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 * Thanks to Ben LaHaise for yelling "hashed waitqueues" loudly
20 * enough at me, Linus for the original (flawed) idea, Matthew
21 * Kirkwood for proof-of-concept implementation.
23 * "The futexes are also cursed."
24 * "But they come in a choice of three flavours!"
26 * This program is free software; you can redistribute it and/or modify
27 * it under the terms of the GNU General Public License as published by
28 * the Free Software Foundation; either version 2 of the License, or
29 * (at your option) any later version.
31 * This program is distributed in the hope that it will be useful,
32 * but WITHOUT ANY WARRANTY; without even the implied warranty of
33 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
34 * GNU General Public License for more details.
36 * You should have received a copy of the GNU General Public License
37 * along with this program; if not, write to the Free Software
38 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
40 #include <linux/slab.h>
41 #include <linux/poll.h>
43 #include <linux/file.h>
44 #include <linux/jhash.h>
45 #include <linux/init.h>
46 #include <linux/futex.h>
47 #include <linux/mount.h>
48 #include <linux/pagemap.h>
49 #include <linux/syscalls.h>
50 #include <linux/signal.h>
51 #include <linux/module.h>
52 #include <asm/futex.h>
54 #include "rtmutex_common.h"
56 #define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)
59 * Priority Inheritance state:
61 struct futex_pi_state
{
63 * list of 'owned' pi_state instances - these have to be
64 * cleaned up in do_exit() if the task exits prematurely:
66 struct list_head list
;
71 struct rt_mutex pi_mutex
;
73 struct task_struct
*owner
;
80 * We use this hashed waitqueue instead of a normal wait_queue_t, so
81 * we can wake only the relevant ones (hashed queues may be shared).
83 * A futex_q has a woken state, just like tasks have TASK_RUNNING.
84 * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0.
85 * The order of wakup is always to make the first condition true, then
86 * wake up q->waiters, then make the second condition true.
89 struct plist_node list
;
90 wait_queue_head_t waiters
;
92 /* Which hash list lock to use: */
95 /* Key which the futex is hashed on: */
98 /* For fd, sigio sent using these: */
102 /* Optional priority inheritance state: */
103 struct futex_pi_state
*pi_state
;
104 struct task_struct
*task
;
108 * Split the global futex_lock into every hash list lock.
110 struct futex_hash_bucket
{
112 struct plist_head chain
;
115 static struct futex_hash_bucket futex_queues
[1<<FUTEX_HASHBITS
];
117 /* Futex-fs vfsmount entry: */
118 static struct vfsmount
*futex_mnt
;
121 * We hash on the keys returned from get_futex_key (see below).
123 static struct futex_hash_bucket
*hash_futex(union futex_key
*key
)
125 u32 hash
= jhash2((u32
*)&key
->both
.word
,
126 (sizeof(key
->both
.word
)+sizeof(key
->both
.ptr
))/4,
128 return &futex_queues
[hash
& ((1 << FUTEX_HASHBITS
)-1)];
132 * Return 1 if two futex_keys are equal, 0 otherwise.
134 static inline int match_futex(union futex_key
*key1
, union futex_key
*key2
)
136 return (key1
->both
.word
== key2
->both
.word
137 && key1
->both
.ptr
== key2
->both
.ptr
138 && key1
->both
.offset
== key2
->both
.offset
);
142 * Get parameters which are the keys for a futex.
144 * For shared mappings, it's (page->index, vma->vm_file->f_path.dentry->d_inode,
145 * offset_within_page). For private mappings, it's (uaddr, current->mm).
146 * We can usually work out the index without swapping in the page.
148 * Returns: 0, or negative error code.
149 * The key words are stored in *key on success.
151 * Should be called with ¤t->mm->mmap_sem but NOT any spinlocks.
153 int get_futex_key(u32 __user
*uaddr
, union futex_key
*key
)
155 unsigned long address
= (unsigned long)uaddr
;
156 struct mm_struct
*mm
= current
->mm
;
157 struct vm_area_struct
*vma
;
162 * The futex address must be "naturally" aligned.
164 key
->both
.offset
= address
% PAGE_SIZE
;
165 if (unlikely((key
->both
.offset
% sizeof(u32
)) != 0))
167 address
-= key
->both
.offset
;
170 * The futex is hashed differently depending on whether
171 * it's in a shared or private mapping. So check vma first.
173 vma
= find_extend_vma(mm
, address
);
180 if (unlikely((vma
->vm_flags
& (VM_IO
|VM_READ
)) != VM_READ
))
181 return (vma
->vm_flags
& VM_IO
) ? -EPERM
: -EACCES
;
184 * Private mappings are handled in a simple way.
186 * NOTE: When userspace waits on a MAP_SHARED mapping, even if
187 * it's a read-only handle, it's expected that futexes attach to
188 * the object not the particular process. Therefore we use
189 * VM_MAYSHARE here, not VM_SHARED which is restricted to shared
190 * mappings of _writable_ handles.
192 if (likely(!(vma
->vm_flags
& VM_MAYSHARE
))) {
193 key
->private.mm
= mm
;
194 key
->private.address
= address
;
199 * Linear file mappings are also simple.
201 key
->shared
.inode
= vma
->vm_file
->f_path
.dentry
->d_inode
;
202 key
->both
.offset
++; /* Bit 0 of offset indicates inode-based key. */
203 if (likely(!(vma
->vm_flags
& VM_NONLINEAR
))) {
204 key
->shared
.pgoff
= (((address
- vma
->vm_start
) >> PAGE_SHIFT
)
210 * We could walk the page table to read the non-linear
211 * pte, and get the page index without fetching the page
212 * from swap. But that's a lot of code to duplicate here
213 * for a rare case, so we simply fetch the page.
215 err
= get_user_pages(current
, mm
, address
, 1, 0, 0, &page
, NULL
);
218 page
->index
<< (PAGE_CACHE_SHIFT
- PAGE_SHIFT
);
224 EXPORT_SYMBOL_GPL(get_futex_key
);
227 * Take a reference to the resource addressed by a key.
228 * Can be called while holding spinlocks.
230 * NOTE: mmap_sem MUST be held between get_futex_key() and calling this
231 * function, if it is called at all. mmap_sem keeps key->shared.inode valid.
233 inline void get_futex_key_refs(union futex_key
*key
)
235 if (key
->both
.ptr
!= 0) {
236 if (key
->both
.offset
& 1)
237 atomic_inc(&key
->shared
.inode
->i_count
);
239 atomic_inc(&key
->private.mm
->mm_count
);
242 EXPORT_SYMBOL_GPL(get_futex_key_refs
);
245 * Drop a reference to the resource addressed by a key.
246 * The hash bucket spinlock must not be held.
248 void drop_futex_key_refs(union futex_key
*key
)
250 if (key
->both
.ptr
!= 0) {
251 if (key
->both
.offset
& 1)
252 iput(key
->shared
.inode
);
254 mmdrop(key
->private.mm
);
257 EXPORT_SYMBOL_GPL(drop_futex_key_refs
);
259 static inline int get_futex_value_locked(u32
*dest
, u32 __user
*from
)
264 ret
= __copy_from_user_inatomic(dest
, from
, sizeof(u32
));
267 return ret
? -EFAULT
: 0;
271 * Fault handling. Called with current->mm->mmap_sem held.
273 static int futex_handle_fault(unsigned long address
, int attempt
)
275 struct vm_area_struct
* vma
;
276 struct mm_struct
*mm
= current
->mm
;
278 if (attempt
> 2 || !(vma
= find_vma(mm
, address
)) ||
279 vma
->vm_start
> address
|| !(vma
->vm_flags
& VM_WRITE
))
282 switch (handle_mm_fault(mm
, vma
, address
, 1)) {
298 static int refill_pi_state_cache(void)
300 struct futex_pi_state
*pi_state
;
302 if (likely(current
->pi_state_cache
))
305 pi_state
= kzalloc(sizeof(*pi_state
), GFP_KERNEL
);
310 INIT_LIST_HEAD(&pi_state
->list
);
311 /* pi_mutex gets initialized later */
312 pi_state
->owner
= NULL
;
313 atomic_set(&pi_state
->refcount
, 1);
315 current
->pi_state_cache
= pi_state
;
320 static struct futex_pi_state
* alloc_pi_state(void)
322 struct futex_pi_state
*pi_state
= current
->pi_state_cache
;
325 current
->pi_state_cache
= NULL
;
330 static void free_pi_state(struct futex_pi_state
*pi_state
)
332 if (!atomic_dec_and_test(&pi_state
->refcount
))
336 * If pi_state->owner is NULL, the owner is most probably dying
337 * and has cleaned up the pi_state already
339 if (pi_state
->owner
) {
340 spin_lock_irq(&pi_state
->owner
->pi_lock
);
341 list_del_init(&pi_state
->list
);
342 spin_unlock_irq(&pi_state
->owner
->pi_lock
);
344 rt_mutex_proxy_unlock(&pi_state
->pi_mutex
, pi_state
->owner
);
347 if (current
->pi_state_cache
)
351 * pi_state->list is already empty.
352 * clear pi_state->owner.
353 * refcount is at 0 - put it back to 1.
355 pi_state
->owner
= NULL
;
356 atomic_set(&pi_state
->refcount
, 1);
357 current
->pi_state_cache
= pi_state
;
362 * Look up the task based on what TID userspace gave us.
365 static struct task_struct
* futex_find_get_task(pid_t pid
)
367 struct task_struct
*p
;
370 p
= find_task_by_pid(pid
);
373 if ((current
->euid
!= p
->euid
) && (current
->euid
!= p
->uid
)) {
377 if (p
->exit_state
!= 0) {
389 * This task is holding PI mutexes at exit time => bad.
390 * Kernel cleans up PI-state, but userspace is likely hosed.
391 * (Robust-futex cleanup is separate and might save the day for userspace.)
393 void exit_pi_state_list(struct task_struct
*curr
)
395 struct list_head
*next
, *head
= &curr
->pi_state_list
;
396 struct futex_pi_state
*pi_state
;
397 struct futex_hash_bucket
*hb
;
401 * We are a ZOMBIE and nobody can enqueue itself on
402 * pi_state_list anymore, but we have to be careful
403 * versus waiters unqueueing themselves:
405 spin_lock_irq(&curr
->pi_lock
);
406 while (!list_empty(head
)) {
409 pi_state
= list_entry(next
, struct futex_pi_state
, list
);
411 hb
= hash_futex(&key
);
412 spin_unlock_irq(&curr
->pi_lock
);
414 spin_lock(&hb
->lock
);
416 spin_lock_irq(&curr
->pi_lock
);
418 * We dropped the pi-lock, so re-check whether this
419 * task still owns the PI-state:
421 if (head
->next
!= next
) {
422 spin_unlock(&hb
->lock
);
426 WARN_ON(pi_state
->owner
!= curr
);
427 WARN_ON(list_empty(&pi_state
->list
));
428 list_del_init(&pi_state
->list
);
429 pi_state
->owner
= NULL
;
430 spin_unlock_irq(&curr
->pi_lock
);
432 rt_mutex_unlock(&pi_state
->pi_mutex
);
434 spin_unlock(&hb
->lock
);
436 spin_lock_irq(&curr
->pi_lock
);
438 spin_unlock_irq(&curr
->pi_lock
);
442 lookup_pi_state(u32 uval
, struct futex_hash_bucket
*hb
, struct futex_q
*me
)
444 struct futex_pi_state
*pi_state
= NULL
;
445 struct futex_q
*this, *next
;
446 struct plist_head
*head
;
447 struct task_struct
*p
;
452 plist_for_each_entry_safe(this, next
, head
, list
) {
453 if (match_futex(&this->key
, &me
->key
)) {
455 * Another waiter already exists - bump up
456 * the refcount and return its pi_state:
458 pi_state
= this->pi_state
;
460 * Userspace might have messed up non PI and PI futexes
462 if (unlikely(!pi_state
))
465 WARN_ON(!atomic_read(&pi_state
->refcount
));
467 atomic_inc(&pi_state
->refcount
);
468 me
->pi_state
= pi_state
;
475 * We are the first waiter - try to look up the real owner and attach
476 * the new pi_state to it, but bail out when the owner died bit is set
479 pid
= uval
& FUTEX_TID_MASK
;
480 if (!pid
&& (uval
& FUTEX_OWNER_DIED
))
482 p
= futex_find_get_task(pid
);
486 pi_state
= alloc_pi_state();
489 * Initialize the pi_mutex in locked state and make 'p'
492 rt_mutex_init_proxy_locked(&pi_state
->pi_mutex
, p
);
494 /* Store the key for possible exit cleanups: */
495 pi_state
->key
= me
->key
;
497 spin_lock_irq(&p
->pi_lock
);
498 WARN_ON(!list_empty(&pi_state
->list
));
499 list_add(&pi_state
->list
, &p
->pi_state_list
);
501 spin_unlock_irq(&p
->pi_lock
);
505 me
->pi_state
= pi_state
;
511 * The hash bucket lock must be held when this is called.
512 * Afterwards, the futex_q must not be accessed.
514 static void wake_futex(struct futex_q
*q
)
516 plist_del(&q
->list
, &q
->list
.plist
);
518 send_sigio(&q
->filp
->f_owner
, q
->fd
, POLL_IN
);
520 * The lock in wake_up_all() is a crucial memory barrier after the
521 * plist_del() and also before assigning to q->lock_ptr.
523 wake_up_all(&q
->waiters
);
525 * The waiting task can free the futex_q as soon as this is written,
526 * without taking any locks. This must come last.
528 * A memory barrier is required here to prevent the following store
529 * to lock_ptr from getting ahead of the wakeup. Clearing the lock
530 * at the end of wake_up_all() does not prevent this store from
537 static int wake_futex_pi(u32 __user
*uaddr
, u32 uval
, struct futex_q
*this)
539 struct task_struct
*new_owner
;
540 struct futex_pi_state
*pi_state
= this->pi_state
;
546 spin_lock(&pi_state
->pi_mutex
.wait_lock
);
547 new_owner
= rt_mutex_next_owner(&pi_state
->pi_mutex
);
550 * This happens when we have stolen the lock and the original
551 * pending owner did not enqueue itself back on the rt_mutex.
552 * Thats not a tragedy. We know that way, that a lock waiter
553 * is on the fly. We make the futex_q waiter the pending owner.
556 new_owner
= this->task
;
559 * We pass it to the next owner. (The WAITERS bit is always
560 * kept enabled while there is PI state around. We must also
561 * preserve the owner died bit.)
563 if (!(uval
& FUTEX_OWNER_DIED
)) {
564 newval
= FUTEX_WAITERS
| new_owner
->pid
;
567 curval
= futex_atomic_cmpxchg_inatomic(uaddr
, uval
, newval
);
569 if (curval
== -EFAULT
)
575 spin_lock_irq(&pi_state
->owner
->pi_lock
);
576 WARN_ON(list_empty(&pi_state
->list
));
577 list_del_init(&pi_state
->list
);
578 spin_unlock_irq(&pi_state
->owner
->pi_lock
);
580 spin_lock_irq(&new_owner
->pi_lock
);
581 WARN_ON(!list_empty(&pi_state
->list
));
582 list_add(&pi_state
->list
, &new_owner
->pi_state_list
);
583 pi_state
->owner
= new_owner
;
584 spin_unlock_irq(&new_owner
->pi_lock
);
586 spin_unlock(&pi_state
->pi_mutex
.wait_lock
);
587 rt_mutex_unlock(&pi_state
->pi_mutex
);
592 static int unlock_futex_pi(u32 __user
*uaddr
, u32 uval
)
597 * There is no waiter, so we unlock the futex. The owner died
598 * bit has not to be preserved here. We are the owner:
601 oldval
= futex_atomic_cmpxchg_inatomic(uaddr
, uval
, 0);
604 if (oldval
== -EFAULT
)
613 * Express the locking dependencies for lockdep:
616 double_lock_hb(struct futex_hash_bucket
*hb1
, struct futex_hash_bucket
*hb2
)
619 spin_lock(&hb1
->lock
);
621 spin_lock_nested(&hb2
->lock
, SINGLE_DEPTH_NESTING
);
622 } else { /* hb1 > hb2 */
623 spin_lock(&hb2
->lock
);
624 spin_lock_nested(&hb1
->lock
, SINGLE_DEPTH_NESTING
);
629 * Wake up all waiters hashed on the physical page that is mapped
630 * to this virtual address:
632 static int futex_wake(u32 __user
*uaddr
, int nr_wake
)
634 struct futex_hash_bucket
*hb
;
635 struct futex_q
*this, *next
;
636 struct plist_head
*head
;
640 down_read(¤t
->mm
->mmap_sem
);
642 ret
= get_futex_key(uaddr
, &key
);
643 if (unlikely(ret
!= 0))
646 hb
= hash_futex(&key
);
647 spin_lock(&hb
->lock
);
650 plist_for_each_entry_safe(this, next
, head
, list
) {
651 if (match_futex (&this->key
, &key
)) {
652 if (this->pi_state
) {
657 if (++ret
>= nr_wake
)
662 spin_unlock(&hb
->lock
);
664 up_read(¤t
->mm
->mmap_sem
);
669 * Wake up all waiters hashed on the physical page that is mapped
670 * to this virtual address:
673 futex_wake_op(u32 __user
*uaddr1
, u32 __user
*uaddr2
,
674 int nr_wake
, int nr_wake2
, int op
)
676 union futex_key key1
, key2
;
677 struct futex_hash_bucket
*hb1
, *hb2
;
678 struct plist_head
*head
;
679 struct futex_q
*this, *next
;
680 int ret
, op_ret
, attempt
= 0;
683 down_read(¤t
->mm
->mmap_sem
);
685 ret
= get_futex_key(uaddr1
, &key1
);
686 if (unlikely(ret
!= 0))
688 ret
= get_futex_key(uaddr2
, &key2
);
689 if (unlikely(ret
!= 0))
692 hb1
= hash_futex(&key1
);
693 hb2
= hash_futex(&key2
);
696 double_lock_hb(hb1
, hb2
);
698 op_ret
= futex_atomic_op_inuser(op
, uaddr2
);
699 if (unlikely(op_ret
< 0)) {
702 spin_unlock(&hb1
->lock
);
704 spin_unlock(&hb2
->lock
);
708 * we don't get EFAULT from MMU faults if we don't have an MMU,
709 * but we might get them from range checking
715 if (unlikely(op_ret
!= -EFAULT
)) {
721 * futex_atomic_op_inuser needs to both read and write
722 * *(int __user *)uaddr2, but we can't modify it
723 * non-atomically. Therefore, if get_user below is not
724 * enough, we need to handle the fault ourselves, while
725 * still holding the mmap_sem.
728 if (futex_handle_fault((unsigned long)uaddr2
,
737 * If we would have faulted, release mmap_sem,
738 * fault it in and start all over again.
740 up_read(¤t
->mm
->mmap_sem
);
742 ret
= get_user(dummy
, uaddr2
);
751 plist_for_each_entry_safe(this, next
, head
, list
) {
752 if (match_futex (&this->key
, &key1
)) {
754 if (++ret
>= nr_wake
)
763 plist_for_each_entry_safe(this, next
, head
, list
) {
764 if (match_futex (&this->key
, &key2
)) {
766 if (++op_ret
>= nr_wake2
)
773 spin_unlock(&hb1
->lock
);
775 spin_unlock(&hb2
->lock
);
777 up_read(¤t
->mm
->mmap_sem
);
782 * Requeue all waiters hashed on one physical page to another
785 static int futex_requeue(u32 __user
*uaddr1
, u32 __user
*uaddr2
,
786 int nr_wake
, int nr_requeue
, u32
*cmpval
)
788 union futex_key key1
, key2
;
789 struct futex_hash_bucket
*hb1
, *hb2
;
790 struct plist_head
*head1
;
791 struct futex_q
*this, *next
;
792 int ret
, drop_count
= 0;
795 down_read(¤t
->mm
->mmap_sem
);
797 ret
= get_futex_key(uaddr1
, &key1
);
798 if (unlikely(ret
!= 0))
800 ret
= get_futex_key(uaddr2
, &key2
);
801 if (unlikely(ret
!= 0))
804 hb1
= hash_futex(&key1
);
805 hb2
= hash_futex(&key2
);
807 double_lock_hb(hb1
, hb2
);
809 if (likely(cmpval
!= NULL
)) {
812 ret
= get_futex_value_locked(&curval
, uaddr1
);
815 spin_unlock(&hb1
->lock
);
817 spin_unlock(&hb2
->lock
);
820 * If we would have faulted, release mmap_sem, fault
821 * it in and start all over again.
823 up_read(¤t
->mm
->mmap_sem
);
825 ret
= get_user(curval
, uaddr1
);
832 if (curval
!= *cmpval
) {
839 plist_for_each_entry_safe(this, next
, head1
, list
) {
840 if (!match_futex (&this->key
, &key1
))
842 if (++ret
<= nr_wake
) {
846 * If key1 and key2 hash to the same bucket, no need to
849 if (likely(head1
!= &hb2
->chain
)) {
850 plist_del(&this->list
, &hb1
->chain
);
851 plist_add(&this->list
, &hb2
->chain
);
852 this->lock_ptr
= &hb2
->lock
;
853 #ifdef CONFIG_DEBUG_PI_LIST
854 this->list
.plist
.lock
= &hb2
->lock
;
858 get_futex_key_refs(&key2
);
861 if (ret
- nr_wake
>= nr_requeue
)
867 spin_unlock(&hb1
->lock
);
869 spin_unlock(&hb2
->lock
);
871 /* drop_futex_key_refs() must be called outside the spinlocks. */
872 while (--drop_count
>= 0)
873 drop_futex_key_refs(&key1
);
876 up_read(¤t
->mm
->mmap_sem
);
880 /* The key must be already stored in q->key. */
881 static inline struct futex_hash_bucket
*
882 queue_lock(struct futex_q
*q
, int fd
, struct file
*filp
)
884 struct futex_hash_bucket
*hb
;
889 init_waitqueue_head(&q
->waiters
);
891 get_futex_key_refs(&q
->key
);
892 hb
= hash_futex(&q
->key
);
893 q
->lock_ptr
= &hb
->lock
;
895 spin_lock(&hb
->lock
);
899 static inline void __queue_me(struct futex_q
*q
, struct futex_hash_bucket
*hb
)
904 * The priority used to register this element is
905 * - either the real thread-priority for the real-time threads
906 * (i.e. threads with a priority lower than MAX_RT_PRIO)
907 * - or MAX_RT_PRIO for non-RT threads.
908 * Thus, all RT-threads are woken first in priority order, and
909 * the others are woken last, in FIFO order.
911 prio
= min(current
->normal_prio
, MAX_RT_PRIO
);
913 plist_node_init(&q
->list
, prio
);
914 #ifdef CONFIG_DEBUG_PI_LIST
915 q
->list
.plist
.lock
= &hb
->lock
;
917 plist_add(&q
->list
, &hb
->chain
);
919 spin_unlock(&hb
->lock
);
923 queue_unlock(struct futex_q
*q
, struct futex_hash_bucket
*hb
)
925 spin_unlock(&hb
->lock
);
926 drop_futex_key_refs(&q
->key
);
930 * queue_me and unqueue_me must be called as a pair, each
931 * exactly once. They are called with the hashed spinlock held.
934 /* The key must be already stored in q->key. */
935 static void queue_me(struct futex_q
*q
, int fd
, struct file
*filp
)
937 struct futex_hash_bucket
*hb
;
939 hb
= queue_lock(q
, fd
, filp
);
943 /* Return 1 if we were still queued (ie. 0 means we were woken) */
944 static int unqueue_me(struct futex_q
*q
)
946 spinlock_t
*lock_ptr
;
949 /* In the common case we don't take the spinlock, which is nice. */
951 lock_ptr
= q
->lock_ptr
;
956 * q->lock_ptr can change between reading it and
957 * spin_lock(), causing us to take the wrong lock. This
958 * corrects the race condition.
960 * Reasoning goes like this: if we have the wrong lock,
961 * q->lock_ptr must have changed (maybe several times)
962 * between reading it and the spin_lock(). It can
963 * change again after the spin_lock() but only if it was
964 * already changed before the spin_lock(). It cannot,
965 * however, change back to the original value. Therefore
966 * we can detect whether we acquired the correct lock.
968 if (unlikely(lock_ptr
!= q
->lock_ptr
)) {
969 spin_unlock(lock_ptr
);
972 WARN_ON(plist_node_empty(&q
->list
));
973 plist_del(&q
->list
, &q
->list
.plist
);
977 spin_unlock(lock_ptr
);
981 drop_futex_key_refs(&q
->key
);
986 * PI futexes can not be requeued and must remove themself from the
987 * hash bucket. The hash bucket lock is held on entry and dropped here.
989 static void unqueue_me_pi(struct futex_q
*q
, struct futex_hash_bucket
*hb
)
991 WARN_ON(plist_node_empty(&q
->list
));
992 plist_del(&q
->list
, &q
->list
.plist
);
994 BUG_ON(!q
->pi_state
);
995 free_pi_state(q
->pi_state
);
998 spin_unlock(&hb
->lock
);
1000 drop_futex_key_refs(&q
->key
);
1003 static long futex_wait_restart(struct restart_block
*restart
);
1004 static int futex_wait(u32 __user
*uaddr
, u32 val
, ktime_t
*abs_time
)
1006 struct task_struct
*curr
= current
;
1007 DECLARE_WAITQUEUE(wait
, curr
);
1008 struct futex_hash_bucket
*hb
;
1012 struct hrtimer_sleeper t
;
1017 down_read(&curr
->mm
->mmap_sem
);
1019 ret
= get_futex_key(uaddr
, &q
.key
);
1020 if (unlikely(ret
!= 0))
1021 goto out_release_sem
;
1023 hb
= queue_lock(&q
, -1, NULL
);
1026 * Access the page AFTER the futex is queued.
1027 * Order is important:
1029 * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val);
1030 * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); }
1032 * The basic logical guarantee of a futex is that it blocks ONLY
1033 * if cond(var) is known to be true at the time of blocking, for
1034 * any cond. If we queued after testing *uaddr, that would open
1035 * a race condition where we could block indefinitely with
1036 * cond(var) false, which would violate the guarantee.
1038 * A consequence is that futex_wait() can return zero and absorb
1039 * a wakeup when *uaddr != val on entry to the syscall. This is
1042 * We hold the mmap semaphore, so the mapping cannot have changed
1043 * since we looked it up in get_futex_key.
1045 ret
= get_futex_value_locked(&uval
, uaddr
);
1047 if (unlikely(ret
)) {
1048 queue_unlock(&q
, hb
);
1051 * If we would have faulted, release mmap_sem, fault it in and
1052 * start all over again.
1054 up_read(&curr
->mm
->mmap_sem
);
1056 ret
= get_user(uval
, uaddr
);
1064 goto out_unlock_release_sem
;
1066 /* Only actually queue if *uaddr contained val. */
1070 * Now the futex is queued and we have checked the data, we
1071 * don't want to hold mmap_sem while we sleep.
1073 up_read(&curr
->mm
->mmap_sem
);
1076 * There might have been scheduling since the queue_me(), as we
1077 * cannot hold a spinlock across the get_user() in case it
1078 * faults, and we cannot just set TASK_INTERRUPTIBLE state when
1079 * queueing ourselves into the futex hash. This code thus has to
1080 * rely on the futex_wake() code removing us from hash when it
1084 /* add_wait_queue is the barrier after __set_current_state. */
1085 __set_current_state(TASK_INTERRUPTIBLE
);
1086 add_wait_queue(&q
.waiters
, &wait
);
1088 * !plist_node_empty() is safe here without any lock.
1089 * q.lock_ptr != 0 is not safe, because of ordering against wakeup.
1091 if (likely(!plist_node_empty(&q
.list
))) {
1095 hrtimer_init(&t
.timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_ABS
);
1096 hrtimer_init_sleeper(&t
, current
);
1097 t
.timer
.expires
= *abs_time
;
1099 hrtimer_start(&t
.timer
, t
.timer
.expires
, HRTIMER_MODE_ABS
);
1102 * the timer could have already expired, in which
1103 * case current would be flagged for rescheduling.
1104 * Don't bother calling schedule.
1109 hrtimer_cancel(&t
.timer
);
1111 /* Flag if a timeout occured */
1112 rem
= (t
.task
== NULL
);
1115 __set_current_state(TASK_RUNNING
);
1118 * NOTE: we don't remove ourselves from the waitqueue because
1119 * we are the only user of it.
1122 /* If we were woken (and unqueued), we succeeded, whatever. */
1123 if (!unqueue_me(&q
))
1129 * We expect signal_pending(current), but another thread may
1130 * have handled it for us already.
1133 return -ERESTARTSYS
;
1135 struct restart_block
*restart
;
1136 restart
= ¤t_thread_info()->restart_block
;
1137 restart
->fn
= futex_wait_restart
;
1138 restart
->arg0
= (unsigned long)uaddr
;
1139 restart
->arg1
= (unsigned long)val
;
1140 restart
->arg2
= (unsigned long)abs_time
;
1141 return -ERESTART_RESTARTBLOCK
;
1144 out_unlock_release_sem
:
1145 queue_unlock(&q
, hb
);
1148 up_read(&curr
->mm
->mmap_sem
);
1153 static long futex_wait_restart(struct restart_block
*restart
)
1155 u32 __user
*uaddr
= (u32 __user
*)restart
->arg0
;
1156 u32 val
= (u32
)restart
->arg1
;
1157 ktime_t
*abs_time
= (ktime_t
*)restart
->arg2
;
1159 restart
->fn
= do_no_restart_syscall
;
1160 return (long)futex_wait(uaddr
, val
, abs_time
);
1165 * Userspace tried a 0 -> TID atomic transition of the futex value
1166 * and failed. The kernel side here does the whole locking operation:
1167 * if there are waiters then it will block, it does PI, etc. (Due to
1168 * races the kernel might see a 0 value of the futex too.)
1170 static int futex_lock_pi(u32 __user
*uaddr
, int detect
, ktime_t
*time
,
1173 struct hrtimer_sleeper timeout
, *to
= NULL
;
1174 struct task_struct
*curr
= current
;
1175 struct futex_hash_bucket
*hb
;
1176 u32 uval
, newval
, curval
;
1178 int ret
, attempt
= 0;
1180 if (refill_pi_state_cache())
1185 hrtimer_init(&to
->timer
, CLOCK_REALTIME
, HRTIMER_MODE_ABS
);
1186 hrtimer_init_sleeper(to
, current
);
1187 to
->timer
.expires
= *time
;
1192 down_read(&curr
->mm
->mmap_sem
);
1194 ret
= get_futex_key(uaddr
, &q
.key
);
1195 if (unlikely(ret
!= 0))
1196 goto out_release_sem
;
1198 hb
= queue_lock(&q
, -1, NULL
);
1202 * To avoid races, we attempt to take the lock here again
1203 * (by doing a 0 -> TID atomic cmpxchg), while holding all
1204 * the locks. It will most likely not succeed.
1206 newval
= current
->pid
;
1208 pagefault_disable();
1209 curval
= futex_atomic_cmpxchg_inatomic(uaddr
, 0, newval
);
1212 if (unlikely(curval
== -EFAULT
))
1215 /* We own the lock already */
1216 if (unlikely((curval
& FUTEX_TID_MASK
) == current
->pid
)) {
1218 force_sig(SIGKILL
, current
);
1220 goto out_unlock_release_sem
;
1224 * Surprise - we got the lock. Just return
1227 if (unlikely(!curval
))
1228 goto out_unlock_release_sem
;
1231 newval
= uval
| FUTEX_WAITERS
;
1233 pagefault_disable();
1234 curval
= futex_atomic_cmpxchg_inatomic(uaddr
, uval
, newval
);
1237 if (unlikely(curval
== -EFAULT
))
1239 if (unlikely(curval
!= uval
))
1243 * We dont have the lock. Look up the PI state (or create it if
1244 * we are the first waiter):
1246 ret
= lookup_pi_state(uval
, hb
, &q
);
1248 if (unlikely(ret
)) {
1250 * There were no waiters and the owner task lookup
1251 * failed. When the OWNER_DIED bit is set, then we
1252 * know that this is a robust futex and we actually
1253 * take the lock. This is safe as we are protected by
1254 * the hash bucket lock. We also set the waiters bit
1255 * unconditionally here, to simplify glibc handling of
1256 * multiple tasks racing to acquire the lock and
1257 * cleanup the problems which were left by the dead
1260 if (curval
& FUTEX_OWNER_DIED
) {
1262 newval
= current
->pid
|
1263 FUTEX_OWNER_DIED
| FUTEX_WAITERS
;
1265 pagefault_disable();
1266 curval
= futex_atomic_cmpxchg_inatomic(uaddr
,
1270 if (unlikely(curval
== -EFAULT
))
1272 if (unlikely(curval
!= uval
))
1276 goto out_unlock_release_sem
;
1280 * Only actually queue now that the atomic ops are done:
1285 * Now the futex is queued and we have checked the data, we
1286 * don't want to hold mmap_sem while we sleep.
1288 up_read(&curr
->mm
->mmap_sem
);
1290 WARN_ON(!q
.pi_state
);
1292 * Block on the PI mutex:
1295 ret
= rt_mutex_timed_lock(&q
.pi_state
->pi_mutex
, to
, 1);
1297 ret
= rt_mutex_trylock(&q
.pi_state
->pi_mutex
);
1298 /* Fixup the trylock return value: */
1299 ret
= ret
? 0 : -EWOULDBLOCK
;
1302 down_read(&curr
->mm
->mmap_sem
);
1303 spin_lock(q
.lock_ptr
);
1306 * Got the lock. We might not be the anticipated owner if we
1307 * did a lock-steal - fix up the PI-state in that case.
1309 if (!ret
&& q
.pi_state
->owner
!= curr
) {
1310 u32 newtid
= current
->pid
| FUTEX_WAITERS
;
1313 if (q
.pi_state
->owner
!= NULL
) {
1314 spin_lock_irq(&q
.pi_state
->owner
->pi_lock
);
1315 WARN_ON(list_empty(&q
.pi_state
->list
));
1316 list_del_init(&q
.pi_state
->list
);
1317 spin_unlock_irq(&q
.pi_state
->owner
->pi_lock
);
1319 newtid
|= FUTEX_OWNER_DIED
;
1321 q
.pi_state
->owner
= current
;
1323 spin_lock_irq(¤t
->pi_lock
);
1324 WARN_ON(!list_empty(&q
.pi_state
->list
));
1325 list_add(&q
.pi_state
->list
, ¤t
->pi_state_list
);
1326 spin_unlock_irq(¤t
->pi_lock
);
1328 /* Unqueue and drop the lock */
1329 unqueue_me_pi(&q
, hb
);
1330 up_read(&curr
->mm
->mmap_sem
);
1332 * We own it, so we have to replace the pending owner
1333 * TID. This must be atomic as we have preserve the
1334 * owner died bit here.
1336 ret
= get_user(uval
, uaddr
);
1338 newval
= (uval
& FUTEX_OWNER_DIED
) | newtid
;
1339 curval
= futex_atomic_cmpxchg_inatomic(uaddr
,
1341 if (curval
== -EFAULT
)
1349 * Catch the rare case, where the lock was released
1350 * when we were on the way back before we locked
1353 if (ret
&& q
.pi_state
->owner
== curr
) {
1354 if (rt_mutex_trylock(&q
.pi_state
->pi_mutex
))
1357 /* Unqueue and drop the lock */
1358 unqueue_me_pi(&q
, hb
);
1359 up_read(&curr
->mm
->mmap_sem
);
1362 if (!detect
&& ret
== -EDEADLK
&& 0)
1363 force_sig(SIGKILL
, current
);
1365 return ret
!= -EINTR
? ret
: -ERESTARTNOINTR
;
1367 out_unlock_release_sem
:
1368 queue_unlock(&q
, hb
);
1371 up_read(&curr
->mm
->mmap_sem
);
1376 * We have to r/w *(int __user *)uaddr, but we can't modify it
1377 * non-atomically. Therefore, if get_user below is not
1378 * enough, we need to handle the fault ourselves, while
1379 * still holding the mmap_sem.
1382 if (futex_handle_fault((unsigned long)uaddr
, attempt
)) {
1384 goto out_unlock_release_sem
;
1389 queue_unlock(&q
, hb
);
1390 up_read(&curr
->mm
->mmap_sem
);
1392 ret
= get_user(uval
, uaddr
);
1393 if (!ret
&& (uval
!= -EFAULT
))
1400 * Userspace attempted a TID -> 0 atomic transition, and failed.
1401 * This is the in-kernel slowpath: we look up the PI state (if any),
1402 * and do the rt-mutex unlock.
1404 static int futex_unlock_pi(u32 __user
*uaddr
)
1406 struct futex_hash_bucket
*hb
;
1407 struct futex_q
*this, *next
;
1409 struct plist_head
*head
;
1410 union futex_key key
;
1411 int ret
, attempt
= 0;
1414 if (get_user(uval
, uaddr
))
1417 * We release only a lock we actually own:
1419 if ((uval
& FUTEX_TID_MASK
) != current
->pid
)
1422 * First take all the futex related locks:
1424 down_read(¤t
->mm
->mmap_sem
);
1426 ret
= get_futex_key(uaddr
, &key
);
1427 if (unlikely(ret
!= 0))
1430 hb
= hash_futex(&key
);
1431 spin_lock(&hb
->lock
);
1435 * To avoid races, try to do the TID -> 0 atomic transition
1436 * again. If it succeeds then we can return without waking
1439 if (!(uval
& FUTEX_OWNER_DIED
)) {
1440 pagefault_disable();
1441 uval
= futex_atomic_cmpxchg_inatomic(uaddr
, current
->pid
, 0);
1445 if (unlikely(uval
== -EFAULT
))
1448 * Rare case: we managed to release the lock atomically,
1449 * no need to wake anyone else up:
1451 if (unlikely(uval
== current
->pid
))
1455 * Ok, other tasks may need to be woken up - check waiters
1456 * and do the wakeup if necessary:
1460 plist_for_each_entry_safe(this, next
, head
, list
) {
1461 if (!match_futex (&this->key
, &key
))
1463 ret
= wake_futex_pi(uaddr
, uval
, this);
1465 * The atomic access to the futex value
1466 * generated a pagefault, so retry the
1467 * user-access and the wakeup:
1474 * No waiters - kernel unlocks the futex:
1476 if (!(uval
& FUTEX_OWNER_DIED
)) {
1477 ret
= unlock_futex_pi(uaddr
, uval
);
1483 spin_unlock(&hb
->lock
);
1485 up_read(¤t
->mm
->mmap_sem
);
1491 * We have to r/w *(int __user *)uaddr, but we can't modify it
1492 * non-atomically. Therefore, if get_user below is not
1493 * enough, we need to handle the fault ourselves, while
1494 * still holding the mmap_sem.
1497 if (futex_handle_fault((unsigned long)uaddr
, attempt
)) {
1504 spin_unlock(&hb
->lock
);
1505 up_read(¤t
->mm
->mmap_sem
);
1507 ret
= get_user(uval
, uaddr
);
1508 if (!ret
&& (uval
!= -EFAULT
))
1514 static int futex_close(struct inode
*inode
, struct file
*filp
)
1516 struct futex_q
*q
= filp
->private_data
;
1524 /* This is one-shot: once it's gone off you need a new fd */
1525 static unsigned int futex_poll(struct file
*filp
,
1526 struct poll_table_struct
*wait
)
1528 struct futex_q
*q
= filp
->private_data
;
1531 poll_wait(filp
, &q
->waiters
, wait
);
1534 * plist_node_empty() is safe here without any lock.
1535 * q->lock_ptr != 0 is not safe, because of ordering against wakeup.
1537 if (plist_node_empty(&q
->list
))
1538 ret
= POLLIN
| POLLRDNORM
;
1543 static const struct file_operations futex_fops
= {
1544 .release
= futex_close
,
1549 * Signal allows caller to avoid the race which would occur if they
1550 * set the sigio stuff up afterwards.
1552 static int futex_fd(u32 __user
*uaddr
, int signal
)
1557 static unsigned long printk_interval
;
1559 if (printk_timed_ratelimit(&printk_interval
, 60 * 60 * 1000)) {
1560 printk(KERN_WARNING
"Process `%s' used FUTEX_FD, which "
1561 "will be removed from the kernel in June 2007\n",
1566 if (!valid_signal(signal
))
1569 ret
= get_unused_fd();
1572 filp
= get_empty_filp();
1578 filp
->f_op
= &futex_fops
;
1579 filp
->f_path
.mnt
= mntget(futex_mnt
);
1580 filp
->f_path
.dentry
= dget(futex_mnt
->mnt_root
);
1581 filp
->f_mapping
= filp
->f_path
.dentry
->d_inode
->i_mapping
;
1584 err
= __f_setown(filp
, task_pid(current
), PIDTYPE_PID
, 1);
1588 filp
->f_owner
.signum
= signal
;
1591 q
= kmalloc(sizeof(*q
), GFP_KERNEL
);
1598 down_read(¤t
->mm
->mmap_sem
);
1599 err
= get_futex_key(uaddr
, &q
->key
);
1601 if (unlikely(err
!= 0)) {
1602 up_read(¤t
->mm
->mmap_sem
);
1608 * queue_me() must be called before releasing mmap_sem, because
1609 * key->shared.inode needs to be referenced while holding it.
1611 filp
->private_data
= q
;
1613 queue_me(q
, ret
, filp
);
1614 up_read(¤t
->mm
->mmap_sem
);
1616 /* Now we map fd to filp, so userspace can access it */
1617 fd_install(ret
, filp
);
1628 * Support for robust futexes: the kernel cleans up held futexes at
1631 * Implementation: user-space maintains a per-thread list of locks it
1632 * is holding. Upon do_exit(), the kernel carefully walks this list,
1633 * and marks all locks that are owned by this thread with the
1634 * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is
1635 * always manipulated with the lock held, so the list is private and
1636 * per-thread. Userspace also maintains a per-thread 'list_op_pending'
1637 * field, to allow the kernel to clean up if the thread dies after
1638 * acquiring the lock, but just before it could have added itself to
1639 * the list. There can only be one such pending lock.
1643 * sys_set_robust_list - set the robust-futex list head of a task
1644 * @head: pointer to the list-head
1645 * @len: length of the list-head, as userspace expects
1648 sys_set_robust_list(struct robust_list_head __user
*head
,
1652 * The kernel knows only one size for now:
1654 if (unlikely(len
!= sizeof(*head
)))
1657 current
->robust_list
= head
;
1663 * sys_get_robust_list - get the robust-futex list head of a task
1664 * @pid: pid of the process [zero for current task]
1665 * @head_ptr: pointer to a list-head pointer, the kernel fills it in
1666 * @len_ptr: pointer to a length field, the kernel fills in the header size
1669 sys_get_robust_list(int pid
, struct robust_list_head __user
* __user
*head_ptr
,
1670 size_t __user
*len_ptr
)
1672 struct robust_list_head __user
*head
;
1676 head
= current
->robust_list
;
1678 struct task_struct
*p
;
1682 p
= find_task_by_pid(pid
);
1686 if ((current
->euid
!= p
->euid
) && (current
->euid
!= p
->uid
) &&
1687 !capable(CAP_SYS_PTRACE
))
1689 head
= p
->robust_list
;
1693 if (put_user(sizeof(*head
), len_ptr
))
1695 return put_user(head
, head_ptr
);
1704 * Process a futex-list entry, check whether it's owned by the
1705 * dying task, and do notification if so:
1707 int handle_futex_death(u32 __user
*uaddr
, struct task_struct
*curr
, int pi
)
1709 u32 uval
, nval
, mval
;
1712 if (get_user(uval
, uaddr
))
1715 if ((uval
& FUTEX_TID_MASK
) == curr
->pid
) {
1717 * Ok, this dying thread is truly holding a futex
1718 * of interest. Set the OWNER_DIED bit atomically
1719 * via cmpxchg, and if the value had FUTEX_WAITERS
1720 * set, wake up a waiter (if any). (We have to do a
1721 * futex_wake() even if OWNER_DIED is already set -
1722 * to handle the rare but possible case of recursive
1723 * thread-death.) The rest of the cleanup is done in
1726 mval
= (uval
& FUTEX_WAITERS
) | FUTEX_OWNER_DIED
;
1727 nval
= futex_atomic_cmpxchg_inatomic(uaddr
, uval
, mval
);
1729 if (nval
== -EFAULT
)
1736 * Wake robust non-PI futexes here. The wakeup of
1737 * PI futexes happens in exit_pi_state():
1740 if (uval
& FUTEX_WAITERS
)
1741 futex_wake(uaddr
, 1);
1748 * Fetch a robust-list pointer. Bit 0 signals PI futexes:
1750 static inline int fetch_robust_entry(struct robust_list __user
**entry
,
1751 struct robust_list __user
* __user
*head
,
1754 unsigned long uentry
;
1756 if (get_user(uentry
, (unsigned long __user
*)head
))
1759 *entry
= (void __user
*)(uentry
& ~1UL);
1766 * Walk curr->robust_list (very carefully, it's a userspace list!)
1767 * and mark any locks found there dead, and notify any waiters.
1769 * We silently return on any sign of list-walking problem.
1771 void exit_robust_list(struct task_struct
*curr
)
1773 struct robust_list_head __user
*head
= curr
->robust_list
;
1774 struct robust_list __user
*entry
, *pending
;
1775 unsigned int limit
= ROBUST_LIST_LIMIT
, pi
, pip
;
1776 unsigned long futex_offset
;
1779 * Fetch the list head (which was registered earlier, via
1780 * sys_set_robust_list()):
1782 if (fetch_robust_entry(&entry
, &head
->list
.next
, &pi
))
1785 * Fetch the relative futex offset:
1787 if (get_user(futex_offset
, &head
->futex_offset
))
1790 * Fetch any possibly pending lock-add first, and handle it
1793 if (fetch_robust_entry(&pending
, &head
->list_op_pending
, &pip
))
1797 handle_futex_death((void __user
*)pending
+ futex_offset
, curr
, pip
);
1799 while (entry
!= &head
->list
) {
1801 * A pending lock might already be on the list, so
1802 * don't process it twice:
1804 if (entry
!= pending
)
1805 if (handle_futex_death((void __user
*)entry
+ futex_offset
,
1809 * Fetch the next entry in the list:
1811 if (fetch_robust_entry(&entry
, &entry
->next
, &pi
))
1814 * Avoid excessively long or circular lists:
1823 long do_futex(u32 __user
*uaddr
, int op
, u32 val
, ktime_t
*timeout
,
1824 u32 __user
*uaddr2
, u32 val2
, u32 val3
)
1830 ret
= futex_wait(uaddr
, val
, timeout
);
1833 ret
= futex_wake(uaddr
, val
);
1836 /* non-zero val means F_SETOWN(getpid()) & F_SETSIG(val) */
1837 ret
= futex_fd(uaddr
, val
);
1840 ret
= futex_requeue(uaddr
, uaddr2
, val
, val2
, NULL
);
1842 case FUTEX_CMP_REQUEUE
:
1843 ret
= futex_requeue(uaddr
, uaddr2
, val
, val2
, &val3
);
1846 ret
= futex_wake_op(uaddr
, uaddr2
, val
, val2
, val3
);
1849 ret
= futex_lock_pi(uaddr
, val
, timeout
, 0);
1851 case FUTEX_UNLOCK_PI
:
1852 ret
= futex_unlock_pi(uaddr
);
1854 case FUTEX_TRYLOCK_PI
:
1855 ret
= futex_lock_pi(uaddr
, 0, timeout
, 1);
1864 asmlinkage
long sys_futex(u32 __user
*uaddr
, int op
, u32 val
,
1865 struct timespec __user
*utime
, u32 __user
*uaddr2
,
1869 ktime_t t
, *tp
= NULL
;
1872 if (utime
&& (op
== FUTEX_WAIT
|| op
== FUTEX_LOCK_PI
)) {
1873 if (copy_from_user(&ts
, utime
, sizeof(ts
)) != 0)
1875 if (!timespec_valid(&ts
))
1878 t
= timespec_to_ktime(ts
);
1879 if (op
== FUTEX_WAIT
)
1880 t
= ktime_add(ktime_get(), t
);
1884 * requeue parameter in 'utime' if op == FUTEX_REQUEUE.
1886 if (op
== FUTEX_REQUEUE
|| op
== FUTEX_CMP_REQUEUE
)
1887 val2
= (u32
) (unsigned long) utime
;
1889 return do_futex(uaddr
, op
, val
, tp
, uaddr2
, val2
, val3
);
1892 static int futexfs_get_sb(struct file_system_type
*fs_type
,
1893 int flags
, const char *dev_name
, void *data
,
1894 struct vfsmount
*mnt
)
1896 return get_sb_pseudo(fs_type
, "futex", NULL
, 0xBAD1DEA, mnt
);
1899 static struct file_system_type futex_fs_type
= {
1901 .get_sb
= futexfs_get_sb
,
1902 .kill_sb
= kill_anon_super
,
1905 static int __init
init(void)
1907 int i
= register_filesystem(&futex_fs_type
);
1912 futex_mnt
= kern_mount(&futex_fs_type
);
1913 if (IS_ERR(futex_mnt
)) {
1914 unregister_filesystem(&futex_fs_type
);
1915 return PTR_ERR(futex_mnt
);
1918 for (i
= 0; i
< ARRAY_SIZE(futex_queues
); i
++) {
1919 plist_head_init(&futex_queues
[i
].chain
, &futex_queues
[i
].lock
);
1920 spin_lock_init(&futex_queues
[i
].lock
);