2 * Fast Userspace Mutexes (which I call "Futexes!").
3 * (C) Rusty Russell, IBM 2002
5 * Generalized futexes, futex requeueing, misc fixes by Ingo Molnar
6 * (C) Copyright 2003 Red Hat Inc, All Rights Reserved
8 * Removed page pinning, fix privately mapped COW pages and other cleanups
9 * (C) Copyright 2003, 2004 Jamie Lokier
11 * Robust futex support started by Ingo Molnar
12 * (C) Copyright 2006 Red Hat Inc, All Rights Reserved
13 * Thanks to Thomas Gleixner for suggestions, analysis and fixes.
15 * PI-futex support started by Ingo Molnar and Thomas Gleixner
16 * Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
17 * Copyright (C) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com>
19 * PRIVATE futexes by Eric Dumazet
20 * Copyright (C) 2007 Eric Dumazet <dada1@cosmosbay.com>
22 * Thanks to Ben LaHaise for yelling "hashed waitqueues" loudly
23 * enough at me, Linus for the original (flawed) idea, Matthew
24 * Kirkwood for proof-of-concept implementation.
26 * "The futexes are also cursed."
27 * "But they come in a choice of three flavours!"
29 * This program is free software; you can redistribute it and/or modify
30 * it under the terms of the GNU General Public License as published by
31 * the Free Software Foundation; either version 2 of the License, or
32 * (at your option) any later version.
34 * This program is distributed in the hope that it will be useful,
35 * but WITHOUT ANY WARRANTY; without even the implied warranty of
36 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
37 * GNU General Public License for more details.
39 * You should have received a copy of the GNU General Public License
40 * along with this program; if not, write to the Free Software
41 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
43 #include <linux/slab.h>
44 #include <linux/poll.h>
46 #include <linux/file.h>
47 #include <linux/jhash.h>
48 #include <linux/init.h>
49 #include <linux/futex.h>
50 #include <linux/mount.h>
51 #include <linux/pagemap.h>
52 #include <linux/syscalls.h>
53 #include <linux/signal.h>
54 #include <linux/module.h>
55 #include <linux/magic.h>
56 #include <linux/pid.h>
57 #include <linux/nsproxy.h>
59 #include <asm/futex.h>
61 #include "rtmutex_common.h"
63 int __read_mostly futex_cmpxchg_enabled;
65 #define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)
68 * Priority Inheritance state:
70 struct futex_pi_state {
72 * list of 'owned' pi_state instances - these have to be
73 * cleaned up in do_exit() if the task exits prematurely:
75 struct list_head list;
80 struct rt_mutex pi_mutex;
82 struct task_struct *owner;
89 * We use this hashed waitqueue instead of a normal wait_queue_t, so
90 * we can wake only the relevant ones (hashed queues may be shared).
92 * A futex_q has a woken state, just like tasks have TASK_RUNNING.
93 * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0.
94 * The order of wakup is always to make the first condition true, then
95 * wake up q->waiter, then make the second condition true.
98 struct plist_node list;
99 /* There can only be a single waiter */
100 wait_queue_head_t waiter;
102 /* Which hash list lock to use: */
103 spinlock_t *lock_ptr;
105 /* Key which the futex is hashed on: */
108 /* Optional priority inheritance state: */
109 struct futex_pi_state *pi_state;
110 struct task_struct *task;
112 /* Bitset for the optional bitmasked wakeup */
117 * Split the global futex_lock into every hash list lock.
119 struct futex_hash_bucket {
121 struct plist_head chain;
124 static struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS];
127 * We hash on the keys returned from get_futex_key (see below).
129 static struct futex_hash_bucket *hash_futex(union futex_key *key)
131 u32 hash = jhash2((u32*)&key->both.word,
132 (sizeof(key->both.word)+sizeof(key->both.ptr))/4,
134 return &futex_queues[hash & ((1 << FUTEX_HASHBITS)-1)];
138 * Return 1 if two futex_keys are equal, 0 otherwise.
140 static inline int match_futex(union futex_key *key1, union futex_key *key2)
142 return (key1->both.word == key2->both.word
143 && key1->both.ptr == key2->both.ptr
144 && key1->both.offset == key2->both.offset);
148 * Take a reference to the resource addressed by a key.
149 * Can be called while holding spinlocks.
152 static void get_futex_key_refs(union futex_key *key)
157 switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
159 atomic_inc(&key->shared.inode->i_count);
161 case FUT_OFF_MMSHARED:
162 atomic_inc(&key->private.mm->mm_count);
168 * Drop a reference to the resource addressed by a key.
169 * The hash bucket spinlock must not be held.
171 static void drop_futex_key_refs(union futex_key *key)
176 switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
178 iput(key->shared.inode);
180 case FUT_OFF_MMSHARED:
181 mmdrop(key->private.mm);
187 * get_futex_key - Get parameters which are the keys for a futex.
188 * @uaddr: virtual address of the futex
189 * @shared: NULL for a PROCESS_PRIVATE futex,
190 * ¤t->mm->mmap_sem for a PROCESS_SHARED futex
191 * @key: address where result is stored.
193 * Returns a negative error code or 0
194 * The key words are stored in *key on success.
196 * For shared mappings, it's (page->index, vma->vm_file->f_path.dentry->d_inode,
197 * offset_within_page). For private mappings, it's (uaddr, current->mm).
198 * We can usually work out the index without swapping in the page.
200 * fshared is NULL for PROCESS_PRIVATE futexes
201 * For other futexes, it points to ¤t->mm->mmap_sem and
202 * caller must have taken the reader lock. but NOT any spinlocks.
204 static int get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key)
206 unsigned long address = (unsigned long)uaddr;
207 struct mm_struct *mm = current->mm;
212 * The futex address must be "naturally" aligned.
214 key->both.offset = address % PAGE_SIZE;
215 if (unlikely((address % sizeof(u32)) != 0))
217 address -= key->both.offset;
220 * PROCESS_PRIVATE futexes are fast.
221 * As the mm cannot disappear under us and the 'key' only needs
222 * virtual address, we dont even have to find the underlying vma.
223 * Note : We do have to check 'uaddr' is a valid user address,
224 * but access_ok() should be faster than find_vma()
227 if (unlikely(!access_ok(VERIFY_WRITE, uaddr, sizeof(u32))))
229 key->private.mm = mm;
230 key->private.address = address;
231 get_futex_key_refs(key);
236 err = get_user_pages_fast(address, 1, 0, &page);
241 if (!page->mapping) {
248 * Private mappings are handled in a simple way.
250 * NOTE: When userspace waits on a MAP_SHARED mapping, even if
251 * it's a read-only handle, it's expected that futexes attach to
252 * the object not the particular process.
254 if (PageAnon(page)) {
255 key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */
256 key->private.mm = mm;
257 key->private.address = address;
259 key->both.offset |= FUT_OFF_INODE; /* inode-based key */
260 key->shared.inode = page->mapping->host;
261 key->shared.pgoff = page->index;
264 get_futex_key_refs(key);
272 void put_futex_key(int fshared, union futex_key *key)
274 drop_futex_key_refs(key);
277 static u32 cmpxchg_futex_value_locked(u32 __user *uaddr, u32 uval, u32 newval)
282 curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval);
288 static int get_futex_value_locked(u32 *dest, u32 __user *from)
293 ret = __copy_from_user_inatomic(dest, from, sizeof(u32));
296 return ret ? -EFAULT : 0;
302 static int futex_handle_fault(unsigned long address, int attempt)
304 struct vm_area_struct * vma;
305 struct mm_struct *mm = current->mm;
311 down_read(&mm->mmap_sem);
312 vma = find_vma(mm, address);
313 if (vma && address >= vma->vm_start &&
314 (vma->vm_flags & VM_WRITE)) {
316 fault = handle_mm_fault(mm, vma, address, 1);
317 if (unlikely((fault & VM_FAULT_ERROR))) {
319 /* XXX: let's do this when we verify it is OK */
320 if (ret & VM_FAULT_OOM)
325 if (fault & VM_FAULT_MAJOR)
331 up_read(&mm->mmap_sem);
338 static int refill_pi_state_cache(void)
340 struct futex_pi_state *pi_state;
342 if (likely(current->pi_state_cache))
345 pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL);
350 INIT_LIST_HEAD(&pi_state->list);
351 /* pi_mutex gets initialized later */
352 pi_state->owner = NULL;
353 atomic_set(&pi_state->refcount, 1);
354 pi_state->key = FUTEX_KEY_INIT;
356 current->pi_state_cache = pi_state;
361 static struct futex_pi_state * alloc_pi_state(void)
363 struct futex_pi_state *pi_state = current->pi_state_cache;
366 current->pi_state_cache = NULL;
371 static void free_pi_state(struct futex_pi_state *pi_state)
373 if (!atomic_dec_and_test(&pi_state->refcount))
377 * If pi_state->owner is NULL, the owner is most probably dying
378 * and has cleaned up the pi_state already
380 if (pi_state->owner) {
381 spin_lock_irq(&pi_state->owner->pi_lock);
382 list_del_init(&pi_state->list);
383 spin_unlock_irq(&pi_state->owner->pi_lock);
385 rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner);
388 if (current->pi_state_cache)
392 * pi_state->list is already empty.
393 * clear pi_state->owner.
394 * refcount is at 0 - put it back to 1.
396 pi_state->owner = NULL;
397 atomic_set(&pi_state->refcount, 1);
398 current->pi_state_cache = pi_state;
403 * Look up the task based on what TID userspace gave us.
406 static struct task_struct * futex_find_get_task(pid_t pid)
408 struct task_struct *p;
411 p = find_task_by_vpid(pid);
412 if (!p || ((current->euid != p->euid) && (current->euid != p->uid)))
423 * This task is holding PI mutexes at exit time => bad.
424 * Kernel cleans up PI-state, but userspace is likely hosed.
425 * (Robust-futex cleanup is separate and might save the day for userspace.)
427 void exit_pi_state_list(struct task_struct *curr)
429 struct list_head *next, *head = &curr->pi_state_list;
430 struct futex_pi_state *pi_state;
431 struct futex_hash_bucket *hb;
432 union futex_key key = FUTEX_KEY_INIT;
434 if (!futex_cmpxchg_enabled)
437 * We are a ZOMBIE and nobody can enqueue itself on
438 * pi_state_list anymore, but we have to be careful
439 * versus waiters unqueueing themselves:
441 spin_lock_irq(&curr->pi_lock);
442 while (!list_empty(head)) {
445 pi_state = list_entry(next, struct futex_pi_state, list);
447 hb = hash_futex(&key);
448 spin_unlock_irq(&curr->pi_lock);
450 spin_lock(&hb->lock);
452 spin_lock_irq(&curr->pi_lock);
454 * We dropped the pi-lock, so re-check whether this
455 * task still owns the PI-state:
457 if (head->next != next) {
458 spin_unlock(&hb->lock);
462 WARN_ON(pi_state->owner != curr);
463 WARN_ON(list_empty(&pi_state->list));
464 list_del_init(&pi_state->list);
465 pi_state->owner = NULL;
466 spin_unlock_irq(&curr->pi_lock);
468 rt_mutex_unlock(&pi_state->pi_mutex);
470 spin_unlock(&hb->lock);
472 spin_lock_irq(&curr->pi_lock);
474 spin_unlock_irq(&curr->pi_lock);
478 lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
479 union futex_key *key, struct futex_pi_state **ps)
481 struct futex_pi_state *pi_state = NULL;
482 struct futex_q *this, *next;
483 struct plist_head *head;
484 struct task_struct *p;
485 pid_t pid = uval & FUTEX_TID_MASK;
489 plist_for_each_entry_safe(this, next, head, list) {
490 if (match_futex(&this->key, key)) {
492 * Another waiter already exists - bump up
493 * the refcount and return its pi_state:
495 pi_state = this->pi_state;
497 * Userspace might have messed up non PI and PI futexes
499 if (unlikely(!pi_state))
502 WARN_ON(!atomic_read(&pi_state->refcount));
503 WARN_ON(pid && pi_state->owner &&
504 pi_state->owner->pid != pid);
506 atomic_inc(&pi_state->refcount);
514 * We are the first waiter - try to look up the real owner and attach
515 * the new pi_state to it, but bail out when TID = 0
519 p = futex_find_get_task(pid);
524 * We need to look at the task state flags to figure out,
525 * whether the task is exiting. To protect against the do_exit
526 * change of the task flags, we do this protected by
529 spin_lock_irq(&p->pi_lock);
530 if (unlikely(p->flags & PF_EXITING)) {
532 * The task is on the way out. When PF_EXITPIDONE is
533 * set, we know that the task has finished the
536 int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN;
538 spin_unlock_irq(&p->pi_lock);
543 pi_state = alloc_pi_state();
546 * Initialize the pi_mutex in locked state and make 'p'
549 rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p);
551 /* Store the key for possible exit cleanups: */
552 pi_state->key = *key;
554 WARN_ON(!list_empty(&pi_state->list));
555 list_add(&pi_state->list, &p->pi_state_list);
557 spin_unlock_irq(&p->pi_lock);
567 * The hash bucket lock must be held when this is called.
568 * Afterwards, the futex_q must not be accessed.
570 static void wake_futex(struct futex_q *q)
572 plist_del(&q->list, &q->list.plist);
574 * The lock in wake_up_all() is a crucial memory barrier after the
575 * plist_del() and also before assigning to q->lock_ptr.
579 * The waiting task can free the futex_q as soon as this is written,
580 * without taking any locks. This must come last.
582 * A memory barrier is required here to prevent the following store
583 * to lock_ptr from getting ahead of the wakeup. Clearing the lock
584 * at the end of wake_up_all() does not prevent this store from
591 static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)
593 struct task_struct *new_owner;
594 struct futex_pi_state *pi_state = this->pi_state;
600 spin_lock(&pi_state->pi_mutex.wait_lock);
601 new_owner = rt_mutex_next_owner(&pi_state->pi_mutex);
604 * This happens when we have stolen the lock and the original
605 * pending owner did not enqueue itself back on the rt_mutex.
606 * Thats not a tragedy. We know that way, that a lock waiter
607 * is on the fly. We make the futex_q waiter the pending owner.
610 new_owner = this->task;
613 * We pass it to the next owner. (The WAITERS bit is always
614 * kept enabled while there is PI state around. We must also
615 * preserve the owner died bit.)
617 if (!(uval & FUTEX_OWNER_DIED)) {
620 newval = FUTEX_WAITERS | task_pid_vnr(new_owner);
622 curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
624 if (curval == -EFAULT)
626 else if (curval != uval)
629 spin_unlock(&pi_state->pi_mutex.wait_lock);
634 spin_lock_irq(&pi_state->owner->pi_lock);
635 WARN_ON(list_empty(&pi_state->list));
636 list_del_init(&pi_state->list);
637 spin_unlock_irq(&pi_state->owner->pi_lock);
639 spin_lock_irq(&new_owner->pi_lock);
640 WARN_ON(!list_empty(&pi_state->list));
641 list_add(&pi_state->list, &new_owner->pi_state_list);
642 pi_state->owner = new_owner;
643 spin_unlock_irq(&new_owner->pi_lock);
645 spin_unlock(&pi_state->pi_mutex.wait_lock);
646 rt_mutex_unlock(&pi_state->pi_mutex);
651 static int unlock_futex_pi(u32 __user *uaddr, u32 uval)
656 * There is no waiter, so we unlock the futex. The owner died
657 * bit has not to be preserved here. We are the owner:
659 oldval = cmpxchg_futex_value_locked(uaddr, uval, 0);
661 if (oldval == -EFAULT)
670 * Express the locking dependencies for lockdep:
673 double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
676 spin_lock(&hb1->lock);
678 spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING);
679 } else { /* hb1 > hb2 */
680 spin_lock(&hb2->lock);
681 spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING);
686 * Wake up all waiters hashed on the physical page that is mapped
687 * to this virtual address:
689 static int futex_wake(u32 __user *uaddr, int fshared, int nr_wake, u32 bitset)
691 struct futex_hash_bucket *hb;
692 struct futex_q *this, *next;
693 struct plist_head *head;
694 union futex_key key = FUTEX_KEY_INIT;
700 ret = get_futex_key(uaddr, fshared, &key);
701 if (unlikely(ret != 0))
704 hb = hash_futex(&key);
705 spin_lock(&hb->lock);
708 plist_for_each_entry_safe(this, next, head, list) {
709 if (match_futex (&this->key, &key)) {
710 if (this->pi_state) {
715 /* Check if one of the bits is set in both bitsets */
716 if (!(this->bitset & bitset))
720 if (++ret >= nr_wake)
725 spin_unlock(&hb->lock);
727 put_futex_key(fshared, &key);
732 * Wake up all waiters hashed on the physical page that is mapped
733 * to this virtual address:
736 futex_wake_op(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
737 int nr_wake, int nr_wake2, int op)
739 union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
740 struct futex_hash_bucket *hb1, *hb2;
741 struct plist_head *head;
742 struct futex_q *this, *next;
743 int ret, op_ret, attempt = 0;
746 ret = get_futex_key(uaddr1, fshared, &key1);
747 if (unlikely(ret != 0))
749 ret = get_futex_key(uaddr2, fshared, &key2);
750 if (unlikely(ret != 0))
753 hb1 = hash_futex(&key1);
754 hb2 = hash_futex(&key2);
757 double_lock_hb(hb1, hb2);
759 op_ret = futex_atomic_op_inuser(op, uaddr2);
760 if (unlikely(op_ret < 0)) {
763 spin_unlock(&hb1->lock);
765 spin_unlock(&hb2->lock);
769 * we don't get EFAULT from MMU faults if we don't have an MMU,
770 * but we might get them from range checking
776 if (unlikely(op_ret != -EFAULT)) {
782 * futex_atomic_op_inuser needs to both read and write
783 * *(int __user *)uaddr2, but we can't modify it
784 * non-atomically. Therefore, if get_user below is not
785 * enough, we need to handle the fault ourselves, while
786 * still holding the mmap_sem.
789 ret = futex_handle_fault((unsigned long)uaddr2,
796 ret = get_user(dummy, uaddr2);
805 plist_for_each_entry_safe(this, next, head, list) {
806 if (match_futex (&this->key, &key1)) {
808 if (++ret >= nr_wake)
817 plist_for_each_entry_safe(this, next, head, list) {
818 if (match_futex (&this->key, &key2)) {
820 if (++op_ret >= nr_wake2)
827 spin_unlock(&hb1->lock);
829 spin_unlock(&hb2->lock);
831 put_futex_key(fshared, &key2);
832 put_futex_key(fshared, &key1);
838 * Requeue all waiters hashed on one physical page to another
841 static int futex_requeue(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
842 int nr_wake, int nr_requeue, u32 *cmpval)
844 union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
845 struct futex_hash_bucket *hb1, *hb2;
846 struct plist_head *head1;
847 struct futex_q *this, *next;
848 int ret, drop_count = 0;
851 ret = get_futex_key(uaddr1, fshared, &key1);
852 if (unlikely(ret != 0))
854 ret = get_futex_key(uaddr2, fshared, &key2);
855 if (unlikely(ret != 0))
858 hb1 = hash_futex(&key1);
859 hb2 = hash_futex(&key2);
861 double_lock_hb(hb1, hb2);
863 if (likely(cmpval != NULL)) {
866 ret = get_futex_value_locked(&curval, uaddr1);
869 spin_unlock(&hb1->lock);
871 spin_unlock(&hb2->lock);
873 ret = get_user(curval, uaddr1);
880 if (curval != *cmpval) {
887 plist_for_each_entry_safe(this, next, head1, list) {
888 if (!match_futex (&this->key, &key1))
890 if (++ret <= nr_wake) {
894 * If key1 and key2 hash to the same bucket, no need to
897 if (likely(head1 != &hb2->chain)) {
898 plist_del(&this->list, &hb1->chain);
899 plist_add(&this->list, &hb2->chain);
900 this->lock_ptr = &hb2->lock;
901 #ifdef CONFIG_DEBUG_PI_LIST
902 this->list.plist.lock = &hb2->lock;
906 get_futex_key_refs(&key2);
909 if (ret - nr_wake >= nr_requeue)
915 spin_unlock(&hb1->lock);
917 spin_unlock(&hb2->lock);
919 /* drop_futex_key_refs() must be called outside the spinlocks. */
920 while (--drop_count >= 0)
921 drop_futex_key_refs(&key1);
924 put_futex_key(fshared, &key2);
925 put_futex_key(fshared, &key1);
929 /* The key must be already stored in q->key. */
930 static inline struct futex_hash_bucket *queue_lock(struct futex_q *q)
932 struct futex_hash_bucket *hb;
934 init_waitqueue_head(&q->waiter);
936 get_futex_key_refs(&q->key);
937 hb = hash_futex(&q->key);
938 q->lock_ptr = &hb->lock;
940 spin_lock(&hb->lock);
944 static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb)
949 * The priority used to register this element is
950 * - either the real thread-priority for the real-time threads
951 * (i.e. threads with a priority lower than MAX_RT_PRIO)
952 * - or MAX_RT_PRIO for non-RT threads.
953 * Thus, all RT-threads are woken first in priority order, and
954 * the others are woken last, in FIFO order.
956 prio = min(current->normal_prio, MAX_RT_PRIO);
958 plist_node_init(&q->list, prio);
959 #ifdef CONFIG_DEBUG_PI_LIST
960 q->list.plist.lock = &hb->lock;
962 plist_add(&q->list, &hb->chain);
964 spin_unlock(&hb->lock);
968 queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb)
970 spin_unlock(&hb->lock);
971 drop_futex_key_refs(&q->key);
975 * queue_me and unqueue_me must be called as a pair, each
976 * exactly once. They are called with the hashed spinlock held.
979 /* Return 1 if we were still queued (ie. 0 means we were woken) */
980 static int unqueue_me(struct futex_q *q)
982 spinlock_t *lock_ptr;
985 /* In the common case we don't take the spinlock, which is nice. */
987 lock_ptr = q->lock_ptr;
989 if (lock_ptr != NULL) {
992 * q->lock_ptr can change between reading it and
993 * spin_lock(), causing us to take the wrong lock. This
994 * corrects the race condition.
996 * Reasoning goes like this: if we have the wrong lock,
997 * q->lock_ptr must have changed (maybe several times)
998 * between reading it and the spin_lock(). It can
999 * change again after the spin_lock() but only if it was
1000 * already changed before the spin_lock(). It cannot,
1001 * however, change back to the original value. Therefore
1002 * we can detect whether we acquired the correct lock.
1004 if (unlikely(lock_ptr != q->lock_ptr)) {
1005 spin_unlock(lock_ptr);
1008 WARN_ON(plist_node_empty(&q->list));
1009 plist_del(&q->list, &q->list.plist);
1011 BUG_ON(q->pi_state);
1013 spin_unlock(lock_ptr);
1017 drop_futex_key_refs(&q->key);
1022 * PI futexes can not be requeued and must remove themself from the
1023 * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry
1026 static void unqueue_me_pi(struct futex_q *q)
1028 WARN_ON(plist_node_empty(&q->list));
1029 plist_del(&q->list, &q->list.plist);
1031 BUG_ON(!q->pi_state);
1032 free_pi_state(q->pi_state);
1035 spin_unlock(q->lock_ptr);
1037 drop_futex_key_refs(&q->key);
1041 * Fixup the pi_state owner with the new owner.
1043 * Must be called with hash bucket lock held and mm->sem held for non
1046 static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
1047 struct task_struct *newowner, int fshared)
1049 u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS;
1050 struct futex_pi_state *pi_state = q->pi_state;
1051 struct task_struct *oldowner = pi_state->owner;
1052 u32 uval, curval, newval;
1053 int ret, attempt = 0;
1056 if (!pi_state->owner)
1057 newtid |= FUTEX_OWNER_DIED;
1060 * We are here either because we stole the rtmutex from the
1061 * pending owner or we are the pending owner which failed to
1062 * get the rtmutex. We have to replace the pending owner TID
1063 * in the user space variable. This must be atomic as we have
1064 * to preserve the owner died bit here.
1066 * Note: We write the user space value _before_ changing the
1067 * pi_state because we can fault here. Imagine swapped out
1068 * pages or a fork, which was running right before we acquired
1069 * mmap_sem, that marked all the anonymous memory readonly for
1072 * Modifying pi_state _before_ the user space value would
1073 * leave the pi_state in an inconsistent state when we fault
1074 * here, because we need to drop the hash bucket lock to
1075 * handle the fault. This might be observed in the PID check
1076 * in lookup_pi_state.
1079 if (get_futex_value_locked(&uval, uaddr))
1083 newval = (uval & FUTEX_OWNER_DIED) | newtid;
1085 curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
1087 if (curval == -EFAULT)
1095 * We fixed up user space. Now we need to fix the pi_state
1098 if (pi_state->owner != NULL) {
1099 spin_lock_irq(&pi_state->owner->pi_lock);
1100 WARN_ON(list_empty(&pi_state->list));
1101 list_del_init(&pi_state->list);
1102 spin_unlock_irq(&pi_state->owner->pi_lock);
1105 pi_state->owner = newowner;
1107 spin_lock_irq(&newowner->pi_lock);
1108 WARN_ON(!list_empty(&pi_state->list));
1109 list_add(&pi_state->list, &newowner->pi_state_list);
1110 spin_unlock_irq(&newowner->pi_lock);
1114 * To handle the page fault we need to drop the hash bucket
1115 * lock here. That gives the other task (either the pending
1116 * owner itself or the task which stole the rtmutex) the
1117 * chance to try the fixup of the pi_state. So once we are
1118 * back from handling the fault we need to check the pi_state
1119 * after reacquiring the hash bucket lock and before trying to
1120 * do another fixup. When the fixup has been done already we
1124 spin_unlock(q->lock_ptr);
1126 ret = futex_handle_fault((unsigned long)uaddr, attempt++);
1128 spin_lock(q->lock_ptr);
1131 * Check if someone else fixed it for us:
1133 if (pi_state->owner != oldowner)
1143 * In case we must use restart_block to restart a futex_wait,
1144 * we encode in the 'flags' shared capability
1146 #define FLAGS_SHARED 0x01
1147 #define FLAGS_CLOCKRT 0x02
1149 static long futex_wait_restart(struct restart_block *restart);
1151 static int futex_wait(u32 __user *uaddr, int fshared,
1152 u32 val, ktime_t *abs_time, u32 bitset, int clockrt)
1154 struct task_struct *curr = current;
1155 DECLARE_WAITQUEUE(wait, curr);
1156 struct futex_hash_bucket *hb;
1160 struct hrtimer_sleeper t;
1169 q.key = FUTEX_KEY_INIT;
1170 ret = get_futex_key(uaddr, fshared, &q.key);
1171 if (unlikely(ret != 0))
1172 goto out_release_sem;
1174 hb = queue_lock(&q);
1177 * Access the page AFTER the futex is queued.
1178 * Order is important:
1180 * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val);
1181 * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); }
1183 * The basic logical guarantee of a futex is that it blocks ONLY
1184 * if cond(var) is known to be true at the time of blocking, for
1185 * any cond. If we queued after testing *uaddr, that would open
1186 * a race condition where we could block indefinitely with
1187 * cond(var) false, which would violate the guarantee.
1189 * A consequence is that futex_wait() can return zero and absorb
1190 * a wakeup when *uaddr != val on entry to the syscall. This is
1193 * for shared futexes, we hold the mmap semaphore, so the mapping
1194 * cannot have changed since we looked it up in get_futex_key.
1196 ret = get_futex_value_locked(&uval, uaddr);
1198 if (unlikely(ret)) {
1199 queue_unlock(&q, hb);
1201 ret = get_user(uval, uaddr);
1209 goto out_unlock_release_sem;
1211 /* Only actually queue if *uaddr contained val. */
1215 * There might have been scheduling since the queue_me(), as we
1216 * cannot hold a spinlock across the get_user() in case it
1217 * faults, and we cannot just set TASK_INTERRUPTIBLE state when
1218 * queueing ourselves into the futex hash. This code thus has to
1219 * rely on the futex_wake() code removing us from hash when it
1223 /* add_wait_queue is the barrier after __set_current_state. */
1224 __set_current_state(TASK_INTERRUPTIBLE);
1225 add_wait_queue(&q.waiter, &wait);
1227 * !plist_node_empty() is safe here without any lock.
1228 * q.lock_ptr != 0 is not safe, because of ordering against wakeup.
1230 if (likely(!plist_node_empty(&q.list))) {
1234 unsigned long slack;
1235 slack = current->timer_slack_ns;
1236 if (rt_task(current))
1238 hrtimer_init_on_stack(&t.timer,
1239 clockrt ? CLOCK_REALTIME :
1242 hrtimer_init_sleeper(&t, current);
1243 hrtimer_set_expires_range_ns(&t.timer, *abs_time, slack);
1245 hrtimer_start_expires(&t.timer, HRTIMER_MODE_ABS);
1246 if (!hrtimer_active(&t.timer))
1250 * the timer could have already expired, in which
1251 * case current would be flagged for rescheduling.
1252 * Don't bother calling schedule.
1257 hrtimer_cancel(&t.timer);
1259 /* Flag if a timeout occured */
1260 rem = (t.task == NULL);
1262 destroy_hrtimer_on_stack(&t.timer);
1265 __set_current_state(TASK_RUNNING);
1268 * NOTE: we don't remove ourselves from the waitqueue because
1269 * we are the only user of it.
1272 /* If we were woken (and unqueued), we succeeded, whatever. */
1273 if (!unqueue_me(&q))
1279 * We expect signal_pending(current), but another thread may
1280 * have handled it for us already.
1283 return -ERESTARTSYS;
1285 struct restart_block *restart;
1286 restart = ¤t_thread_info()->restart_block;
1287 restart->fn = futex_wait_restart;
1288 restart->futex.uaddr = (u32 *)uaddr;
1289 restart->futex.val = val;
1290 restart->futex.time = abs_time->tv64;
1291 restart->futex.bitset = bitset;
1292 restart->futex.flags = 0;
1295 restart->futex.flags |= FLAGS_SHARED;
1297 restart->futex.flags |= FLAGS_CLOCKRT;
1298 return -ERESTART_RESTARTBLOCK;
1301 out_unlock_release_sem:
1302 queue_unlock(&q, hb);
1305 put_futex_key(fshared, &q.key);
1310 static long futex_wait_restart(struct restart_block *restart)
1312 u32 __user *uaddr = (u32 __user *)restart->futex.uaddr;
1316 t.tv64 = restart->futex.time;
1317 restart->fn = do_no_restart_syscall;
1318 if (restart->futex.flags & FLAGS_SHARED)
1320 return (long)futex_wait(uaddr, fshared, restart->futex.val, &t,
1321 restart->futex.bitset,
1322 restart->futex.flags & FLAGS_CLOCKRT);
1327 * Userspace tried a 0 -> TID atomic transition of the futex value
1328 * and failed. The kernel side here does the whole locking operation:
1329 * if there are waiters then it will block, it does PI, etc. (Due to
1330 * races the kernel might see a 0 value of the futex too.)
1332 static int futex_lock_pi(u32 __user *uaddr, int fshared,
1333 int detect, ktime_t *time, int trylock)
1335 struct hrtimer_sleeper timeout, *to = NULL;
1336 struct task_struct *curr = current;
1337 struct futex_hash_bucket *hb;
1338 u32 uval, newval, curval;
1340 int ret, lock_taken, ownerdied = 0, attempt = 0;
1342 if (refill_pi_state_cache())
1347 hrtimer_init_on_stack(&to->timer, CLOCK_REALTIME,
1349 hrtimer_init_sleeper(to, current);
1350 hrtimer_set_expires(&to->timer, *time);
1355 q.key = FUTEX_KEY_INIT;
1356 ret = get_futex_key(uaddr, fshared, &q.key);
1357 if (unlikely(ret != 0))
1358 goto out_release_sem;
1361 hb = queue_lock(&q);
1364 ret = lock_taken = 0;
1367 * To avoid races, we attempt to take the lock here again
1368 * (by doing a 0 -> TID atomic cmpxchg), while holding all
1369 * the locks. It will most likely not succeed.
1371 newval = task_pid_vnr(current);
1373 curval = cmpxchg_futex_value_locked(uaddr, 0, newval);
1375 if (unlikely(curval == -EFAULT))
1379 * Detect deadlocks. In case of REQUEUE_PI this is a valid
1380 * situation and we return success to user space.
1382 if (unlikely((curval & FUTEX_TID_MASK) == task_pid_vnr(current))) {
1384 goto out_unlock_release_sem;
1388 * Surprise - we got the lock. Just return to userspace:
1390 if (unlikely(!curval))
1391 goto out_unlock_release_sem;
1396 * Set the WAITERS flag, so the owner will know it has someone
1397 * to wake at next unlock
1399 newval = curval | FUTEX_WAITERS;
1402 * There are two cases, where a futex might have no owner (the
1403 * owner TID is 0): OWNER_DIED. We take over the futex in this
1404 * case. We also do an unconditional take over, when the owner
1405 * of the futex died.
1407 * This is safe as we are protected by the hash bucket lock !
1409 if (unlikely(ownerdied || !(curval & FUTEX_TID_MASK))) {
1410 /* Keep the OWNER_DIED bit */
1411 newval = (curval & ~FUTEX_TID_MASK) | task_pid_vnr(current);
1416 curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
1418 if (unlikely(curval == -EFAULT))
1420 if (unlikely(curval != uval))
1424 * We took the lock due to owner died take over.
1426 if (unlikely(lock_taken))
1427 goto out_unlock_release_sem;
1430 * We dont have the lock. Look up the PI state (or create it if
1431 * we are the first waiter):
1433 ret = lookup_pi_state(uval, hb, &q.key, &q.pi_state);
1435 if (unlikely(ret)) {
1440 * Task is exiting and we just wait for the
1443 queue_unlock(&q, hb);
1449 * No owner found for this futex. Check if the
1450 * OWNER_DIED bit is set to figure out whether
1451 * this is a robust futex or not.
1453 if (get_futex_value_locked(&curval, uaddr))
1457 * We simply start over in case of a robust
1458 * futex. The code above will take the futex
1461 if (curval & FUTEX_OWNER_DIED) {
1466 goto out_unlock_release_sem;
1471 * Only actually queue now that the atomic ops are done:
1475 WARN_ON(!q.pi_state);
1477 * Block on the PI mutex:
1480 ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1);
1482 ret = rt_mutex_trylock(&q.pi_state->pi_mutex);
1483 /* Fixup the trylock return value: */
1484 ret = ret ? 0 : -EWOULDBLOCK;
1487 spin_lock(q.lock_ptr);
1491 * Got the lock. We might not be the anticipated owner
1492 * if we did a lock-steal - fix up the PI-state in
1495 if (q.pi_state->owner != curr)
1496 ret = fixup_pi_state_owner(uaddr, &q, curr, fshared);
1499 * Catch the rare case, where the lock was released
1500 * when we were on the way back before we locked the
1503 if (q.pi_state->owner == curr) {
1505 * Try to get the rt_mutex now. This might
1506 * fail as some other task acquired the
1507 * rt_mutex after we removed ourself from the
1508 * rt_mutex waiters list.
1510 if (rt_mutex_trylock(&q.pi_state->pi_mutex))
1514 * pi_state is incorrect, some other
1515 * task did a lock steal and we
1516 * returned due to timeout or signal
1517 * without taking the rt_mutex. Too
1518 * late. We can access the
1519 * rt_mutex_owner without locking, as
1520 * the other task is now blocked on
1521 * the hash bucket lock. Fix the state
1524 struct task_struct *owner;
1527 owner = rt_mutex_owner(&q.pi_state->pi_mutex);
1528 res = fixup_pi_state_owner(uaddr, &q, owner,
1531 /* propagate -EFAULT, if the fixup failed */
1537 * Paranoia check. If we did not take the lock
1538 * in the trylock above, then we should not be
1539 * the owner of the rtmutex, neither the real
1540 * nor the pending one:
1542 if (rt_mutex_owner(&q.pi_state->pi_mutex) == curr)
1543 printk(KERN_ERR "futex_lock_pi: ret = %d "
1544 "pi-mutex: %p pi-state %p\n", ret,
1545 q.pi_state->pi_mutex.owner,
1550 /* Unqueue and drop the lock */
1554 destroy_hrtimer_on_stack(&to->timer);
1555 return ret != -EINTR ? ret : -ERESTARTNOINTR;
1557 out_unlock_release_sem:
1558 queue_unlock(&q, hb);
1561 put_futex_key(fshared, &q.key);
1563 destroy_hrtimer_on_stack(&to->timer);
1568 * We have to r/w *(int __user *)uaddr, and we have to modify it
1569 * atomically. Therefore, if we continue to fault after get_user()
1570 * below, we need to handle the fault ourselves, while still holding
1571 * the mmap_sem. This can occur if the uaddr is under contention as
1572 * we have to drop the mmap_sem in order to call get_user().
1574 queue_unlock(&q, hb);
1577 ret = futex_handle_fault((unsigned long)uaddr, attempt);
1579 goto out_release_sem;
1580 goto retry_unlocked;
1583 ret = get_user(uval, uaddr);
1588 destroy_hrtimer_on_stack(&to->timer);
1593 * Userspace attempted a TID -> 0 atomic transition, and failed.
1594 * This is the in-kernel slowpath: we look up the PI state (if any),
1595 * and do the rt-mutex unlock.
1597 static int futex_unlock_pi(u32 __user *uaddr, int fshared)
1599 struct futex_hash_bucket *hb;
1600 struct futex_q *this, *next;
1602 struct plist_head *head;
1603 union futex_key key = FUTEX_KEY_INIT;
1604 int ret, attempt = 0;
1607 if (get_user(uval, uaddr))
1610 * We release only a lock we actually own:
1612 if ((uval & FUTEX_TID_MASK) != task_pid_vnr(current))
1615 ret = get_futex_key(uaddr, fshared, &key);
1616 if (unlikely(ret != 0))
1619 hb = hash_futex(&key);
1621 spin_lock(&hb->lock);
1624 * To avoid races, try to do the TID -> 0 atomic transition
1625 * again. If it succeeds then we can return without waking
1628 if (!(uval & FUTEX_OWNER_DIED))
1629 uval = cmpxchg_futex_value_locked(uaddr, task_pid_vnr(current), 0);
1632 if (unlikely(uval == -EFAULT))
1635 * Rare case: we managed to release the lock atomically,
1636 * no need to wake anyone else up:
1638 if (unlikely(uval == task_pid_vnr(current)))
1642 * Ok, other tasks may need to be woken up - check waiters
1643 * and do the wakeup if necessary:
1647 plist_for_each_entry_safe(this, next, head, list) {
1648 if (!match_futex (&this->key, &key))
1650 ret = wake_futex_pi(uaddr, uval, this);
1652 * The atomic access to the futex value
1653 * generated a pagefault, so retry the
1654 * user-access and the wakeup:
1661 * No waiters - kernel unlocks the futex:
1663 if (!(uval & FUTEX_OWNER_DIED)) {
1664 ret = unlock_futex_pi(uaddr, uval);
1670 spin_unlock(&hb->lock);
1672 put_futex_key(fshared, &key);
1678 * We have to r/w *(int __user *)uaddr, and we have to modify it
1679 * atomically. Therefore, if we continue to fault after get_user()
1680 * below, we need to handle the fault ourselves, while still holding
1681 * the mmap_sem. This can occur if the uaddr is under contention as
1682 * we have to drop the mmap_sem in order to call get_user().
1684 spin_unlock(&hb->lock);
1687 ret = futex_handle_fault((unsigned long)uaddr, attempt);
1691 goto retry_unlocked;
1694 ret = get_user(uval, uaddr);
1702 * Support for robust futexes: the kernel cleans up held futexes at
1705 * Implementation: user-space maintains a per-thread list of locks it
1706 * is holding. Upon do_exit(), the kernel carefully walks this list,
1707 * and marks all locks that are owned by this thread with the
1708 * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is
1709 * always manipulated with the lock held, so the list is private and
1710 * per-thread. Userspace also maintains a per-thread 'list_op_pending'
1711 * field, to allow the kernel to clean up if the thread dies after
1712 * acquiring the lock, but just before it could have added itself to
1713 * the list. There can only be one such pending lock.
1717 * sys_set_robust_list - set the robust-futex list head of a task
1718 * @head: pointer to the list-head
1719 * @len: length of the list-head, as userspace expects
1722 sys_set_robust_list(struct robust_list_head __user *head,
1725 if (!futex_cmpxchg_enabled)
1728 * The kernel knows only one size for now:
1730 if (unlikely(len != sizeof(*head)))
1733 current->robust_list = head;
1739 * sys_get_robust_list - get the robust-futex list head of a task
1740 * @pid: pid of the process [zero for current task]
1741 * @head_ptr: pointer to a list-head pointer, the kernel fills it in
1742 * @len_ptr: pointer to a length field, the kernel fills in the header size
1745 sys_get_robust_list(int pid, struct robust_list_head __user * __user *head_ptr,
1746 size_t __user *len_ptr)
1748 struct robust_list_head __user *head;
1751 if (!futex_cmpxchg_enabled)
1755 head = current->robust_list;
1757 struct task_struct *p;
1761 p = find_task_by_vpid(pid);
1765 if ((current->euid != p->euid) && (current->euid != p->uid) &&
1766 !capable(CAP_SYS_PTRACE))
1768 head = p->robust_list;
1772 if (put_user(sizeof(*head), len_ptr))
1774 return put_user(head, head_ptr);
1783 * Process a futex-list entry, check whether it's owned by the
1784 * dying task, and do notification if so:
1786 int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi)
1788 u32 uval, nval, mval;
1791 if (get_user(uval, uaddr))
1794 if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) {
1796 * Ok, this dying thread is truly holding a futex
1797 * of interest. Set the OWNER_DIED bit atomically
1798 * via cmpxchg, and if the value had FUTEX_WAITERS
1799 * set, wake up a waiter (if any). (We have to do a
1800 * futex_wake() even if OWNER_DIED is already set -
1801 * to handle the rare but possible case of recursive
1802 * thread-death.) The rest of the cleanup is done in
1805 mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED;
1806 nval = futex_atomic_cmpxchg_inatomic(uaddr, uval, mval);
1808 if (nval == -EFAULT)
1815 * Wake robust non-PI futexes here. The wakeup of
1816 * PI futexes happens in exit_pi_state():
1818 if (!pi && (uval & FUTEX_WAITERS))
1819 futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY);
1825 * Fetch a robust-list pointer. Bit 0 signals PI futexes:
1827 static inline int fetch_robust_entry(struct robust_list __user **entry,
1828 struct robust_list __user * __user *head,
1831 unsigned long uentry;
1833 if (get_user(uentry, (unsigned long __user *)head))
1836 *entry = (void __user *)(uentry & ~1UL);
1843 * Walk curr->robust_list (very carefully, it's a userspace list!)
1844 * and mark any locks found there dead, and notify any waiters.
1846 * We silently return on any sign of list-walking problem.
1848 void exit_robust_list(struct task_struct *curr)
1850 struct robust_list_head __user *head = curr->robust_list;
1851 struct robust_list __user *entry, *next_entry, *pending;
1852 unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip;
1853 unsigned long futex_offset;
1856 if (!futex_cmpxchg_enabled)
1860 * Fetch the list head (which was registered earlier, via
1861 * sys_set_robust_list()):
1863 if (fetch_robust_entry(&entry, &head->list.next, &pi))
1866 * Fetch the relative futex offset:
1868 if (get_user(futex_offset, &head->futex_offset))
1871 * Fetch any possibly pending lock-add first, and handle it
1874 if (fetch_robust_entry(&pending, &head->list_op_pending, &pip))
1877 next_entry = NULL; /* avoid warning with gcc */
1878 while (entry != &head->list) {
1880 * Fetch the next entry in the list before calling
1881 * handle_futex_death:
1883 rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi);
1885 * A pending lock might already be on the list, so
1886 * don't process it twice:
1888 if (entry != pending)
1889 if (handle_futex_death((void __user *)entry + futex_offset,
1897 * Avoid excessively long or circular lists:
1906 handle_futex_death((void __user *)pending + futex_offset,
1910 long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
1911 u32 __user *uaddr2, u32 val2, u32 val3)
1913 int clockrt, ret = -ENOSYS;
1914 int cmd = op & FUTEX_CMD_MASK;
1917 if (!(op & FUTEX_PRIVATE_FLAG))
1920 clockrt = op & FUTEX_CLOCK_REALTIME;
1921 if (clockrt && cmd != FUTEX_WAIT_BITSET)
1926 val3 = FUTEX_BITSET_MATCH_ANY;
1927 case FUTEX_WAIT_BITSET:
1928 ret = futex_wait(uaddr, fshared, val, timeout, val3, clockrt);
1931 val3 = FUTEX_BITSET_MATCH_ANY;
1932 case FUTEX_WAKE_BITSET:
1933 ret = futex_wake(uaddr, fshared, val, val3);
1936 ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, NULL);
1938 case FUTEX_CMP_REQUEUE:
1939 ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3);
1942 ret = futex_wake_op(uaddr, fshared, uaddr2, val, val2, val3);
1945 if (futex_cmpxchg_enabled)
1946 ret = futex_lock_pi(uaddr, fshared, val, timeout, 0);
1948 case FUTEX_UNLOCK_PI:
1949 if (futex_cmpxchg_enabled)
1950 ret = futex_unlock_pi(uaddr, fshared);
1952 case FUTEX_TRYLOCK_PI:
1953 if (futex_cmpxchg_enabled)
1954 ret = futex_lock_pi(uaddr, fshared, 0, timeout, 1);
1963 asmlinkage long sys_futex(u32 __user *uaddr, int op, u32 val,
1964 struct timespec __user *utime, u32 __user *uaddr2,
1968 ktime_t t, *tp = NULL;
1970 int cmd = op & FUTEX_CMD_MASK;
1972 if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
1973 cmd == FUTEX_WAIT_BITSET)) {
1974 if (copy_from_user(&ts, utime, sizeof(ts)) != 0)
1976 if (!timespec_valid(&ts))
1979 t = timespec_to_ktime(ts);
1980 if (cmd == FUTEX_WAIT)
1981 t = ktime_add_safe(ktime_get(), t);
1985 * requeue parameter in 'utime' if cmd == FUTEX_REQUEUE.
1986 * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP.
1988 if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
1989 cmd == FUTEX_WAKE_OP)
1990 val2 = (u32) (unsigned long) utime;
1992 return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
1995 static int __init futex_init(void)
2001 * This will fail and we want it. Some arch implementations do
2002 * runtime detection of the futex_atomic_cmpxchg_inatomic()
2003 * functionality. We want to know that before we call in any
2004 * of the complex code paths. Also we want to prevent
2005 * registration of robust lists in that case. NULL is
2006 * guaranteed to fault and we get -EFAULT on functional
2007 * implementation, the non functional ones will return
2010 curval = cmpxchg_futex_value_locked(NULL, 0, 0);
2011 if (curval == -EFAULT)
2012 futex_cmpxchg_enabled = 1;
2014 for (i = 0; i < ARRAY_SIZE(futex_queues); i++) {
2015 plist_head_init(&futex_queues[i].chain, &futex_queues[i].lock);
2016 spin_lock_init(&futex_queues[i].lock);
2021 __initcall(futex_init);