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->waiters, then make the second condition true.
98 struct plist_node list;
99 wait_queue_head_t waiters;
101 /* Which hash list lock to use: */
102 spinlock_t *lock_ptr;
104 /* Key which the futex is hashed on: */
107 /* Optional priority inheritance state: */
108 struct futex_pi_state *pi_state;
109 struct task_struct *task;
111 /* Bitset for the optional bitmasked wakeup */
116 * Split the global futex_lock into every hash list lock.
118 struct futex_hash_bucket {
120 struct plist_head chain;
123 static struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS];
126 * Take mm->mmap_sem, when futex is shared
128 static inline void futex_lock_mm(struct rw_semaphore *fshared)
135 * Release mm->mmap_sem, when the futex is shared
137 static inline void futex_unlock_mm(struct rw_semaphore *fshared)
144 * We hash on the keys returned from get_futex_key (see below).
146 static struct futex_hash_bucket *hash_futex(union futex_key *key)
148 u32 hash = jhash2((u32*)&key->both.word,
149 (sizeof(key->both.word)+sizeof(key->both.ptr))/4,
151 return &futex_queues[hash & ((1 << FUTEX_HASHBITS)-1)];
155 * Return 1 if two futex_keys are equal, 0 otherwise.
157 static inline int match_futex(union futex_key *key1, union futex_key *key2)
159 return (key1->both.word == key2->both.word
160 && key1->both.ptr == key2->both.ptr
161 && key1->both.offset == key2->both.offset);
165 * Take a reference to the resource addressed by a key.
166 * Can be called while holding spinlocks.
169 static void get_futex_key_refs(union futex_key *key)
174 switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
176 atomic_inc(&key->shared.inode->i_count);
178 case FUT_OFF_MMSHARED:
179 atomic_inc(&key->private.mm->mm_count);
185 * Drop a reference to the resource addressed by a key.
186 * The hash bucket spinlock must not be held.
188 static void drop_futex_key_refs(union futex_key *key)
193 switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
195 iput(key->shared.inode);
197 case FUT_OFF_MMSHARED:
198 mmdrop(key->private.mm);
204 * get_futex_key - Get parameters which are the keys for a futex.
205 * @uaddr: virtual address of the futex
206 * @shared: NULL for a PROCESS_PRIVATE futex,
207 * ¤t->mm->mmap_sem for a PROCESS_SHARED futex
208 * @key: address where result is stored.
210 * Returns a negative error code or 0
211 * The key words are stored in *key on success.
213 * For shared mappings, it's (page->index, vma->vm_file->f_path.dentry->d_inode,
214 * offset_within_page). For private mappings, it's (uaddr, current->mm).
215 * We can usually work out the index without swapping in the page.
217 * fshared is NULL for PROCESS_PRIVATE futexes
218 * For other futexes, it points to ¤t->mm->mmap_sem and
219 * caller must have taken the reader lock. but NOT any spinlocks.
221 static int get_futex_key(u32 __user *uaddr, struct rw_semaphore *fshared,
222 union futex_key *key)
224 unsigned long address = (unsigned long)uaddr;
225 struct mm_struct *mm = current->mm;
230 * The futex address must be "naturally" aligned.
232 key->both.offset = address % PAGE_SIZE;
233 if (unlikely((address % sizeof(u32)) != 0))
235 address -= key->both.offset;
238 * PROCESS_PRIVATE futexes are fast.
239 * As the mm cannot disappear under us and the 'key' only needs
240 * virtual address, we dont even have to find the underlying vma.
241 * Note : We do have to check 'uaddr' is a valid user address,
242 * but access_ok() should be faster than find_vma()
245 if (unlikely(!access_ok(VERIFY_WRITE, uaddr, sizeof(u32))))
247 key->private.mm = mm;
248 key->private.address = address;
253 err = get_user_pages(current, mm, address, 1, 0, 0, &page, NULL);
258 if (!page->mapping) {
265 * Private mappings are handled in a simple way.
267 * NOTE: When userspace waits on a MAP_SHARED mapping, even if
268 * it's a read-only handle, it's expected that futexes attach to
269 * the object not the particular process.
271 if (PageAnon(page)) {
272 key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */
273 key->private.mm = mm;
274 key->private.address = address;
276 key->both.offset |= FUT_OFF_INODE; /* inode-based key */
277 key->shared.inode = page->mapping->host;
278 key->shared.pgoff = page->index;
281 get_futex_key_refs(key);
289 void put_futex_key(struct rw_semaphore *fshared, union futex_key *key)
291 drop_futex_key_refs(key);
294 static u32 cmpxchg_futex_value_locked(u32 __user *uaddr, u32 uval, u32 newval)
299 curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval);
305 static int get_futex_value_locked(u32 *dest, u32 __user *from)
310 ret = __copy_from_user_inatomic(dest, from, sizeof(u32));
313 return ret ? -EFAULT : 0;
318 * if fshared is non NULL, current->mm->mmap_sem is already held
320 static int futex_handle_fault(unsigned long address,
321 struct rw_semaphore *fshared, int attempt)
323 struct vm_area_struct * vma;
324 struct mm_struct *mm = current->mm;
331 down_read(&mm->mmap_sem);
332 vma = find_vma(mm, address);
333 if (vma && address >= vma->vm_start &&
334 (vma->vm_flags & VM_WRITE)) {
336 fault = handle_mm_fault(mm, vma, address, 1);
337 if (unlikely((fault & VM_FAULT_ERROR))) {
339 /* XXX: let's do this when we verify it is OK */
340 if (ret & VM_FAULT_OOM)
345 if (fault & VM_FAULT_MAJOR)
352 up_read(&mm->mmap_sem);
359 static int refill_pi_state_cache(void)
361 struct futex_pi_state *pi_state;
363 if (likely(current->pi_state_cache))
366 pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL);
371 INIT_LIST_HEAD(&pi_state->list);
372 /* pi_mutex gets initialized later */
373 pi_state->owner = NULL;
374 atomic_set(&pi_state->refcount, 1);
375 pi_state->key = FUTEX_KEY_INIT;
377 current->pi_state_cache = pi_state;
382 static struct futex_pi_state * alloc_pi_state(void)
384 struct futex_pi_state *pi_state = current->pi_state_cache;
387 current->pi_state_cache = NULL;
392 static void free_pi_state(struct futex_pi_state *pi_state)
394 if (!atomic_dec_and_test(&pi_state->refcount))
398 * If pi_state->owner is NULL, the owner is most probably dying
399 * and has cleaned up the pi_state already
401 if (pi_state->owner) {
402 spin_lock_irq(&pi_state->owner->pi_lock);
403 list_del_init(&pi_state->list);
404 spin_unlock_irq(&pi_state->owner->pi_lock);
406 rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner);
409 if (current->pi_state_cache)
413 * pi_state->list is already empty.
414 * clear pi_state->owner.
415 * refcount is at 0 - put it back to 1.
417 pi_state->owner = NULL;
418 atomic_set(&pi_state->refcount, 1);
419 current->pi_state_cache = pi_state;
424 * Look up the task based on what TID userspace gave us.
427 static struct task_struct * futex_find_get_task(pid_t pid)
429 struct task_struct *p;
432 p = find_task_by_vpid(pid);
433 if (!p || ((current->euid != p->euid) && (current->euid != p->uid)))
444 * This task is holding PI mutexes at exit time => bad.
445 * Kernel cleans up PI-state, but userspace is likely hosed.
446 * (Robust-futex cleanup is separate and might save the day for userspace.)
448 void exit_pi_state_list(struct task_struct *curr)
450 struct list_head *next, *head = &curr->pi_state_list;
451 struct futex_pi_state *pi_state;
452 struct futex_hash_bucket *hb;
453 union futex_key key = FUTEX_KEY_INIT;
455 if (!futex_cmpxchg_enabled)
458 * We are a ZOMBIE and nobody can enqueue itself on
459 * pi_state_list anymore, but we have to be careful
460 * versus waiters unqueueing themselves:
462 spin_lock_irq(&curr->pi_lock);
463 while (!list_empty(head)) {
466 pi_state = list_entry(next, struct futex_pi_state, list);
468 hb = hash_futex(&key);
469 spin_unlock_irq(&curr->pi_lock);
471 spin_lock(&hb->lock);
473 spin_lock_irq(&curr->pi_lock);
475 * We dropped the pi-lock, so re-check whether this
476 * task still owns the PI-state:
478 if (head->next != next) {
479 spin_unlock(&hb->lock);
483 WARN_ON(pi_state->owner != curr);
484 WARN_ON(list_empty(&pi_state->list));
485 list_del_init(&pi_state->list);
486 pi_state->owner = NULL;
487 spin_unlock_irq(&curr->pi_lock);
489 rt_mutex_unlock(&pi_state->pi_mutex);
491 spin_unlock(&hb->lock);
493 spin_lock_irq(&curr->pi_lock);
495 spin_unlock_irq(&curr->pi_lock);
499 lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
500 union futex_key *key, struct futex_pi_state **ps)
502 struct futex_pi_state *pi_state = NULL;
503 struct futex_q *this, *next;
504 struct plist_head *head;
505 struct task_struct *p;
506 pid_t pid = uval & FUTEX_TID_MASK;
510 plist_for_each_entry_safe(this, next, head, list) {
511 if (match_futex(&this->key, key)) {
513 * Another waiter already exists - bump up
514 * the refcount and return its pi_state:
516 pi_state = this->pi_state;
518 * Userspace might have messed up non PI and PI futexes
520 if (unlikely(!pi_state))
523 WARN_ON(!atomic_read(&pi_state->refcount));
524 WARN_ON(pid && pi_state->owner &&
525 pi_state->owner->pid != pid);
527 atomic_inc(&pi_state->refcount);
535 * We are the first waiter - try to look up the real owner and attach
536 * the new pi_state to it, but bail out when TID = 0
540 p = futex_find_get_task(pid);
545 * We need to look at the task state flags to figure out,
546 * whether the task is exiting. To protect against the do_exit
547 * change of the task flags, we do this protected by
550 spin_lock_irq(&p->pi_lock);
551 if (unlikely(p->flags & PF_EXITING)) {
553 * The task is on the way out. When PF_EXITPIDONE is
554 * set, we know that the task has finished the
557 int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN;
559 spin_unlock_irq(&p->pi_lock);
564 pi_state = alloc_pi_state();
567 * Initialize the pi_mutex in locked state and make 'p'
570 rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p);
572 /* Store the key for possible exit cleanups: */
573 pi_state->key = *key;
575 WARN_ON(!list_empty(&pi_state->list));
576 list_add(&pi_state->list, &p->pi_state_list);
578 spin_unlock_irq(&p->pi_lock);
588 * The hash bucket lock must be held when this is called.
589 * Afterwards, the futex_q must not be accessed.
591 static void wake_futex(struct futex_q *q)
593 plist_del(&q->list, &q->list.plist);
595 * The lock in wake_up_all() is a crucial memory barrier after the
596 * plist_del() and also before assigning to q->lock_ptr.
598 wake_up_all(&q->waiters);
600 * The waiting task can free the futex_q as soon as this is written,
601 * without taking any locks. This must come last.
603 * A memory barrier is required here to prevent the following store
604 * to lock_ptr from getting ahead of the wakeup. Clearing the lock
605 * at the end of wake_up_all() does not prevent this store from
612 static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)
614 struct task_struct *new_owner;
615 struct futex_pi_state *pi_state = this->pi_state;
621 spin_lock(&pi_state->pi_mutex.wait_lock);
622 new_owner = rt_mutex_next_owner(&pi_state->pi_mutex);
625 * This happens when we have stolen the lock and the original
626 * pending owner did not enqueue itself back on the rt_mutex.
627 * Thats not a tragedy. We know that way, that a lock waiter
628 * is on the fly. We make the futex_q waiter the pending owner.
631 new_owner = this->task;
634 * We pass it to the next owner. (The WAITERS bit is always
635 * kept enabled while there is PI state around. We must also
636 * preserve the owner died bit.)
638 if (!(uval & FUTEX_OWNER_DIED)) {
641 newval = FUTEX_WAITERS | task_pid_vnr(new_owner);
643 curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
645 if (curval == -EFAULT)
647 else if (curval != uval)
650 spin_unlock(&pi_state->pi_mutex.wait_lock);
655 spin_lock_irq(&pi_state->owner->pi_lock);
656 WARN_ON(list_empty(&pi_state->list));
657 list_del_init(&pi_state->list);
658 spin_unlock_irq(&pi_state->owner->pi_lock);
660 spin_lock_irq(&new_owner->pi_lock);
661 WARN_ON(!list_empty(&pi_state->list));
662 list_add(&pi_state->list, &new_owner->pi_state_list);
663 pi_state->owner = new_owner;
664 spin_unlock_irq(&new_owner->pi_lock);
666 spin_unlock(&pi_state->pi_mutex.wait_lock);
667 rt_mutex_unlock(&pi_state->pi_mutex);
672 static int unlock_futex_pi(u32 __user *uaddr, u32 uval)
677 * There is no waiter, so we unlock the futex. The owner died
678 * bit has not to be preserved here. We are the owner:
680 oldval = cmpxchg_futex_value_locked(uaddr, uval, 0);
682 if (oldval == -EFAULT)
691 * Express the locking dependencies for lockdep:
694 double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
697 spin_lock(&hb1->lock);
699 spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING);
700 } else { /* hb1 > hb2 */
701 spin_lock(&hb2->lock);
702 spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING);
707 * Wake up all waiters hashed on the physical page that is mapped
708 * to this virtual address:
710 static int futex_wake(u32 __user *uaddr, struct rw_semaphore *fshared,
711 int nr_wake, u32 bitset)
713 struct futex_hash_bucket *hb;
714 struct futex_q *this, *next;
715 struct plist_head *head;
716 union futex_key key = FUTEX_KEY_INIT;
722 futex_lock_mm(fshared);
724 ret = get_futex_key(uaddr, fshared, &key);
725 if (unlikely(ret != 0))
728 hb = hash_futex(&key);
729 spin_lock(&hb->lock);
732 plist_for_each_entry_safe(this, next, head, list) {
733 if (match_futex (&this->key, &key)) {
734 if (this->pi_state) {
739 /* Check if one of the bits is set in both bitsets */
740 if (!(this->bitset & bitset))
744 if (++ret >= nr_wake)
749 spin_unlock(&hb->lock);
751 put_futex_key(fshared, &key);
752 futex_unlock_mm(fshared);
757 * Wake up all waiters hashed on the physical page that is mapped
758 * to this virtual address:
761 futex_wake_op(u32 __user *uaddr1, struct rw_semaphore *fshared,
763 int nr_wake, int nr_wake2, int op)
765 union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
766 struct futex_hash_bucket *hb1, *hb2;
767 struct plist_head *head;
768 struct futex_q *this, *next;
769 int ret, op_ret, attempt = 0;
772 futex_lock_mm(fshared);
774 ret = get_futex_key(uaddr1, fshared, &key1);
775 if (unlikely(ret != 0))
777 ret = get_futex_key(uaddr2, fshared, &key2);
778 if (unlikely(ret != 0))
781 hb1 = hash_futex(&key1);
782 hb2 = hash_futex(&key2);
785 double_lock_hb(hb1, hb2);
787 op_ret = futex_atomic_op_inuser(op, uaddr2);
788 if (unlikely(op_ret < 0)) {
791 spin_unlock(&hb1->lock);
793 spin_unlock(&hb2->lock);
797 * we don't get EFAULT from MMU faults if we don't have an MMU,
798 * but we might get them from range checking
804 if (unlikely(op_ret != -EFAULT)) {
810 * futex_atomic_op_inuser needs to both read and write
811 * *(int __user *)uaddr2, but we can't modify it
812 * non-atomically. Therefore, if get_user below is not
813 * enough, we need to handle the fault ourselves, while
814 * still holding the mmap_sem.
817 ret = futex_handle_fault((unsigned long)uaddr2,
825 * If we would have faulted, release mmap_sem,
826 * fault it in and start all over again.
828 futex_unlock_mm(fshared);
830 ret = get_user(dummy, uaddr2);
839 plist_for_each_entry_safe(this, next, head, list) {
840 if (match_futex (&this->key, &key1)) {
842 if (++ret >= nr_wake)
851 plist_for_each_entry_safe(this, next, head, list) {
852 if (match_futex (&this->key, &key2)) {
854 if (++op_ret >= nr_wake2)
861 spin_unlock(&hb1->lock);
863 spin_unlock(&hb2->lock);
865 put_futex_key(fshared, &key2);
866 put_futex_key(fshared, &key1);
867 futex_unlock_mm(fshared);
873 * Requeue all waiters hashed on one physical page to another
876 static int futex_requeue(u32 __user *uaddr1, struct rw_semaphore *fshared,
878 int nr_wake, int nr_requeue, u32 *cmpval)
880 union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
881 struct futex_hash_bucket *hb1, *hb2;
882 struct plist_head *head1;
883 struct futex_q *this, *next;
884 int ret, drop_count = 0;
887 futex_lock_mm(fshared);
889 ret = get_futex_key(uaddr1, fshared, &key1);
890 if (unlikely(ret != 0))
892 ret = get_futex_key(uaddr2, fshared, &key2);
893 if (unlikely(ret != 0))
896 hb1 = hash_futex(&key1);
897 hb2 = hash_futex(&key2);
899 double_lock_hb(hb1, hb2);
901 if (likely(cmpval != NULL)) {
904 ret = get_futex_value_locked(&curval, uaddr1);
907 spin_unlock(&hb1->lock);
909 spin_unlock(&hb2->lock);
912 * If we would have faulted, release mmap_sem, fault
913 * it in and start all over again.
915 futex_unlock_mm(fshared);
917 ret = get_user(curval, uaddr1);
924 if (curval != *cmpval) {
931 plist_for_each_entry_safe(this, next, head1, list) {
932 if (!match_futex (&this->key, &key1))
934 if (++ret <= nr_wake) {
938 * If key1 and key2 hash to the same bucket, no need to
941 if (likely(head1 != &hb2->chain)) {
942 plist_del(&this->list, &hb1->chain);
943 plist_add(&this->list, &hb2->chain);
944 this->lock_ptr = &hb2->lock;
945 #ifdef CONFIG_DEBUG_PI_LIST
946 this->list.plist.lock = &hb2->lock;
950 get_futex_key_refs(&key2);
953 if (ret - nr_wake >= nr_requeue)
959 spin_unlock(&hb1->lock);
961 spin_unlock(&hb2->lock);
963 /* drop_futex_key_refs() must be called outside the spinlocks. */
964 while (--drop_count >= 0)
965 drop_futex_key_refs(&key1);
968 put_futex_key(fshared, &key2);
969 put_futex_key(fshared, &key1);
970 futex_unlock_mm(fshared);
974 /* The key must be already stored in q->key. */
975 static inline struct futex_hash_bucket *queue_lock(struct futex_q *q)
977 struct futex_hash_bucket *hb;
979 init_waitqueue_head(&q->waiters);
981 get_futex_key_refs(&q->key);
982 hb = hash_futex(&q->key);
983 q->lock_ptr = &hb->lock;
985 spin_lock(&hb->lock);
989 static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb)
994 * The priority used to register this element is
995 * - either the real thread-priority for the real-time threads
996 * (i.e. threads with a priority lower than MAX_RT_PRIO)
997 * - or MAX_RT_PRIO for non-RT threads.
998 * Thus, all RT-threads are woken first in priority order, and
999 * the others are woken last, in FIFO order.
1001 prio = min(current->normal_prio, MAX_RT_PRIO);
1003 plist_node_init(&q->list, prio);
1004 #ifdef CONFIG_DEBUG_PI_LIST
1005 q->list.plist.lock = &hb->lock;
1007 plist_add(&q->list, &hb->chain);
1009 spin_unlock(&hb->lock);
1013 queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb)
1015 spin_unlock(&hb->lock);
1016 drop_futex_key_refs(&q->key);
1020 * queue_me and unqueue_me must be called as a pair, each
1021 * exactly once. They are called with the hashed spinlock held.
1024 /* Return 1 if we were still queued (ie. 0 means we were woken) */
1025 static int unqueue_me(struct futex_q *q)
1027 spinlock_t *lock_ptr;
1030 /* In the common case we don't take the spinlock, which is nice. */
1032 lock_ptr = q->lock_ptr;
1034 if (lock_ptr != NULL) {
1035 spin_lock(lock_ptr);
1037 * q->lock_ptr can change between reading it and
1038 * spin_lock(), causing us to take the wrong lock. This
1039 * corrects the race condition.
1041 * Reasoning goes like this: if we have the wrong lock,
1042 * q->lock_ptr must have changed (maybe several times)
1043 * between reading it and the spin_lock(). It can
1044 * change again after the spin_lock() but only if it was
1045 * already changed before the spin_lock(). It cannot,
1046 * however, change back to the original value. Therefore
1047 * we can detect whether we acquired the correct lock.
1049 if (unlikely(lock_ptr != q->lock_ptr)) {
1050 spin_unlock(lock_ptr);
1053 WARN_ON(plist_node_empty(&q->list));
1054 plist_del(&q->list, &q->list.plist);
1056 BUG_ON(q->pi_state);
1058 spin_unlock(lock_ptr);
1062 drop_futex_key_refs(&q->key);
1067 * PI futexes can not be requeued and must remove themself from the
1068 * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry
1071 static void unqueue_me_pi(struct futex_q *q)
1073 WARN_ON(plist_node_empty(&q->list));
1074 plist_del(&q->list, &q->list.plist);
1076 BUG_ON(!q->pi_state);
1077 free_pi_state(q->pi_state);
1080 spin_unlock(q->lock_ptr);
1082 drop_futex_key_refs(&q->key);
1086 * Fixup the pi_state owner with the new owner.
1088 * Must be called with hash bucket lock held and mm->sem held for non
1091 static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
1092 struct task_struct *newowner,
1093 struct rw_semaphore *fshared)
1095 u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS;
1096 struct futex_pi_state *pi_state = q->pi_state;
1097 struct task_struct *oldowner = pi_state->owner;
1098 u32 uval, curval, newval;
1099 int ret, attempt = 0;
1102 if (!pi_state->owner)
1103 newtid |= FUTEX_OWNER_DIED;
1106 * We are here either because we stole the rtmutex from the
1107 * pending owner or we are the pending owner which failed to
1108 * get the rtmutex. We have to replace the pending owner TID
1109 * in the user space variable. This must be atomic as we have
1110 * to preserve the owner died bit here.
1112 * Note: We write the user space value _before_ changing the
1113 * pi_state because we can fault here. Imagine swapped out
1114 * pages or a fork, which was running right before we acquired
1115 * mmap_sem, that marked all the anonymous memory readonly for
1118 * Modifying pi_state _before_ the user space value would
1119 * leave the pi_state in an inconsistent state when we fault
1120 * here, because we need to drop the hash bucket lock to
1121 * handle the fault. This might be observed in the PID check
1122 * in lookup_pi_state.
1125 if (get_futex_value_locked(&uval, uaddr))
1129 newval = (uval & FUTEX_OWNER_DIED) | newtid;
1131 curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
1133 if (curval == -EFAULT)
1141 * We fixed up user space. Now we need to fix the pi_state
1144 if (pi_state->owner != NULL) {
1145 spin_lock_irq(&pi_state->owner->pi_lock);
1146 WARN_ON(list_empty(&pi_state->list));
1147 list_del_init(&pi_state->list);
1148 spin_unlock_irq(&pi_state->owner->pi_lock);
1151 pi_state->owner = newowner;
1153 spin_lock_irq(&newowner->pi_lock);
1154 WARN_ON(!list_empty(&pi_state->list));
1155 list_add(&pi_state->list, &newowner->pi_state_list);
1156 spin_unlock_irq(&newowner->pi_lock);
1160 * To handle the page fault we need to drop the hash bucket
1161 * lock here. That gives the other task (either the pending
1162 * owner itself or the task which stole the rtmutex) the
1163 * chance to try the fixup of the pi_state. So once we are
1164 * back from handling the fault we need to check the pi_state
1165 * after reacquiring the hash bucket lock and before trying to
1166 * do another fixup. When the fixup has been done already we
1170 spin_unlock(q->lock_ptr);
1172 ret = futex_handle_fault((unsigned long)uaddr, fshared, attempt++);
1174 spin_lock(q->lock_ptr);
1177 * Check if someone else fixed it for us:
1179 if (pi_state->owner != oldowner)
1189 * In case we must use restart_block to restart a futex_wait,
1190 * we encode in the 'flags' shared capability
1192 #define FLAGS_SHARED 1
1194 static long futex_wait_restart(struct restart_block *restart);
1196 static int futex_wait(u32 __user *uaddr, struct rw_semaphore *fshared,
1197 u32 val, ktime_t *abs_time, u32 bitset)
1199 struct task_struct *curr = current;
1200 DECLARE_WAITQUEUE(wait, curr);
1201 struct futex_hash_bucket *hb;
1205 struct hrtimer_sleeper t;
1214 futex_lock_mm(fshared);
1216 q.key = FUTEX_KEY_INIT;
1217 ret = get_futex_key(uaddr, fshared, &q.key);
1218 if (unlikely(ret != 0))
1219 goto out_release_sem;
1221 hb = queue_lock(&q);
1224 * Access the page AFTER the futex is queued.
1225 * Order is important:
1227 * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val);
1228 * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); }
1230 * The basic logical guarantee of a futex is that it blocks ONLY
1231 * if cond(var) is known to be true at the time of blocking, for
1232 * any cond. If we queued after testing *uaddr, that would open
1233 * a race condition where we could block indefinitely with
1234 * cond(var) false, which would violate the guarantee.
1236 * A consequence is that futex_wait() can return zero and absorb
1237 * a wakeup when *uaddr != val on entry to the syscall. This is
1240 * for shared futexes, we hold the mmap semaphore, so the mapping
1241 * cannot have changed since we looked it up in get_futex_key.
1243 ret = get_futex_value_locked(&uval, uaddr);
1245 if (unlikely(ret)) {
1246 queue_unlock(&q, hb);
1249 * If we would have faulted, release mmap_sem, fault it in and
1250 * start all over again.
1252 futex_unlock_mm(fshared);
1254 ret = get_user(uval, uaddr);
1262 goto out_unlock_release_sem;
1264 /* Only actually queue if *uaddr contained val. */
1268 * Now the futex is queued and we have checked the data, we
1269 * don't want to hold mmap_sem while we sleep.
1271 futex_unlock_mm(fshared);
1274 * There might have been scheduling since the queue_me(), as we
1275 * cannot hold a spinlock across the get_user() in case it
1276 * faults, and we cannot just set TASK_INTERRUPTIBLE state when
1277 * queueing ourselves into the futex hash. This code thus has to
1278 * rely on the futex_wake() code removing us from hash when it
1282 /* add_wait_queue is the barrier after __set_current_state. */
1283 __set_current_state(TASK_INTERRUPTIBLE);
1284 add_wait_queue(&q.waiters, &wait);
1286 * !plist_node_empty() is safe here without any lock.
1287 * q.lock_ptr != 0 is not safe, because of ordering against wakeup.
1289 if (likely(!plist_node_empty(&q.list))) {
1293 hrtimer_init_on_stack(&t.timer, CLOCK_MONOTONIC,
1295 hrtimer_init_sleeper(&t, current);
1296 t.timer.expires = *abs_time;
1298 hrtimer_start(&t.timer, t.timer.expires,
1300 if (!hrtimer_active(&t.timer))
1304 * the timer could have already expired, in which
1305 * case current would be flagged for rescheduling.
1306 * Don't bother calling schedule.
1311 hrtimer_cancel(&t.timer);
1313 /* Flag if a timeout occured */
1314 rem = (t.task == NULL);
1316 destroy_hrtimer_on_stack(&t.timer);
1319 __set_current_state(TASK_RUNNING);
1322 * NOTE: we don't remove ourselves from the waitqueue because
1323 * we are the only user of it.
1326 /* If we were woken (and unqueued), we succeeded, whatever. */
1327 if (!unqueue_me(&q))
1333 * We expect signal_pending(current), but another thread may
1334 * have handled it for us already.
1337 return -ERESTARTSYS;
1339 struct restart_block *restart;
1340 restart = ¤t_thread_info()->restart_block;
1341 restart->fn = futex_wait_restart;
1342 restart->futex.uaddr = (u32 *)uaddr;
1343 restart->futex.val = val;
1344 restart->futex.time = abs_time->tv64;
1345 restart->futex.bitset = bitset;
1346 restart->futex.flags = 0;
1349 restart->futex.flags |= FLAGS_SHARED;
1350 return -ERESTART_RESTARTBLOCK;
1353 out_unlock_release_sem:
1354 queue_unlock(&q, hb);
1357 put_futex_key(fshared, &q.key);
1358 futex_unlock_mm(fshared);
1363 static long futex_wait_restart(struct restart_block *restart)
1365 u32 __user *uaddr = (u32 __user *)restart->futex.uaddr;
1366 struct rw_semaphore *fshared = NULL;
1369 t.tv64 = restart->futex.time;
1370 restart->fn = do_no_restart_syscall;
1371 if (restart->futex.flags & FLAGS_SHARED)
1372 fshared = ¤t->mm->mmap_sem;
1373 return (long)futex_wait(uaddr, fshared, restart->futex.val, &t,
1374 restart->futex.bitset);
1379 * Userspace tried a 0 -> TID atomic transition of the futex value
1380 * and failed. The kernel side here does the whole locking operation:
1381 * if there are waiters then it will block, it does PI, etc. (Due to
1382 * races the kernel might see a 0 value of the futex too.)
1384 static int futex_lock_pi(u32 __user *uaddr, struct rw_semaphore *fshared,
1385 int detect, ktime_t *time, int trylock)
1387 struct hrtimer_sleeper timeout, *to = NULL;
1388 struct task_struct *curr = current;
1389 struct futex_hash_bucket *hb;
1390 u32 uval, newval, curval;
1392 int ret, lock_taken, ownerdied = 0, attempt = 0;
1394 if (refill_pi_state_cache())
1399 hrtimer_init_on_stack(&to->timer, CLOCK_REALTIME,
1401 hrtimer_init_sleeper(to, current);
1402 to->timer.expires = *time;
1407 futex_lock_mm(fshared);
1409 q.key = FUTEX_KEY_INIT;
1410 ret = get_futex_key(uaddr, fshared, &q.key);
1411 if (unlikely(ret != 0))
1412 goto out_release_sem;
1415 hb = queue_lock(&q);
1418 ret = lock_taken = 0;
1421 * To avoid races, we attempt to take the lock here again
1422 * (by doing a 0 -> TID atomic cmpxchg), while holding all
1423 * the locks. It will most likely not succeed.
1425 newval = task_pid_vnr(current);
1427 curval = cmpxchg_futex_value_locked(uaddr, 0, newval);
1429 if (unlikely(curval == -EFAULT))
1433 * Detect deadlocks. In case of REQUEUE_PI this is a valid
1434 * situation and we return success to user space.
1436 if (unlikely((curval & FUTEX_TID_MASK) == task_pid_vnr(current))) {
1438 goto out_unlock_release_sem;
1442 * Surprise - we got the lock. Just return to userspace:
1444 if (unlikely(!curval))
1445 goto out_unlock_release_sem;
1450 * Set the WAITERS flag, so the owner will know it has someone
1451 * to wake at next unlock
1453 newval = curval | FUTEX_WAITERS;
1456 * There are two cases, where a futex might have no owner (the
1457 * owner TID is 0): OWNER_DIED. We take over the futex in this
1458 * case. We also do an unconditional take over, when the owner
1459 * of the futex died.
1461 * This is safe as we are protected by the hash bucket lock !
1463 if (unlikely(ownerdied || !(curval & FUTEX_TID_MASK))) {
1464 /* Keep the OWNER_DIED bit */
1465 newval = (curval & ~FUTEX_TID_MASK) | task_pid_vnr(current);
1470 curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
1472 if (unlikely(curval == -EFAULT))
1474 if (unlikely(curval != uval))
1478 * We took the lock due to owner died take over.
1480 if (unlikely(lock_taken))
1481 goto out_unlock_release_sem;
1484 * We dont have the lock. Look up the PI state (or create it if
1485 * we are the first waiter):
1487 ret = lookup_pi_state(uval, hb, &q.key, &q.pi_state);
1489 if (unlikely(ret)) {
1494 * Task is exiting and we just wait for the
1497 queue_unlock(&q, hb);
1498 futex_unlock_mm(fshared);
1504 * No owner found for this futex. Check if the
1505 * OWNER_DIED bit is set to figure out whether
1506 * this is a robust futex or not.
1508 if (get_futex_value_locked(&curval, uaddr))
1512 * We simply start over in case of a robust
1513 * futex. The code above will take the futex
1516 if (curval & FUTEX_OWNER_DIED) {
1521 goto out_unlock_release_sem;
1526 * Only actually queue now that the atomic ops are done:
1531 * Now the futex is queued and we have checked the data, we
1532 * don't want to hold mmap_sem while we sleep.
1534 futex_unlock_mm(fshared);
1536 WARN_ON(!q.pi_state);
1538 * Block on the PI mutex:
1541 ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1);
1543 ret = rt_mutex_trylock(&q.pi_state->pi_mutex);
1544 /* Fixup the trylock return value: */
1545 ret = ret ? 0 : -EWOULDBLOCK;
1548 futex_lock_mm(fshared);
1549 spin_lock(q.lock_ptr);
1553 * Got the lock. We might not be the anticipated owner
1554 * if we did a lock-steal - fix up the PI-state in
1557 if (q.pi_state->owner != curr)
1558 ret = fixup_pi_state_owner(uaddr, &q, curr, fshared);
1561 * Catch the rare case, where the lock was released
1562 * when we were on the way back before we locked the
1565 if (q.pi_state->owner == curr) {
1567 * Try to get the rt_mutex now. This might
1568 * fail as some other task acquired the
1569 * rt_mutex after we removed ourself from the
1570 * rt_mutex waiters list.
1572 if (rt_mutex_trylock(&q.pi_state->pi_mutex))
1576 * pi_state is incorrect, some other
1577 * task did a lock steal and we
1578 * returned due to timeout or signal
1579 * without taking the rt_mutex. Too
1580 * late. We can access the
1581 * rt_mutex_owner without locking, as
1582 * the other task is now blocked on
1583 * the hash bucket lock. Fix the state
1586 struct task_struct *owner;
1589 owner = rt_mutex_owner(&q.pi_state->pi_mutex);
1590 res = fixup_pi_state_owner(uaddr, &q, owner,
1593 /* propagate -EFAULT, if the fixup failed */
1599 * Paranoia check. If we did not take the lock
1600 * in the trylock above, then we should not be
1601 * the owner of the rtmutex, neither the real
1602 * nor the pending one:
1604 if (rt_mutex_owner(&q.pi_state->pi_mutex) == curr)
1605 printk(KERN_ERR "futex_lock_pi: ret = %d "
1606 "pi-mutex: %p pi-state %p\n", ret,
1607 q.pi_state->pi_mutex.owner,
1612 /* Unqueue and drop the lock */
1614 futex_unlock_mm(fshared);
1617 destroy_hrtimer_on_stack(&to->timer);
1618 return ret != -EINTR ? ret : -ERESTARTNOINTR;
1620 out_unlock_release_sem:
1621 queue_unlock(&q, hb);
1624 put_futex_key(fshared, &q.key);
1625 futex_unlock_mm(fshared);
1627 destroy_hrtimer_on_stack(&to->timer);
1632 * We have to r/w *(int __user *)uaddr, but we can't modify it
1633 * non-atomically. Therefore, if get_user below is not
1634 * enough, we need to handle the fault ourselves, while
1635 * still holding the mmap_sem.
1637 * ... and hb->lock. :-) --ANK
1639 queue_unlock(&q, hb);
1642 ret = futex_handle_fault((unsigned long)uaddr, fshared,
1645 goto out_release_sem;
1646 goto retry_unlocked;
1649 futex_unlock_mm(fshared);
1651 ret = get_user(uval, uaddr);
1652 if (!ret && (uval != -EFAULT))
1656 destroy_hrtimer_on_stack(&to->timer);
1661 * Userspace attempted a TID -> 0 atomic transition, and failed.
1662 * This is the in-kernel slowpath: we look up the PI state (if any),
1663 * and do the rt-mutex unlock.
1665 static int futex_unlock_pi(u32 __user *uaddr, struct rw_semaphore *fshared)
1667 struct futex_hash_bucket *hb;
1668 struct futex_q *this, *next;
1670 struct plist_head *head;
1671 union futex_key key = FUTEX_KEY_INIT;
1672 int ret, attempt = 0;
1675 if (get_user(uval, uaddr))
1678 * We release only a lock we actually own:
1680 if ((uval & FUTEX_TID_MASK) != task_pid_vnr(current))
1683 * First take all the futex related locks:
1685 futex_lock_mm(fshared);
1687 ret = get_futex_key(uaddr, fshared, &key);
1688 if (unlikely(ret != 0))
1691 hb = hash_futex(&key);
1693 spin_lock(&hb->lock);
1696 * To avoid races, try to do the TID -> 0 atomic transition
1697 * again. If it succeeds then we can return without waking
1700 if (!(uval & FUTEX_OWNER_DIED))
1701 uval = cmpxchg_futex_value_locked(uaddr, task_pid_vnr(current), 0);
1704 if (unlikely(uval == -EFAULT))
1707 * Rare case: we managed to release the lock atomically,
1708 * no need to wake anyone else up:
1710 if (unlikely(uval == task_pid_vnr(current)))
1714 * Ok, other tasks may need to be woken up - check waiters
1715 * and do the wakeup if necessary:
1719 plist_for_each_entry_safe(this, next, head, list) {
1720 if (!match_futex (&this->key, &key))
1722 ret = wake_futex_pi(uaddr, uval, this);
1724 * The atomic access to the futex value
1725 * generated a pagefault, so retry the
1726 * user-access and the wakeup:
1733 * No waiters - kernel unlocks the futex:
1735 if (!(uval & FUTEX_OWNER_DIED)) {
1736 ret = unlock_futex_pi(uaddr, uval);
1742 spin_unlock(&hb->lock);
1744 put_futex_key(fshared, &key);
1745 futex_unlock_mm(fshared);
1751 * We have to r/w *(int __user *)uaddr, but we can't modify it
1752 * non-atomically. Therefore, if get_user below is not
1753 * enough, we need to handle the fault ourselves, while
1754 * still holding the mmap_sem.
1756 * ... and hb->lock. --ANK
1758 spin_unlock(&hb->lock);
1761 ret = futex_handle_fault((unsigned long)uaddr, fshared,
1766 goto retry_unlocked;
1769 futex_unlock_mm(fshared);
1771 ret = get_user(uval, uaddr);
1772 if (!ret && (uval != -EFAULT))
1779 * Support for robust futexes: the kernel cleans up held futexes at
1782 * Implementation: user-space maintains a per-thread list of locks it
1783 * is holding. Upon do_exit(), the kernel carefully walks this list,
1784 * and marks all locks that are owned by this thread with the
1785 * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is
1786 * always manipulated with the lock held, so the list is private and
1787 * per-thread. Userspace also maintains a per-thread 'list_op_pending'
1788 * field, to allow the kernel to clean up if the thread dies after
1789 * acquiring the lock, but just before it could have added itself to
1790 * the list. There can only be one such pending lock.
1794 * sys_set_robust_list - set the robust-futex list head of a task
1795 * @head: pointer to the list-head
1796 * @len: length of the list-head, as userspace expects
1799 sys_set_robust_list(struct robust_list_head __user *head,
1802 if (!futex_cmpxchg_enabled)
1805 * The kernel knows only one size for now:
1807 if (unlikely(len != sizeof(*head)))
1810 current->robust_list = head;
1816 * sys_get_robust_list - get the robust-futex list head of a task
1817 * @pid: pid of the process [zero for current task]
1818 * @head_ptr: pointer to a list-head pointer, the kernel fills it in
1819 * @len_ptr: pointer to a length field, the kernel fills in the header size
1822 sys_get_robust_list(int pid, struct robust_list_head __user * __user *head_ptr,
1823 size_t __user *len_ptr)
1825 struct robust_list_head __user *head;
1828 if (!futex_cmpxchg_enabled)
1832 head = current->robust_list;
1834 struct task_struct *p;
1838 p = find_task_by_vpid(pid);
1842 if ((current->euid != p->euid) && (current->euid != p->uid) &&
1843 !capable(CAP_SYS_PTRACE))
1845 head = p->robust_list;
1849 if (put_user(sizeof(*head), len_ptr))
1851 return put_user(head, head_ptr);
1860 * Process a futex-list entry, check whether it's owned by the
1861 * dying task, and do notification if so:
1863 int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi)
1865 u32 uval, nval, mval;
1868 if (get_user(uval, uaddr))
1871 if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) {
1873 * Ok, this dying thread is truly holding a futex
1874 * of interest. Set the OWNER_DIED bit atomically
1875 * via cmpxchg, and if the value had FUTEX_WAITERS
1876 * set, wake up a waiter (if any). (We have to do a
1877 * futex_wake() even if OWNER_DIED is already set -
1878 * to handle the rare but possible case of recursive
1879 * thread-death.) The rest of the cleanup is done in
1882 mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED;
1883 nval = futex_atomic_cmpxchg_inatomic(uaddr, uval, mval);
1885 if (nval == -EFAULT)
1892 * Wake robust non-PI futexes here. The wakeup of
1893 * PI futexes happens in exit_pi_state():
1895 if (!pi && (uval & FUTEX_WAITERS))
1896 futex_wake(uaddr, &curr->mm->mmap_sem, 1,
1897 FUTEX_BITSET_MATCH_ANY);
1903 * Fetch a robust-list pointer. Bit 0 signals PI futexes:
1905 static inline int fetch_robust_entry(struct robust_list __user **entry,
1906 struct robust_list __user * __user *head,
1909 unsigned long uentry;
1911 if (get_user(uentry, (unsigned long __user *)head))
1914 *entry = (void __user *)(uentry & ~1UL);
1921 * Walk curr->robust_list (very carefully, it's a userspace list!)
1922 * and mark any locks found there dead, and notify any waiters.
1924 * We silently return on any sign of list-walking problem.
1926 void exit_robust_list(struct task_struct *curr)
1928 struct robust_list_head __user *head = curr->robust_list;
1929 struct robust_list __user *entry, *next_entry, *pending;
1930 unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip;
1931 unsigned long futex_offset;
1934 if (!futex_cmpxchg_enabled)
1938 * Fetch the list head (which was registered earlier, via
1939 * sys_set_robust_list()):
1941 if (fetch_robust_entry(&entry, &head->list.next, &pi))
1944 * Fetch the relative futex offset:
1946 if (get_user(futex_offset, &head->futex_offset))
1949 * Fetch any possibly pending lock-add first, and handle it
1952 if (fetch_robust_entry(&pending, &head->list_op_pending, &pip))
1955 next_entry = NULL; /* avoid warning with gcc */
1956 while (entry != &head->list) {
1958 * Fetch the next entry in the list before calling
1959 * handle_futex_death:
1961 rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi);
1963 * A pending lock might already be on the list, so
1964 * don't process it twice:
1966 if (entry != pending)
1967 if (handle_futex_death((void __user *)entry + futex_offset,
1975 * Avoid excessively long or circular lists:
1984 handle_futex_death((void __user *)pending + futex_offset,
1988 long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
1989 u32 __user *uaddr2, u32 val2, u32 val3)
1992 int cmd = op & FUTEX_CMD_MASK;
1993 struct rw_semaphore *fshared = NULL;
1995 if (!(op & FUTEX_PRIVATE_FLAG))
1996 fshared = ¤t->mm->mmap_sem;
2000 val3 = FUTEX_BITSET_MATCH_ANY;
2001 case FUTEX_WAIT_BITSET:
2002 ret = futex_wait(uaddr, fshared, val, timeout, val3);
2005 val3 = FUTEX_BITSET_MATCH_ANY;
2006 case FUTEX_WAKE_BITSET:
2007 ret = futex_wake(uaddr, fshared, val, val3);
2010 ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, NULL);
2012 case FUTEX_CMP_REQUEUE:
2013 ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3);
2016 ret = futex_wake_op(uaddr, fshared, uaddr2, val, val2, val3);
2019 if (futex_cmpxchg_enabled)
2020 ret = futex_lock_pi(uaddr, fshared, val, timeout, 0);
2022 case FUTEX_UNLOCK_PI:
2023 if (futex_cmpxchg_enabled)
2024 ret = futex_unlock_pi(uaddr, fshared);
2026 case FUTEX_TRYLOCK_PI:
2027 if (futex_cmpxchg_enabled)
2028 ret = futex_lock_pi(uaddr, fshared, 0, timeout, 1);
2037 asmlinkage long sys_futex(u32 __user *uaddr, int op, u32 val,
2038 struct timespec __user *utime, u32 __user *uaddr2,
2042 ktime_t t, *tp = NULL;
2044 int cmd = op & FUTEX_CMD_MASK;
2046 if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
2047 cmd == FUTEX_WAIT_BITSET)) {
2048 if (copy_from_user(&ts, utime, sizeof(ts)) != 0)
2050 if (!timespec_valid(&ts))
2053 t = timespec_to_ktime(ts);
2054 if (cmd == FUTEX_WAIT)
2055 t = ktime_add_safe(ktime_get(), t);
2059 * requeue parameter in 'utime' if cmd == FUTEX_REQUEUE.
2060 * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP.
2062 if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
2063 cmd == FUTEX_WAKE_OP)
2064 val2 = (u32) (unsigned long) utime;
2066 return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
2069 static int __init futex_init(void)
2075 * This will fail and we want it. Some arch implementations do
2076 * runtime detection of the futex_atomic_cmpxchg_inatomic()
2077 * functionality. We want to know that before we call in any
2078 * of the complex code paths. Also we want to prevent
2079 * registration of robust lists in that case. NULL is
2080 * guaranteed to fault and we get -EFAULT on functional
2081 * implementation, the non functional ones will return
2084 curval = cmpxchg_futex_value_locked(NULL, 0, 0);
2085 if (curval == -EFAULT)
2086 futex_cmpxchg_enabled = 1;
2088 for (i = 0; i < ARRAY_SIZE(futex_queues); i++) {
2089 plist_head_init(&futex_queues[i].chain, &futex_queues[i].lock);
2090 spin_lock_init(&futex_queues[i].lock);
2095 __initcall(futex_init);