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 * Requeue-PI support by Darren Hart <dvhltc@us.ibm.com>
23 * Copyright (C) IBM Corporation, 2009
24 * Thanks to Thomas Gleixner for conceptual design and careful reviews.
26 * Thanks to Ben LaHaise for yelling "hashed waitqueues" loudly
27 * enough at me, Linus for the original (flawed) idea, Matthew
28 * Kirkwood for proof-of-concept implementation.
30 * "The futexes are also cursed."
31 * "But they come in a choice of three flavours!"
33 * This program is free software; you can redistribute it and/or modify
34 * it under the terms of the GNU General Public License as published by
35 * the Free Software Foundation; either version 2 of the License, or
36 * (at your option) any later version.
38 * This program is distributed in the hope that it will be useful,
39 * but WITHOUT ANY WARRANTY; without even the implied warranty of
40 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
41 * GNU General Public License for more details.
43 * You should have received a copy of the GNU General Public License
44 * along with this program; if not, write to the Free Software
45 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
47 #include <linux/slab.h>
48 #include <linux/poll.h>
50 #include <linux/file.h>
51 #include <linux/jhash.h>
52 #include <linux/init.h>
53 #include <linux/futex.h>
54 #include <linux/mount.h>
55 #include <linux/pagemap.h>
56 #include <linux/syscalls.h>
57 #include <linux/signal.h>
58 #include <linux/module.h>
59 #include <linux/magic.h>
60 #include <linux/pid.h>
61 #include <linux/nsproxy.h>
63 #include <asm/futex.h>
65 #include "rtmutex_common.h"
67 int __read_mostly futex_cmpxchg_enabled
;
69 #define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)
72 * Futex flags used to encode options to functions and preserve them across
75 #define FLAGS_SHARED 0x01
76 #define FLAGS_CLOCKRT 0x02
77 #define FLAGS_HAS_TIMEOUT 0x04
80 * Priority Inheritance state:
82 struct futex_pi_state
{
84 * list of 'owned' pi_state instances - these have to be
85 * cleaned up in do_exit() if the task exits prematurely:
87 struct list_head list
;
92 struct rt_mutex pi_mutex
;
94 struct task_struct
*owner
;
101 * struct futex_q - The hashed futex queue entry, one per waiting task
102 * @list: priority-sorted list of tasks waiting on this futex
103 * @task: the task waiting on the futex
104 * @lock_ptr: the hash bucket lock
105 * @key: the key the futex is hashed on
106 * @pi_state: optional priority inheritance state
107 * @rt_waiter: rt_waiter storage for use with requeue_pi
108 * @requeue_pi_key: the requeue_pi target futex key
109 * @bitset: bitset for the optional bitmasked wakeup
111 * We use this hashed waitqueue, instead of a normal wait_queue_t, so
112 * we can wake only the relevant ones (hashed queues may be shared).
114 * A futex_q has a woken state, just like tasks have TASK_RUNNING.
115 * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0.
116 * The order of wakeup is always to make the first condition true, then
119 * PI futexes are typically woken before they are removed from the hash list via
120 * the rt_mutex code. See unqueue_me_pi().
123 struct plist_node list
;
125 struct task_struct
*task
;
126 spinlock_t
*lock_ptr
;
128 struct futex_pi_state
*pi_state
;
129 struct rt_mutex_waiter
*rt_waiter
;
130 union futex_key
*requeue_pi_key
;
134 static const struct futex_q futex_q_init
= {
135 /* list gets initialized in queue_me()*/
136 .key
= FUTEX_KEY_INIT
,
137 .bitset
= FUTEX_BITSET_MATCH_ANY
141 * Hash buckets are shared by all the futex_keys that hash to the same
142 * location. Each key may have multiple futex_q structures, one for each task
143 * waiting on a futex.
145 struct futex_hash_bucket
{
147 struct plist_head chain
;
150 static struct futex_hash_bucket futex_queues
[1<<FUTEX_HASHBITS
];
153 * We hash on the keys returned from get_futex_key (see below).
155 static struct futex_hash_bucket
*hash_futex(union futex_key
*key
)
157 u32 hash
= jhash2((u32
*)&key
->both
.word
,
158 (sizeof(key
->both
.word
)+sizeof(key
->both
.ptr
))/4,
160 return &futex_queues
[hash
& ((1 << FUTEX_HASHBITS
)-1)];
164 * Return 1 if two futex_keys are equal, 0 otherwise.
166 static inline int match_futex(union futex_key
*key1
, union futex_key
*key2
)
169 && key1
->both
.word
== key2
->both
.word
170 && key1
->both
.ptr
== key2
->both
.ptr
171 && key1
->both
.offset
== key2
->both
.offset
);
175 * Take a reference to the resource addressed by a key.
176 * Can be called while holding spinlocks.
179 static void get_futex_key_refs(union futex_key
*key
)
184 switch (key
->both
.offset
& (FUT_OFF_INODE
|FUT_OFF_MMSHARED
)) {
186 ihold(key
->shared
.inode
);
188 case FUT_OFF_MMSHARED
:
189 atomic_inc(&key
->private.mm
->mm_count
);
195 * Drop a reference to the resource addressed by a key.
196 * The hash bucket spinlock must not be held.
198 static void drop_futex_key_refs(union futex_key
*key
)
200 if (!key
->both
.ptr
) {
201 /* If we're here then we tried to put a key we failed to get */
206 switch (key
->both
.offset
& (FUT_OFF_INODE
|FUT_OFF_MMSHARED
)) {
208 iput(key
->shared
.inode
);
210 case FUT_OFF_MMSHARED
:
211 mmdrop(key
->private.mm
);
217 * get_futex_key() - Get parameters which are the keys for a futex
218 * @uaddr: virtual address of the futex
219 * @fshared: 0 for a PROCESS_PRIVATE futex, 1 for PROCESS_SHARED
220 * @key: address where result is stored.
222 * Returns a negative error code or 0
223 * The key words are stored in *key on success.
225 * For shared mappings, it's (page->index, vma->vm_file->f_path.dentry->d_inode,
226 * offset_within_page). For private mappings, it's (uaddr, current->mm).
227 * We can usually work out the index without swapping in the page.
229 * lock_page() might sleep, the caller should not hold a spinlock.
232 get_futex_key(u32 __user
*uaddr
, int fshared
, union futex_key
*key
)
234 unsigned long address
= (unsigned long)uaddr
;
235 struct mm_struct
*mm
= current
->mm
;
236 struct page
*page
, *page_head
;
240 * The futex address must be "naturally" aligned.
242 key
->both
.offset
= address
% PAGE_SIZE
;
243 if (unlikely((address
% sizeof(u32
)) != 0))
245 address
-= key
->both
.offset
;
248 * PROCESS_PRIVATE futexes are fast.
249 * As the mm cannot disappear under us and the 'key' only needs
250 * virtual address, we dont even have to find the underlying vma.
251 * Note : We do have to check 'uaddr' is a valid user address,
252 * but access_ok() should be faster than find_vma()
255 if (unlikely(!access_ok(VERIFY_WRITE
, uaddr
, sizeof(u32
))))
257 key
->private.mm
= mm
;
258 key
->private.address
= address
;
259 get_futex_key_refs(key
);
264 err
= get_user_pages_fast(address
, 1, 1, &page
);
268 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
270 if (unlikely(PageTail(page
))) {
272 /* serialize against __split_huge_page_splitting() */
274 if (likely(__get_user_pages_fast(address
, 1, 1, &page
) == 1)) {
275 page_head
= compound_head(page
);
277 * page_head is valid pointer but we must pin
278 * it before taking the PG_lock and/or
279 * PG_compound_lock. The moment we re-enable
280 * irqs __split_huge_page_splitting() can
281 * return and the head page can be freed from
282 * under us. We can't take the PG_lock and/or
283 * PG_compound_lock on a page that could be
284 * freed from under us.
286 if (page
!= page_head
) {
297 page_head
= compound_head(page
);
298 if (page
!= page_head
) {
304 lock_page(page_head
);
305 if (!page_head
->mapping
) {
306 unlock_page(page_head
);
312 * Private mappings are handled in a simple way.
314 * NOTE: When userspace waits on a MAP_SHARED mapping, even if
315 * it's a read-only handle, it's expected that futexes attach to
316 * the object not the particular process.
318 if (PageAnon(page_head
)) {
319 key
->both
.offset
|= FUT_OFF_MMSHARED
; /* ref taken on mm */
320 key
->private.mm
= mm
;
321 key
->private.address
= address
;
323 key
->both
.offset
|= FUT_OFF_INODE
; /* inode-based key */
324 key
->shared
.inode
= page_head
->mapping
->host
;
325 key
->shared
.pgoff
= page_head
->index
;
328 get_futex_key_refs(key
);
330 unlock_page(page_head
);
335 static inline void put_futex_key(union futex_key
*key
)
337 drop_futex_key_refs(key
);
341 * fault_in_user_writeable() - Fault in user address and verify RW access
342 * @uaddr: pointer to faulting user space address
344 * Slow path to fixup the fault we just took in the atomic write
347 * We have no generic implementation of a non-destructive write to the
348 * user address. We know that we faulted in the atomic pagefault
349 * disabled section so we can as well avoid the #PF overhead by
350 * calling get_user_pages() right away.
352 static int fault_in_user_writeable(u32 __user
*uaddr
)
354 struct mm_struct
*mm
= current
->mm
;
357 down_read(&mm
->mmap_sem
);
358 ret
= get_user_pages(current
, mm
, (unsigned long)uaddr
,
359 1, 1, 0, NULL
, NULL
);
360 up_read(&mm
->mmap_sem
);
362 return ret
< 0 ? ret
: 0;
366 * futex_top_waiter() - Return the highest priority waiter on a futex
367 * @hb: the hash bucket the futex_q's reside in
368 * @key: the futex key (to distinguish it from other futex futex_q's)
370 * Must be called with the hb lock held.
372 static struct futex_q
*futex_top_waiter(struct futex_hash_bucket
*hb
,
373 union futex_key
*key
)
375 struct futex_q
*this;
377 plist_for_each_entry(this, &hb
->chain
, list
) {
378 if (match_futex(&this->key
, key
))
384 static int cmpxchg_futex_value_locked(u32
*curval
, u32 __user
*uaddr
,
385 u32 uval
, u32 newval
)
390 ret
= futex_atomic_cmpxchg_inatomic(curval
, uaddr
, uval
, newval
);
396 static int get_futex_value_locked(u32
*dest
, u32 __user
*from
)
401 ret
= __copy_from_user_inatomic(dest
, from
, sizeof(u32
));
404 return ret
? -EFAULT
: 0;
411 static int refill_pi_state_cache(void)
413 struct futex_pi_state
*pi_state
;
415 if (likely(current
->pi_state_cache
))
418 pi_state
= kzalloc(sizeof(*pi_state
), GFP_KERNEL
);
423 INIT_LIST_HEAD(&pi_state
->list
);
424 /* pi_mutex gets initialized later */
425 pi_state
->owner
= NULL
;
426 atomic_set(&pi_state
->refcount
, 1);
427 pi_state
->key
= FUTEX_KEY_INIT
;
429 current
->pi_state_cache
= pi_state
;
434 static struct futex_pi_state
* alloc_pi_state(void)
436 struct futex_pi_state
*pi_state
= current
->pi_state_cache
;
439 current
->pi_state_cache
= NULL
;
444 static void free_pi_state(struct futex_pi_state
*pi_state
)
446 if (!atomic_dec_and_test(&pi_state
->refcount
))
450 * If pi_state->owner is NULL, the owner is most probably dying
451 * and has cleaned up the pi_state already
453 if (pi_state
->owner
) {
454 raw_spin_lock_irq(&pi_state
->owner
->pi_lock
);
455 list_del_init(&pi_state
->list
);
456 raw_spin_unlock_irq(&pi_state
->owner
->pi_lock
);
458 rt_mutex_proxy_unlock(&pi_state
->pi_mutex
, pi_state
->owner
);
461 if (current
->pi_state_cache
)
465 * pi_state->list is already empty.
466 * clear pi_state->owner.
467 * refcount is at 0 - put it back to 1.
469 pi_state
->owner
= NULL
;
470 atomic_set(&pi_state
->refcount
, 1);
471 current
->pi_state_cache
= pi_state
;
476 * Look up the task based on what TID userspace gave us.
479 static struct task_struct
* futex_find_get_task(pid_t pid
)
481 struct task_struct
*p
;
484 p
= find_task_by_vpid(pid
);
494 * This task is holding PI mutexes at exit time => bad.
495 * Kernel cleans up PI-state, but userspace is likely hosed.
496 * (Robust-futex cleanup is separate and might save the day for userspace.)
498 void exit_pi_state_list(struct task_struct
*curr
)
500 struct list_head
*next
, *head
= &curr
->pi_state_list
;
501 struct futex_pi_state
*pi_state
;
502 struct futex_hash_bucket
*hb
;
503 union futex_key key
= FUTEX_KEY_INIT
;
505 if (!futex_cmpxchg_enabled
)
508 * We are a ZOMBIE and nobody can enqueue itself on
509 * pi_state_list anymore, but we have to be careful
510 * versus waiters unqueueing themselves:
512 raw_spin_lock_irq(&curr
->pi_lock
);
513 while (!list_empty(head
)) {
516 pi_state
= list_entry(next
, struct futex_pi_state
, list
);
518 hb
= hash_futex(&key
);
519 raw_spin_unlock_irq(&curr
->pi_lock
);
521 spin_lock(&hb
->lock
);
523 raw_spin_lock_irq(&curr
->pi_lock
);
525 * We dropped the pi-lock, so re-check whether this
526 * task still owns the PI-state:
528 if (head
->next
!= next
) {
529 spin_unlock(&hb
->lock
);
533 WARN_ON(pi_state
->owner
!= curr
);
534 WARN_ON(list_empty(&pi_state
->list
));
535 list_del_init(&pi_state
->list
);
536 pi_state
->owner
= NULL
;
537 raw_spin_unlock_irq(&curr
->pi_lock
);
539 rt_mutex_unlock(&pi_state
->pi_mutex
);
541 spin_unlock(&hb
->lock
);
543 raw_spin_lock_irq(&curr
->pi_lock
);
545 raw_spin_unlock_irq(&curr
->pi_lock
);
549 lookup_pi_state(u32 uval
, struct futex_hash_bucket
*hb
,
550 union futex_key
*key
, struct futex_pi_state
**ps
)
552 struct futex_pi_state
*pi_state
= NULL
;
553 struct futex_q
*this, *next
;
554 struct plist_head
*head
;
555 struct task_struct
*p
;
556 pid_t pid
= uval
& FUTEX_TID_MASK
;
560 plist_for_each_entry_safe(this, next
, head
, list
) {
561 if (match_futex(&this->key
, key
)) {
563 * Another waiter already exists - bump up
564 * the refcount and return its pi_state:
566 pi_state
= this->pi_state
;
568 * Userspace might have messed up non-PI and PI futexes
570 if (unlikely(!pi_state
))
573 WARN_ON(!atomic_read(&pi_state
->refcount
));
576 * When pi_state->owner is NULL then the owner died
577 * and another waiter is on the fly. pi_state->owner
578 * is fixed up by the task which acquires
579 * pi_state->rt_mutex.
581 * We do not check for pid == 0 which can happen when
582 * the owner died and robust_list_exit() cleared the
585 if (pid
&& pi_state
->owner
) {
587 * Bail out if user space manipulated the
590 if (pid
!= task_pid_vnr(pi_state
->owner
))
594 atomic_inc(&pi_state
->refcount
);
602 * We are the first waiter - try to look up the real owner and attach
603 * the new pi_state to it, but bail out when TID = 0
607 p
= futex_find_get_task(pid
);
612 * We need to look at the task state flags to figure out,
613 * whether the task is exiting. To protect against the do_exit
614 * change of the task flags, we do this protected by
617 raw_spin_lock_irq(&p
->pi_lock
);
618 if (unlikely(p
->flags
& PF_EXITING
)) {
620 * The task is on the way out. When PF_EXITPIDONE is
621 * set, we know that the task has finished the
624 int ret
= (p
->flags
& PF_EXITPIDONE
) ? -ESRCH
: -EAGAIN
;
626 raw_spin_unlock_irq(&p
->pi_lock
);
631 pi_state
= alloc_pi_state();
634 * Initialize the pi_mutex in locked state and make 'p'
637 rt_mutex_init_proxy_locked(&pi_state
->pi_mutex
, p
);
639 /* Store the key for possible exit cleanups: */
640 pi_state
->key
= *key
;
642 WARN_ON(!list_empty(&pi_state
->list
));
643 list_add(&pi_state
->list
, &p
->pi_state_list
);
645 raw_spin_unlock_irq(&p
->pi_lock
);
655 * futex_lock_pi_atomic() - Atomic work required to acquire a pi aware futex
656 * @uaddr: the pi futex user address
657 * @hb: the pi futex hash bucket
658 * @key: the futex key associated with uaddr and hb
659 * @ps: the pi_state pointer where we store the result of the
661 * @task: the task to perform the atomic lock work for. This will
662 * be "current" except in the case of requeue pi.
663 * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0)
667 * 1 - acquired the lock
670 * The hb->lock and futex_key refs shall be held by the caller.
672 static int futex_lock_pi_atomic(u32 __user
*uaddr
, struct futex_hash_bucket
*hb
,
673 union futex_key
*key
,
674 struct futex_pi_state
**ps
,
675 struct task_struct
*task
, int set_waiters
)
677 int lock_taken
, ret
, ownerdied
= 0;
678 u32 uval
, newval
, curval
, vpid
= task_pid_vnr(task
);
681 ret
= lock_taken
= 0;
684 * To avoid races, we attempt to take the lock here again
685 * (by doing a 0 -> TID atomic cmpxchg), while holding all
686 * the locks. It will most likely not succeed.
690 newval
|= FUTEX_WAITERS
;
692 if (unlikely(cmpxchg_futex_value_locked(&curval
, uaddr
, 0, newval
)))
698 if ((unlikely((curval
& FUTEX_TID_MASK
) == vpid
)))
702 * Surprise - we got the lock. Just return to userspace:
704 if (unlikely(!curval
))
710 * Set the FUTEX_WAITERS flag, so the owner will know it has someone
711 * to wake at the next unlock.
713 newval
= curval
| FUTEX_WAITERS
;
716 * There are two cases, where a futex might have no owner (the
717 * owner TID is 0): OWNER_DIED. We take over the futex in this
718 * case. We also do an unconditional take over, when the owner
721 * This is safe as we are protected by the hash bucket lock !
723 if (unlikely(ownerdied
|| !(curval
& FUTEX_TID_MASK
))) {
724 /* Keep the OWNER_DIED bit */
725 newval
= (curval
& ~FUTEX_TID_MASK
) | vpid
;
730 if (unlikely(cmpxchg_futex_value_locked(&curval
, uaddr
, uval
, newval
)))
732 if (unlikely(curval
!= uval
))
736 * We took the lock due to owner died take over.
738 if (unlikely(lock_taken
))
742 * We dont have the lock. Look up the PI state (or create it if
743 * we are the first waiter):
745 ret
= lookup_pi_state(uval
, hb
, key
, ps
);
751 * No owner found for this futex. Check if the
752 * OWNER_DIED bit is set to figure out whether
753 * this is a robust futex or not.
755 if (get_futex_value_locked(&curval
, uaddr
))
759 * We simply start over in case of a robust
760 * futex. The code above will take the futex
763 if (curval
& FUTEX_OWNER_DIED
) {
776 * The hash bucket lock must be held when this is called.
777 * Afterwards, the futex_q must not be accessed.
779 static void wake_futex(struct futex_q
*q
)
781 struct task_struct
*p
= q
->task
;
784 * We set q->lock_ptr = NULL _before_ we wake up the task. If
785 * a non-futex wake up happens on another CPU then the task
786 * might exit and p would dereference a non-existing task
787 * struct. Prevent this by holding a reference on p across the
792 plist_del(&q
->list
, &q
->list
.plist
);
794 * The waiting task can free the futex_q as soon as
795 * q->lock_ptr = NULL is written, without taking any locks. A
796 * memory barrier is required here to prevent the following
797 * store to lock_ptr from getting ahead of the plist_del.
802 wake_up_state(p
, TASK_NORMAL
);
806 static int wake_futex_pi(u32 __user
*uaddr
, u32 uval
, struct futex_q
*this)
808 struct task_struct
*new_owner
;
809 struct futex_pi_state
*pi_state
= this->pi_state
;
816 * If current does not own the pi_state then the futex is
817 * inconsistent and user space fiddled with the futex value.
819 if (pi_state
->owner
!= current
)
822 raw_spin_lock(&pi_state
->pi_mutex
.wait_lock
);
823 new_owner
= rt_mutex_next_owner(&pi_state
->pi_mutex
);
826 * It is possible that the next waiter (the one that brought
827 * this owner to the kernel) timed out and is no longer
828 * waiting on the lock.
831 new_owner
= this->task
;
834 * We pass it to the next owner. (The WAITERS bit is always
835 * kept enabled while there is PI state around. We must also
836 * preserve the owner died bit.)
838 if (!(uval
& FUTEX_OWNER_DIED
)) {
841 newval
= FUTEX_WAITERS
| task_pid_vnr(new_owner
);
843 if (cmpxchg_futex_value_locked(&curval
, uaddr
, uval
, newval
))
845 else if (curval
!= uval
)
848 raw_spin_unlock(&pi_state
->pi_mutex
.wait_lock
);
853 raw_spin_lock_irq(&pi_state
->owner
->pi_lock
);
854 WARN_ON(list_empty(&pi_state
->list
));
855 list_del_init(&pi_state
->list
);
856 raw_spin_unlock_irq(&pi_state
->owner
->pi_lock
);
858 raw_spin_lock_irq(&new_owner
->pi_lock
);
859 WARN_ON(!list_empty(&pi_state
->list
));
860 list_add(&pi_state
->list
, &new_owner
->pi_state_list
);
861 pi_state
->owner
= new_owner
;
862 raw_spin_unlock_irq(&new_owner
->pi_lock
);
864 raw_spin_unlock(&pi_state
->pi_mutex
.wait_lock
);
865 rt_mutex_unlock(&pi_state
->pi_mutex
);
870 static int unlock_futex_pi(u32 __user
*uaddr
, u32 uval
)
875 * There is no waiter, so we unlock the futex. The owner died
876 * bit has not to be preserved here. We are the owner:
878 if (cmpxchg_futex_value_locked(&oldval
, uaddr
, uval
, 0))
887 * Express the locking dependencies for lockdep:
890 double_lock_hb(struct futex_hash_bucket
*hb1
, struct futex_hash_bucket
*hb2
)
893 spin_lock(&hb1
->lock
);
895 spin_lock_nested(&hb2
->lock
, SINGLE_DEPTH_NESTING
);
896 } else { /* hb1 > hb2 */
897 spin_lock(&hb2
->lock
);
898 spin_lock_nested(&hb1
->lock
, SINGLE_DEPTH_NESTING
);
903 double_unlock_hb(struct futex_hash_bucket
*hb1
, struct futex_hash_bucket
*hb2
)
905 spin_unlock(&hb1
->lock
);
907 spin_unlock(&hb2
->lock
);
911 * Wake up waiters matching bitset queued on this futex (uaddr).
914 futex_wake(u32 __user
*uaddr
, unsigned int flags
, int nr_wake
, u32 bitset
)
916 struct futex_hash_bucket
*hb
;
917 struct futex_q
*this, *next
;
918 struct plist_head
*head
;
919 union futex_key key
= FUTEX_KEY_INIT
;
925 ret
= get_futex_key(uaddr
, flags
& FLAGS_SHARED
, &key
);
926 if (unlikely(ret
!= 0))
929 hb
= hash_futex(&key
);
930 spin_lock(&hb
->lock
);
933 plist_for_each_entry_safe(this, next
, head
, list
) {
934 if (match_futex (&this->key
, &key
)) {
935 if (this->pi_state
|| this->rt_waiter
) {
940 /* Check if one of the bits is set in both bitsets */
941 if (!(this->bitset
& bitset
))
945 if (++ret
>= nr_wake
)
950 spin_unlock(&hb
->lock
);
957 * Wake up all waiters hashed on the physical page that is mapped
958 * to this virtual address:
961 futex_wake_op(u32 __user
*uaddr1
, unsigned int flags
, u32 __user
*uaddr2
,
962 int nr_wake
, int nr_wake2
, int op
)
964 union futex_key key1
= FUTEX_KEY_INIT
, key2
= FUTEX_KEY_INIT
;
965 struct futex_hash_bucket
*hb1
, *hb2
;
966 struct plist_head
*head
;
967 struct futex_q
*this, *next
;
971 ret
= get_futex_key(uaddr1
, flags
& FLAGS_SHARED
, &key1
);
972 if (unlikely(ret
!= 0))
974 ret
= get_futex_key(uaddr2
, flags
& FLAGS_SHARED
, &key2
);
975 if (unlikely(ret
!= 0))
978 hb1
= hash_futex(&key1
);
979 hb2
= hash_futex(&key2
);
982 double_lock_hb(hb1
, hb2
);
983 op_ret
= futex_atomic_op_inuser(op
, uaddr2
);
984 if (unlikely(op_ret
< 0)) {
986 double_unlock_hb(hb1
, hb2
);
990 * we don't get EFAULT from MMU faults if we don't have an MMU,
991 * but we might get them from range checking
997 if (unlikely(op_ret
!= -EFAULT
)) {
1002 ret
= fault_in_user_writeable(uaddr2
);
1006 if (!(flags
& FLAGS_SHARED
))
1009 put_futex_key(&key2
);
1010 put_futex_key(&key1
);
1016 plist_for_each_entry_safe(this, next
, head
, list
) {
1017 if (match_futex (&this->key
, &key1
)) {
1019 if (++ret
>= nr_wake
)
1028 plist_for_each_entry_safe(this, next
, head
, list
) {
1029 if (match_futex (&this->key
, &key2
)) {
1031 if (++op_ret
>= nr_wake2
)
1038 double_unlock_hb(hb1
, hb2
);
1040 put_futex_key(&key2
);
1042 put_futex_key(&key1
);
1048 * requeue_futex() - Requeue a futex_q from one hb to another
1049 * @q: the futex_q to requeue
1050 * @hb1: the source hash_bucket
1051 * @hb2: the target hash_bucket
1052 * @key2: the new key for the requeued futex_q
1055 void requeue_futex(struct futex_q
*q
, struct futex_hash_bucket
*hb1
,
1056 struct futex_hash_bucket
*hb2
, union futex_key
*key2
)
1060 * If key1 and key2 hash to the same bucket, no need to
1063 if (likely(&hb1
->chain
!= &hb2
->chain
)) {
1064 plist_del(&q
->list
, &hb1
->chain
);
1065 plist_add(&q
->list
, &hb2
->chain
);
1066 q
->lock_ptr
= &hb2
->lock
;
1067 #ifdef CONFIG_DEBUG_PI_LIST
1068 q
->list
.plist
.spinlock
= &hb2
->lock
;
1071 get_futex_key_refs(key2
);
1076 * requeue_pi_wake_futex() - Wake a task that acquired the lock during requeue
1078 * @key: the key of the requeue target futex
1079 * @hb: the hash_bucket of the requeue target futex
1081 * During futex_requeue, with requeue_pi=1, it is possible to acquire the
1082 * target futex if it is uncontended or via a lock steal. Set the futex_q key
1083 * to the requeue target futex so the waiter can detect the wakeup on the right
1084 * futex, but remove it from the hb and NULL the rt_waiter so it can detect
1085 * atomic lock acquisition. Set the q->lock_ptr to the requeue target hb->lock
1086 * to protect access to the pi_state to fixup the owner later. Must be called
1087 * with both q->lock_ptr and hb->lock held.
1090 void requeue_pi_wake_futex(struct futex_q
*q
, union futex_key
*key
,
1091 struct futex_hash_bucket
*hb
)
1093 get_futex_key_refs(key
);
1096 WARN_ON(plist_node_empty(&q
->list
));
1097 plist_del(&q
->list
, &q
->list
.plist
);
1099 WARN_ON(!q
->rt_waiter
);
1100 q
->rt_waiter
= NULL
;
1102 q
->lock_ptr
= &hb
->lock
;
1103 #ifdef CONFIG_DEBUG_PI_LIST
1104 q
->list
.plist
.spinlock
= &hb
->lock
;
1107 wake_up_state(q
->task
, TASK_NORMAL
);
1111 * futex_proxy_trylock_atomic() - Attempt an atomic lock for the top waiter
1112 * @pifutex: the user address of the to futex
1113 * @hb1: the from futex hash bucket, must be locked by the caller
1114 * @hb2: the to futex hash bucket, must be locked by the caller
1115 * @key1: the from futex key
1116 * @key2: the to futex key
1117 * @ps: address to store the pi_state pointer
1118 * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0)
1120 * Try and get the lock on behalf of the top waiter if we can do it atomically.
1121 * Wake the top waiter if we succeed. If the caller specified set_waiters,
1122 * then direct futex_lock_pi_atomic() to force setting the FUTEX_WAITERS bit.
1123 * hb1 and hb2 must be held by the caller.
1126 * 0 - failed to acquire the lock atomicly
1127 * 1 - acquired the lock
1130 static int futex_proxy_trylock_atomic(u32 __user
*pifutex
,
1131 struct futex_hash_bucket
*hb1
,
1132 struct futex_hash_bucket
*hb2
,
1133 union futex_key
*key1
, union futex_key
*key2
,
1134 struct futex_pi_state
**ps
, int set_waiters
)
1136 struct futex_q
*top_waiter
= NULL
;
1140 if (get_futex_value_locked(&curval
, pifutex
))
1144 * Find the top_waiter and determine if there are additional waiters.
1145 * If the caller intends to requeue more than 1 waiter to pifutex,
1146 * force futex_lock_pi_atomic() to set the FUTEX_WAITERS bit now,
1147 * as we have means to handle the possible fault. If not, don't set
1148 * the bit unecessarily as it will force the subsequent unlock to enter
1151 top_waiter
= futex_top_waiter(hb1
, key1
);
1153 /* There are no waiters, nothing for us to do. */
1157 /* Ensure we requeue to the expected futex. */
1158 if (!match_futex(top_waiter
->requeue_pi_key
, key2
))
1162 * Try to take the lock for top_waiter. Set the FUTEX_WAITERS bit in
1163 * the contended case or if set_waiters is 1. The pi_state is returned
1164 * in ps in contended cases.
1166 ret
= futex_lock_pi_atomic(pifutex
, hb2
, key2
, ps
, top_waiter
->task
,
1169 requeue_pi_wake_futex(top_waiter
, key2
, hb2
);
1175 * futex_requeue() - Requeue waiters from uaddr1 to uaddr2
1176 * @uaddr1: source futex user address
1177 * @flags: futex flags (FLAGS_SHARED, etc.)
1178 * @uaddr2: target futex user address
1179 * @nr_wake: number of waiters to wake (must be 1 for requeue_pi)
1180 * @nr_requeue: number of waiters to requeue (0-INT_MAX)
1181 * @cmpval: @uaddr1 expected value (or %NULL)
1182 * @requeue_pi: if we are attempting to requeue from a non-pi futex to a
1183 * pi futex (pi to pi requeue is not supported)
1185 * Requeue waiters on uaddr1 to uaddr2. In the requeue_pi case, try to acquire
1186 * uaddr2 atomically on behalf of the top waiter.
1189 * >=0 - on success, the number of tasks requeued or woken
1192 static int futex_requeue(u32 __user
*uaddr1
, unsigned int flags
,
1193 u32 __user
*uaddr2
, int nr_wake
, int nr_requeue
,
1194 u32
*cmpval
, int requeue_pi
)
1196 union futex_key key1
= FUTEX_KEY_INIT
, key2
= FUTEX_KEY_INIT
;
1197 int drop_count
= 0, task_count
= 0, ret
;
1198 struct futex_pi_state
*pi_state
= NULL
;
1199 struct futex_hash_bucket
*hb1
, *hb2
;
1200 struct plist_head
*head1
;
1201 struct futex_q
*this, *next
;
1206 * requeue_pi requires a pi_state, try to allocate it now
1207 * without any locks in case it fails.
1209 if (refill_pi_state_cache())
1212 * requeue_pi must wake as many tasks as it can, up to nr_wake
1213 * + nr_requeue, since it acquires the rt_mutex prior to
1214 * returning to userspace, so as to not leave the rt_mutex with
1215 * waiters and no owner. However, second and third wake-ups
1216 * cannot be predicted as they involve race conditions with the
1217 * first wake and a fault while looking up the pi_state. Both
1218 * pthread_cond_signal() and pthread_cond_broadcast() should
1226 if (pi_state
!= NULL
) {
1228 * We will have to lookup the pi_state again, so free this one
1229 * to keep the accounting correct.
1231 free_pi_state(pi_state
);
1235 ret
= get_futex_key(uaddr1
, flags
& FLAGS_SHARED
, &key1
);
1236 if (unlikely(ret
!= 0))
1238 ret
= get_futex_key(uaddr2
, flags
& FLAGS_SHARED
, &key2
);
1239 if (unlikely(ret
!= 0))
1242 hb1
= hash_futex(&key1
);
1243 hb2
= hash_futex(&key2
);
1246 double_lock_hb(hb1
, hb2
);
1248 if (likely(cmpval
!= NULL
)) {
1251 ret
= get_futex_value_locked(&curval
, uaddr1
);
1253 if (unlikely(ret
)) {
1254 double_unlock_hb(hb1
, hb2
);
1256 ret
= get_user(curval
, uaddr1
);
1260 if (!(flags
& FLAGS_SHARED
))
1263 put_futex_key(&key2
);
1264 put_futex_key(&key1
);
1267 if (curval
!= *cmpval
) {
1273 if (requeue_pi
&& (task_count
- nr_wake
< nr_requeue
)) {
1275 * Attempt to acquire uaddr2 and wake the top waiter. If we
1276 * intend to requeue waiters, force setting the FUTEX_WAITERS
1277 * bit. We force this here where we are able to easily handle
1278 * faults rather in the requeue loop below.
1280 ret
= futex_proxy_trylock_atomic(uaddr2
, hb1
, hb2
, &key1
,
1281 &key2
, &pi_state
, nr_requeue
);
1284 * At this point the top_waiter has either taken uaddr2 or is
1285 * waiting on it. If the former, then the pi_state will not
1286 * exist yet, look it up one more time to ensure we have a
1293 ret
= get_futex_value_locked(&curval2
, uaddr2
);
1295 ret
= lookup_pi_state(curval2
, hb2
, &key2
,
1303 double_unlock_hb(hb1
, hb2
);
1304 put_futex_key(&key2
);
1305 put_futex_key(&key1
);
1306 ret
= fault_in_user_writeable(uaddr2
);
1311 /* The owner was exiting, try again. */
1312 double_unlock_hb(hb1
, hb2
);
1313 put_futex_key(&key2
);
1314 put_futex_key(&key1
);
1322 head1
= &hb1
->chain
;
1323 plist_for_each_entry_safe(this, next
, head1
, list
) {
1324 if (task_count
- nr_wake
>= nr_requeue
)
1327 if (!match_futex(&this->key
, &key1
))
1331 * FUTEX_WAIT_REQEUE_PI and FUTEX_CMP_REQUEUE_PI should always
1332 * be paired with each other and no other futex ops.
1334 if ((requeue_pi
&& !this->rt_waiter
) ||
1335 (!requeue_pi
&& this->rt_waiter
)) {
1341 * Wake nr_wake waiters. For requeue_pi, if we acquired the
1342 * lock, we already woke the top_waiter. If not, it will be
1343 * woken by futex_unlock_pi().
1345 if (++task_count
<= nr_wake
&& !requeue_pi
) {
1350 /* Ensure we requeue to the expected futex for requeue_pi. */
1351 if (requeue_pi
&& !match_futex(this->requeue_pi_key
, &key2
)) {
1357 * Requeue nr_requeue waiters and possibly one more in the case
1358 * of requeue_pi if we couldn't acquire the lock atomically.
1361 /* Prepare the waiter to take the rt_mutex. */
1362 atomic_inc(&pi_state
->refcount
);
1363 this->pi_state
= pi_state
;
1364 ret
= rt_mutex_start_proxy_lock(&pi_state
->pi_mutex
,
1368 /* We got the lock. */
1369 requeue_pi_wake_futex(this, &key2
, hb2
);
1374 this->pi_state
= NULL
;
1375 free_pi_state(pi_state
);
1379 requeue_futex(this, hb1
, hb2
, &key2
);
1384 double_unlock_hb(hb1
, hb2
);
1387 * drop_futex_key_refs() must be called outside the spinlocks. During
1388 * the requeue we moved futex_q's from the hash bucket at key1 to the
1389 * one at key2 and updated their key pointer. We no longer need to
1390 * hold the references to key1.
1392 while (--drop_count
>= 0)
1393 drop_futex_key_refs(&key1
);
1396 put_futex_key(&key2
);
1398 put_futex_key(&key1
);
1400 if (pi_state
!= NULL
)
1401 free_pi_state(pi_state
);
1402 return ret
? ret
: task_count
;
1405 /* The key must be already stored in q->key. */
1406 static inline struct futex_hash_bucket
*queue_lock(struct futex_q
*q
)
1407 __acquires(&hb
->lock
)
1409 struct futex_hash_bucket
*hb
;
1411 hb
= hash_futex(&q
->key
);
1412 q
->lock_ptr
= &hb
->lock
;
1414 spin_lock(&hb
->lock
);
1419 queue_unlock(struct futex_q
*q
, struct futex_hash_bucket
*hb
)
1420 __releases(&hb
->lock
)
1422 spin_unlock(&hb
->lock
);
1426 * queue_me() - Enqueue the futex_q on the futex_hash_bucket
1427 * @q: The futex_q to enqueue
1428 * @hb: The destination hash bucket
1430 * The hb->lock must be held by the caller, and is released here. A call to
1431 * queue_me() is typically paired with exactly one call to unqueue_me(). The
1432 * exceptions involve the PI related operations, which may use unqueue_me_pi()
1433 * or nothing if the unqueue is done as part of the wake process and the unqueue
1434 * state is implicit in the state of woken task (see futex_wait_requeue_pi() for
1437 static inline void queue_me(struct futex_q
*q
, struct futex_hash_bucket
*hb
)
1438 __releases(&hb
->lock
)
1443 * The priority used to register this element is
1444 * - either the real thread-priority for the real-time threads
1445 * (i.e. threads with a priority lower than MAX_RT_PRIO)
1446 * - or MAX_RT_PRIO for non-RT threads.
1447 * Thus, all RT-threads are woken first in priority order, and
1448 * the others are woken last, in FIFO order.
1450 prio
= min(current
->normal_prio
, MAX_RT_PRIO
);
1452 plist_node_init(&q
->list
, prio
);
1453 #ifdef CONFIG_DEBUG_PI_LIST
1454 q
->list
.plist
.spinlock
= &hb
->lock
;
1456 plist_add(&q
->list
, &hb
->chain
);
1458 spin_unlock(&hb
->lock
);
1462 * unqueue_me() - Remove the futex_q from its futex_hash_bucket
1463 * @q: The futex_q to unqueue
1465 * The q->lock_ptr must not be held by the caller. A call to unqueue_me() must
1466 * be paired with exactly one earlier call to queue_me().
1469 * 1 - if the futex_q was still queued (and we removed unqueued it)
1470 * 0 - if the futex_q was already removed by the waking thread
1472 static int unqueue_me(struct futex_q
*q
)
1474 spinlock_t
*lock_ptr
;
1477 /* In the common case we don't take the spinlock, which is nice. */
1479 lock_ptr
= q
->lock_ptr
;
1481 if (lock_ptr
!= NULL
) {
1482 spin_lock(lock_ptr
);
1484 * q->lock_ptr can change between reading it and
1485 * spin_lock(), causing us to take the wrong lock. This
1486 * corrects the race condition.
1488 * Reasoning goes like this: if we have the wrong lock,
1489 * q->lock_ptr must have changed (maybe several times)
1490 * between reading it and the spin_lock(). It can
1491 * change again after the spin_lock() but only if it was
1492 * already changed before the spin_lock(). It cannot,
1493 * however, change back to the original value. Therefore
1494 * we can detect whether we acquired the correct lock.
1496 if (unlikely(lock_ptr
!= q
->lock_ptr
)) {
1497 spin_unlock(lock_ptr
);
1500 WARN_ON(plist_node_empty(&q
->list
));
1501 plist_del(&q
->list
, &q
->list
.plist
);
1503 BUG_ON(q
->pi_state
);
1505 spin_unlock(lock_ptr
);
1509 drop_futex_key_refs(&q
->key
);
1514 * PI futexes can not be requeued and must remove themself from the
1515 * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry
1518 static void unqueue_me_pi(struct futex_q
*q
)
1519 __releases(q
->lock_ptr
)
1521 WARN_ON(plist_node_empty(&q
->list
));
1522 plist_del(&q
->list
, &q
->list
.plist
);
1524 BUG_ON(!q
->pi_state
);
1525 free_pi_state(q
->pi_state
);
1528 spin_unlock(q
->lock_ptr
);
1532 * Fixup the pi_state owner with the new owner.
1534 * Must be called with hash bucket lock held and mm->sem held for non
1537 static int fixup_pi_state_owner(u32 __user
*uaddr
, struct futex_q
*q
,
1538 struct task_struct
*newowner
)
1540 u32 newtid
= task_pid_vnr(newowner
) | FUTEX_WAITERS
;
1541 struct futex_pi_state
*pi_state
= q
->pi_state
;
1542 struct task_struct
*oldowner
= pi_state
->owner
;
1543 u32 uval
, curval
, newval
;
1547 if (!pi_state
->owner
)
1548 newtid
|= FUTEX_OWNER_DIED
;
1551 * We are here either because we stole the rtmutex from the
1552 * pending owner or we are the pending owner which failed to
1553 * get the rtmutex. We have to replace the pending owner TID
1554 * in the user space variable. This must be atomic as we have
1555 * to preserve the owner died bit here.
1557 * Note: We write the user space value _before_ changing the pi_state
1558 * because we can fault here. Imagine swapped out pages or a fork
1559 * that marked all the anonymous memory readonly for cow.
1561 * Modifying pi_state _before_ the user space value would
1562 * leave the pi_state in an inconsistent state when we fault
1563 * here, because we need to drop the hash bucket lock to
1564 * handle the fault. This might be observed in the PID check
1565 * in lookup_pi_state.
1568 if (get_futex_value_locked(&uval
, uaddr
))
1572 newval
= (uval
& FUTEX_OWNER_DIED
) | newtid
;
1574 if (cmpxchg_futex_value_locked(&curval
, uaddr
, uval
, newval
))
1582 * We fixed up user space. Now we need to fix the pi_state
1585 if (pi_state
->owner
!= NULL
) {
1586 raw_spin_lock_irq(&pi_state
->owner
->pi_lock
);
1587 WARN_ON(list_empty(&pi_state
->list
));
1588 list_del_init(&pi_state
->list
);
1589 raw_spin_unlock_irq(&pi_state
->owner
->pi_lock
);
1592 pi_state
->owner
= newowner
;
1594 raw_spin_lock_irq(&newowner
->pi_lock
);
1595 WARN_ON(!list_empty(&pi_state
->list
));
1596 list_add(&pi_state
->list
, &newowner
->pi_state_list
);
1597 raw_spin_unlock_irq(&newowner
->pi_lock
);
1601 * To handle the page fault we need to drop the hash bucket
1602 * lock here. That gives the other task (either the pending
1603 * owner itself or the task which stole the rtmutex) the
1604 * chance to try the fixup of the pi_state. So once we are
1605 * back from handling the fault we need to check the pi_state
1606 * after reacquiring the hash bucket lock and before trying to
1607 * do another fixup. When the fixup has been done already we
1611 spin_unlock(q
->lock_ptr
);
1613 ret
= fault_in_user_writeable(uaddr
);
1615 spin_lock(q
->lock_ptr
);
1618 * Check if someone else fixed it for us:
1620 if (pi_state
->owner
!= oldowner
)
1629 static long futex_wait_restart(struct restart_block
*restart
);
1632 * fixup_owner() - Post lock pi_state and corner case management
1633 * @uaddr: user address of the futex
1634 * @q: futex_q (contains pi_state and access to the rt_mutex)
1635 * @locked: if the attempt to take the rt_mutex succeeded (1) or not (0)
1637 * After attempting to lock an rt_mutex, this function is called to cleanup
1638 * the pi_state owner as well as handle race conditions that may allow us to
1639 * acquire the lock. Must be called with the hb lock held.
1642 * 1 - success, lock taken
1643 * 0 - success, lock not taken
1644 * <0 - on error (-EFAULT)
1646 static int fixup_owner(u32 __user
*uaddr
, struct futex_q
*q
, int locked
)
1648 struct task_struct
*owner
;
1653 * Got the lock. We might not be the anticipated owner if we
1654 * did a lock-steal - fix up the PI-state in that case:
1656 if (q
->pi_state
->owner
!= current
)
1657 ret
= fixup_pi_state_owner(uaddr
, q
, current
);
1662 * Catch the rare case, where the lock was released when we were on the
1663 * way back before we locked the hash bucket.
1665 if (q
->pi_state
->owner
== current
) {
1667 * Try to get the rt_mutex now. This might fail as some other
1668 * task acquired the rt_mutex after we removed ourself from the
1669 * rt_mutex waiters list.
1671 if (rt_mutex_trylock(&q
->pi_state
->pi_mutex
)) {
1677 * pi_state is incorrect, some other task did a lock steal and
1678 * we returned due to timeout or signal without taking the
1679 * rt_mutex. Too late. We can access the rt_mutex_owner without
1680 * locking, as the other task is now blocked on the hash bucket
1681 * lock. Fix the state up.
1683 owner
= rt_mutex_owner(&q
->pi_state
->pi_mutex
);
1684 ret
= fixup_pi_state_owner(uaddr
, q
, owner
);
1689 * Paranoia check. If we did not take the lock, then we should not be
1690 * the owner, nor the pending owner, of the rt_mutex.
1692 if (rt_mutex_owner(&q
->pi_state
->pi_mutex
) == current
)
1693 printk(KERN_ERR
"fixup_owner: ret = %d pi-mutex: %p "
1694 "pi-state %p\n", ret
,
1695 q
->pi_state
->pi_mutex
.owner
,
1696 q
->pi_state
->owner
);
1699 return ret
? ret
: locked
;
1703 * futex_wait_queue_me() - queue_me() and wait for wakeup, timeout, or signal
1704 * @hb: the futex hash bucket, must be locked by the caller
1705 * @q: the futex_q to queue up on
1706 * @timeout: the prepared hrtimer_sleeper, or null for no timeout
1708 static void futex_wait_queue_me(struct futex_hash_bucket
*hb
, struct futex_q
*q
,
1709 struct hrtimer_sleeper
*timeout
)
1712 * The task state is guaranteed to be set before another task can
1713 * wake it. set_current_state() is implemented using set_mb() and
1714 * queue_me() calls spin_unlock() upon completion, both serializing
1715 * access to the hash list and forcing another memory barrier.
1717 set_current_state(TASK_INTERRUPTIBLE
);
1722 hrtimer_start_expires(&timeout
->timer
, HRTIMER_MODE_ABS
);
1723 if (!hrtimer_active(&timeout
->timer
))
1724 timeout
->task
= NULL
;
1728 * If we have been removed from the hash list, then another task
1729 * has tried to wake us, and we can skip the call to schedule().
1731 if (likely(!plist_node_empty(&q
->list
))) {
1733 * If the timer has already expired, current will already be
1734 * flagged for rescheduling. Only call schedule if there
1735 * is no timeout, or if it has yet to expire.
1737 if (!timeout
|| timeout
->task
)
1740 __set_current_state(TASK_RUNNING
);
1744 * futex_wait_setup() - Prepare to wait on a futex
1745 * @uaddr: the futex userspace address
1746 * @val: the expected value
1747 * @flags: futex flags (FLAGS_SHARED, etc.)
1748 * @q: the associated futex_q
1749 * @hb: storage for hash_bucket pointer to be returned to caller
1751 * Setup the futex_q and locate the hash_bucket. Get the futex value and
1752 * compare it with the expected value. Handle atomic faults internally.
1753 * Return with the hb lock held and a q.key reference on success, and unlocked
1754 * with no q.key reference on failure.
1757 * 0 - uaddr contains val and hb has been locked
1758 * <1 - -EFAULT or -EWOULDBLOCK (uaddr does not contain val) and hb is unlcoked
1760 static int futex_wait_setup(u32 __user
*uaddr
, u32 val
, unsigned int flags
,
1761 struct futex_q
*q
, struct futex_hash_bucket
**hb
)
1767 * Access the page AFTER the hash-bucket is locked.
1768 * Order is important:
1770 * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val);
1771 * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); }
1773 * The basic logical guarantee of a futex is that it blocks ONLY
1774 * if cond(var) is known to be true at the time of blocking, for
1775 * any cond. If we locked the hash-bucket after testing *uaddr, that
1776 * would open a race condition where we could block indefinitely with
1777 * cond(var) false, which would violate the guarantee.
1779 * On the other hand, we insert q and release the hash-bucket only
1780 * after testing *uaddr. This guarantees that futex_wait() will NOT
1781 * absorb a wakeup if *uaddr does not match the desired values
1782 * while the syscall executes.
1785 ret
= get_futex_key(uaddr
, flags
& FLAGS_SHARED
, &q
->key
);
1786 if (unlikely(ret
!= 0))
1790 *hb
= queue_lock(q
);
1792 ret
= get_futex_value_locked(&uval
, uaddr
);
1795 queue_unlock(q
, *hb
);
1797 ret
= get_user(uval
, uaddr
);
1801 if (!(flags
& FLAGS_SHARED
))
1804 put_futex_key(&q
->key
);
1809 queue_unlock(q
, *hb
);
1815 put_futex_key(&q
->key
);
1819 static int futex_wait(u32 __user
*uaddr
, unsigned int flags
, u32 val
,
1820 ktime_t
*abs_time
, u32 bitset
)
1822 struct hrtimer_sleeper timeout
, *to
= NULL
;
1823 struct restart_block
*restart
;
1824 struct futex_hash_bucket
*hb
;
1825 struct futex_q q
= futex_q_init
;
1835 hrtimer_init_on_stack(&to
->timer
, (flags
& FLAGS_CLOCKRT
) ?
1836 CLOCK_REALTIME
: CLOCK_MONOTONIC
,
1838 hrtimer_init_sleeper(to
, current
);
1839 hrtimer_set_expires_range_ns(&to
->timer
, *abs_time
,
1840 current
->timer_slack_ns
);
1845 * Prepare to wait on uaddr. On success, holds hb lock and increments
1848 ret
= futex_wait_setup(uaddr
, val
, flags
, &q
, &hb
);
1852 /* queue_me and wait for wakeup, timeout, or a signal. */
1853 futex_wait_queue_me(hb
, &q
, to
);
1855 /* If we were woken (and unqueued), we succeeded, whatever. */
1857 /* unqueue_me() drops q.key ref */
1858 if (!unqueue_me(&q
))
1861 if (to
&& !to
->task
)
1865 * We expect signal_pending(current), but we might be the
1866 * victim of a spurious wakeup as well.
1868 if (!signal_pending(current
))
1875 restart
= ¤t_thread_info()->restart_block
;
1876 restart
->fn
= futex_wait_restart
;
1877 restart
->futex
.uaddr
= uaddr
;
1878 restart
->futex
.val
= val
;
1879 restart
->futex
.time
= abs_time
->tv64
;
1880 restart
->futex
.bitset
= bitset
;
1881 restart
->futex
.flags
= flags
;
1883 ret
= -ERESTART_RESTARTBLOCK
;
1887 hrtimer_cancel(&to
->timer
);
1888 destroy_hrtimer_on_stack(&to
->timer
);
1894 static long futex_wait_restart(struct restart_block
*restart
)
1896 u32 __user
*uaddr
= restart
->futex
.uaddr
;
1897 ktime_t t
, *tp
= NULL
;
1899 if (restart
->futex
.flags
& FLAGS_HAS_TIMEOUT
) {
1900 t
.tv64
= restart
->futex
.time
;
1903 restart
->fn
= do_no_restart_syscall
;
1905 return (long)futex_wait(uaddr
, restart
->futex
.flags
,
1906 restart
->futex
.val
, tp
, restart
->futex
.bitset
);
1911 * Userspace tried a 0 -> TID atomic transition of the futex value
1912 * and failed. The kernel side here does the whole locking operation:
1913 * if there are waiters then it will block, it does PI, etc. (Due to
1914 * races the kernel might see a 0 value of the futex too.)
1916 static int futex_lock_pi(u32 __user
*uaddr
, unsigned int flags
, int detect
,
1917 ktime_t
*time
, int trylock
)
1919 struct hrtimer_sleeper timeout
, *to
= NULL
;
1920 struct futex_hash_bucket
*hb
;
1921 struct futex_q q
= futex_q_init
;
1924 if (refill_pi_state_cache())
1929 hrtimer_init_on_stack(&to
->timer
, CLOCK_REALTIME
,
1931 hrtimer_init_sleeper(to
, current
);
1932 hrtimer_set_expires(&to
->timer
, *time
);
1936 ret
= get_futex_key(uaddr
, flags
& FLAGS_SHARED
, &q
.key
);
1937 if (unlikely(ret
!= 0))
1941 hb
= queue_lock(&q
);
1943 ret
= futex_lock_pi_atomic(uaddr
, hb
, &q
.key
, &q
.pi_state
, current
, 0);
1944 if (unlikely(ret
)) {
1947 /* We got the lock. */
1949 goto out_unlock_put_key
;
1954 * Task is exiting and we just wait for the
1957 queue_unlock(&q
, hb
);
1958 put_futex_key(&q
.key
);
1962 goto out_unlock_put_key
;
1967 * Only actually queue now that the atomic ops are done:
1971 WARN_ON(!q
.pi_state
);
1973 * Block on the PI mutex:
1976 ret
= rt_mutex_timed_lock(&q
.pi_state
->pi_mutex
, to
, 1);
1978 ret
= rt_mutex_trylock(&q
.pi_state
->pi_mutex
);
1979 /* Fixup the trylock return value: */
1980 ret
= ret
? 0 : -EWOULDBLOCK
;
1983 spin_lock(q
.lock_ptr
);
1985 * Fixup the pi_state owner and possibly acquire the lock if we
1988 res
= fixup_owner(uaddr
, &q
, !ret
);
1990 * If fixup_owner() returned an error, proprogate that. If it acquired
1991 * the lock, clear our -ETIMEDOUT or -EINTR.
1994 ret
= (res
< 0) ? res
: 0;
1997 * If fixup_owner() faulted and was unable to handle the fault, unlock
1998 * it and return the fault to userspace.
2000 if (ret
&& (rt_mutex_owner(&q
.pi_state
->pi_mutex
) == current
))
2001 rt_mutex_unlock(&q
.pi_state
->pi_mutex
);
2003 /* Unqueue and drop the lock */
2009 queue_unlock(&q
, hb
);
2012 put_futex_key(&q
.key
);
2015 destroy_hrtimer_on_stack(&to
->timer
);
2016 return ret
!= -EINTR
? ret
: -ERESTARTNOINTR
;
2019 queue_unlock(&q
, hb
);
2021 ret
= fault_in_user_writeable(uaddr
);
2025 if (!(flags
& FLAGS_SHARED
))
2028 put_futex_key(&q
.key
);
2033 * Userspace attempted a TID -> 0 atomic transition, and failed.
2034 * This is the in-kernel slowpath: we look up the PI state (if any),
2035 * and do the rt-mutex unlock.
2037 static int futex_unlock_pi(u32 __user
*uaddr
, unsigned int flags
)
2039 struct futex_hash_bucket
*hb
;
2040 struct futex_q
*this, *next
;
2041 struct plist_head
*head
;
2042 union futex_key key
= FUTEX_KEY_INIT
;
2043 u32 uval
, vpid
= task_pid_vnr(current
);
2047 if (get_user(uval
, uaddr
))
2050 * We release only a lock we actually own:
2052 if ((uval
& FUTEX_TID_MASK
) != vpid
)
2055 ret
= get_futex_key(uaddr
, flags
& FLAGS_SHARED
, &key
);
2056 if (unlikely(ret
!= 0))
2059 hb
= hash_futex(&key
);
2060 spin_lock(&hb
->lock
);
2063 * To avoid races, try to do the TID -> 0 atomic transition
2064 * again. If it succeeds then we can return without waking
2067 if (!(uval
& FUTEX_OWNER_DIED
) &&
2068 cmpxchg_futex_value_locked(&uval
, uaddr
, vpid
, 0))
2071 * Rare case: we managed to release the lock atomically,
2072 * no need to wake anyone else up:
2074 if (unlikely(uval
== vpid
))
2078 * Ok, other tasks may need to be woken up - check waiters
2079 * and do the wakeup if necessary:
2083 plist_for_each_entry_safe(this, next
, head
, list
) {
2084 if (!match_futex (&this->key
, &key
))
2086 ret
= wake_futex_pi(uaddr
, uval
, this);
2088 * The atomic access to the futex value
2089 * generated a pagefault, so retry the
2090 * user-access and the wakeup:
2097 * No waiters - kernel unlocks the futex:
2099 if (!(uval
& FUTEX_OWNER_DIED
)) {
2100 ret
= unlock_futex_pi(uaddr
, uval
);
2106 spin_unlock(&hb
->lock
);
2107 put_futex_key(&key
);
2113 spin_unlock(&hb
->lock
);
2114 put_futex_key(&key
);
2116 ret
= fault_in_user_writeable(uaddr
);
2124 * handle_early_requeue_pi_wakeup() - Detect early wakeup on the initial futex
2125 * @hb: the hash_bucket futex_q was original enqueued on
2126 * @q: the futex_q woken while waiting to be requeued
2127 * @key2: the futex_key of the requeue target futex
2128 * @timeout: the timeout associated with the wait (NULL if none)
2130 * Detect if the task was woken on the initial futex as opposed to the requeue
2131 * target futex. If so, determine if it was a timeout or a signal that caused
2132 * the wakeup and return the appropriate error code to the caller. Must be
2133 * called with the hb lock held.
2136 * 0 - no early wakeup detected
2137 * <0 - -ETIMEDOUT or -ERESTARTNOINTR
2140 int handle_early_requeue_pi_wakeup(struct futex_hash_bucket
*hb
,
2141 struct futex_q
*q
, union futex_key
*key2
,
2142 struct hrtimer_sleeper
*timeout
)
2147 * With the hb lock held, we avoid races while we process the wakeup.
2148 * We only need to hold hb (and not hb2) to ensure atomicity as the
2149 * wakeup code can't change q.key from uaddr to uaddr2 if we hold hb.
2150 * It can't be requeued from uaddr2 to something else since we don't
2151 * support a PI aware source futex for requeue.
2153 if (!match_futex(&q
->key
, key2
)) {
2154 WARN_ON(q
->lock_ptr
&& (&hb
->lock
!= q
->lock_ptr
));
2156 * We were woken prior to requeue by a timeout or a signal.
2157 * Unqueue the futex_q and determine which it was.
2159 plist_del(&q
->list
, &q
->list
.plist
);
2161 /* Handle spurious wakeups gracefully */
2163 if (timeout
&& !timeout
->task
)
2165 else if (signal_pending(current
))
2166 ret
= -ERESTARTNOINTR
;
2172 * futex_wait_requeue_pi() - Wait on uaddr and take uaddr2
2173 * @uaddr: the futex we initially wait on (non-pi)
2174 * @flags: futex flags (FLAGS_SHARED, FLAGS_CLOCKRT, etc.), they must be
2175 * the same type, no requeueing from private to shared, etc.
2176 * @val: the expected value of uaddr
2177 * @abs_time: absolute timeout
2178 * @bitset: 32 bit wakeup bitset set by userspace, defaults to all
2179 * @clockrt: whether to use CLOCK_REALTIME (1) or CLOCK_MONOTONIC (0)
2180 * @uaddr2: the pi futex we will take prior to returning to user-space
2182 * The caller will wait on uaddr and will be requeued by futex_requeue() to
2183 * uaddr2 which must be PI aware. Normal wakeup will wake on uaddr2 and
2184 * complete the acquisition of the rt_mutex prior to returning to userspace.
2185 * This ensures the rt_mutex maintains an owner when it has waiters; without
2186 * one, the pi logic wouldn't know which task to boost/deboost, if there was a
2189 * We call schedule in futex_wait_queue_me() when we enqueue and return there
2190 * via the following:
2191 * 1) wakeup on uaddr2 after an atomic lock acquisition by futex_requeue()
2192 * 2) wakeup on uaddr2 after a requeue
2196 * If 3, cleanup and return -ERESTARTNOINTR.
2198 * If 2, we may then block on trying to take the rt_mutex and return via:
2199 * 5) successful lock
2202 * 8) other lock acquisition failure
2204 * If 6, return -EWOULDBLOCK (restarting the syscall would do the same).
2206 * If 4 or 7, we cleanup and return with -ETIMEDOUT.
2212 static int futex_wait_requeue_pi(u32 __user
*uaddr
, unsigned int flags
,
2213 u32 val
, ktime_t
*abs_time
, u32 bitset
,
2216 struct hrtimer_sleeper timeout
, *to
= NULL
;
2217 struct rt_mutex_waiter rt_waiter
;
2218 struct rt_mutex
*pi_mutex
= NULL
;
2219 struct futex_hash_bucket
*hb
;
2220 union futex_key key2
= FUTEX_KEY_INIT
;
2221 struct futex_q q
= futex_q_init
;
2229 hrtimer_init_on_stack(&to
->timer
, (flags
& FLAGS_CLOCKRT
) ?
2230 CLOCK_REALTIME
: CLOCK_MONOTONIC
,
2232 hrtimer_init_sleeper(to
, current
);
2233 hrtimer_set_expires_range_ns(&to
->timer
, *abs_time
,
2234 current
->timer_slack_ns
);
2238 * The waiter is allocated on our stack, manipulated by the requeue
2239 * code while we sleep on uaddr.
2241 debug_rt_mutex_init_waiter(&rt_waiter
);
2242 rt_waiter
.task
= NULL
;
2244 ret
= get_futex_key(uaddr2
, flags
& FLAGS_SHARED
, &key2
);
2245 if (unlikely(ret
!= 0))
2249 q
.rt_waiter
= &rt_waiter
;
2250 q
.requeue_pi_key
= &key2
;
2253 * Prepare to wait on uaddr. On success, increments q.key (key1) ref
2256 ret
= futex_wait_setup(uaddr
, val
, flags
, &q
, &hb
);
2260 /* Queue the futex_q, drop the hb lock, wait for wakeup. */
2261 futex_wait_queue_me(hb
, &q
, to
);
2263 spin_lock(&hb
->lock
);
2264 ret
= handle_early_requeue_pi_wakeup(hb
, &q
, &key2
, to
);
2265 spin_unlock(&hb
->lock
);
2270 * In order for us to be here, we know our q.key == key2, and since
2271 * we took the hb->lock above, we also know that futex_requeue() has
2272 * completed and we no longer have to concern ourselves with a wakeup
2273 * race with the atomic proxy lock acquisition by the requeue code. The
2274 * futex_requeue dropped our key1 reference and incremented our key2
2278 /* Check if the requeue code acquired the second futex for us. */
2281 * Got the lock. We might not be the anticipated owner if we
2282 * did a lock-steal - fix up the PI-state in that case.
2284 if (q
.pi_state
&& (q
.pi_state
->owner
!= current
)) {
2285 spin_lock(q
.lock_ptr
);
2286 ret
= fixup_pi_state_owner(uaddr2
, &q
, current
);
2287 spin_unlock(q
.lock_ptr
);
2291 * We have been woken up by futex_unlock_pi(), a timeout, or a
2292 * signal. futex_unlock_pi() will not destroy the lock_ptr nor
2295 WARN_ON(!&q
.pi_state
);
2296 pi_mutex
= &q
.pi_state
->pi_mutex
;
2297 ret
= rt_mutex_finish_proxy_lock(pi_mutex
, to
, &rt_waiter
, 1);
2298 debug_rt_mutex_free_waiter(&rt_waiter
);
2300 spin_lock(q
.lock_ptr
);
2302 * Fixup the pi_state owner and possibly acquire the lock if we
2305 res
= fixup_owner(uaddr2
, &q
, !ret
);
2307 * If fixup_owner() returned an error, proprogate that. If it
2308 * acquired the lock, clear -ETIMEDOUT or -EINTR.
2311 ret
= (res
< 0) ? res
: 0;
2313 /* Unqueue and drop the lock. */
2318 * If fixup_pi_state_owner() faulted and was unable to handle the
2319 * fault, unlock the rt_mutex and return the fault to userspace.
2321 if (ret
== -EFAULT
) {
2322 if (rt_mutex_owner(pi_mutex
) == current
)
2323 rt_mutex_unlock(pi_mutex
);
2324 } else if (ret
== -EINTR
) {
2326 * We've already been requeued, but cannot restart by calling
2327 * futex_lock_pi() directly. We could restart this syscall, but
2328 * it would detect that the user space "val" changed and return
2329 * -EWOULDBLOCK. Save the overhead of the restart and return
2330 * -EWOULDBLOCK directly.
2336 put_futex_key(&q
.key
);
2338 put_futex_key(&key2
);
2342 hrtimer_cancel(&to
->timer
);
2343 destroy_hrtimer_on_stack(&to
->timer
);
2349 * Support for robust futexes: the kernel cleans up held futexes at
2352 * Implementation: user-space maintains a per-thread list of locks it
2353 * is holding. Upon do_exit(), the kernel carefully walks this list,
2354 * and marks all locks that are owned by this thread with the
2355 * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is
2356 * always manipulated with the lock held, so the list is private and
2357 * per-thread. Userspace also maintains a per-thread 'list_op_pending'
2358 * field, to allow the kernel to clean up if the thread dies after
2359 * acquiring the lock, but just before it could have added itself to
2360 * the list. There can only be one such pending lock.
2364 * sys_set_robust_list() - Set the robust-futex list head of a task
2365 * @head: pointer to the list-head
2366 * @len: length of the list-head, as userspace expects
2368 SYSCALL_DEFINE2(set_robust_list
, struct robust_list_head __user
*, head
,
2371 if (!futex_cmpxchg_enabled
)
2374 * The kernel knows only one size for now:
2376 if (unlikely(len
!= sizeof(*head
)))
2379 current
->robust_list
= head
;
2385 * sys_get_robust_list() - Get the robust-futex list head of a task
2386 * @pid: pid of the process [zero for current task]
2387 * @head_ptr: pointer to a list-head pointer, the kernel fills it in
2388 * @len_ptr: pointer to a length field, the kernel fills in the header size
2390 SYSCALL_DEFINE3(get_robust_list
, int, pid
,
2391 struct robust_list_head __user
* __user
*, head_ptr
,
2392 size_t __user
*, len_ptr
)
2394 struct robust_list_head __user
*head
;
2396 const struct cred
*cred
= current_cred(), *pcred
;
2398 if (!futex_cmpxchg_enabled
)
2402 head
= current
->robust_list
;
2404 struct task_struct
*p
;
2408 p
= find_task_by_vpid(pid
);
2412 pcred
= __task_cred(p
);
2413 if (cred
->euid
!= pcred
->euid
&&
2414 cred
->euid
!= pcred
->uid
&&
2415 !capable(CAP_SYS_PTRACE
))
2417 head
= p
->robust_list
;
2421 if (put_user(sizeof(*head
), len_ptr
))
2423 return put_user(head
, head_ptr
);
2432 * Process a futex-list entry, check whether it's owned by the
2433 * dying task, and do notification if so:
2435 int handle_futex_death(u32 __user
*uaddr
, struct task_struct
*curr
, int pi
)
2437 u32 uval
, nval
, mval
;
2440 if (get_user(uval
, uaddr
))
2443 if ((uval
& FUTEX_TID_MASK
) == task_pid_vnr(curr
)) {
2445 * Ok, this dying thread is truly holding a futex
2446 * of interest. Set the OWNER_DIED bit atomically
2447 * via cmpxchg, and if the value had FUTEX_WAITERS
2448 * set, wake up a waiter (if any). (We have to do a
2449 * futex_wake() even if OWNER_DIED is already set -
2450 * to handle the rare but possible case of recursive
2451 * thread-death.) The rest of the cleanup is done in
2454 mval
= (uval
& FUTEX_WAITERS
) | FUTEX_OWNER_DIED
;
2455 if (futex_atomic_cmpxchg_inatomic(&nval
, uaddr
, uval
, mval
))
2462 * Wake robust non-PI futexes here. The wakeup of
2463 * PI futexes happens in exit_pi_state():
2465 if (!pi
&& (uval
& FUTEX_WAITERS
))
2466 futex_wake(uaddr
, 1, 1, FUTEX_BITSET_MATCH_ANY
);
2472 * Fetch a robust-list pointer. Bit 0 signals PI futexes:
2474 static inline int fetch_robust_entry(struct robust_list __user
**entry
,
2475 struct robust_list __user
* __user
*head
,
2478 unsigned long uentry
;
2480 if (get_user(uentry
, (unsigned long __user
*)head
))
2483 *entry
= (void __user
*)(uentry
& ~1UL);
2490 * Walk curr->robust_list (very carefully, it's a userspace list!)
2491 * and mark any locks found there dead, and notify any waiters.
2493 * We silently return on any sign of list-walking problem.
2495 void exit_robust_list(struct task_struct
*curr
)
2497 struct robust_list_head __user
*head
= curr
->robust_list
;
2498 struct robust_list __user
*entry
, *next_entry
, *pending
;
2499 unsigned int limit
= ROBUST_LIST_LIMIT
, pi
, pip
;
2500 unsigned int uninitialized_var(next_pi
);
2501 unsigned long futex_offset
;
2504 if (!futex_cmpxchg_enabled
)
2508 * Fetch the list head (which was registered earlier, via
2509 * sys_set_robust_list()):
2511 if (fetch_robust_entry(&entry
, &head
->list
.next
, &pi
))
2514 * Fetch the relative futex offset:
2516 if (get_user(futex_offset
, &head
->futex_offset
))
2519 * Fetch any possibly pending lock-add first, and handle it
2522 if (fetch_robust_entry(&pending
, &head
->list_op_pending
, &pip
))
2525 next_entry
= NULL
; /* avoid warning with gcc */
2526 while (entry
!= &head
->list
) {
2528 * Fetch the next entry in the list before calling
2529 * handle_futex_death:
2531 rc
= fetch_robust_entry(&next_entry
, &entry
->next
, &next_pi
);
2533 * A pending lock might already be on the list, so
2534 * don't process it twice:
2536 if (entry
!= pending
)
2537 if (handle_futex_death((void __user
*)entry
+ futex_offset
,
2545 * Avoid excessively long or circular lists:
2554 handle_futex_death((void __user
*)pending
+ futex_offset
,
2558 long do_futex(u32 __user
*uaddr
, int op
, u32 val
, ktime_t
*timeout
,
2559 u32 __user
*uaddr2
, u32 val2
, u32 val3
)
2561 int ret
= -ENOSYS
, cmd
= op
& FUTEX_CMD_MASK
;
2562 unsigned int flags
= 0;
2564 if (!(op
& FUTEX_PRIVATE_FLAG
))
2565 flags
|= FLAGS_SHARED
;
2567 if (op
& FUTEX_CLOCK_REALTIME
) {
2568 flags
|= FLAGS_CLOCKRT
;
2569 if (cmd
!= FUTEX_WAIT_BITSET
&& cmd
!= FUTEX_WAIT_REQUEUE_PI
)
2575 val3
= FUTEX_BITSET_MATCH_ANY
;
2576 case FUTEX_WAIT_BITSET
:
2577 ret
= futex_wait(uaddr
, flags
, val
, timeout
, val3
);
2580 val3
= FUTEX_BITSET_MATCH_ANY
;
2581 case FUTEX_WAKE_BITSET
:
2582 ret
= futex_wake(uaddr
, flags
, val
, val3
);
2585 ret
= futex_requeue(uaddr
, flags
, uaddr2
, val
, val2
, NULL
, 0);
2587 case FUTEX_CMP_REQUEUE
:
2588 ret
= futex_requeue(uaddr
, flags
, uaddr2
, val
, val2
, &val3
, 0);
2591 ret
= futex_wake_op(uaddr
, flags
, uaddr2
, val
, val2
, val3
);
2594 if (futex_cmpxchg_enabled
)
2595 ret
= futex_lock_pi(uaddr
, flags
, val
, timeout
, 0);
2597 case FUTEX_UNLOCK_PI
:
2598 if (futex_cmpxchg_enabled
)
2599 ret
= futex_unlock_pi(uaddr
, flags
);
2601 case FUTEX_TRYLOCK_PI
:
2602 if (futex_cmpxchg_enabled
)
2603 ret
= futex_lock_pi(uaddr
, flags
, 0, timeout
, 1);
2605 case FUTEX_WAIT_REQUEUE_PI
:
2606 val3
= FUTEX_BITSET_MATCH_ANY
;
2607 ret
= futex_wait_requeue_pi(uaddr
, flags
, val
, timeout
, val3
,
2610 case FUTEX_CMP_REQUEUE_PI
:
2611 ret
= futex_requeue(uaddr
, flags
, uaddr2
, val
, val2
, &val3
, 1);
2620 SYSCALL_DEFINE6(futex
, u32 __user
*, uaddr
, int, op
, u32
, val
,
2621 struct timespec __user
*, utime
, u32 __user
*, uaddr2
,
2625 ktime_t t
, *tp
= NULL
;
2627 int cmd
= op
& FUTEX_CMD_MASK
;
2629 if (utime
&& (cmd
== FUTEX_WAIT
|| cmd
== FUTEX_LOCK_PI
||
2630 cmd
== FUTEX_WAIT_BITSET
||
2631 cmd
== FUTEX_WAIT_REQUEUE_PI
)) {
2632 if (copy_from_user(&ts
, utime
, sizeof(ts
)) != 0)
2634 if (!timespec_valid(&ts
))
2637 t
= timespec_to_ktime(ts
);
2638 if (cmd
== FUTEX_WAIT
)
2639 t
= ktime_add_safe(ktime_get(), t
);
2643 * requeue parameter in 'utime' if cmd == FUTEX_*_REQUEUE_*.
2644 * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP.
2646 if (cmd
== FUTEX_REQUEUE
|| cmd
== FUTEX_CMP_REQUEUE
||
2647 cmd
== FUTEX_CMP_REQUEUE_PI
|| cmd
== FUTEX_WAKE_OP
)
2648 val2
= (u32
) (unsigned long) utime
;
2650 return do_futex(uaddr
, op
, val
, tp
, uaddr2
, val2
, val3
);
2653 static int __init
futex_init(void)
2659 * This will fail and we want it. Some arch implementations do
2660 * runtime detection of the futex_atomic_cmpxchg_inatomic()
2661 * functionality. We want to know that before we call in any
2662 * of the complex code paths. Also we want to prevent
2663 * registration of robust lists in that case. NULL is
2664 * guaranteed to fault and we get -EFAULT on functional
2665 * implementation, the non-functional ones will return
2668 if (cmpxchg_futex_value_locked(&curval
, NULL
, 0, 0) == -EFAULT
)
2669 futex_cmpxchg_enabled
= 1;
2671 for (i
= 0; i
< ARRAY_SIZE(futex_queues
); i
++) {
2672 plist_head_init(&futex_queues
[i
].chain
, &futex_queues
[i
].lock
);
2673 spin_lock_init(&futex_queues
[i
].lock
);
2678 __initcall(futex_init
);