295 lines
8.1 KiB
C
295 lines
8.1 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _FUTEX_H
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#define _FUTEX_H
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#include <linux/futex.h>
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#include <linux/rtmutex.h>
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#include <linux/sched/wake_q.h>
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#ifdef CONFIG_PREEMPT_RT
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#include <linux/rcuwait.h>
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#endif
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#include <asm/futex.h>
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/*
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* Futex flags used to encode options to functions and preserve them across
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* restarts.
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*/
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#ifdef CONFIG_MMU
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# define FLAGS_SHARED 0x01
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#else
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/*
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* NOMMU does not have per process address space. Let the compiler optimize
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* code away.
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*/
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# define FLAGS_SHARED 0x00
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#endif
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#define FLAGS_CLOCKRT 0x02
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#define FLAGS_HAS_TIMEOUT 0x04
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#ifdef CONFIG_FAIL_FUTEX
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extern bool should_fail_futex(bool fshared);
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#else
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static inline bool should_fail_futex(bool fshared)
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{
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return false;
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}
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#endif
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/*
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* Hash buckets are shared by all the futex_keys that hash to the same
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* location. Each key may have multiple futex_q structures, one for each task
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* waiting on a futex.
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*/
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struct futex_hash_bucket {
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atomic_t waiters;
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spinlock_t lock;
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struct plist_head chain;
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} ____cacheline_aligned_in_smp;
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/*
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* Priority Inheritance state:
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*/
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struct futex_pi_state {
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/*
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* list of 'owned' pi_state instances - these have to be
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* cleaned up in do_exit() if the task exits prematurely:
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*/
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struct list_head list;
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/*
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* The PI object:
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*/
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struct rt_mutex_base pi_mutex;
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struct task_struct *owner;
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refcount_t refcount;
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union futex_key key;
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} __randomize_layout;
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/**
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* struct futex_q - The hashed futex queue entry, one per waiting task
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* @list: priority-sorted list of tasks waiting on this futex
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* @task: the task waiting on the futex
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* @lock_ptr: the hash bucket lock
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* @key: the key the futex is hashed on
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* @pi_state: optional priority inheritance state
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* @rt_waiter: rt_waiter storage for use with requeue_pi
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* @requeue_pi_key: the requeue_pi target futex key
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* @bitset: bitset for the optional bitmasked wakeup
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* @requeue_state: State field for futex_requeue_pi()
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* @requeue_wait: RCU wait for futex_requeue_pi() (RT only)
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*
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* We use this hashed waitqueue, instead of a normal wait_queue_entry_t, so
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* we can wake only the relevant ones (hashed queues may be shared).
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*
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* A futex_q has a woken state, just like tasks have TASK_RUNNING.
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* It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0.
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* The order of wakeup is always to make the first condition true, then
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* the second.
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*
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* PI futexes are typically woken before they are removed from the hash list via
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* the rt_mutex code. See futex_unqueue_pi().
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*/
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struct futex_q {
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struct plist_node list;
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struct task_struct *task;
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spinlock_t *lock_ptr;
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union futex_key key;
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struct futex_pi_state *pi_state;
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struct rt_mutex_waiter *rt_waiter;
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union futex_key *requeue_pi_key;
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u32 bitset;
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atomic_t requeue_state;
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#ifdef CONFIG_PREEMPT_RT
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struct rcuwait requeue_wait;
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#endif
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} __randomize_layout;
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extern const struct futex_q futex_q_init;
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enum futex_access {
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FUTEX_READ,
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FUTEX_WRITE
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};
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extern int get_futex_key(u32 __user *uaddr, bool fshared, union futex_key *key,
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enum futex_access rw);
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extern struct hrtimer_sleeper *
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futex_setup_timer(ktime_t *time, struct hrtimer_sleeper *timeout,
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int flags, u64 range_ns);
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extern struct futex_hash_bucket *futex_hash(union futex_key *key);
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/**
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* futex_match - Check whether two futex keys are equal
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* @key1: Pointer to key1
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* @key2: Pointer to key2
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*
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* Return 1 if two futex_keys are equal, 0 otherwise.
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*/
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static inline int futex_match(union futex_key *key1, union futex_key *key2)
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{
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return (key1 && key2
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&& key1->both.word == key2->both.word
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&& key1->both.ptr == key2->both.ptr
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&& key1->both.offset == key2->both.offset);
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}
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extern int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags,
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struct futex_q *q, struct futex_hash_bucket **hb);
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extern void futex_wait_queue(struct futex_hash_bucket *hb, struct futex_q *q,
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struct hrtimer_sleeper *timeout);
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extern void futex_wake_mark(struct wake_q_head *wake_q, struct futex_q *q);
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extern int fault_in_user_writeable(u32 __user *uaddr);
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extern int futex_cmpxchg_value_locked(u32 *curval, u32 __user *uaddr, u32 uval, u32 newval);
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extern int futex_get_value_locked(u32 *dest, u32 __user *from);
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extern struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb, union futex_key *key);
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extern void __futex_unqueue(struct futex_q *q);
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extern void __futex_queue(struct futex_q *q, struct futex_hash_bucket *hb);
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extern int futex_unqueue(struct futex_q *q);
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/**
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* futex_queue() - Enqueue the futex_q on the futex_hash_bucket
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* @q: The futex_q to enqueue
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* @hb: The destination hash bucket
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*
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* The hb->lock must be held by the caller, and is released here. A call to
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* futex_queue() is typically paired with exactly one call to futex_unqueue(). The
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* exceptions involve the PI related operations, which may use futex_unqueue_pi()
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* or nothing if the unqueue is done as part of the wake process and the unqueue
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* state is implicit in the state of woken task (see futex_wait_requeue_pi() for
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* an example).
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*/
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static inline void futex_queue(struct futex_q *q, struct futex_hash_bucket *hb)
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__releases(&hb->lock)
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{
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__futex_queue(q, hb);
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spin_unlock(&hb->lock);
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}
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extern void futex_unqueue_pi(struct futex_q *q);
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extern void wait_for_owner_exiting(int ret, struct task_struct *exiting);
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/*
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* Reflects a new waiter being added to the waitqueue.
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*/
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static inline void futex_hb_waiters_inc(struct futex_hash_bucket *hb)
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{
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#ifdef CONFIG_SMP
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atomic_inc(&hb->waiters);
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/*
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* Full barrier (A), see the ordering comment above.
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*/
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smp_mb__after_atomic();
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#endif
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}
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/*
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* Reflects a waiter being removed from the waitqueue by wakeup
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* paths.
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*/
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static inline void futex_hb_waiters_dec(struct futex_hash_bucket *hb)
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{
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#ifdef CONFIG_SMP
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atomic_dec(&hb->waiters);
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#endif
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}
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static inline int futex_hb_waiters_pending(struct futex_hash_bucket *hb)
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{
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#ifdef CONFIG_SMP
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/*
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* Full barrier (B), see the ordering comment above.
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*/
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smp_mb();
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return atomic_read(&hb->waiters);
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#else
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return 1;
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#endif
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}
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extern struct futex_hash_bucket *futex_q_lock(struct futex_q *q);
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extern void futex_q_unlock(struct futex_hash_bucket *hb);
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extern int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb,
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union futex_key *key,
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struct futex_pi_state **ps,
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struct task_struct *task,
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struct task_struct **exiting,
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int set_waiters);
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extern int refill_pi_state_cache(void);
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extern void get_pi_state(struct futex_pi_state *pi_state);
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extern void put_pi_state(struct futex_pi_state *pi_state);
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extern int fixup_pi_owner(u32 __user *uaddr, struct futex_q *q, int locked);
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/*
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* Express the locking dependencies for lockdep:
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*/
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static inline void
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double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
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{
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if (hb1 > hb2)
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swap(hb1, hb2);
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spin_lock(&hb1->lock);
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if (hb1 != hb2)
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spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING);
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}
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static inline void
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double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
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{
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spin_unlock(&hb1->lock);
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if (hb1 != hb2)
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spin_unlock(&hb2->lock);
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}
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/* syscalls */
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extern int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags, u32
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val, ktime_t *abs_time, u32 bitset, u32 __user
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*uaddr2);
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extern int futex_requeue(u32 __user *uaddr1, unsigned int flags,
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u32 __user *uaddr2, int nr_wake, int nr_requeue,
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u32 *cmpval, int requeue_pi);
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extern int futex_wait(u32 __user *uaddr, unsigned int flags, u32 val,
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ktime_t *abs_time, u32 bitset);
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/**
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* struct futex_vector - Auxiliary struct for futex_waitv()
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* @w: Userspace provided data
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* @q: Kernel side data
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*
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* Struct used to build an array with all data need for futex_waitv()
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*/
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struct futex_vector {
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struct futex_waitv w;
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struct futex_q q;
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};
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extern int futex_wait_multiple(struct futex_vector *vs, unsigned int count,
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struct hrtimer_sleeper *to);
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extern int futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset);
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extern int futex_wake_op(u32 __user *uaddr1, unsigned int flags,
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u32 __user *uaddr2, int nr_wake, int nr_wake2, int op);
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extern int futex_unlock_pi(u32 __user *uaddr, unsigned int flags);
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extern int futex_lock_pi(u32 __user *uaddr, unsigned int flags, ktime_t *time, int trylock);
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#endif /* _FUTEX_H */
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