2 * Fast Userspace Mutexes (which I call "Futexes!").
3 * (C) Rusty Russell, IBM 2002
5 * Generalized futexes, futex requeueing, misc fixes by Ingo Molnar
6 * (C) Copyright 2003 Red Hat Inc, All Rights Reserved
8 * Removed page pinning, fix privately mapped COW pages and other cleanups
9 * (C) Copyright 2003, 2004 Jamie Lokier
11 * Robust futex support started by Ingo Molnar
12 * (C) Copyright 2006 Red Hat Inc, All Rights Reserved
13 * Thanks to Thomas Gleixner for suggestions, analysis and fixes.
15 * PI-futex support started by Ingo Molnar and Thomas Gleixner
16 * Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
17 * Copyright (C) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com>
19 * PRIVATE futexes by Eric Dumazet
20 * Copyright (C) 2007 Eric Dumazet <dada1@cosmosbay.com>
22 * Thanks to Ben LaHaise for yelling "hashed waitqueues" loudly
23 * enough at me, Linus for the original (flawed) idea, Matthew
24 * Kirkwood for proof-of-concept implementation.
26 * "The futexes are also cursed."
27 * "But they come in a choice of three flavours!"
29 * This program is free software; you can redistribute it and/or modify
30 * it under the terms of the GNU General Public License as published by
31 * the Free Software Foundation; either version 2 of the License, or
32 * (at your option) any later version.
34 * This program is distributed in the hope that it will be useful,
35 * but WITHOUT ANY WARRANTY; without even the implied warranty of
36 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
37 * GNU General Public License for more details.
39 * You should have received a copy of the GNU General Public License
40 * along with this program; if not, write to the Free Software
41 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
43 #include <linux/slab.h>
44 #include <linux/poll.h>
46 #include <linux/file.h>
47 #include <linux/jhash.h>
48 #include <linux/init.h>
49 #include <linux/futex.h>
50 #include <linux/mount.h>
51 #include <linux/pagemap.h>
52 #include <linux/syscalls.h>
53 #include <linux/signal.h>
54 #include <linux/module.h>
55 #include <linux/magic.h>
56 #include <linux/pid.h>
57 #include <linux/nsproxy.h>
59 #include <asm/futex.h>
61 #include "rtmutex_common.h"
63 int __read_mostly futex_cmpxchg_enabled
;
65 #define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)
68 * Priority Inheritance state:
70 struct futex_pi_state
{
72 * list of 'owned' pi_state instances - these have to be
73 * cleaned up in do_exit() if the task exits prematurely:
75 struct list_head list
;
80 struct rt_mutex pi_mutex
;
82 struct task_struct
*owner
;
89 * We use this hashed waitqueue instead of a normal wait_queue_t, so
90 * we can wake only the relevant ones (hashed queues may be shared).
92 * A futex_q has a woken state, just like tasks have TASK_RUNNING.
93 * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0.
94 * The order of wakup is always to make the first condition true, then
95 * wake up q->waiter, then make the second condition true.
98 struct plist_node list
;
99 /* There can only be a single waiter */
100 wait_queue_head_t waiter
;
102 /* Which hash list lock to use: */
103 spinlock_t
*lock_ptr
;
105 /* Key which the futex is hashed on: */
108 /* Optional priority inheritance state: */
109 struct futex_pi_state
*pi_state
;
110 struct task_struct
*task
;
112 /* Bitset for the optional bitmasked wakeup */
117 * Split the global futex_lock into every hash list lock.
119 struct futex_hash_bucket
{
121 struct plist_head chain
;
124 static struct futex_hash_bucket futex_queues
[1<<FUTEX_HASHBITS
];
127 * We hash on the keys returned from get_futex_key (see below).
129 static struct futex_hash_bucket
*hash_futex(union futex_key
*key
)
131 u32 hash
= jhash2((u32
*)&key
->both
.word
,
132 (sizeof(key
->both
.word
)+sizeof(key
->both
.ptr
))/4,
134 return &futex_queues
[hash
& ((1 << FUTEX_HASHBITS
)-1)];
138 * Return 1 if two futex_keys are equal, 0 otherwise.
140 static inline int match_futex(union futex_key
*key1
, union futex_key
*key2
)
142 return (key1
->both
.word
== key2
->both
.word
143 && key1
->both
.ptr
== key2
->both
.ptr
144 && key1
->both
.offset
== key2
->both
.offset
);
148 * Take a reference to the resource addressed by a key.
149 * Can be called while holding spinlocks.
152 static void get_futex_key_refs(union futex_key
*key
)
157 switch (key
->both
.offset
& (FUT_OFF_INODE
|FUT_OFF_MMSHARED
)) {
159 atomic_inc(&key
->shared
.inode
->i_count
);
161 case FUT_OFF_MMSHARED
:
162 atomic_inc(&key
->private.mm
->mm_count
);
168 * Drop a reference to the resource addressed by a key.
169 * The hash bucket spinlock must not be held.
171 static void drop_futex_key_refs(union futex_key
*key
)
173 if (!key
->both
.ptr
) {
174 /* If we're here then we tried to put a key we failed to get */
179 switch (key
->both
.offset
& (FUT_OFF_INODE
|FUT_OFF_MMSHARED
)) {
181 iput(key
->shared
.inode
);
183 case FUT_OFF_MMSHARED
:
184 mmdrop(key
->private.mm
);
190 * get_futex_key - Get parameters which are the keys for a futex.
191 * @uaddr: virtual address of the futex
192 * @shared: NULL for a PROCESS_PRIVATE futex,
193 * ¤t->mm->mmap_sem for a PROCESS_SHARED futex
194 * @key: address where result is stored.
196 * Returns a negative error code or 0
197 * The key words are stored in *key on success.
199 * For shared mappings, it's (page->index, vma->vm_file->f_path.dentry->d_inode,
200 * offset_within_page). For private mappings, it's (uaddr, current->mm).
201 * We can usually work out the index without swapping in the page.
203 * fshared is NULL for PROCESS_PRIVATE futexes
204 * For other futexes, it points to ¤t->mm->mmap_sem and
205 * caller must have taken the reader lock. but NOT any spinlocks.
207 static int get_futex_key(u32 __user
*uaddr
, int fshared
, union futex_key
*key
)
209 unsigned long address
= (unsigned long)uaddr
;
210 struct mm_struct
*mm
= current
->mm
;
215 * The futex address must be "naturally" aligned.
217 key
->both
.offset
= address
% PAGE_SIZE
;
218 if (unlikely((address
% sizeof(u32
)) != 0))
220 address
-= key
->both
.offset
;
223 * PROCESS_PRIVATE futexes are fast.
224 * As the mm cannot disappear under us and the 'key' only needs
225 * virtual address, we dont even have to find the underlying vma.
226 * Note : We do have to check 'uaddr' is a valid user address,
227 * but access_ok() should be faster than find_vma()
230 if (unlikely(!access_ok(VERIFY_WRITE
, uaddr
, sizeof(u32
))))
232 key
->private.mm
= mm
;
233 key
->private.address
= address
;
234 get_futex_key_refs(key
);
239 err
= get_user_pages_fast(address
, 1, 0, &page
);
244 if (!page
->mapping
) {
251 * Private mappings are handled in a simple way.
253 * NOTE: When userspace waits on a MAP_SHARED mapping, even if
254 * it's a read-only handle, it's expected that futexes attach to
255 * the object not the particular process.
257 if (PageAnon(page
)) {
258 key
->both
.offset
|= FUT_OFF_MMSHARED
; /* ref taken on mm */
259 key
->private.mm
= mm
;
260 key
->private.address
= address
;
262 key
->both
.offset
|= FUT_OFF_INODE
; /* inode-based key */
263 key
->shared
.inode
= page
->mapping
->host
;
264 key
->shared
.pgoff
= page
->index
;
267 get_futex_key_refs(key
);
275 void put_futex_key(int fshared
, union futex_key
*key
)
277 drop_futex_key_refs(key
);
280 static u32
cmpxchg_futex_value_locked(u32 __user
*uaddr
, u32 uval
, u32 newval
)
285 curval
= futex_atomic_cmpxchg_inatomic(uaddr
, uval
, newval
);
291 static int get_futex_value_locked(u32
*dest
, u32 __user
*from
)
296 ret
= __copy_from_user_inatomic(dest
, from
, sizeof(u32
));
299 return ret
? -EFAULT
: 0;
305 static int futex_handle_fault(unsigned long address
, int attempt
)
307 struct vm_area_struct
* vma
;
308 struct mm_struct
*mm
= current
->mm
;
314 down_read(&mm
->mmap_sem
);
315 vma
= find_vma(mm
, address
);
316 if (vma
&& address
>= vma
->vm_start
&&
317 (vma
->vm_flags
& VM_WRITE
)) {
319 fault
= handle_mm_fault(mm
, vma
, address
, 1);
320 if (unlikely((fault
& VM_FAULT_ERROR
))) {
322 /* XXX: let's do this when we verify it is OK */
323 if (ret
& VM_FAULT_OOM
)
328 if (fault
& VM_FAULT_MAJOR
)
334 up_read(&mm
->mmap_sem
);
341 static int refill_pi_state_cache(void)
343 struct futex_pi_state
*pi_state
;
345 if (likely(current
->pi_state_cache
))
348 pi_state
= kzalloc(sizeof(*pi_state
), GFP_KERNEL
);
353 INIT_LIST_HEAD(&pi_state
->list
);
354 /* pi_mutex gets initialized later */
355 pi_state
->owner
= NULL
;
356 atomic_set(&pi_state
->refcount
, 1);
357 pi_state
->key
= FUTEX_KEY_INIT
;
359 current
->pi_state_cache
= pi_state
;
364 static struct futex_pi_state
* alloc_pi_state(void)
366 struct futex_pi_state
*pi_state
= current
->pi_state_cache
;
369 current
->pi_state_cache
= NULL
;
374 static void free_pi_state(struct futex_pi_state
*pi_state
)
376 if (!atomic_dec_and_test(&pi_state
->refcount
))
380 * If pi_state->owner is NULL, the owner is most probably dying
381 * and has cleaned up the pi_state already
383 if (pi_state
->owner
) {
384 spin_lock_irq(&pi_state
->owner
->pi_lock
);
385 list_del_init(&pi_state
->list
);
386 spin_unlock_irq(&pi_state
->owner
->pi_lock
);
388 rt_mutex_proxy_unlock(&pi_state
->pi_mutex
, pi_state
->owner
);
391 if (current
->pi_state_cache
)
395 * pi_state->list is already empty.
396 * clear pi_state->owner.
397 * refcount is at 0 - put it back to 1.
399 pi_state
->owner
= NULL
;
400 atomic_set(&pi_state
->refcount
, 1);
401 current
->pi_state_cache
= pi_state
;
406 * Look up the task based on what TID userspace gave us.
409 static struct task_struct
* futex_find_get_task(pid_t pid
)
411 struct task_struct
*p
;
412 const struct cred
*cred
= current_cred(), *pcred
;
415 p
= find_task_by_vpid(pid
);
419 pcred
= __task_cred(p
);
420 if (cred
->euid
!= pcred
->euid
&&
421 cred
->euid
!= pcred
->uid
)
433 * This task is holding PI mutexes at exit time => bad.
434 * Kernel cleans up PI-state, but userspace is likely hosed.
435 * (Robust-futex cleanup is separate and might save the day for userspace.)
437 void exit_pi_state_list(struct task_struct
*curr
)
439 struct list_head
*next
, *head
= &curr
->pi_state_list
;
440 struct futex_pi_state
*pi_state
;
441 struct futex_hash_bucket
*hb
;
442 union futex_key key
= FUTEX_KEY_INIT
;
444 if (!futex_cmpxchg_enabled
)
447 * We are a ZOMBIE and nobody can enqueue itself on
448 * pi_state_list anymore, but we have to be careful
449 * versus waiters unqueueing themselves:
451 spin_lock_irq(&curr
->pi_lock
);
452 while (!list_empty(head
)) {
455 pi_state
= list_entry(next
, struct futex_pi_state
, list
);
457 hb
= hash_futex(&key
);
458 spin_unlock_irq(&curr
->pi_lock
);
460 spin_lock(&hb
->lock
);
462 spin_lock_irq(&curr
->pi_lock
);
464 * We dropped the pi-lock, so re-check whether this
465 * task still owns the PI-state:
467 if (head
->next
!= next
) {
468 spin_unlock(&hb
->lock
);
472 WARN_ON(pi_state
->owner
!= curr
);
473 WARN_ON(list_empty(&pi_state
->list
));
474 list_del_init(&pi_state
->list
);
475 pi_state
->owner
= NULL
;
476 spin_unlock_irq(&curr
->pi_lock
);
478 rt_mutex_unlock(&pi_state
->pi_mutex
);
480 spin_unlock(&hb
->lock
);
482 spin_lock_irq(&curr
->pi_lock
);
484 spin_unlock_irq(&curr
->pi_lock
);
488 lookup_pi_state(u32 uval
, struct futex_hash_bucket
*hb
,
489 union futex_key
*key
, struct futex_pi_state
**ps
)
491 struct futex_pi_state
*pi_state
= NULL
;
492 struct futex_q
*this, *next
;
493 struct plist_head
*head
;
494 struct task_struct
*p
;
495 pid_t pid
= uval
& FUTEX_TID_MASK
;
499 plist_for_each_entry_safe(this, next
, head
, list
) {
500 if (match_futex(&this->key
, key
)) {
502 * Another waiter already exists - bump up
503 * the refcount and return its pi_state:
505 pi_state
= this->pi_state
;
507 * Userspace might have messed up non PI and PI futexes
509 if (unlikely(!pi_state
))
512 WARN_ON(!atomic_read(&pi_state
->refcount
));
513 WARN_ON(pid
&& pi_state
->owner
&&
514 pi_state
->owner
->pid
!= pid
);
516 atomic_inc(&pi_state
->refcount
);
524 * We are the first waiter - try to look up the real owner and attach
525 * the new pi_state to it, but bail out when TID = 0
529 p
= futex_find_get_task(pid
);
534 * We need to look at the task state flags to figure out,
535 * whether the task is exiting. To protect against the do_exit
536 * change of the task flags, we do this protected by
539 spin_lock_irq(&p
->pi_lock
);
540 if (unlikely(p
->flags
& PF_EXITING
)) {
542 * The task is on the way out. When PF_EXITPIDONE is
543 * set, we know that the task has finished the
546 int ret
= (p
->flags
& PF_EXITPIDONE
) ? -ESRCH
: -EAGAIN
;
548 spin_unlock_irq(&p
->pi_lock
);
553 pi_state
= alloc_pi_state();
556 * Initialize the pi_mutex in locked state and make 'p'
559 rt_mutex_init_proxy_locked(&pi_state
->pi_mutex
, p
);
561 /* Store the key for possible exit cleanups: */
562 pi_state
->key
= *key
;
564 WARN_ON(!list_empty(&pi_state
->list
));
565 list_add(&pi_state
->list
, &p
->pi_state_list
);
567 spin_unlock_irq(&p
->pi_lock
);
577 * The hash bucket lock must be held when this is called.
578 * Afterwards, the futex_q must not be accessed.
580 static void wake_futex(struct futex_q
*q
)
582 plist_del(&q
->list
, &q
->list
.plist
);
584 * The lock in wake_up_all() is a crucial memory barrier after the
585 * plist_del() and also before assigning to q->lock_ptr.
589 * The waiting task can free the futex_q as soon as this is written,
590 * without taking any locks. This must come last.
592 * A memory barrier is required here to prevent the following store
593 * to lock_ptr from getting ahead of the wakeup. Clearing the lock
594 * at the end of wake_up_all() does not prevent this store from
601 static int wake_futex_pi(u32 __user
*uaddr
, u32 uval
, struct futex_q
*this)
603 struct task_struct
*new_owner
;
604 struct futex_pi_state
*pi_state
= this->pi_state
;
610 spin_lock(&pi_state
->pi_mutex
.wait_lock
);
611 new_owner
= rt_mutex_next_owner(&pi_state
->pi_mutex
);
614 * This happens when we have stolen the lock and the original
615 * pending owner did not enqueue itself back on the rt_mutex.
616 * Thats not a tragedy. We know that way, that a lock waiter
617 * is on the fly. We make the futex_q waiter the pending owner.
620 new_owner
= this->task
;
623 * We pass it to the next owner. (The WAITERS bit is always
624 * kept enabled while there is PI state around. We must also
625 * preserve the owner died bit.)
627 if (!(uval
& FUTEX_OWNER_DIED
)) {
630 newval
= FUTEX_WAITERS
| task_pid_vnr(new_owner
);
632 curval
= cmpxchg_futex_value_locked(uaddr
, uval
, newval
);
634 if (curval
== -EFAULT
)
636 else if (curval
!= uval
)
639 spin_unlock(&pi_state
->pi_mutex
.wait_lock
);
644 spin_lock_irq(&pi_state
->owner
->pi_lock
);
645 WARN_ON(list_empty(&pi_state
->list
));
646 list_del_init(&pi_state
->list
);
647 spin_unlock_irq(&pi_state
->owner
->pi_lock
);
649 spin_lock_irq(&new_owner
->pi_lock
);
650 WARN_ON(!list_empty(&pi_state
->list
));
651 list_add(&pi_state
->list
, &new_owner
->pi_state_list
);
652 pi_state
->owner
= new_owner
;
653 spin_unlock_irq(&new_owner
->pi_lock
);
655 spin_unlock(&pi_state
->pi_mutex
.wait_lock
);
656 rt_mutex_unlock(&pi_state
->pi_mutex
);
661 static int unlock_futex_pi(u32 __user
*uaddr
, u32 uval
)
666 * There is no waiter, so we unlock the futex. The owner died
667 * bit has not to be preserved here. We are the owner:
669 oldval
= cmpxchg_futex_value_locked(uaddr
, uval
, 0);
671 if (oldval
== -EFAULT
)
680 * Express the locking dependencies for lockdep:
683 double_lock_hb(struct futex_hash_bucket
*hb1
, struct futex_hash_bucket
*hb2
)
686 spin_lock(&hb1
->lock
);
688 spin_lock_nested(&hb2
->lock
, SINGLE_DEPTH_NESTING
);
689 } else { /* hb1 > hb2 */
690 spin_lock(&hb2
->lock
);
691 spin_lock_nested(&hb1
->lock
, SINGLE_DEPTH_NESTING
);
696 * Wake up all waiters hashed on the physical page that is mapped
697 * to this virtual address:
699 static int futex_wake(u32 __user
*uaddr
, int fshared
, int nr_wake
, u32 bitset
)
701 struct futex_hash_bucket
*hb
;
702 struct futex_q
*this, *next
;
703 struct plist_head
*head
;
704 union futex_key key
= FUTEX_KEY_INIT
;
710 ret
= get_futex_key(uaddr
, fshared
, &key
);
711 if (unlikely(ret
!= 0))
714 hb
= hash_futex(&key
);
715 spin_lock(&hb
->lock
);
718 plist_for_each_entry_safe(this, next
, head
, list
) {
719 if (match_futex (&this->key
, &key
)) {
720 if (this->pi_state
) {
725 /* Check if one of the bits is set in both bitsets */
726 if (!(this->bitset
& bitset
))
730 if (++ret
>= nr_wake
)
735 spin_unlock(&hb
->lock
);
736 put_futex_key(fshared
, &key
);
742 * Wake up all waiters hashed on the physical page that is mapped
743 * to this virtual address:
746 futex_wake_op(u32 __user
*uaddr1
, int fshared
, u32 __user
*uaddr2
,
747 int nr_wake
, int nr_wake2
, int op
)
749 union futex_key key1
= FUTEX_KEY_INIT
, key2
= FUTEX_KEY_INIT
;
750 struct futex_hash_bucket
*hb1
, *hb2
;
751 struct plist_head
*head
;
752 struct futex_q
*this, *next
;
753 int ret
, op_ret
, attempt
= 0;
756 ret
= get_futex_key(uaddr1
, fshared
, &key1
);
757 if (unlikely(ret
!= 0))
759 ret
= get_futex_key(uaddr2
, fshared
, &key2
);
760 if (unlikely(ret
!= 0))
763 hb1
= hash_futex(&key1
);
764 hb2
= hash_futex(&key2
);
767 double_lock_hb(hb1
, hb2
);
769 op_ret
= futex_atomic_op_inuser(op
, uaddr2
);
770 if (unlikely(op_ret
< 0)) {
773 spin_unlock(&hb1
->lock
);
775 spin_unlock(&hb2
->lock
);
779 * we don't get EFAULT from MMU faults if we don't have an MMU,
780 * but we might get them from range checking
786 if (unlikely(op_ret
!= -EFAULT
)) {
792 * futex_atomic_op_inuser needs to both read and write
793 * *(int __user *)uaddr2, but we can't modify it
794 * non-atomically. Therefore, if get_user below is not
795 * enough, we need to handle the fault ourselves, while
796 * still holding the mmap_sem.
799 ret
= futex_handle_fault((unsigned long)uaddr2
,
806 ret
= get_user(dummy
, uaddr2
);
815 plist_for_each_entry_safe(this, next
, head
, list
) {
816 if (match_futex (&this->key
, &key1
)) {
818 if (++ret
>= nr_wake
)
827 plist_for_each_entry_safe(this, next
, head
, list
) {
828 if (match_futex (&this->key
, &key2
)) {
830 if (++op_ret
>= nr_wake2
)
837 spin_unlock(&hb1
->lock
);
839 spin_unlock(&hb2
->lock
);
841 put_futex_key(fshared
, &key2
);
843 put_futex_key(fshared
, &key1
);
849 * Requeue all waiters hashed on one physical page to another
852 static int futex_requeue(u32 __user
*uaddr1
, int fshared
, u32 __user
*uaddr2
,
853 int nr_wake
, int nr_requeue
, u32
*cmpval
)
855 union futex_key key1
= FUTEX_KEY_INIT
, key2
= FUTEX_KEY_INIT
;
856 struct futex_hash_bucket
*hb1
, *hb2
;
857 struct plist_head
*head1
;
858 struct futex_q
*this, *next
;
859 int ret
, drop_count
= 0;
862 ret
= get_futex_key(uaddr1
, fshared
, &key1
);
863 if (unlikely(ret
!= 0))
865 ret
= get_futex_key(uaddr2
, fshared
, &key2
);
866 if (unlikely(ret
!= 0))
869 hb1
= hash_futex(&key1
);
870 hb2
= hash_futex(&key2
);
872 double_lock_hb(hb1
, hb2
);
874 if (likely(cmpval
!= NULL
)) {
877 ret
= get_futex_value_locked(&curval
, uaddr1
);
880 spin_unlock(&hb1
->lock
);
882 spin_unlock(&hb2
->lock
);
884 ret
= get_user(curval
, uaddr1
);
891 if (curval
!= *cmpval
) {
898 plist_for_each_entry_safe(this, next
, head1
, list
) {
899 if (!match_futex (&this->key
, &key1
))
901 if (++ret
<= nr_wake
) {
905 * If key1 and key2 hash to the same bucket, no need to
908 if (likely(head1
!= &hb2
->chain
)) {
909 plist_del(&this->list
, &hb1
->chain
);
910 plist_add(&this->list
, &hb2
->chain
);
911 this->lock_ptr
= &hb2
->lock
;
912 #ifdef CONFIG_DEBUG_PI_LIST
913 this->list
.plist
.lock
= &hb2
->lock
;
917 get_futex_key_refs(&key2
);
920 if (ret
- nr_wake
>= nr_requeue
)
926 spin_unlock(&hb1
->lock
);
928 spin_unlock(&hb2
->lock
);
930 /* drop_futex_key_refs() must be called outside the spinlocks. */
931 while (--drop_count
>= 0)
932 drop_futex_key_refs(&key1
);
935 put_futex_key(fshared
, &key2
);
937 put_futex_key(fshared
, &key1
);
942 /* The key must be already stored in q->key. */
943 static inline struct futex_hash_bucket
*queue_lock(struct futex_q
*q
)
945 struct futex_hash_bucket
*hb
;
947 init_waitqueue_head(&q
->waiter
);
949 get_futex_key_refs(&q
->key
);
950 hb
= hash_futex(&q
->key
);
951 q
->lock_ptr
= &hb
->lock
;
953 spin_lock(&hb
->lock
);
957 static inline void queue_me(struct futex_q
*q
, struct futex_hash_bucket
*hb
)
962 * The priority used to register this element is
963 * - either the real thread-priority for the real-time threads
964 * (i.e. threads with a priority lower than MAX_RT_PRIO)
965 * - or MAX_RT_PRIO for non-RT threads.
966 * Thus, all RT-threads are woken first in priority order, and
967 * the others are woken last, in FIFO order.
969 prio
= min(current
->normal_prio
, MAX_RT_PRIO
);
971 plist_node_init(&q
->list
, prio
);
972 #ifdef CONFIG_DEBUG_PI_LIST
973 q
->list
.plist
.lock
= &hb
->lock
;
975 plist_add(&q
->list
, &hb
->chain
);
977 spin_unlock(&hb
->lock
);
981 queue_unlock(struct futex_q
*q
, struct futex_hash_bucket
*hb
)
983 spin_unlock(&hb
->lock
);
984 drop_futex_key_refs(&q
->key
);
988 * queue_me and unqueue_me must be called as a pair, each
989 * exactly once. They are called with the hashed spinlock held.
992 /* Return 1 if we were still queued (ie. 0 means we were woken) */
993 static int unqueue_me(struct futex_q
*q
)
995 spinlock_t
*lock_ptr
;
998 /* In the common case we don't take the spinlock, which is nice. */
1000 lock_ptr
= q
->lock_ptr
;
1002 if (lock_ptr
!= NULL
) {
1003 spin_lock(lock_ptr
);
1005 * q->lock_ptr can change between reading it and
1006 * spin_lock(), causing us to take the wrong lock. This
1007 * corrects the race condition.
1009 * Reasoning goes like this: if we have the wrong lock,
1010 * q->lock_ptr must have changed (maybe several times)
1011 * between reading it and the spin_lock(). It can
1012 * change again after the spin_lock() but only if it was
1013 * already changed before the spin_lock(). It cannot,
1014 * however, change back to the original value. Therefore
1015 * we can detect whether we acquired the correct lock.
1017 if (unlikely(lock_ptr
!= q
->lock_ptr
)) {
1018 spin_unlock(lock_ptr
);
1021 WARN_ON(plist_node_empty(&q
->list
));
1022 plist_del(&q
->list
, &q
->list
.plist
);
1024 BUG_ON(q
->pi_state
);
1026 spin_unlock(lock_ptr
);
1030 drop_futex_key_refs(&q
->key
);
1035 * PI futexes can not be requeued and must remove themself from the
1036 * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry
1039 static void unqueue_me_pi(struct futex_q
*q
)
1041 WARN_ON(plist_node_empty(&q
->list
));
1042 plist_del(&q
->list
, &q
->list
.plist
);
1044 BUG_ON(!q
->pi_state
);
1045 free_pi_state(q
->pi_state
);
1048 spin_unlock(q
->lock_ptr
);
1050 drop_futex_key_refs(&q
->key
);
1054 * Fixup the pi_state owner with the new owner.
1056 * Must be called with hash bucket lock held and mm->sem held for non
1059 static int fixup_pi_state_owner(u32 __user
*uaddr
, struct futex_q
*q
,
1060 struct task_struct
*newowner
, int fshared
)
1062 u32 newtid
= task_pid_vnr(newowner
) | FUTEX_WAITERS
;
1063 struct futex_pi_state
*pi_state
= q
->pi_state
;
1064 struct task_struct
*oldowner
= pi_state
->owner
;
1065 u32 uval
, curval
, newval
;
1066 int ret
, attempt
= 0;
1069 if (!pi_state
->owner
)
1070 newtid
|= FUTEX_OWNER_DIED
;
1073 * We are here either because we stole the rtmutex from the
1074 * pending owner or we are the pending owner which failed to
1075 * get the rtmutex. We have to replace the pending owner TID
1076 * in the user space variable. This must be atomic as we have
1077 * to preserve the owner died bit here.
1079 * Note: We write the user space value _before_ changing the
1080 * pi_state because we can fault here. Imagine swapped out
1081 * pages or a fork, which was running right before we acquired
1082 * mmap_sem, that marked all the anonymous memory readonly for
1085 * Modifying pi_state _before_ the user space value would
1086 * leave the pi_state in an inconsistent state when we fault
1087 * here, because we need to drop the hash bucket lock to
1088 * handle the fault. This might be observed in the PID check
1089 * in lookup_pi_state.
1092 if (get_futex_value_locked(&uval
, uaddr
))
1096 newval
= (uval
& FUTEX_OWNER_DIED
) | newtid
;
1098 curval
= cmpxchg_futex_value_locked(uaddr
, uval
, newval
);
1100 if (curval
== -EFAULT
)
1108 * We fixed up user space. Now we need to fix the pi_state
1111 if (pi_state
->owner
!= NULL
) {
1112 spin_lock_irq(&pi_state
->owner
->pi_lock
);
1113 WARN_ON(list_empty(&pi_state
->list
));
1114 list_del_init(&pi_state
->list
);
1115 spin_unlock_irq(&pi_state
->owner
->pi_lock
);
1118 pi_state
->owner
= newowner
;
1120 spin_lock_irq(&newowner
->pi_lock
);
1121 WARN_ON(!list_empty(&pi_state
->list
));
1122 list_add(&pi_state
->list
, &newowner
->pi_state_list
);
1123 spin_unlock_irq(&newowner
->pi_lock
);
1127 * To handle the page fault we need to drop the hash bucket
1128 * lock here. That gives the other task (either the pending
1129 * owner itself or the task which stole the rtmutex) the
1130 * chance to try the fixup of the pi_state. So once we are
1131 * back from handling the fault we need to check the pi_state
1132 * after reacquiring the hash bucket lock and before trying to
1133 * do another fixup. When the fixup has been done already we
1137 spin_unlock(q
->lock_ptr
);
1139 ret
= futex_handle_fault((unsigned long)uaddr
, attempt
++);
1141 spin_lock(q
->lock_ptr
);
1144 * Check if someone else fixed it for us:
1146 if (pi_state
->owner
!= oldowner
)
1156 * In case we must use restart_block to restart a futex_wait,
1157 * we encode in the 'flags' shared capability
1159 #define FLAGS_SHARED 0x01
1160 #define FLAGS_CLOCKRT 0x02
1162 static long futex_wait_restart(struct restart_block
*restart
);
1164 static int futex_wait(u32 __user
*uaddr
, int fshared
,
1165 u32 val
, ktime_t
*abs_time
, u32 bitset
, int clockrt
)
1167 struct task_struct
*curr
= current
;
1168 DECLARE_WAITQUEUE(wait
, curr
);
1169 struct futex_hash_bucket
*hb
;
1173 struct hrtimer_sleeper t
;
1182 q
.key
= FUTEX_KEY_INIT
;
1183 ret
= get_futex_key(uaddr
, fshared
, &q
.key
);
1184 if (unlikely(ret
!= 0))
1187 hb
= queue_lock(&q
);
1190 * Access the page AFTER the futex is queued.
1191 * Order is important:
1193 * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val);
1194 * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); }
1196 * The basic logical guarantee of a futex is that it blocks ONLY
1197 * if cond(var) is known to be true at the time of blocking, for
1198 * any cond. If we queued after testing *uaddr, that would open
1199 * a race condition where we could block indefinitely with
1200 * cond(var) false, which would violate the guarantee.
1202 * A consequence is that futex_wait() can return zero and absorb
1203 * a wakeup when *uaddr != val on entry to the syscall. This is
1206 * for shared futexes, we hold the mmap semaphore, so the mapping
1207 * cannot have changed since we looked it up in get_futex_key.
1209 ret
= get_futex_value_locked(&uval
, uaddr
);
1211 if (unlikely(ret
)) {
1212 queue_unlock(&q
, hb
);
1213 put_futex_key(fshared
, &q
.key
);
1215 ret
= get_user(uval
, uaddr
);
1223 goto out_unlock_put_key
;
1225 /* Only actually queue if *uaddr contained val. */
1229 * There might have been scheduling since the queue_me(), as we
1230 * cannot hold a spinlock across the get_user() in case it
1231 * faults, and we cannot just set TASK_INTERRUPTIBLE state when
1232 * queueing ourselves into the futex hash. This code thus has to
1233 * rely on the futex_wake() code removing us from hash when it
1237 /* add_wait_queue is the barrier after __set_current_state. */
1238 __set_current_state(TASK_INTERRUPTIBLE
);
1239 add_wait_queue(&q
.waiter
, &wait
);
1241 * !plist_node_empty() is safe here without any lock.
1242 * q.lock_ptr != 0 is not safe, because of ordering against wakeup.
1244 if (likely(!plist_node_empty(&q
.list
))) {
1248 unsigned long slack
;
1249 slack
= current
->timer_slack_ns
;
1250 if (rt_task(current
))
1252 hrtimer_init_on_stack(&t
.timer
,
1253 clockrt
? CLOCK_REALTIME
:
1256 hrtimer_init_sleeper(&t
, current
);
1257 hrtimer_set_expires_range_ns(&t
.timer
, *abs_time
, slack
);
1259 hrtimer_start_expires(&t
.timer
, HRTIMER_MODE_ABS
);
1260 if (!hrtimer_active(&t
.timer
))
1264 * the timer could have already expired, in which
1265 * case current would be flagged for rescheduling.
1266 * Don't bother calling schedule.
1271 hrtimer_cancel(&t
.timer
);
1273 /* Flag if a timeout occured */
1274 rem
= (t
.task
== NULL
);
1276 destroy_hrtimer_on_stack(&t
.timer
);
1279 __set_current_state(TASK_RUNNING
);
1282 * NOTE: we don't remove ourselves from the waitqueue because
1283 * we are the only user of it.
1286 /* If we were woken (and unqueued), we succeeded, whatever. */
1287 if (!unqueue_me(&q
))
1293 * We expect signal_pending(current), but another thread may
1294 * have handled it for us already.
1297 return -ERESTARTSYS
;
1299 struct restart_block
*restart
;
1300 restart
= ¤t_thread_info()->restart_block
;
1301 restart
->fn
= futex_wait_restart
;
1302 restart
->futex
.uaddr
= (u32
*)uaddr
;
1303 restart
->futex
.val
= val
;
1304 restart
->futex
.time
= abs_time
->tv64
;
1305 restart
->futex
.bitset
= bitset
;
1306 restart
->futex
.flags
= 0;
1309 restart
->futex
.flags
|= FLAGS_SHARED
;
1311 restart
->futex
.flags
|= FLAGS_CLOCKRT
;
1312 return -ERESTART_RESTARTBLOCK
;
1316 queue_unlock(&q
, hb
);
1317 put_futex_key(fshared
, &q
.key
);
1324 static long futex_wait_restart(struct restart_block
*restart
)
1326 u32 __user
*uaddr
= (u32 __user
*)restart
->futex
.uaddr
;
1330 t
.tv64
= restart
->futex
.time
;
1331 restart
->fn
= do_no_restart_syscall
;
1332 if (restart
->futex
.flags
& FLAGS_SHARED
)
1334 return (long)futex_wait(uaddr
, fshared
, restart
->futex
.val
, &t
,
1335 restart
->futex
.bitset
,
1336 restart
->futex
.flags
& FLAGS_CLOCKRT
);
1341 * Userspace tried a 0 -> TID atomic transition of the futex value
1342 * and failed. The kernel side here does the whole locking operation:
1343 * if there are waiters then it will block, it does PI, etc. (Due to
1344 * races the kernel might see a 0 value of the futex too.)
1346 static int futex_lock_pi(u32 __user
*uaddr
, int fshared
,
1347 int detect
, ktime_t
*time
, int trylock
)
1349 struct hrtimer_sleeper timeout
, *to
= NULL
;
1350 struct task_struct
*curr
= current
;
1351 struct futex_hash_bucket
*hb
;
1352 u32 uval
, newval
, curval
;
1354 int ret
, lock_taken
, ownerdied
= 0, attempt
= 0;
1356 if (refill_pi_state_cache())
1361 hrtimer_init_on_stack(&to
->timer
, CLOCK_REALTIME
,
1363 hrtimer_init_sleeper(to
, current
);
1364 hrtimer_set_expires(&to
->timer
, *time
);
1369 q
.key
= FUTEX_KEY_INIT
;
1370 ret
= get_futex_key(uaddr
, fshared
, &q
.key
);
1371 if (unlikely(ret
!= 0))
1375 hb
= queue_lock(&q
);
1378 ret
= lock_taken
= 0;
1381 * To avoid races, we attempt to take the lock here again
1382 * (by doing a 0 -> TID atomic cmpxchg), while holding all
1383 * the locks. It will most likely not succeed.
1385 newval
= task_pid_vnr(current
);
1387 curval
= cmpxchg_futex_value_locked(uaddr
, 0, newval
);
1389 if (unlikely(curval
== -EFAULT
))
1393 * Detect deadlocks. In case of REQUEUE_PI this is a valid
1394 * situation and we return success to user space.
1396 if (unlikely((curval
& FUTEX_TID_MASK
) == task_pid_vnr(current
))) {
1398 goto out_unlock_put_key
;
1402 * Surprise - we got the lock. Just return to userspace:
1404 if (unlikely(!curval
))
1405 goto out_unlock_put_key
;
1410 * Set the WAITERS flag, so the owner will know it has someone
1411 * to wake at next unlock
1413 newval
= curval
| FUTEX_WAITERS
;
1416 * There are two cases, where a futex might have no owner (the
1417 * owner TID is 0): OWNER_DIED. We take over the futex in this
1418 * case. We also do an unconditional take over, when the owner
1419 * of the futex died.
1421 * This is safe as we are protected by the hash bucket lock !
1423 if (unlikely(ownerdied
|| !(curval
& FUTEX_TID_MASK
))) {
1424 /* Keep the OWNER_DIED bit */
1425 newval
= (curval
& ~FUTEX_TID_MASK
) | task_pid_vnr(current
);
1430 curval
= cmpxchg_futex_value_locked(uaddr
, uval
, newval
);
1432 if (unlikely(curval
== -EFAULT
))
1434 if (unlikely(curval
!= uval
))
1438 * We took the lock due to owner died take over.
1440 if (unlikely(lock_taken
))
1441 goto out_unlock_put_key
;
1444 * We dont have the lock. Look up the PI state (or create it if
1445 * we are the first waiter):
1447 ret
= lookup_pi_state(uval
, hb
, &q
.key
, &q
.pi_state
);
1449 if (unlikely(ret
)) {
1454 * Task is exiting and we just wait for the
1457 queue_unlock(&q
, hb
);
1463 * No owner found for this futex. Check if the
1464 * OWNER_DIED bit is set to figure out whether
1465 * this is a robust futex or not.
1467 if (get_futex_value_locked(&curval
, uaddr
))
1471 * We simply start over in case of a robust
1472 * futex. The code above will take the futex
1475 if (curval
& FUTEX_OWNER_DIED
) {
1480 goto out_unlock_put_key
;
1485 * Only actually queue now that the atomic ops are done:
1489 WARN_ON(!q
.pi_state
);
1491 * Block on the PI mutex:
1494 ret
= rt_mutex_timed_lock(&q
.pi_state
->pi_mutex
, to
, 1);
1496 ret
= rt_mutex_trylock(&q
.pi_state
->pi_mutex
);
1497 /* Fixup the trylock return value: */
1498 ret
= ret
? 0 : -EWOULDBLOCK
;
1501 spin_lock(q
.lock_ptr
);
1505 * Got the lock. We might not be the anticipated owner
1506 * if we did a lock-steal - fix up the PI-state in
1509 if (q
.pi_state
->owner
!= curr
)
1510 ret
= fixup_pi_state_owner(uaddr
, &q
, curr
, fshared
);
1513 * Catch the rare case, where the lock was released
1514 * when we were on the way back before we locked the
1517 if (q
.pi_state
->owner
== curr
) {
1519 * Try to get the rt_mutex now. This might
1520 * fail as some other task acquired the
1521 * rt_mutex after we removed ourself from the
1522 * rt_mutex waiters list.
1524 if (rt_mutex_trylock(&q
.pi_state
->pi_mutex
))
1528 * pi_state is incorrect, some other
1529 * task did a lock steal and we
1530 * returned due to timeout or signal
1531 * without taking the rt_mutex. Too
1532 * late. We can access the
1533 * rt_mutex_owner without locking, as
1534 * the other task is now blocked on
1535 * the hash bucket lock. Fix the state
1538 struct task_struct
*owner
;
1541 owner
= rt_mutex_owner(&q
.pi_state
->pi_mutex
);
1542 res
= fixup_pi_state_owner(uaddr
, &q
, owner
,
1545 /* propagate -EFAULT, if the fixup failed */
1551 * Paranoia check. If we did not take the lock
1552 * in the trylock above, then we should not be
1553 * the owner of the rtmutex, neither the real
1554 * nor the pending one:
1556 if (rt_mutex_owner(&q
.pi_state
->pi_mutex
) == curr
)
1557 printk(KERN_ERR
"futex_lock_pi: ret = %d "
1558 "pi-mutex: %p pi-state %p\n", ret
,
1559 q
.pi_state
->pi_mutex
.owner
,
1564 /* Unqueue and drop the lock */
1568 destroy_hrtimer_on_stack(&to
->timer
);
1569 return ret
!= -EINTR
? ret
: -ERESTARTNOINTR
;
1572 queue_unlock(&q
, hb
);
1575 put_futex_key(fshared
, &q
.key
);
1578 destroy_hrtimer_on_stack(&to
->timer
);
1583 * We have to r/w *(int __user *)uaddr, and we have to modify it
1584 * atomically. Therefore, if we continue to fault after get_user()
1585 * below, we need to handle the fault ourselves, while still holding
1586 * the mmap_sem. This can occur if the uaddr is under contention as
1587 * we have to drop the mmap_sem in order to call get_user().
1589 queue_unlock(&q
, hb
);
1592 ret
= futex_handle_fault((unsigned long)uaddr
, attempt
);
1595 goto retry_unlocked
;
1598 ret
= get_user(uval
, uaddr
);
1603 destroy_hrtimer_on_stack(&to
->timer
);
1608 * Userspace attempted a TID -> 0 atomic transition, and failed.
1609 * This is the in-kernel slowpath: we look up the PI state (if any),
1610 * and do the rt-mutex unlock.
1612 static int futex_unlock_pi(u32 __user
*uaddr
, int fshared
)
1614 struct futex_hash_bucket
*hb
;
1615 struct futex_q
*this, *next
;
1617 struct plist_head
*head
;
1618 union futex_key key
= FUTEX_KEY_INIT
;
1619 int ret
, attempt
= 0;
1622 if (get_user(uval
, uaddr
))
1625 * We release only a lock we actually own:
1627 if ((uval
& FUTEX_TID_MASK
) != task_pid_vnr(current
))
1630 ret
= get_futex_key(uaddr
, fshared
, &key
);
1631 if (unlikely(ret
!= 0))
1634 hb
= hash_futex(&key
);
1636 spin_lock(&hb
->lock
);
1639 * To avoid races, try to do the TID -> 0 atomic transition
1640 * again. If it succeeds then we can return without waking
1643 if (!(uval
& FUTEX_OWNER_DIED
))
1644 uval
= cmpxchg_futex_value_locked(uaddr
, task_pid_vnr(current
), 0);
1647 if (unlikely(uval
== -EFAULT
))
1650 * Rare case: we managed to release the lock atomically,
1651 * no need to wake anyone else up:
1653 if (unlikely(uval
== task_pid_vnr(current
)))
1657 * Ok, other tasks may need to be woken up - check waiters
1658 * and do the wakeup if necessary:
1662 plist_for_each_entry_safe(this, next
, head
, list
) {
1663 if (!match_futex (&this->key
, &key
))
1665 ret
= wake_futex_pi(uaddr
, uval
, this);
1667 * The atomic access to the futex value
1668 * generated a pagefault, so retry the
1669 * user-access and the wakeup:
1676 * No waiters - kernel unlocks the futex:
1678 if (!(uval
& FUTEX_OWNER_DIED
)) {
1679 ret
= unlock_futex_pi(uaddr
, uval
);
1685 spin_unlock(&hb
->lock
);
1686 put_futex_key(fshared
, &key
);
1693 * We have to r/w *(int __user *)uaddr, and we have to modify it
1694 * atomically. Therefore, if we continue to fault after get_user()
1695 * below, we need to handle the fault ourselves, while still holding
1696 * the mmap_sem. This can occur if the uaddr is under contention as
1697 * we have to drop the mmap_sem in order to call get_user().
1699 spin_unlock(&hb
->lock
);
1702 ret
= futex_handle_fault((unsigned long)uaddr
, attempt
);
1706 goto retry_unlocked
;
1709 ret
= get_user(uval
, uaddr
);
1717 * Support for robust futexes: the kernel cleans up held futexes at
1720 * Implementation: user-space maintains a per-thread list of locks it
1721 * is holding. Upon do_exit(), the kernel carefully walks this list,
1722 * and marks all locks that are owned by this thread with the
1723 * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is
1724 * always manipulated with the lock held, so the list is private and
1725 * per-thread. Userspace also maintains a per-thread 'list_op_pending'
1726 * field, to allow the kernel to clean up if the thread dies after
1727 * acquiring the lock, but just before it could have added itself to
1728 * the list. There can only be one such pending lock.
1732 * sys_set_robust_list - set the robust-futex list head of a task
1733 * @head: pointer to the list-head
1734 * @len: length of the list-head, as userspace expects
1737 sys_set_robust_list(struct robust_list_head __user
*head
,
1740 if (!futex_cmpxchg_enabled
)
1743 * The kernel knows only one size for now:
1745 if (unlikely(len
!= sizeof(*head
)))
1748 current
->robust_list
= head
;
1754 * sys_get_robust_list - get the robust-futex list head of a task
1755 * @pid: pid of the process [zero for current task]
1756 * @head_ptr: pointer to a list-head pointer, the kernel fills it in
1757 * @len_ptr: pointer to a length field, the kernel fills in the header size
1760 sys_get_robust_list(int pid
, struct robust_list_head __user
* __user
*head_ptr
,
1761 size_t __user
*len_ptr
)
1763 struct robust_list_head __user
*head
;
1765 const struct cred
*cred
= current_cred(), *pcred
;
1767 if (!futex_cmpxchg_enabled
)
1771 head
= current
->robust_list
;
1773 struct task_struct
*p
;
1777 p
= find_task_by_vpid(pid
);
1781 pcred
= __task_cred(p
);
1782 if (cred
->euid
!= pcred
->euid
&&
1783 cred
->euid
!= pcred
->uid
&&
1784 !capable(CAP_SYS_PTRACE
))
1786 head
= p
->robust_list
;
1790 if (put_user(sizeof(*head
), len_ptr
))
1792 return put_user(head
, head_ptr
);
1801 * Process a futex-list entry, check whether it's owned by the
1802 * dying task, and do notification if so:
1804 int handle_futex_death(u32 __user
*uaddr
, struct task_struct
*curr
, int pi
)
1806 u32 uval
, nval
, mval
;
1809 if (get_user(uval
, uaddr
))
1812 if ((uval
& FUTEX_TID_MASK
) == task_pid_vnr(curr
)) {
1814 * Ok, this dying thread is truly holding a futex
1815 * of interest. Set the OWNER_DIED bit atomically
1816 * via cmpxchg, and if the value had FUTEX_WAITERS
1817 * set, wake up a waiter (if any). (We have to do a
1818 * futex_wake() even if OWNER_DIED is already set -
1819 * to handle the rare but possible case of recursive
1820 * thread-death.) The rest of the cleanup is done in
1823 mval
= (uval
& FUTEX_WAITERS
) | FUTEX_OWNER_DIED
;
1824 nval
= futex_atomic_cmpxchg_inatomic(uaddr
, uval
, mval
);
1826 if (nval
== -EFAULT
)
1833 * Wake robust non-PI futexes here. The wakeup of
1834 * PI futexes happens in exit_pi_state():
1836 if (!pi
&& (uval
& FUTEX_WAITERS
))
1837 futex_wake(uaddr
, 1, 1, FUTEX_BITSET_MATCH_ANY
);
1843 * Fetch a robust-list pointer. Bit 0 signals PI futexes:
1845 static inline int fetch_robust_entry(struct robust_list __user
**entry
,
1846 struct robust_list __user
* __user
*head
,
1849 unsigned long uentry
;
1851 if (get_user(uentry
, (unsigned long __user
*)head
))
1854 *entry
= (void __user
*)(uentry
& ~1UL);
1861 * Walk curr->robust_list (very carefully, it's a userspace list!)
1862 * and mark any locks found there dead, and notify any waiters.
1864 * We silently return on any sign of list-walking problem.
1866 void exit_robust_list(struct task_struct
*curr
)
1868 struct robust_list_head __user
*head
= curr
->robust_list
;
1869 struct robust_list __user
*entry
, *next_entry
, *pending
;
1870 unsigned int limit
= ROBUST_LIST_LIMIT
, pi
, next_pi
, pip
;
1871 unsigned long futex_offset
;
1874 if (!futex_cmpxchg_enabled
)
1878 * Fetch the list head (which was registered earlier, via
1879 * sys_set_robust_list()):
1881 if (fetch_robust_entry(&entry
, &head
->list
.next
, &pi
))
1884 * Fetch the relative futex offset:
1886 if (get_user(futex_offset
, &head
->futex_offset
))
1889 * Fetch any possibly pending lock-add first, and handle it
1892 if (fetch_robust_entry(&pending
, &head
->list_op_pending
, &pip
))
1895 next_entry
= NULL
; /* avoid warning with gcc */
1896 while (entry
!= &head
->list
) {
1898 * Fetch the next entry in the list before calling
1899 * handle_futex_death:
1901 rc
= fetch_robust_entry(&next_entry
, &entry
->next
, &next_pi
);
1903 * A pending lock might already be on the list, so
1904 * don't process it twice:
1906 if (entry
!= pending
)
1907 if (handle_futex_death((void __user
*)entry
+ futex_offset
,
1915 * Avoid excessively long or circular lists:
1924 handle_futex_death((void __user
*)pending
+ futex_offset
,
1928 long do_futex(u32 __user
*uaddr
, int op
, u32 val
, ktime_t
*timeout
,
1929 u32 __user
*uaddr2
, u32 val2
, u32 val3
)
1931 int clockrt
, ret
= -ENOSYS
;
1932 int cmd
= op
& FUTEX_CMD_MASK
;
1935 if (!(op
& FUTEX_PRIVATE_FLAG
))
1938 clockrt
= op
& FUTEX_CLOCK_REALTIME
;
1939 if (clockrt
&& cmd
!= FUTEX_WAIT_BITSET
)
1944 val3
= FUTEX_BITSET_MATCH_ANY
;
1945 case FUTEX_WAIT_BITSET
:
1946 ret
= futex_wait(uaddr
, fshared
, val
, timeout
, val3
, clockrt
);
1949 val3
= FUTEX_BITSET_MATCH_ANY
;
1950 case FUTEX_WAKE_BITSET
:
1951 ret
= futex_wake(uaddr
, fshared
, val
, val3
);
1954 ret
= futex_requeue(uaddr
, fshared
, uaddr2
, val
, val2
, NULL
);
1956 case FUTEX_CMP_REQUEUE
:
1957 ret
= futex_requeue(uaddr
, fshared
, uaddr2
, val
, val2
, &val3
);
1960 ret
= futex_wake_op(uaddr
, fshared
, uaddr2
, val
, val2
, val3
);
1963 if (futex_cmpxchg_enabled
)
1964 ret
= futex_lock_pi(uaddr
, fshared
, val
, timeout
, 0);
1966 case FUTEX_UNLOCK_PI
:
1967 if (futex_cmpxchg_enabled
)
1968 ret
= futex_unlock_pi(uaddr
, fshared
);
1970 case FUTEX_TRYLOCK_PI
:
1971 if (futex_cmpxchg_enabled
)
1972 ret
= futex_lock_pi(uaddr
, fshared
, 0, timeout
, 1);
1981 asmlinkage
long sys_futex(u32 __user
*uaddr
, int op
, u32 val
,
1982 struct timespec __user
*utime
, u32 __user
*uaddr2
,
1986 ktime_t t
, *tp
= NULL
;
1988 int cmd
= op
& FUTEX_CMD_MASK
;
1990 if (utime
&& (cmd
== FUTEX_WAIT
|| cmd
== FUTEX_LOCK_PI
||
1991 cmd
== FUTEX_WAIT_BITSET
)) {
1992 if (copy_from_user(&ts
, utime
, sizeof(ts
)) != 0)
1994 if (!timespec_valid(&ts
))
1997 t
= timespec_to_ktime(ts
);
1998 if (cmd
== FUTEX_WAIT
)
1999 t
= ktime_add_safe(ktime_get(), t
);
2003 * requeue parameter in 'utime' if cmd == FUTEX_REQUEUE.
2004 * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP.
2006 if (cmd
== FUTEX_REQUEUE
|| cmd
== FUTEX_CMP_REQUEUE
||
2007 cmd
== FUTEX_WAKE_OP
)
2008 val2
= (u32
) (unsigned long) utime
;
2010 return do_futex(uaddr
, op
, val
, tp
, uaddr2
, val2
, val3
);
2013 static int __init
futex_init(void)
2019 * This will fail and we want it. Some arch implementations do
2020 * runtime detection of the futex_atomic_cmpxchg_inatomic()
2021 * functionality. We want to know that before we call in any
2022 * of the complex code paths. Also we want to prevent
2023 * registration of robust lists in that case. NULL is
2024 * guaranteed to fault and we get -EFAULT on functional
2025 * implementation, the non functional ones will return
2028 curval
= cmpxchg_futex_value_locked(NULL
, 0, 0);
2029 if (curval
== -EFAULT
)
2030 futex_cmpxchg_enabled
= 1;
2032 for (i
= 0; i
< ARRAY_SIZE(futex_queues
); i
++) {
2033 plist_head_init(&futex_queues
[i
].chain
, &futex_queues
[i
].lock
);
2034 spin_lock_init(&futex_queues
[i
].lock
);
2039 __initcall(futex_init
);