucket **hb); 145extern void futex_wait_queue(struct futex_hash_bucket *hb, struct futex_q *q, 146 struct hrtimer_sleeper *timeout); 147extern void futex_wake_mark(struct wake_q_head *wake_q, struct futex_q *q); 148 149extern int fault_in_user_writeable(u32 __user *uaddr); 150extern int futex_cmpxchg_value_locked(u32 *curval, u32 __user *uaddr, u32 uval, u32 newval); 151extern int futex_get_value_locked(u32 *dest, u32 __user *from); 152extern struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb, union futex_key *key); 153 154extern void __futex_unqueue(struct futex_q *q); 155extern void __futex_queue(struct futex_q *q, struct futex_hash_bucket *hb); 156extern int futex_unqueue(struct futex_q *q); 157 158/** 159 * futex_queue() - Enqueue the futex_q on the futex_hash_bucket 160 * @q: The futex_q to enqueue 161 * @hb: The destination hash bucket 162 * 163 * The hb->lock must be held by the caller, and is released here. A call to 164 * futex_queue() is typically paired with exactly one call to futex_unqueue(). The 165 * exceptions involve the PI related operations, which may use futex_unqueue_pi() 166 * or nothing if the unqueue is done as part of the wake process and the unqueue 167 * state is implicit in the state of woken task (see futex_wait_requeue_pi() for 168 * an example). 169 */ 170static inline void futex_queue(struct futex_q *q, struct futex_hash_bucket *hb) 171 __releases(&hb->lock) 172{ 173 __futex_queue(q, hb); 174 spin_unlock(&hb->lock); 175} 176 177extern void futex_unqueue_pi(struct futex_q *q); 178 179extern void wait_for_owner_exiting(int ret, struct task_struct *exiting); 180 181/* 182 * Reflects a new waiter being added to the waitqueue. 183 */ 184static inline void futex_hb_waiters_inc(struct futex_hash_bucket *hb) 185{ 186#ifdef CONFIG_SMP 187 atomic_inc(&hb->waiters); 188 /* 189 * Full barrier (A), see the ordering comment above. 190 */ 191 smp_mb__after_atomic(); 192#endif 193} 194 195/* 196 * Reflects a waiter being removed from the waitqueue by wakeup 197 * paths. 198 */ 199static inline void futex_hb_waiters_dec(struct futex_hash_bucket *hb) 200{ 201#ifdef CONFIG_SMP 202 atomic_dec(&hb->waiters); 203#endif 204} 205 206static inline int futex_hb_waiters_pending(struct futex_hash_bucket *hb) 207{ 208#ifdef CONFIG_SMP 209 /* 210 * Full barrier (B), see the ordering comment above. 211 */ 212 smp_mb(); 213 return atomic_read(&hb->waiters); 214#else 215 return 1; 216#endif 217} 218 219extern struct futex_hash_bucket *futex_q_lock(struct futex_q *q); 220extern void futex_q_unlock(struct futex_hash_bucket *hb); 221 222 223extern int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb, 224 union futex_key *key, 225 struct futex_pi_state **ps, 226 struct task_struct *task, 227 struct task_struct **exiting, 228 int set_waiters); 229 230extern int refill_pi_state_cache(void); 231extern void get_pi_state(struct futex_pi_state *pi_state); 232extern void put_pi_state(struct futex_pi_state *pi_state); 233extern int fixup_pi_owner(u32 __user *uaddr, struct futex_q *q, int locked); 234 235/* 236 * Express the locking dependencies for lockdep: 237 */ 238static inline void 239double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) 240{ 241 if (hb1 > hb2) 242 swap(hb1, hb2); 243 244 spin_lock(&hb1->lock); 245 if (hb1 != hb2) 246 spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING); 247} 248 249static inline void 250double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) 251{ 252 spin_unlock(&hb1->lock); 253 if (hb1 != hb2) 254 spin_unlock(&hb2->lock); 255} 256 257/* syscalls */ 258 259extern int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags, u32 260 val, ktime_t *abs_time, u32 bitset, u32 __user 261 *uaddr2); 262 263extern int futex_requeue(u32 __user *uaddr1, unsigned int flags, 264 u32 __user *uaddr2, int nr_wake, int nr_requeue, 265 u32 *cmpval, int requeue_pi); 266 267extern int futex_wait(u32 __user *uaddr, unsigned int flags, u32 val, 268 ktime_t *abs_time, u32 bitset); 269 270/** 271 * struct futex_vector - Auxiliary struct for futex_waitv() 272 * @w: Userspace provided data 273 * @q: Kernel side data 274 * 275 * Struct used to build an array with all data need for futex_waitv() 276 */ 277struct futex_vector { 278 struct futex_waitv w; 279 struct futex_q q; 280}; 281 282extern int futex_wait_multiple(struct futex_vector *vs, unsigned int count, 283 struct hrtimer_sleeper *to); 284 285extern int futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset); 286 287extern int futex_wake_op(u32 __user *uaddr1, unsigned int flags, 288 u32 __user *uaddr2, int nr_wake, int nr_wake2, int op); 289 290extern int futex_unlock_pi(u32 __user *uaddr, unsigned int flags); 291 292extern int futex_lock_pi(u32 __user *uaddr, unsigned int flags, ktime_t *time, int trylock); 293 294#endif /* _FUTEX_H */