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/export.h>
59 #include <linux/magic.h>
60 #include <linux/pid.h>
61 #include <linux/nsproxy.h>
62 #include <linux/ptrace.h>
63 #include <linux/sched/rt.h>
64 #include <linux/hugetlb.h>
65 #include <linux/freezer.h>
67 #include <asm/futex.h>
69 #include "locking/rtmutex_common.h"
71 int __read_mostly futex_cmpxchg_enabled
;
73 #define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)
76 * Futex flags used to encode options to functions and preserve them across
79 #define FLAGS_SHARED 0x01
80 #define FLAGS_CLOCKRT 0x02
81 #define FLAGS_HAS_TIMEOUT 0x04
84 * Priority Inheritance state:
86 struct futex_pi_state
{
88 * list of 'owned' pi_state instances - these have to be
89 * cleaned up in do_exit() if the task exits prematurely:
91 struct list_head list
;
96 struct rt_mutex pi_mutex
;
98 struct task_struct
*owner
;
105 * struct futex_q - The hashed futex queue entry, one per waiting task
106 * @list: priority-sorted list of tasks waiting on this futex
107 * @task: the task waiting on the futex
108 * @lock_ptr: the hash bucket lock
109 * @key: the key the futex is hashed on
110 * @pi_state: optional priority inheritance state
111 * @rt_waiter: rt_waiter storage for use with requeue_pi
112 * @requeue_pi_key: the requeue_pi target futex key
113 * @bitset: bitset for the optional bitmasked wakeup
115 * We use this hashed waitqueue, instead of a normal wait_queue_t, so
116 * we can wake only the relevant ones (hashed queues may be shared).
118 * A futex_q has a woken state, just like tasks have TASK_RUNNING.
119 * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0.
120 * The order of wakeup is always to make the first condition true, then
123 * PI futexes are typically woken before they are removed from the hash list via
124 * the rt_mutex code. See unqueue_me_pi().
127 struct plist_node list
;
129 struct task_struct
*task
;
130 spinlock_t
*lock_ptr
;
132 struct futex_pi_state
*pi_state
;
133 struct rt_mutex_waiter
*rt_waiter
;
134 union futex_key
*requeue_pi_key
;
138 static const struct futex_q futex_q_init
= {
139 /* list gets initialized in queue_me()*/
140 .key
= FUTEX_KEY_INIT
,
141 .bitset
= FUTEX_BITSET_MATCH_ANY
145 * Hash buckets are shared by all the futex_keys that hash to the same
146 * location. Each key may have multiple futex_q structures, one for each task
147 * waiting on a futex.
149 struct futex_hash_bucket
{
151 struct plist_head chain
;
154 static struct futex_hash_bucket futex_queues
[1<<FUTEX_HASHBITS
];
157 * We hash on the keys returned from get_futex_key (see below).
159 static struct futex_hash_bucket
*hash_futex(union futex_key
*key
)
161 u32 hash
= jhash2((u32
*)&key
->both
.word
,
162 (sizeof(key
->both
.word
)+sizeof(key
->both
.ptr
))/4,
164 return &futex_queues
[hash
& ((1 << FUTEX_HASHBITS
)-1)];
168 * Return 1 if two futex_keys are equal, 0 otherwise.
170 static inline int match_futex(union futex_key
*key1
, union futex_key
*key2
)
173 && key1
->both
.word
== key2
->both
.word
174 && key1
->both
.ptr
== key2
->both
.ptr
175 && key1
->both
.offset
== key2
->both
.offset
);
179 * Take a reference to the resource addressed by a key.
180 * Can be called while holding spinlocks.
183 static void get_futex_key_refs(union futex_key
*key
)
188 switch (key
->both
.offset
& (FUT_OFF_INODE
|FUT_OFF_MMSHARED
)) {
190 ihold(key
->shared
.inode
);
192 case FUT_OFF_MMSHARED
:
193 atomic_inc(&key
->private.mm
->mm_count
);
199 * Drop a reference to the resource addressed by a key.
200 * The hash bucket spinlock must not be held.
202 static void drop_futex_key_refs(union futex_key
*key
)
204 if (!key
->both
.ptr
) {
205 /* If we're here then we tried to put a key we failed to get */
210 switch (key
->both
.offset
& (FUT_OFF_INODE
|FUT_OFF_MMSHARED
)) {
212 iput(key
->shared
.inode
);
214 case FUT_OFF_MMSHARED
:
215 mmdrop(key
->private.mm
);
221 * get_futex_key() - Get parameters which are the keys for a futex
222 * @uaddr: virtual address of the futex
223 * @fshared: 0 for a PROCESS_PRIVATE futex, 1 for PROCESS_SHARED
224 * @key: address where result is stored.
225 * @rw: mapping needs to be read/write (values: VERIFY_READ,
228 * Return: a negative error code or 0
230 * The key words are stored in *key on success.
232 * For shared mappings, it's (page->index, file_inode(vma->vm_file),
233 * offset_within_page). For private mappings, it's (uaddr, current->mm).
234 * We can usually work out the index without swapping in the page.
236 * lock_page() might sleep, the caller should not hold a spinlock.
239 get_futex_key(u32 __user
*uaddr
, int fshared
, union futex_key
*key
, int rw
)
241 unsigned long address
= (unsigned long)uaddr
;
242 struct mm_struct
*mm
= current
->mm
;
243 struct page
*page
, *page_head
;
247 * The futex address must be "naturally" aligned.
249 key
->both
.offset
= address
% PAGE_SIZE
;
250 if (unlikely((address
% sizeof(u32
)) != 0))
252 address
-= key
->both
.offset
;
254 if (unlikely(!access_ok(rw
, uaddr
, sizeof(u32
))))
258 * PROCESS_PRIVATE futexes are fast.
259 * As the mm cannot disappear under us and the 'key' only needs
260 * virtual address, we dont even have to find the underlying vma.
261 * Note : We do have to check 'uaddr' is a valid user address,
262 * but access_ok() should be faster than find_vma()
265 key
->private.mm
= mm
;
266 key
->private.address
= address
;
267 get_futex_key_refs(key
);
272 err
= get_user_pages_fast(address
, 1, 1, &page
);
274 * If write access is not required (eg. FUTEX_WAIT), try
275 * and get read-only access.
277 if (err
== -EFAULT
&& rw
== VERIFY_READ
) {
278 err
= get_user_pages_fast(address
, 1, 0, &page
);
286 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
288 if (unlikely(PageTail(page
))) {
290 /* serialize against __split_huge_page_splitting() */
292 if (likely(__get_user_pages_fast(address
, 1, !ro
, &page
) == 1)) {
293 page_head
= compound_head(page
);
295 * page_head is valid pointer but we must pin
296 * it before taking the PG_lock and/or
297 * PG_compound_lock. The moment we re-enable
298 * irqs __split_huge_page_splitting() can
299 * return and the head page can be freed from
300 * under us. We can't take the PG_lock and/or
301 * PG_compound_lock on a page that could be
302 * freed from under us.
304 if (page
!= page_head
) {
315 page_head
= compound_head(page
);
316 if (page
!= page_head
) {
322 lock_page(page_head
);
325 * If page_head->mapping is NULL, then it cannot be a PageAnon
326 * page; but it might be the ZERO_PAGE or in the gate area or
327 * in a special mapping (all cases which we are happy to fail);
328 * or it may have been a good file page when get_user_pages_fast
329 * found it, but truncated or holepunched or subjected to
330 * invalidate_complete_page2 before we got the page lock (also
331 * cases which we are happy to fail). And we hold a reference,
332 * so refcount care in invalidate_complete_page's remove_mapping
333 * prevents drop_caches from setting mapping to NULL beneath us.
335 * The case we do have to guard against is when memory pressure made
336 * shmem_writepage move it from filecache to swapcache beneath us:
337 * an unlikely race, but we do need to retry for page_head->mapping.
339 if (!page_head
->mapping
) {
340 int shmem_swizzled
= PageSwapCache(page_head
);
341 unlock_page(page_head
);
349 * Private mappings are handled in a simple way.
351 * NOTE: When userspace waits on a MAP_SHARED mapping, even if
352 * it's a read-only handle, it's expected that futexes attach to
353 * the object not the particular process.
355 if (PageAnon(page_head
)) {
357 * A RO anonymous page will never change and thus doesn't make
358 * sense for futex operations.
365 key
->both
.offset
|= FUT_OFF_MMSHARED
; /* ref taken on mm */
366 key
->private.mm
= mm
;
367 key
->private.address
= address
;
369 key
->both
.offset
|= FUT_OFF_INODE
; /* inode-based key */
370 key
->shared
.inode
= page_head
->mapping
->host
;
371 key
->shared
.pgoff
= basepage_index(page
);
374 get_futex_key_refs(key
);
377 unlock_page(page_head
);
382 static inline void put_futex_key(union futex_key
*key
)
384 drop_futex_key_refs(key
);
388 * fault_in_user_writeable() - Fault in user address and verify RW access
389 * @uaddr: pointer to faulting user space address
391 * Slow path to fixup the fault we just took in the atomic write
394 * We have no generic implementation of a non-destructive write to the
395 * user address. We know that we faulted in the atomic pagefault
396 * disabled section so we can as well avoid the #PF overhead by
397 * calling get_user_pages() right away.
399 static int fault_in_user_writeable(u32 __user
*uaddr
)
401 struct mm_struct
*mm
= current
->mm
;
404 down_read(&mm
->mmap_sem
);
405 ret
= fixup_user_fault(current
, mm
, (unsigned long)uaddr
,
407 up_read(&mm
->mmap_sem
);
409 return ret
< 0 ? ret
: 0;
413 * futex_top_waiter() - Return the highest priority waiter on a futex
414 * @hb: the hash bucket the futex_q's reside in
415 * @key: the futex key (to distinguish it from other futex futex_q's)
417 * Must be called with the hb lock held.
419 static struct futex_q
*futex_top_waiter(struct futex_hash_bucket
*hb
,
420 union futex_key
*key
)
422 struct futex_q
*this;
424 plist_for_each_entry(this, &hb
->chain
, list
) {
425 if (match_futex(&this->key
, key
))
431 static int cmpxchg_futex_value_locked(u32
*curval
, u32 __user
*uaddr
,
432 u32 uval
, u32 newval
)
437 ret
= futex_atomic_cmpxchg_inatomic(curval
, uaddr
, uval
, newval
);
443 static int get_futex_value_locked(u32
*dest
, u32 __user
*from
)
448 ret
= __copy_from_user_inatomic(dest
, from
, sizeof(u32
));
451 return ret
? -EFAULT
: 0;
458 static int refill_pi_state_cache(void)
460 struct futex_pi_state
*pi_state
;
462 if (likely(current
->pi_state_cache
))
465 pi_state
= kzalloc(sizeof(*pi_state
), GFP_KERNEL
);
470 INIT_LIST_HEAD(&pi_state
->list
);
471 /* pi_mutex gets initialized later */
472 pi_state
->owner
= NULL
;
473 atomic_set(&pi_state
->refcount
, 1);
474 pi_state
->key
= FUTEX_KEY_INIT
;
476 current
->pi_state_cache
= pi_state
;
481 static struct futex_pi_state
* alloc_pi_state(void)
483 struct futex_pi_state
*pi_state
= current
->pi_state_cache
;
486 current
->pi_state_cache
= NULL
;
491 static void free_pi_state(struct futex_pi_state
*pi_state
)
493 if (!atomic_dec_and_test(&pi_state
->refcount
))
497 * If pi_state->owner is NULL, the owner is most probably dying
498 * and has cleaned up the pi_state already
500 if (pi_state
->owner
) {
501 raw_spin_lock_irq(&pi_state
->owner
->pi_lock
);
502 list_del_init(&pi_state
->list
);
503 raw_spin_unlock_irq(&pi_state
->owner
->pi_lock
);
505 rt_mutex_proxy_unlock(&pi_state
->pi_mutex
, pi_state
->owner
);
508 if (current
->pi_state_cache
)
512 * pi_state->list is already empty.
513 * clear pi_state->owner.
514 * refcount is at 0 - put it back to 1.
516 pi_state
->owner
= NULL
;
517 atomic_set(&pi_state
->refcount
, 1);
518 current
->pi_state_cache
= pi_state
;
523 * Look up the task based on what TID userspace gave us.
526 static struct task_struct
* futex_find_get_task(pid_t pid
)
528 struct task_struct
*p
;
531 p
= find_task_by_vpid(pid
);
541 * This task is holding PI mutexes at exit time => bad.
542 * Kernel cleans up PI-state, but userspace is likely hosed.
543 * (Robust-futex cleanup is separate and might save the day for userspace.)
545 void exit_pi_state_list(struct task_struct
*curr
)
547 struct list_head
*next
, *head
= &curr
->pi_state_list
;
548 struct futex_pi_state
*pi_state
;
549 struct futex_hash_bucket
*hb
;
550 union futex_key key
= FUTEX_KEY_INIT
;
552 if (!futex_cmpxchg_enabled
)
555 * We are a ZOMBIE and nobody can enqueue itself on
556 * pi_state_list anymore, but we have to be careful
557 * versus waiters unqueueing themselves:
559 raw_spin_lock_irq(&curr
->pi_lock
);
560 while (!list_empty(head
)) {
563 pi_state
= list_entry(next
, struct futex_pi_state
, list
);
565 hb
= hash_futex(&key
);
566 raw_spin_unlock_irq(&curr
->pi_lock
);
568 spin_lock(&hb
->lock
);
570 raw_spin_lock_irq(&curr
->pi_lock
);
572 * We dropped the pi-lock, so re-check whether this
573 * task still owns the PI-state:
575 if (head
->next
!= next
) {
576 spin_unlock(&hb
->lock
);
580 WARN_ON(pi_state
->owner
!= curr
);
581 WARN_ON(list_empty(&pi_state
->list
));
582 list_del_init(&pi_state
->list
);
583 pi_state
->owner
= NULL
;
584 raw_spin_unlock_irq(&curr
->pi_lock
);
586 rt_mutex_unlock(&pi_state
->pi_mutex
);
588 spin_unlock(&hb
->lock
);
590 raw_spin_lock_irq(&curr
->pi_lock
);
592 raw_spin_unlock_irq(&curr
->pi_lock
);
596 lookup_pi_state(u32 uval
, struct futex_hash_bucket
*hb
,
597 union futex_key
*key
, struct futex_pi_state
**ps
)
599 struct futex_pi_state
*pi_state
= NULL
;
600 struct futex_q
*this, *next
;
601 struct plist_head
*head
;
602 struct task_struct
*p
;
603 pid_t pid
= uval
& FUTEX_TID_MASK
;
607 plist_for_each_entry_safe(this, next
, head
, list
) {
608 if (match_futex(&this->key
, key
)) {
610 * Another waiter already exists - bump up
611 * the refcount and return its pi_state:
613 pi_state
= this->pi_state
;
615 * Userspace might have messed up non-PI and PI futexes
617 if (unlikely(!pi_state
))
620 WARN_ON(!atomic_read(&pi_state
->refcount
));
623 * When pi_state->owner is NULL then the owner died
624 * and another waiter is on the fly. pi_state->owner
625 * is fixed up by the task which acquires
626 * pi_state->rt_mutex.
628 * We do not check for pid == 0 which can happen when
629 * the owner died and robust_list_exit() cleared the
632 if (pid
&& pi_state
->owner
) {
634 * Bail out if user space manipulated the
637 if (pid
!= task_pid_vnr(pi_state
->owner
))
641 atomic_inc(&pi_state
->refcount
);
649 * We are the first waiter - try to look up the real owner and attach
650 * the new pi_state to it, but bail out when TID = 0
654 p
= futex_find_get_task(pid
);
659 * We need to look at the task state flags to figure out,
660 * whether the task is exiting. To protect against the do_exit
661 * change of the task flags, we do this protected by
664 raw_spin_lock_irq(&p
->pi_lock
);
665 if (unlikely(p
->flags
& PF_EXITING
)) {
667 * The task is on the way out. When PF_EXITPIDONE is
668 * set, we know that the task has finished the
671 int ret
= (p
->flags
& PF_EXITPIDONE
) ? -ESRCH
: -EAGAIN
;
673 raw_spin_unlock_irq(&p
->pi_lock
);
678 pi_state
= alloc_pi_state();
681 * Initialize the pi_mutex in locked state and make 'p'
684 rt_mutex_init_proxy_locked(&pi_state
->pi_mutex
, p
);
686 /* Store the key for possible exit cleanups: */
687 pi_state
->key
= *key
;
689 WARN_ON(!list_empty(&pi_state
->list
));
690 list_add(&pi_state
->list
, &p
->pi_state_list
);
692 raw_spin_unlock_irq(&p
->pi_lock
);
702 * futex_lock_pi_atomic() - Atomic work required to acquire a pi aware futex
703 * @uaddr: the pi futex user address
704 * @hb: the pi futex hash bucket
705 * @key: the futex key associated with uaddr and hb
706 * @ps: the pi_state pointer where we store the result of the
708 * @task: the task to perform the atomic lock work for. This will
709 * be "current" except in the case of requeue pi.
710 * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0)
714 * 1 - acquired the lock;
717 * The hb->lock and futex_key refs shall be held by the caller.
719 static int futex_lock_pi_atomic(u32 __user
*uaddr
, struct futex_hash_bucket
*hb
,
720 union futex_key
*key
,
721 struct futex_pi_state
**ps
,
722 struct task_struct
*task
, int set_waiters
)
724 int lock_taken
, ret
, force_take
= 0;
725 u32 uval
, newval
, curval
, vpid
= task_pid_vnr(task
);
728 ret
= lock_taken
= 0;
731 * To avoid races, we attempt to take the lock here again
732 * (by doing a 0 -> TID atomic cmpxchg), while holding all
733 * the locks. It will most likely not succeed.
737 newval
|= FUTEX_WAITERS
;
739 if (unlikely(cmpxchg_futex_value_locked(&curval
, uaddr
, 0, newval
)))
745 if ((unlikely((curval
& FUTEX_TID_MASK
) == vpid
)))
749 * Surprise - we got the lock. Just return to userspace:
751 if (unlikely(!curval
))
757 * Set the FUTEX_WAITERS flag, so the owner will know it has someone
758 * to wake at the next unlock.
760 newval
= curval
| FUTEX_WAITERS
;
763 * Should we force take the futex? See below.
765 if (unlikely(force_take
)) {
767 * Keep the OWNER_DIED and the WAITERS bit and set the
770 newval
= (curval
& ~FUTEX_TID_MASK
) | vpid
;
775 if (unlikely(cmpxchg_futex_value_locked(&curval
, uaddr
, uval
, newval
)))
777 if (unlikely(curval
!= uval
))
781 * We took the lock due to forced take over.
783 if (unlikely(lock_taken
))
787 * We dont have the lock. Look up the PI state (or create it if
788 * we are the first waiter):
790 ret
= lookup_pi_state(uval
, hb
, key
, ps
);
796 * We failed to find an owner for this
797 * futex. So we have no pi_state to block
798 * on. This can happen in two cases:
801 * 2) A stale FUTEX_WAITERS bit
803 * Re-read the futex value.
805 if (get_futex_value_locked(&curval
, uaddr
))
809 * If the owner died or we have a stale
810 * WAITERS bit the owner TID in the user space
813 if (!(curval
& FUTEX_TID_MASK
)) {
826 * __unqueue_futex() - Remove the futex_q from its futex_hash_bucket
827 * @q: The futex_q to unqueue
829 * The q->lock_ptr must not be NULL and must be held by the caller.
831 static void __unqueue_futex(struct futex_q
*q
)
833 struct futex_hash_bucket
*hb
;
835 if (WARN_ON_SMP(!q
->lock_ptr
|| !spin_is_locked(q
->lock_ptr
))
836 || WARN_ON(plist_node_empty(&q
->list
)))
839 hb
= container_of(q
->lock_ptr
, struct futex_hash_bucket
, lock
);
840 plist_del(&q
->list
, &hb
->chain
);
844 * The hash bucket lock must be held when this is called.
845 * Afterwards, the futex_q must not be accessed.
847 static void wake_futex(struct futex_q
*q
)
849 struct task_struct
*p
= q
->task
;
851 if (WARN(q
->pi_state
|| q
->rt_waiter
, "refusing to wake PI futex\n"))
855 * We set q->lock_ptr = NULL _before_ we wake up the task. If
856 * a non-futex wake up happens on another CPU then the task
857 * might exit and p would dereference a non-existing task
858 * struct. Prevent this by holding a reference on p across the
865 * The waiting task can free the futex_q as soon as
866 * q->lock_ptr = NULL is written, without taking any locks. A
867 * memory barrier is required here to prevent the following
868 * store to lock_ptr from getting ahead of the plist_del.
873 wake_up_state(p
, TASK_NORMAL
);
877 static int wake_futex_pi(u32 __user
*uaddr
, u32 uval
, struct futex_q
*this)
879 struct task_struct
*new_owner
;
880 struct futex_pi_state
*pi_state
= this->pi_state
;
881 u32
uninitialized_var(curval
), newval
;
887 * If current does not own the pi_state then the futex is
888 * inconsistent and user space fiddled with the futex value.
890 if (pi_state
->owner
!= current
)
893 raw_spin_lock(&pi_state
->pi_mutex
.wait_lock
);
894 new_owner
= rt_mutex_next_owner(&pi_state
->pi_mutex
);
897 * It is possible that the next waiter (the one that brought
898 * this owner to the kernel) timed out and is no longer
899 * waiting on the lock.
902 new_owner
= this->task
;
905 * We pass it to the next owner. (The WAITERS bit is always
906 * kept enabled while there is PI state around. We must also
907 * preserve the owner died bit.)
909 if (!(uval
& FUTEX_OWNER_DIED
)) {
912 newval
= FUTEX_WAITERS
| task_pid_vnr(new_owner
);
914 if (cmpxchg_futex_value_locked(&curval
, uaddr
, uval
, newval
))
916 else if (curval
!= uval
)
919 raw_spin_unlock(&pi_state
->pi_mutex
.wait_lock
);
924 raw_spin_lock_irq(&pi_state
->owner
->pi_lock
);
925 WARN_ON(list_empty(&pi_state
->list
));
926 list_del_init(&pi_state
->list
);
927 raw_spin_unlock_irq(&pi_state
->owner
->pi_lock
);
929 raw_spin_lock_irq(&new_owner
->pi_lock
);
930 WARN_ON(!list_empty(&pi_state
->list
));
931 list_add(&pi_state
->list
, &new_owner
->pi_state_list
);
932 pi_state
->owner
= new_owner
;
933 raw_spin_unlock_irq(&new_owner
->pi_lock
);
935 raw_spin_unlock(&pi_state
->pi_mutex
.wait_lock
);
936 rt_mutex_unlock(&pi_state
->pi_mutex
);
941 static int unlock_futex_pi(u32 __user
*uaddr
, u32 uval
)
943 u32
uninitialized_var(oldval
);
946 * There is no waiter, so we unlock the futex. The owner died
947 * bit has not to be preserved here. We are the owner:
949 if (cmpxchg_futex_value_locked(&oldval
, uaddr
, uval
, 0))
958 * Express the locking dependencies for lockdep:
961 double_lock_hb(struct futex_hash_bucket
*hb1
, struct futex_hash_bucket
*hb2
)
964 spin_lock(&hb1
->lock
);
966 spin_lock_nested(&hb2
->lock
, SINGLE_DEPTH_NESTING
);
967 } else { /* hb1 > hb2 */
968 spin_lock(&hb2
->lock
);
969 spin_lock_nested(&hb1
->lock
, SINGLE_DEPTH_NESTING
);
974 double_unlock_hb(struct futex_hash_bucket
*hb1
, struct futex_hash_bucket
*hb2
)
976 spin_unlock(&hb1
->lock
);
978 spin_unlock(&hb2
->lock
);
982 * Wake up waiters matching bitset queued on this futex (uaddr).
985 futex_wake(u32 __user
*uaddr
, unsigned int flags
, int nr_wake
, u32 bitset
)
987 struct futex_hash_bucket
*hb
;
988 struct futex_q
*this, *next
;
989 struct plist_head
*head
;
990 union futex_key key
= FUTEX_KEY_INIT
;
996 ret
= get_futex_key(uaddr
, flags
& FLAGS_SHARED
, &key
, VERIFY_READ
);
997 if (unlikely(ret
!= 0))
1000 hb
= hash_futex(&key
);
1001 spin_lock(&hb
->lock
);
1004 plist_for_each_entry_safe(this, next
, head
, list
) {
1005 if (match_futex (&this->key
, &key
)) {
1006 if (this->pi_state
|| this->rt_waiter
) {
1011 /* Check if one of the bits is set in both bitsets */
1012 if (!(this->bitset
& bitset
))
1016 if (++ret
>= nr_wake
)
1021 spin_unlock(&hb
->lock
);
1022 put_futex_key(&key
);
1028 * Wake up all waiters hashed on the physical page that is mapped
1029 * to this virtual address:
1032 futex_wake_op(u32 __user
*uaddr1
, unsigned int flags
, u32 __user
*uaddr2
,
1033 int nr_wake
, int nr_wake2
, int op
)
1035 union futex_key key1
= FUTEX_KEY_INIT
, key2
= FUTEX_KEY_INIT
;
1036 struct futex_hash_bucket
*hb1
, *hb2
;
1037 struct plist_head
*head
;
1038 struct futex_q
*this, *next
;
1042 ret
= get_futex_key(uaddr1
, flags
& FLAGS_SHARED
, &key1
, VERIFY_READ
);
1043 if (unlikely(ret
!= 0))
1045 ret
= get_futex_key(uaddr2
, flags
& FLAGS_SHARED
, &key2
, VERIFY_WRITE
);
1046 if (unlikely(ret
!= 0))
1049 hb1
= hash_futex(&key1
);
1050 hb2
= hash_futex(&key2
);
1053 double_lock_hb(hb1
, hb2
);
1054 op_ret
= futex_atomic_op_inuser(op
, uaddr2
);
1055 if (unlikely(op_ret
< 0)) {
1057 double_unlock_hb(hb1
, hb2
);
1061 * we don't get EFAULT from MMU faults if we don't have an MMU,
1062 * but we might get them from range checking
1068 if (unlikely(op_ret
!= -EFAULT
)) {
1073 ret
= fault_in_user_writeable(uaddr2
);
1077 if (!(flags
& FLAGS_SHARED
))
1080 put_futex_key(&key2
);
1081 put_futex_key(&key1
);
1087 plist_for_each_entry_safe(this, next
, head
, list
) {
1088 if (match_futex (&this->key
, &key1
)) {
1089 if (this->pi_state
|| this->rt_waiter
) {
1094 if (++ret
>= nr_wake
)
1103 plist_for_each_entry_safe(this, next
, head
, list
) {
1104 if (match_futex (&this->key
, &key2
)) {
1105 if (this->pi_state
|| this->rt_waiter
) {
1110 if (++op_ret
>= nr_wake2
)
1118 double_unlock_hb(hb1
, hb2
);
1120 put_futex_key(&key2
);
1122 put_futex_key(&key1
);
1128 * requeue_futex() - Requeue a futex_q from one hb to another
1129 * @q: the futex_q to requeue
1130 * @hb1: the source hash_bucket
1131 * @hb2: the target hash_bucket
1132 * @key2: the new key for the requeued futex_q
1135 void requeue_futex(struct futex_q
*q
, struct futex_hash_bucket
*hb1
,
1136 struct futex_hash_bucket
*hb2
, union futex_key
*key2
)
1140 * If key1 and key2 hash to the same bucket, no need to
1143 if (likely(&hb1
->chain
!= &hb2
->chain
)) {
1144 plist_del(&q
->list
, &hb1
->chain
);
1145 plist_add(&q
->list
, &hb2
->chain
);
1146 q
->lock_ptr
= &hb2
->lock
;
1148 get_futex_key_refs(key2
);
1153 * requeue_pi_wake_futex() - Wake a task that acquired the lock during requeue
1155 * @key: the key of the requeue target futex
1156 * @hb: the hash_bucket of the requeue target futex
1158 * During futex_requeue, with requeue_pi=1, it is possible to acquire the
1159 * target futex if it is uncontended or via a lock steal. Set the futex_q key
1160 * to the requeue target futex so the waiter can detect the wakeup on the right
1161 * futex, but remove it from the hb and NULL the rt_waiter so it can detect
1162 * atomic lock acquisition. Set the q->lock_ptr to the requeue target hb->lock
1163 * to protect access to the pi_state to fixup the owner later. Must be called
1164 * with both q->lock_ptr and hb->lock held.
1167 void requeue_pi_wake_futex(struct futex_q
*q
, union futex_key
*key
,
1168 struct futex_hash_bucket
*hb
)
1170 get_futex_key_refs(key
);
1175 WARN_ON(!q
->rt_waiter
);
1176 q
->rt_waiter
= NULL
;
1178 q
->lock_ptr
= &hb
->lock
;
1180 wake_up_state(q
->task
, TASK_NORMAL
);
1184 * futex_proxy_trylock_atomic() - Attempt an atomic lock for the top waiter
1185 * @pifutex: the user address of the to futex
1186 * @hb1: the from futex hash bucket, must be locked by the caller
1187 * @hb2: the to futex hash bucket, must be locked by the caller
1188 * @key1: the from futex key
1189 * @key2: the to futex key
1190 * @ps: address to store the pi_state pointer
1191 * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0)
1193 * Try and get the lock on behalf of the top waiter if we can do it atomically.
1194 * Wake the top waiter if we succeed. If the caller specified set_waiters,
1195 * then direct futex_lock_pi_atomic() to force setting the FUTEX_WAITERS bit.
1196 * hb1 and hb2 must be held by the caller.
1199 * 0 - failed to acquire the lock atomically;
1200 * 1 - acquired the lock;
1203 static int futex_proxy_trylock_atomic(u32 __user
*pifutex
,
1204 struct futex_hash_bucket
*hb1
,
1205 struct futex_hash_bucket
*hb2
,
1206 union futex_key
*key1
, union futex_key
*key2
,
1207 struct futex_pi_state
**ps
, int set_waiters
)
1209 struct futex_q
*top_waiter
= NULL
;
1213 if (get_futex_value_locked(&curval
, pifutex
))
1217 * Find the top_waiter and determine if there are additional waiters.
1218 * If the caller intends to requeue more than 1 waiter to pifutex,
1219 * force futex_lock_pi_atomic() to set the FUTEX_WAITERS bit now,
1220 * as we have means to handle the possible fault. If not, don't set
1221 * the bit unecessarily as it will force the subsequent unlock to enter
1224 top_waiter
= futex_top_waiter(hb1
, key1
);
1226 /* There are no waiters, nothing for us to do. */
1230 /* Ensure we requeue to the expected futex. */
1231 if (!match_futex(top_waiter
->requeue_pi_key
, key2
))
1235 * Try to take the lock for top_waiter. Set the FUTEX_WAITERS bit in
1236 * the contended case or if set_waiters is 1. The pi_state is returned
1237 * in ps in contended cases.
1239 ret
= futex_lock_pi_atomic(pifutex
, hb2
, key2
, ps
, top_waiter
->task
,
1242 requeue_pi_wake_futex(top_waiter
, key2
, hb2
);
1248 * futex_requeue() - Requeue waiters from uaddr1 to uaddr2
1249 * @uaddr1: source futex user address
1250 * @flags: futex flags (FLAGS_SHARED, etc.)
1251 * @uaddr2: target futex user address
1252 * @nr_wake: number of waiters to wake (must be 1 for requeue_pi)
1253 * @nr_requeue: number of waiters to requeue (0-INT_MAX)
1254 * @cmpval: @uaddr1 expected value (or %NULL)
1255 * @requeue_pi: if we are attempting to requeue from a non-pi futex to a
1256 * pi futex (pi to pi requeue is not supported)
1258 * Requeue waiters on uaddr1 to uaddr2. In the requeue_pi case, try to acquire
1259 * uaddr2 atomically on behalf of the top waiter.
1262 * >=0 - on success, the number of tasks requeued or woken;
1265 static int futex_requeue(u32 __user
*uaddr1
, unsigned int flags
,
1266 u32 __user
*uaddr2
, int nr_wake
, int nr_requeue
,
1267 u32
*cmpval
, int requeue_pi
)
1269 union futex_key key1
= FUTEX_KEY_INIT
, key2
= FUTEX_KEY_INIT
;
1270 int drop_count
= 0, task_count
= 0, ret
;
1271 struct futex_pi_state
*pi_state
= NULL
;
1272 struct futex_hash_bucket
*hb1
, *hb2
;
1273 struct plist_head
*head1
;
1274 struct futex_q
*this, *next
;
1279 * requeue_pi requires a pi_state, try to allocate it now
1280 * without any locks in case it fails.
1282 if (refill_pi_state_cache())
1285 * requeue_pi must wake as many tasks as it can, up to nr_wake
1286 * + nr_requeue, since it acquires the rt_mutex prior to
1287 * returning to userspace, so as to not leave the rt_mutex with
1288 * waiters and no owner. However, second and third wake-ups
1289 * cannot be predicted as they involve race conditions with the
1290 * first wake and a fault while looking up the pi_state. Both
1291 * pthread_cond_signal() and pthread_cond_broadcast() should
1299 if (pi_state
!= NULL
) {
1301 * We will have to lookup the pi_state again, so free this one
1302 * to keep the accounting correct.
1304 free_pi_state(pi_state
);
1308 ret
= get_futex_key(uaddr1
, flags
& FLAGS_SHARED
, &key1
, VERIFY_READ
);
1309 if (unlikely(ret
!= 0))
1311 ret
= get_futex_key(uaddr2
, flags
& FLAGS_SHARED
, &key2
,
1312 requeue_pi
? VERIFY_WRITE
: VERIFY_READ
);
1313 if (unlikely(ret
!= 0))
1316 hb1
= hash_futex(&key1
);
1317 hb2
= hash_futex(&key2
);
1320 double_lock_hb(hb1
, hb2
);
1322 if (likely(cmpval
!= NULL
)) {
1325 ret
= get_futex_value_locked(&curval
, uaddr1
);
1327 if (unlikely(ret
)) {
1328 double_unlock_hb(hb1
, hb2
);
1330 ret
= get_user(curval
, uaddr1
);
1334 if (!(flags
& FLAGS_SHARED
))
1337 put_futex_key(&key2
);
1338 put_futex_key(&key1
);
1341 if (curval
!= *cmpval
) {
1347 if (requeue_pi
&& (task_count
- nr_wake
< nr_requeue
)) {
1349 * Attempt to acquire uaddr2 and wake the top waiter. If we
1350 * intend to requeue waiters, force setting the FUTEX_WAITERS
1351 * bit. We force this here where we are able to easily handle
1352 * faults rather in the requeue loop below.
1354 ret
= futex_proxy_trylock_atomic(uaddr2
, hb1
, hb2
, &key1
,
1355 &key2
, &pi_state
, nr_requeue
);
1358 * At this point the top_waiter has either taken uaddr2 or is
1359 * waiting on it. If the former, then the pi_state will not
1360 * exist yet, look it up one more time to ensure we have a
1367 ret
= get_futex_value_locked(&curval2
, uaddr2
);
1369 ret
= lookup_pi_state(curval2
, hb2
, &key2
,
1377 double_unlock_hb(hb1
, hb2
);
1378 put_futex_key(&key2
);
1379 put_futex_key(&key1
);
1380 ret
= fault_in_user_writeable(uaddr2
);
1385 /* The owner was exiting, try again. */
1386 double_unlock_hb(hb1
, hb2
);
1387 put_futex_key(&key2
);
1388 put_futex_key(&key1
);
1396 head1
= &hb1
->chain
;
1397 plist_for_each_entry_safe(this, next
, head1
, list
) {
1398 if (task_count
- nr_wake
>= nr_requeue
)
1401 if (!match_futex(&this->key
, &key1
))
1405 * FUTEX_WAIT_REQEUE_PI and FUTEX_CMP_REQUEUE_PI should always
1406 * be paired with each other and no other futex ops.
1408 * We should never be requeueing a futex_q with a pi_state,
1409 * which is awaiting a futex_unlock_pi().
1411 if ((requeue_pi
&& !this->rt_waiter
) ||
1412 (!requeue_pi
&& this->rt_waiter
) ||
1419 * Wake nr_wake waiters. For requeue_pi, if we acquired the
1420 * lock, we already woke the top_waiter. If not, it will be
1421 * woken by futex_unlock_pi().
1423 if (++task_count
<= nr_wake
&& !requeue_pi
) {
1428 /* Ensure we requeue to the expected futex for requeue_pi. */
1429 if (requeue_pi
&& !match_futex(this->requeue_pi_key
, &key2
)) {
1435 * Requeue nr_requeue waiters and possibly one more in the case
1436 * of requeue_pi if we couldn't acquire the lock atomically.
1439 /* Prepare the waiter to take the rt_mutex. */
1440 atomic_inc(&pi_state
->refcount
);
1441 this->pi_state
= pi_state
;
1442 ret
= rt_mutex_start_proxy_lock(&pi_state
->pi_mutex
,
1446 /* We got the lock. */
1447 requeue_pi_wake_futex(this, &key2
, hb2
);
1452 this->pi_state
= NULL
;
1453 free_pi_state(pi_state
);
1457 requeue_futex(this, hb1
, hb2
, &key2
);
1462 double_unlock_hb(hb1
, hb2
);
1465 * drop_futex_key_refs() must be called outside the spinlocks. During
1466 * the requeue we moved futex_q's from the hash bucket at key1 to the
1467 * one at key2 and updated their key pointer. We no longer need to
1468 * hold the references to key1.
1470 while (--drop_count
>= 0)
1471 drop_futex_key_refs(&key1
);
1474 put_futex_key(&key2
);
1476 put_futex_key(&key1
);
1478 if (pi_state
!= NULL
)
1479 free_pi_state(pi_state
);
1480 return ret
? ret
: task_count
;
1483 /* The key must be already stored in q->key. */
1484 static inline struct futex_hash_bucket
*queue_lock(struct futex_q
*q
)
1485 __acquires(&hb
->lock
)
1487 struct futex_hash_bucket
*hb
;
1489 hb
= hash_futex(&q
->key
);
1490 q
->lock_ptr
= &hb
->lock
;
1492 spin_lock(&hb
->lock
);
1497 queue_unlock(struct futex_q
*q
, struct futex_hash_bucket
*hb
)
1498 __releases(&hb
->lock
)
1500 spin_unlock(&hb
->lock
);
1504 * queue_me() - Enqueue the futex_q on the futex_hash_bucket
1505 * @q: The futex_q to enqueue
1506 * @hb: The destination hash bucket
1508 * The hb->lock must be held by the caller, and is released here. A call to
1509 * queue_me() is typically paired with exactly one call to unqueue_me(). The
1510 * exceptions involve the PI related operations, which may use unqueue_me_pi()
1511 * or nothing if the unqueue is done as part of the wake process and the unqueue
1512 * state is implicit in the state of woken task (see futex_wait_requeue_pi() for
1515 static inline void queue_me(struct futex_q
*q
, struct futex_hash_bucket
*hb
)
1516 __releases(&hb
->lock
)
1521 * The priority used to register this element is
1522 * - either the real thread-priority for the real-time threads
1523 * (i.e. threads with a priority lower than MAX_RT_PRIO)
1524 * - or MAX_RT_PRIO for non-RT threads.
1525 * Thus, all RT-threads are woken first in priority order, and
1526 * the others are woken last, in FIFO order.
1528 prio
= min(current
->normal_prio
, MAX_RT_PRIO
);
1530 plist_node_init(&q
->list
, prio
);
1531 plist_add(&q
->list
, &hb
->chain
);
1533 spin_unlock(&hb
->lock
);
1537 * unqueue_me() - Remove the futex_q from its futex_hash_bucket
1538 * @q: The futex_q to unqueue
1540 * The q->lock_ptr must not be held by the caller. A call to unqueue_me() must
1541 * be paired with exactly one earlier call to queue_me().
1544 * 1 - if the futex_q was still queued (and we removed unqueued it);
1545 * 0 - if the futex_q was already removed by the waking thread
1547 static int unqueue_me(struct futex_q
*q
)
1549 spinlock_t
*lock_ptr
;
1552 /* In the common case we don't take the spinlock, which is nice. */
1554 lock_ptr
= q
->lock_ptr
;
1556 if (lock_ptr
!= NULL
) {
1557 spin_lock(lock_ptr
);
1559 * q->lock_ptr can change between reading it and
1560 * spin_lock(), causing us to take the wrong lock. This
1561 * corrects the race condition.
1563 * Reasoning goes like this: if we have the wrong lock,
1564 * q->lock_ptr must have changed (maybe several times)
1565 * between reading it and the spin_lock(). It can
1566 * change again after the spin_lock() but only if it was
1567 * already changed before the spin_lock(). It cannot,
1568 * however, change back to the original value. Therefore
1569 * we can detect whether we acquired the correct lock.
1571 if (unlikely(lock_ptr
!= q
->lock_ptr
)) {
1572 spin_unlock(lock_ptr
);
1577 BUG_ON(q
->pi_state
);
1579 spin_unlock(lock_ptr
);
1583 drop_futex_key_refs(&q
->key
);
1588 * PI futexes can not be requeued and must remove themself from the
1589 * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry
1592 static void unqueue_me_pi(struct futex_q
*q
)
1593 __releases(q
->lock_ptr
)
1597 BUG_ON(!q
->pi_state
);
1598 free_pi_state(q
->pi_state
);
1601 spin_unlock(q
->lock_ptr
);
1605 * Fixup the pi_state owner with the new owner.
1607 * Must be called with hash bucket lock held and mm->sem held for non
1610 static int fixup_pi_state_owner(u32 __user
*uaddr
, struct futex_q
*q
,
1611 struct task_struct
*newowner
)
1613 u32 newtid
= task_pid_vnr(newowner
) | FUTEX_WAITERS
;
1614 struct futex_pi_state
*pi_state
= q
->pi_state
;
1615 struct task_struct
*oldowner
= pi_state
->owner
;
1616 u32 uval
, uninitialized_var(curval
), newval
;
1620 if (!pi_state
->owner
)
1621 newtid
|= FUTEX_OWNER_DIED
;
1624 * We are here either because we stole the rtmutex from the
1625 * previous highest priority waiter or we are the highest priority
1626 * waiter but failed to get the rtmutex the first time.
1627 * We have to replace the newowner TID in the user space variable.
1628 * This must be atomic as we have to preserve the owner died bit here.
1630 * Note: We write the user space value _before_ changing the pi_state
1631 * because we can fault here. Imagine swapped out pages or a fork
1632 * that marked all the anonymous memory readonly for cow.
1634 * Modifying pi_state _before_ the user space value would
1635 * leave the pi_state in an inconsistent state when we fault
1636 * here, because we need to drop the hash bucket lock to
1637 * handle the fault. This might be observed in the PID check
1638 * in lookup_pi_state.
1641 if (get_futex_value_locked(&uval
, uaddr
))
1645 newval
= (uval
& FUTEX_OWNER_DIED
) | newtid
;
1647 if (cmpxchg_futex_value_locked(&curval
, uaddr
, uval
, newval
))
1655 * We fixed up user space. Now we need to fix the pi_state
1658 if (pi_state
->owner
!= NULL
) {
1659 raw_spin_lock_irq(&pi_state
->owner
->pi_lock
);
1660 WARN_ON(list_empty(&pi_state
->list
));
1661 list_del_init(&pi_state
->list
);
1662 raw_spin_unlock_irq(&pi_state
->owner
->pi_lock
);
1665 pi_state
->owner
= newowner
;
1667 raw_spin_lock_irq(&newowner
->pi_lock
);
1668 WARN_ON(!list_empty(&pi_state
->list
));
1669 list_add(&pi_state
->list
, &newowner
->pi_state_list
);
1670 raw_spin_unlock_irq(&newowner
->pi_lock
);
1674 * To handle the page fault we need to drop the hash bucket
1675 * lock here. That gives the other task (either the highest priority
1676 * waiter itself or the task which stole the rtmutex) the
1677 * chance to try the fixup of the pi_state. So once we are
1678 * back from handling the fault we need to check the pi_state
1679 * after reacquiring the hash bucket lock and before trying to
1680 * do another fixup. When the fixup has been done already we
1684 spin_unlock(q
->lock_ptr
);
1686 ret
= fault_in_user_writeable(uaddr
);
1688 spin_lock(q
->lock_ptr
);
1691 * Check if someone else fixed it for us:
1693 if (pi_state
->owner
!= oldowner
)
1702 static long futex_wait_restart(struct restart_block
*restart
);
1705 * fixup_owner() - Post lock pi_state and corner case management
1706 * @uaddr: user address of the futex
1707 * @q: futex_q (contains pi_state and access to the rt_mutex)
1708 * @locked: if the attempt to take the rt_mutex succeeded (1) or not (0)
1710 * After attempting to lock an rt_mutex, this function is called to cleanup
1711 * the pi_state owner as well as handle race conditions that may allow us to
1712 * acquire the lock. Must be called with the hb lock held.
1715 * 1 - success, lock taken;
1716 * 0 - success, lock not taken;
1717 * <0 - on error (-EFAULT)
1719 static int fixup_owner(u32 __user
*uaddr
, struct futex_q
*q
, int locked
)
1721 struct task_struct
*owner
;
1726 * Got the lock. We might not be the anticipated owner if we
1727 * did a lock-steal - fix up the PI-state in that case:
1729 if (q
->pi_state
->owner
!= current
)
1730 ret
= fixup_pi_state_owner(uaddr
, q
, current
);
1735 * Catch the rare case, where the lock was released when we were on the
1736 * way back before we locked the hash bucket.
1738 if (q
->pi_state
->owner
== current
) {
1740 * Try to get the rt_mutex now. This might fail as some other
1741 * task acquired the rt_mutex after we removed ourself from the
1742 * rt_mutex waiters list.
1744 if (rt_mutex_trylock(&q
->pi_state
->pi_mutex
)) {
1750 * pi_state is incorrect, some other task did a lock steal and
1751 * we returned due to timeout or signal without taking the
1752 * rt_mutex. Too late.
1754 raw_spin_lock(&q
->pi_state
->pi_mutex
.wait_lock
);
1755 owner
= rt_mutex_owner(&q
->pi_state
->pi_mutex
);
1757 owner
= rt_mutex_next_owner(&q
->pi_state
->pi_mutex
);
1758 raw_spin_unlock(&q
->pi_state
->pi_mutex
.wait_lock
);
1759 ret
= fixup_pi_state_owner(uaddr
, q
, owner
);
1764 * Paranoia check. If we did not take the lock, then we should not be
1765 * the owner of the rt_mutex.
1767 if (rt_mutex_owner(&q
->pi_state
->pi_mutex
) == current
)
1768 printk(KERN_ERR
"fixup_owner: ret = %d pi-mutex: %p "
1769 "pi-state %p\n", ret
,
1770 q
->pi_state
->pi_mutex
.owner
,
1771 q
->pi_state
->owner
);
1774 return ret
? ret
: locked
;
1778 * futex_wait_queue_me() - queue_me() and wait for wakeup, timeout, or signal
1779 * @hb: the futex hash bucket, must be locked by the caller
1780 * @q: the futex_q to queue up on
1781 * @timeout: the prepared hrtimer_sleeper, or null for no timeout
1783 static void futex_wait_queue_me(struct futex_hash_bucket
*hb
, struct futex_q
*q
,
1784 struct hrtimer_sleeper
*timeout
)
1787 * The task state is guaranteed to be set before another task can
1788 * wake it. set_current_state() is implemented using set_mb() and
1789 * queue_me() calls spin_unlock() upon completion, both serializing
1790 * access to the hash list and forcing another memory barrier.
1792 set_current_state(TASK_INTERRUPTIBLE
);
1797 hrtimer_start_expires(&timeout
->timer
, HRTIMER_MODE_ABS
);
1798 if (!hrtimer_active(&timeout
->timer
))
1799 timeout
->task
= NULL
;
1803 * If we have been removed from the hash list, then another task
1804 * has tried to wake us, and we can skip the call to schedule().
1806 if (likely(!plist_node_empty(&q
->list
))) {
1808 * If the timer has already expired, current will already be
1809 * flagged for rescheduling. Only call schedule if there
1810 * is no timeout, or if it has yet to expire.
1812 if (!timeout
|| timeout
->task
)
1813 freezable_schedule();
1815 __set_current_state(TASK_RUNNING
);
1819 * futex_wait_setup() - Prepare to wait on a futex
1820 * @uaddr: the futex userspace address
1821 * @val: the expected value
1822 * @flags: futex flags (FLAGS_SHARED, etc.)
1823 * @q: the associated futex_q
1824 * @hb: storage for hash_bucket pointer to be returned to caller
1826 * Setup the futex_q and locate the hash_bucket. Get the futex value and
1827 * compare it with the expected value. Handle atomic faults internally.
1828 * Return with the hb lock held and a q.key reference on success, and unlocked
1829 * with no q.key reference on failure.
1832 * 0 - uaddr contains val and hb has been locked;
1833 * <1 - -EFAULT or -EWOULDBLOCK (uaddr does not contain val) and hb is unlocked
1835 static int futex_wait_setup(u32 __user
*uaddr
, u32 val
, unsigned int flags
,
1836 struct futex_q
*q
, struct futex_hash_bucket
**hb
)
1842 * Access the page AFTER the hash-bucket is locked.
1843 * Order is important:
1845 * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val);
1846 * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); }
1848 * The basic logical guarantee of a futex is that it blocks ONLY
1849 * if cond(var) is known to be true at the time of blocking, for
1850 * any cond. If we locked the hash-bucket after testing *uaddr, that
1851 * would open a race condition where we could block indefinitely with
1852 * cond(var) false, which would violate the guarantee.
1854 * On the other hand, we insert q and release the hash-bucket only
1855 * after testing *uaddr. This guarantees that futex_wait() will NOT
1856 * absorb a wakeup if *uaddr does not match the desired values
1857 * while the syscall executes.
1860 ret
= get_futex_key(uaddr
, flags
& FLAGS_SHARED
, &q
->key
, VERIFY_READ
);
1861 if (unlikely(ret
!= 0))
1865 *hb
= queue_lock(q
);
1867 ret
= get_futex_value_locked(&uval
, uaddr
);
1870 queue_unlock(q
, *hb
);
1872 ret
= get_user(uval
, uaddr
);
1876 if (!(flags
& FLAGS_SHARED
))
1879 put_futex_key(&q
->key
);
1884 queue_unlock(q
, *hb
);
1890 put_futex_key(&q
->key
);
1894 static int futex_wait(u32 __user
*uaddr
, unsigned int flags
, u32 val
,
1895 ktime_t
*abs_time
, u32 bitset
)
1897 struct hrtimer_sleeper timeout
, *to
= NULL
;
1898 struct restart_block
*restart
;
1899 struct futex_hash_bucket
*hb
;
1900 struct futex_q q
= futex_q_init
;
1910 hrtimer_init_on_stack(&to
->timer
, (flags
& FLAGS_CLOCKRT
) ?
1911 CLOCK_REALTIME
: CLOCK_MONOTONIC
,
1913 hrtimer_init_sleeper(to
, current
);
1914 hrtimer_set_expires_range_ns(&to
->timer
, *abs_time
,
1915 current
->timer_slack_ns
);
1920 * Prepare to wait on uaddr. On success, holds hb lock and increments
1923 ret
= futex_wait_setup(uaddr
, val
, flags
, &q
, &hb
);
1927 /* queue_me and wait for wakeup, timeout, or a signal. */
1928 futex_wait_queue_me(hb
, &q
, to
);
1930 /* If we were woken (and unqueued), we succeeded, whatever. */
1932 /* unqueue_me() drops q.key ref */
1933 if (!unqueue_me(&q
))
1936 if (to
&& !to
->task
)
1940 * We expect signal_pending(current), but we might be the
1941 * victim of a spurious wakeup as well.
1943 if (!signal_pending(current
))
1950 restart
= ¤t_thread_info()->restart_block
;
1951 restart
->fn
= futex_wait_restart
;
1952 restart
->futex
.uaddr
= uaddr
;
1953 restart
->futex
.val
= val
;
1954 restart
->futex
.time
= abs_time
->tv64
;
1955 restart
->futex
.bitset
= bitset
;
1956 restart
->futex
.flags
= flags
| FLAGS_HAS_TIMEOUT
;
1958 ret
= -ERESTART_RESTARTBLOCK
;
1962 hrtimer_cancel(&to
->timer
);
1963 destroy_hrtimer_on_stack(&to
->timer
);
1969 static long futex_wait_restart(struct restart_block
*restart
)
1971 u32 __user
*uaddr
= restart
->futex
.uaddr
;
1972 ktime_t t
, *tp
= NULL
;
1974 if (restart
->futex
.flags
& FLAGS_HAS_TIMEOUT
) {
1975 t
.tv64
= restart
->futex
.time
;
1978 restart
->fn
= do_no_restart_syscall
;
1980 return (long)futex_wait(uaddr
, restart
->futex
.flags
,
1981 restart
->futex
.val
, tp
, restart
->futex
.bitset
);
1986 * Userspace tried a 0 -> TID atomic transition of the futex value
1987 * and failed. The kernel side here does the whole locking operation:
1988 * if there are waiters then it will block, it does PI, etc. (Due to
1989 * races the kernel might see a 0 value of the futex too.)
1991 static int futex_lock_pi(u32 __user
*uaddr
, unsigned int flags
, int detect
,
1992 ktime_t
*time
, int trylock
)
1994 struct hrtimer_sleeper timeout
, *to
= NULL
;
1995 struct futex_hash_bucket
*hb
;
1996 struct futex_q q
= futex_q_init
;
1999 if (refill_pi_state_cache())
2004 hrtimer_init_on_stack(&to
->timer
, CLOCK_REALTIME
,
2006 hrtimer_init_sleeper(to
, current
);
2007 hrtimer_set_expires(&to
->timer
, *time
);
2011 ret
= get_futex_key(uaddr
, flags
& FLAGS_SHARED
, &q
.key
, VERIFY_WRITE
);
2012 if (unlikely(ret
!= 0))
2016 hb
= queue_lock(&q
);
2018 ret
= futex_lock_pi_atomic(uaddr
, hb
, &q
.key
, &q
.pi_state
, current
, 0);
2019 if (unlikely(ret
)) {
2022 /* We got the lock. */
2024 goto out_unlock_put_key
;
2029 * Task is exiting and we just wait for the
2032 queue_unlock(&q
, hb
);
2033 put_futex_key(&q
.key
);
2037 goto out_unlock_put_key
;
2042 * Only actually queue now that the atomic ops are done:
2046 WARN_ON(!q
.pi_state
);
2048 * Block on the PI mutex:
2051 ret
= rt_mutex_timed_lock(&q
.pi_state
->pi_mutex
, to
, 1);
2053 ret
= rt_mutex_trylock(&q
.pi_state
->pi_mutex
);
2054 /* Fixup the trylock return value: */
2055 ret
= ret
? 0 : -EWOULDBLOCK
;
2058 spin_lock(q
.lock_ptr
);
2060 * Fixup the pi_state owner and possibly acquire the lock if we
2063 res
= fixup_owner(uaddr
, &q
, !ret
);
2065 * If fixup_owner() returned an error, proprogate that. If it acquired
2066 * the lock, clear our -ETIMEDOUT or -EINTR.
2069 ret
= (res
< 0) ? res
: 0;
2072 * If fixup_owner() faulted and was unable to handle the fault, unlock
2073 * it and return the fault to userspace.
2075 if (ret
&& (rt_mutex_owner(&q
.pi_state
->pi_mutex
) == current
))
2076 rt_mutex_unlock(&q
.pi_state
->pi_mutex
);
2078 /* Unqueue and drop the lock */
2084 queue_unlock(&q
, hb
);
2087 put_futex_key(&q
.key
);
2090 destroy_hrtimer_on_stack(&to
->timer
);
2091 return ret
!= -EINTR
? ret
: -ERESTARTNOINTR
;
2094 queue_unlock(&q
, hb
);
2096 ret
= fault_in_user_writeable(uaddr
);
2100 if (!(flags
& FLAGS_SHARED
))
2103 put_futex_key(&q
.key
);
2108 * Userspace attempted a TID -> 0 atomic transition, and failed.
2109 * This is the in-kernel slowpath: we look up the PI state (if any),
2110 * and do the rt-mutex unlock.
2112 static int futex_unlock_pi(u32 __user
*uaddr
, unsigned int flags
)
2114 struct futex_hash_bucket
*hb
;
2115 struct futex_q
*this, *next
;
2116 struct plist_head
*head
;
2117 union futex_key key
= FUTEX_KEY_INIT
;
2118 u32 uval
, vpid
= task_pid_vnr(current
);
2122 if (get_user(uval
, uaddr
))
2125 * We release only a lock we actually own:
2127 if ((uval
& FUTEX_TID_MASK
) != vpid
)
2130 ret
= get_futex_key(uaddr
, flags
& FLAGS_SHARED
, &key
, VERIFY_WRITE
);
2131 if (unlikely(ret
!= 0))
2134 hb
= hash_futex(&key
);
2135 spin_lock(&hb
->lock
);
2138 * To avoid races, try to do the TID -> 0 atomic transition
2139 * again. If it succeeds then we can return without waking
2142 if (!(uval
& FUTEX_OWNER_DIED
) &&
2143 cmpxchg_futex_value_locked(&uval
, uaddr
, vpid
, 0))
2146 * Rare case: we managed to release the lock atomically,
2147 * no need to wake anyone else up:
2149 if (unlikely(uval
== vpid
))
2153 * Ok, other tasks may need to be woken up - check waiters
2154 * and do the wakeup if necessary:
2158 plist_for_each_entry_safe(this, next
, head
, list
) {
2159 if (!match_futex (&this->key
, &key
))
2161 ret
= wake_futex_pi(uaddr
, uval
, this);
2163 * The atomic access to the futex value
2164 * generated a pagefault, so retry the
2165 * user-access and the wakeup:
2172 * No waiters - kernel unlocks the futex:
2174 if (!(uval
& FUTEX_OWNER_DIED
)) {
2175 ret
= unlock_futex_pi(uaddr
, uval
);
2181 spin_unlock(&hb
->lock
);
2182 put_futex_key(&key
);
2188 spin_unlock(&hb
->lock
);
2189 put_futex_key(&key
);
2191 ret
= fault_in_user_writeable(uaddr
);
2199 * handle_early_requeue_pi_wakeup() - Detect early wakeup on the initial futex
2200 * @hb: the hash_bucket futex_q was original enqueued on
2201 * @q: the futex_q woken while waiting to be requeued
2202 * @key2: the futex_key of the requeue target futex
2203 * @timeout: the timeout associated with the wait (NULL if none)
2205 * Detect if the task was woken on the initial futex as opposed to the requeue
2206 * target futex. If so, determine if it was a timeout or a signal that caused
2207 * the wakeup and return the appropriate error code to the caller. Must be
2208 * called with the hb lock held.
2211 * 0 = no early wakeup detected;
2212 * <0 = -ETIMEDOUT or -ERESTARTNOINTR
2215 int handle_early_requeue_pi_wakeup(struct futex_hash_bucket
*hb
,
2216 struct futex_q
*q
, union futex_key
*key2
,
2217 struct hrtimer_sleeper
*timeout
)
2222 * With the hb lock held, we avoid races while we process the wakeup.
2223 * We only need to hold hb (and not hb2) to ensure atomicity as the
2224 * wakeup code can't change q.key from uaddr to uaddr2 if we hold hb.
2225 * It can't be requeued from uaddr2 to something else since we don't
2226 * support a PI aware source futex for requeue.
2228 if (!match_futex(&q
->key
, key2
)) {
2229 WARN_ON(q
->lock_ptr
&& (&hb
->lock
!= q
->lock_ptr
));
2231 * We were woken prior to requeue by a timeout or a signal.
2232 * Unqueue the futex_q and determine which it was.
2234 plist_del(&q
->list
, &hb
->chain
);
2236 /* Handle spurious wakeups gracefully */
2238 if (timeout
&& !timeout
->task
)
2240 else if (signal_pending(current
))
2241 ret
= -ERESTARTNOINTR
;
2247 * futex_wait_requeue_pi() - Wait on uaddr and take uaddr2
2248 * @uaddr: the futex we initially wait on (non-pi)
2249 * @flags: futex flags (FLAGS_SHARED, FLAGS_CLOCKRT, etc.), they must be
2250 * the same type, no requeueing from private to shared, etc.
2251 * @val: the expected value of uaddr
2252 * @abs_time: absolute timeout
2253 * @bitset: 32 bit wakeup bitset set by userspace, defaults to all
2254 * @uaddr2: the pi futex we will take prior to returning to user-space
2256 * The caller will wait on uaddr and will be requeued by futex_requeue() to
2257 * uaddr2 which must be PI aware and unique from uaddr. Normal wakeup will wake
2258 * on uaddr2 and complete the acquisition of the rt_mutex prior to returning to
2259 * userspace. This ensures the rt_mutex maintains an owner when it has waiters;
2260 * without one, the pi logic would not know which task to boost/deboost, if
2261 * there was a need to.
2263 * We call schedule in futex_wait_queue_me() when we enqueue and return there
2264 * via the following--
2265 * 1) wakeup on uaddr2 after an atomic lock acquisition by futex_requeue()
2266 * 2) wakeup on uaddr2 after a requeue
2270 * If 3, cleanup and return -ERESTARTNOINTR.
2272 * If 2, we may then block on trying to take the rt_mutex and return via:
2273 * 5) successful lock
2276 * 8) other lock acquisition failure
2278 * If 6, return -EWOULDBLOCK (restarting the syscall would do the same).
2280 * If 4 or 7, we cleanup and return with -ETIMEDOUT.
2286 static int futex_wait_requeue_pi(u32 __user
*uaddr
, unsigned int flags
,
2287 u32 val
, ktime_t
*abs_time
, u32 bitset
,
2290 struct hrtimer_sleeper timeout
, *to
= NULL
;
2291 struct rt_mutex_waiter rt_waiter
;
2292 struct rt_mutex
*pi_mutex
= NULL
;
2293 struct futex_hash_bucket
*hb
;
2294 union futex_key key2
= FUTEX_KEY_INIT
;
2295 struct futex_q q
= futex_q_init
;
2298 if (uaddr
== uaddr2
)
2306 hrtimer_init_on_stack(&to
->timer
, (flags
& FLAGS_CLOCKRT
) ?
2307 CLOCK_REALTIME
: CLOCK_MONOTONIC
,
2309 hrtimer_init_sleeper(to
, current
);
2310 hrtimer_set_expires_range_ns(&to
->timer
, *abs_time
,
2311 current
->timer_slack_ns
);
2315 * The waiter is allocated on our stack, manipulated by the requeue
2316 * code while we sleep on uaddr.
2318 debug_rt_mutex_init_waiter(&rt_waiter
);
2319 rt_waiter
.task
= NULL
;
2321 ret
= get_futex_key(uaddr2
, flags
& FLAGS_SHARED
, &key2
, VERIFY_WRITE
);
2322 if (unlikely(ret
!= 0))
2326 q
.rt_waiter
= &rt_waiter
;
2327 q
.requeue_pi_key
= &key2
;
2330 * Prepare to wait on uaddr. On success, increments q.key (key1) ref
2333 ret
= futex_wait_setup(uaddr
, val
, flags
, &q
, &hb
);
2337 /* Queue the futex_q, drop the hb lock, wait for wakeup. */
2338 futex_wait_queue_me(hb
, &q
, to
);
2340 spin_lock(&hb
->lock
);
2341 ret
= handle_early_requeue_pi_wakeup(hb
, &q
, &key2
, to
);
2342 spin_unlock(&hb
->lock
);
2347 * In order for us to be here, we know our q.key == key2, and since
2348 * we took the hb->lock above, we also know that futex_requeue() has
2349 * completed and we no longer have to concern ourselves with a wakeup
2350 * race with the atomic proxy lock acquisition by the requeue code. The
2351 * futex_requeue dropped our key1 reference and incremented our key2
2355 /* Check if the requeue code acquired the second futex for us. */
2358 * Got the lock. We might not be the anticipated owner if we
2359 * did a lock-steal - fix up the PI-state in that case.
2361 if (q
.pi_state
&& (q
.pi_state
->owner
!= current
)) {
2362 spin_lock(q
.lock_ptr
);
2363 ret
= fixup_pi_state_owner(uaddr2
, &q
, current
);
2364 spin_unlock(q
.lock_ptr
);
2368 * We have been woken up by futex_unlock_pi(), a timeout, or a
2369 * signal. futex_unlock_pi() will not destroy the lock_ptr nor
2372 WARN_ON(!q
.pi_state
);
2373 pi_mutex
= &q
.pi_state
->pi_mutex
;
2374 ret
= rt_mutex_finish_proxy_lock(pi_mutex
, to
, &rt_waiter
, 1);
2375 debug_rt_mutex_free_waiter(&rt_waiter
);
2377 spin_lock(q
.lock_ptr
);
2379 * Fixup the pi_state owner and possibly acquire the lock if we
2382 res
= fixup_owner(uaddr2
, &q
, !ret
);
2384 * If fixup_owner() returned an error, proprogate that. If it
2385 * acquired the lock, clear -ETIMEDOUT or -EINTR.
2388 ret
= (res
< 0) ? res
: 0;
2390 /* Unqueue and drop the lock. */
2395 * If fixup_pi_state_owner() faulted and was unable to handle the
2396 * fault, unlock the rt_mutex and return the fault to userspace.
2398 if (ret
== -EFAULT
) {
2399 if (pi_mutex
&& rt_mutex_owner(pi_mutex
) == current
)
2400 rt_mutex_unlock(pi_mutex
);
2401 } else if (ret
== -EINTR
) {
2403 * We've already been requeued, but cannot restart by calling
2404 * futex_lock_pi() directly. We could restart this syscall, but
2405 * it would detect that the user space "val" changed and return
2406 * -EWOULDBLOCK. Save the overhead of the restart and return
2407 * -EWOULDBLOCK directly.
2413 put_futex_key(&q
.key
);
2415 put_futex_key(&key2
);
2419 hrtimer_cancel(&to
->timer
);
2420 destroy_hrtimer_on_stack(&to
->timer
);
2426 * Support for robust futexes: the kernel cleans up held futexes at
2429 * Implementation: user-space maintains a per-thread list of locks it
2430 * is holding. Upon do_exit(), the kernel carefully walks this list,
2431 * and marks all locks that are owned by this thread with the
2432 * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is
2433 * always manipulated with the lock held, so the list is private and
2434 * per-thread. Userspace also maintains a per-thread 'list_op_pending'
2435 * field, to allow the kernel to clean up if the thread dies after
2436 * acquiring the lock, but just before it could have added itself to
2437 * the list. There can only be one such pending lock.
2441 * sys_set_robust_list() - Set the robust-futex list head of a task
2442 * @head: pointer to the list-head
2443 * @len: length of the list-head, as userspace expects
2445 SYSCALL_DEFINE2(set_robust_list
, struct robust_list_head __user
*, head
,
2448 if (!futex_cmpxchg_enabled
)
2451 * The kernel knows only one size for now:
2453 if (unlikely(len
!= sizeof(*head
)))
2456 current
->robust_list
= head
;
2462 * sys_get_robust_list() - Get the robust-futex list head of a task
2463 * @pid: pid of the process [zero for current task]
2464 * @head_ptr: pointer to a list-head pointer, the kernel fills it in
2465 * @len_ptr: pointer to a length field, the kernel fills in the header size
2467 SYSCALL_DEFINE3(get_robust_list
, int, pid
,
2468 struct robust_list_head __user
* __user
*, head_ptr
,
2469 size_t __user
*, len_ptr
)
2471 struct robust_list_head __user
*head
;
2473 struct task_struct
*p
;
2475 if (!futex_cmpxchg_enabled
)
2484 p
= find_task_by_vpid(pid
);
2490 if (!ptrace_may_access(p
, PTRACE_MODE_READ
))
2493 head
= p
->robust_list
;
2496 if (put_user(sizeof(*head
), len_ptr
))
2498 return put_user(head
, head_ptr
);
2507 * Process a futex-list entry, check whether it's owned by the
2508 * dying task, and do notification if so:
2510 int handle_futex_death(u32 __user
*uaddr
, struct task_struct
*curr
, int pi
)
2512 u32 uval
, uninitialized_var(nval
), mval
;
2515 if (get_user(uval
, uaddr
))
2518 if ((uval
& FUTEX_TID_MASK
) == task_pid_vnr(curr
)) {
2520 * Ok, this dying thread is truly holding a futex
2521 * of interest. Set the OWNER_DIED bit atomically
2522 * via cmpxchg, and if the value had FUTEX_WAITERS
2523 * set, wake up a waiter (if any). (We have to do a
2524 * futex_wake() even if OWNER_DIED is already set -
2525 * to handle the rare but possible case of recursive
2526 * thread-death.) The rest of the cleanup is done in
2529 mval
= (uval
& FUTEX_WAITERS
) | FUTEX_OWNER_DIED
;
2531 * We are not holding a lock here, but we want to have
2532 * the pagefault_disable/enable() protection because
2533 * we want to handle the fault gracefully. If the
2534 * access fails we try to fault in the futex with R/W
2535 * verification via get_user_pages. get_user() above
2536 * does not guarantee R/W access. If that fails we
2537 * give up and leave the futex locked.
2539 if (cmpxchg_futex_value_locked(&nval
, uaddr
, uval
, mval
)) {
2540 if (fault_in_user_writeable(uaddr
))
2548 * Wake robust non-PI futexes here. The wakeup of
2549 * PI futexes happens in exit_pi_state():
2551 if (!pi
&& (uval
& FUTEX_WAITERS
))
2552 futex_wake(uaddr
, 1, 1, FUTEX_BITSET_MATCH_ANY
);
2558 * Fetch a robust-list pointer. Bit 0 signals PI futexes:
2560 static inline int fetch_robust_entry(struct robust_list __user
**entry
,
2561 struct robust_list __user
* __user
*head
,
2564 unsigned long uentry
;
2566 if (get_user(uentry
, (unsigned long __user
*)head
))
2569 *entry
= (void __user
*)(uentry
& ~1UL);
2576 * Walk curr->robust_list (very carefully, it's a userspace list!)
2577 * and mark any locks found there dead, and notify any waiters.
2579 * We silently return on any sign of list-walking problem.
2581 void exit_robust_list(struct task_struct
*curr
)
2583 struct robust_list_head __user
*head
= curr
->robust_list
;
2584 struct robust_list __user
*entry
, *next_entry
, *pending
;
2585 unsigned int limit
= ROBUST_LIST_LIMIT
, pi
, pip
;
2586 unsigned int uninitialized_var(next_pi
);
2587 unsigned long futex_offset
;
2590 if (!futex_cmpxchg_enabled
)
2594 * Fetch the list head (which was registered earlier, via
2595 * sys_set_robust_list()):
2597 if (fetch_robust_entry(&entry
, &head
->list
.next
, &pi
))
2600 * Fetch the relative futex offset:
2602 if (get_user(futex_offset
, &head
->futex_offset
))
2605 * Fetch any possibly pending lock-add first, and handle it
2608 if (fetch_robust_entry(&pending
, &head
->list_op_pending
, &pip
))
2611 next_entry
= NULL
; /* avoid warning with gcc */
2612 while (entry
!= &head
->list
) {
2614 * Fetch the next entry in the list before calling
2615 * handle_futex_death:
2617 rc
= fetch_robust_entry(&next_entry
, &entry
->next
, &next_pi
);
2619 * A pending lock might already be on the list, so
2620 * don't process it twice:
2622 if (entry
!= pending
)
2623 if (handle_futex_death((void __user
*)entry
+ futex_offset
,
2631 * Avoid excessively long or circular lists:
2640 handle_futex_death((void __user
*)pending
+ futex_offset
,
2644 long do_futex(u32 __user
*uaddr
, int op
, u32 val
, ktime_t
*timeout
,
2645 u32 __user
*uaddr2
, u32 val2
, u32 val3
)
2647 int cmd
= op
& FUTEX_CMD_MASK
;
2648 unsigned int flags
= 0;
2650 if (!(op
& FUTEX_PRIVATE_FLAG
))
2651 flags
|= FLAGS_SHARED
;
2653 if (op
& FUTEX_CLOCK_REALTIME
) {
2654 flags
|= FLAGS_CLOCKRT
;
2655 if (cmd
!= FUTEX_WAIT_BITSET
&& cmd
!= FUTEX_WAIT_REQUEUE_PI
)
2661 case FUTEX_UNLOCK_PI
:
2662 case FUTEX_TRYLOCK_PI
:
2663 case FUTEX_WAIT_REQUEUE_PI
:
2664 case FUTEX_CMP_REQUEUE_PI
:
2665 if (!futex_cmpxchg_enabled
)
2671 val3
= FUTEX_BITSET_MATCH_ANY
;
2672 case FUTEX_WAIT_BITSET
:
2673 return futex_wait(uaddr
, flags
, val
, timeout
, val3
);
2675 val3
= FUTEX_BITSET_MATCH_ANY
;
2676 case FUTEX_WAKE_BITSET
:
2677 return futex_wake(uaddr
, flags
, val
, val3
);
2679 return futex_requeue(uaddr
, flags
, uaddr2
, val
, val2
, NULL
, 0);
2680 case FUTEX_CMP_REQUEUE
:
2681 return futex_requeue(uaddr
, flags
, uaddr2
, val
, val2
, &val3
, 0);
2683 return futex_wake_op(uaddr
, flags
, uaddr2
, val
, val2
, val3
);
2685 return futex_lock_pi(uaddr
, flags
, val
, timeout
, 0);
2686 case FUTEX_UNLOCK_PI
:
2687 return futex_unlock_pi(uaddr
, flags
);
2688 case FUTEX_TRYLOCK_PI
:
2689 return futex_lock_pi(uaddr
, flags
, 0, timeout
, 1);
2690 case FUTEX_WAIT_REQUEUE_PI
:
2691 val3
= FUTEX_BITSET_MATCH_ANY
;
2692 return futex_wait_requeue_pi(uaddr
, flags
, val
, timeout
, val3
,
2694 case FUTEX_CMP_REQUEUE_PI
:
2695 return futex_requeue(uaddr
, flags
, uaddr2
, val
, val2
, &val3
, 1);
2701 SYSCALL_DEFINE6(futex
, u32 __user
*, uaddr
, int, op
, u32
, val
,
2702 struct timespec __user
*, utime
, u32 __user
*, uaddr2
,
2706 ktime_t t
, *tp
= NULL
;
2708 int cmd
= op
& FUTEX_CMD_MASK
;
2710 if (utime
&& (cmd
== FUTEX_WAIT
|| cmd
== FUTEX_LOCK_PI
||
2711 cmd
== FUTEX_WAIT_BITSET
||
2712 cmd
== FUTEX_WAIT_REQUEUE_PI
)) {
2713 if (copy_from_user(&ts
, utime
, sizeof(ts
)) != 0)
2715 if (!timespec_valid(&ts
))
2718 t
= timespec_to_ktime(ts
);
2719 if (cmd
== FUTEX_WAIT
)
2720 t
= ktime_add_safe(ktime_get(), t
);
2724 * requeue parameter in 'utime' if cmd == FUTEX_*_REQUEUE_*.
2725 * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP.
2727 if (cmd
== FUTEX_REQUEUE
|| cmd
== FUTEX_CMP_REQUEUE
||
2728 cmd
== FUTEX_CMP_REQUEUE_PI
|| cmd
== FUTEX_WAKE_OP
)
2729 val2
= (u32
) (unsigned long) utime
;
2731 return do_futex(uaddr
, op
, val
, tp
, uaddr2
, val2
, val3
);
2734 static int __init
futex_init(void)
2740 * This will fail and we want it. Some arch implementations do
2741 * runtime detection of the futex_atomic_cmpxchg_inatomic()
2742 * functionality. We want to know that before we call in any
2743 * of the complex code paths. Also we want to prevent
2744 * registration of robust lists in that case. NULL is
2745 * guaranteed to fault and we get -EFAULT on functional
2746 * implementation, the non-functional ones will return
2749 if (cmpxchg_futex_value_locked(&curval
, NULL
, 0, 0) == -EFAULT
)
2750 futex_cmpxchg_enabled
= 1;
2752 for (i
= 0; i
< ARRAY_SIZE(futex_queues
); i
++) {
2753 plist_head_init(&futex_queues
[i
].chain
);
2754 spin_lock_init(&futex_queues
[i
].lock
);
2759 __initcall(futex_init
);