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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * Fast Userspace Mutexes (which I call "Futexes!").
3 * (C) Rusty Russell, IBM 2002
4 *
5 * Generalized futexes, futex requeueing, misc fixes by Ingo Molnar
6 * (C) Copyright 2003 Red Hat Inc, All Rights Reserved
7 *
8 * Removed page pinning, fix privately mapped COW pages and other cleanups
9 * (C) Copyright 2003, 2004 Jamie Lokier
10 *
Ingo Molnar0771dfe2006-03-27 01:16:22 -080011 * 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.
14 *
Ingo Molnarc87e2832006-06-27 02:54:58 -070015 * 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>
18 *
Eric Dumazet34f01cc2007-05-09 02:35:04 -070019 * PRIVATE futexes by Eric Dumazet
20 * Copyright (C) 2007 Eric Dumazet <dada1@cosmosbay.com>
21 *
Linus Torvalds1da177e2005-04-16 15:20:36 -070022 * 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.
25 *
26 * "The futexes are also cursed."
27 * "But they come in a choice of three flavours!"
28 *
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.
33 *
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.
38 *
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
42 */
43#include <linux/slab.h>
44#include <linux/poll.h>
45#include <linux/fs.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>
Jesper Juhl7ed20e12005-05-01 08:59:14 -070053#include <linux/signal.h>
Rusty Russell9adef582007-05-08 00:26:42 -070054#include <linux/module.h>
Andrey Mirkinfd5eea42007-10-16 23:30:13 -070055#include <linux/magic.h>
Pavel Emelyanovb4888932007-10-18 23:40:14 -070056#include <linux/pid.h>
57#include <linux/nsproxy.h>
58
Jakub Jelinek4732efb2005-09-06 15:16:25 -070059#include <asm/futex.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070060
Ingo Molnarc87e2832006-06-27 02:54:58 -070061#include "rtmutex_common.h"
62
Linus Torvalds1da177e2005-04-16 15:20:36 -070063#define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)
64
65/*
Ingo Molnarc87e2832006-06-27 02:54:58 -070066 * Priority Inheritance state:
67 */
68struct futex_pi_state {
69 /*
70 * list of 'owned' pi_state instances - these have to be
71 * cleaned up in do_exit() if the task exits prematurely:
72 */
73 struct list_head list;
74
75 /*
76 * The PI object:
77 */
78 struct rt_mutex pi_mutex;
79
80 struct task_struct *owner;
81 atomic_t refcount;
82
83 union futex_key key;
84};
85
86/*
Linus Torvalds1da177e2005-04-16 15:20:36 -070087 * We use this hashed waitqueue instead of a normal wait_queue_t, so
88 * we can wake only the relevant ones (hashed queues may be shared).
89 *
90 * A futex_q has a woken state, just like tasks have TASK_RUNNING.
Pierre Peifferec92d082007-05-09 02:35:00 -070091 * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0.
Linus Torvalds1da177e2005-04-16 15:20:36 -070092 * The order of wakup is always to make the first condition true, then
93 * wake up q->waiters, then make the second condition true.
94 */
95struct futex_q {
Pierre Peifferec92d082007-05-09 02:35:00 -070096 struct plist_node list;
Linus Torvalds1da177e2005-04-16 15:20:36 -070097 wait_queue_head_t waiters;
98
Ingo Molnare2970f22006-06-27 02:54:47 -070099 /* Which hash list lock to use: */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700100 spinlock_t *lock_ptr;
101
Ingo Molnare2970f22006-06-27 02:54:47 -0700102 /* Key which the futex is hashed on: */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700103 union futex_key key;
104
Ingo Molnare2970f22006-06-27 02:54:47 -0700105 /* For fd, sigio sent using these: */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700106 int fd;
107 struct file *filp;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700108
109 /* Optional priority inheritance state: */
110 struct futex_pi_state *pi_state;
111 struct task_struct *task;
Thomas Gleixnercd689982008-02-01 17:45:14 +0100112
113 /* Bitset for the optional bitmasked wakeup */
114 u32 bitset;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115};
116
117/*
118 * Split the global futex_lock into every hash list lock.
119 */
120struct futex_hash_bucket {
Pierre Peifferec92d082007-05-09 02:35:00 -0700121 spinlock_t lock;
122 struct plist_head chain;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700123};
124
125static struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS];
126
127/* Futex-fs vfsmount entry: */
128static struct vfsmount *futex_mnt;
129
130/*
Thomas Gleixner36cf3b52007-07-15 23:41:20 -0700131 * Take mm->mmap_sem, when futex is shared
132 */
133static inline void futex_lock_mm(struct rw_semaphore *fshared)
134{
135 if (fshared)
136 down_read(fshared);
137}
138
139/*
140 * Release mm->mmap_sem, when the futex is shared
141 */
142static inline void futex_unlock_mm(struct rw_semaphore *fshared)
143{
144 if (fshared)
145 up_read(fshared);
146}
147
148/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700149 * We hash on the keys returned from get_futex_key (see below).
150 */
151static struct futex_hash_bucket *hash_futex(union futex_key *key)
152{
153 u32 hash = jhash2((u32*)&key->both.word,
154 (sizeof(key->both.word)+sizeof(key->both.ptr))/4,
155 key->both.offset);
156 return &futex_queues[hash & ((1 << FUTEX_HASHBITS)-1)];
157}
158
159/*
160 * Return 1 if two futex_keys are equal, 0 otherwise.
161 */
162static inline int match_futex(union futex_key *key1, union futex_key *key2)
163{
164 return (key1->both.word == key2->both.word
165 && key1->both.ptr == key2->both.ptr
166 && key1->both.offset == key2->both.offset);
167}
168
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700169/**
170 * get_futex_key - Get parameters which are the keys for a futex.
171 * @uaddr: virtual address of the futex
172 * @shared: NULL for a PROCESS_PRIVATE futex,
173 * &current->mm->mmap_sem for a PROCESS_SHARED futex
174 * @key: address where result is stored.
175 *
176 * Returns a negative error code or 0
177 * The key words are stored in *key on success.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700178 *
Josef "Jeff" Sipekf3a43f32006-12-08 02:36:43 -0800179 * For shared mappings, it's (page->index, vma->vm_file->f_path.dentry->d_inode,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700180 * offset_within_page). For private mappings, it's (uaddr, current->mm).
181 * We can usually work out the index without swapping in the page.
182 *
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700183 * fshared is NULL for PROCESS_PRIVATE futexes
184 * For other futexes, it points to &current->mm->mmap_sem and
185 * caller must have taken the reader lock. but NOT any spinlocks.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700186 */
Adrian Bunkfad23fc2007-11-02 16:43:22 +0100187static int get_futex_key(u32 __user *uaddr, struct rw_semaphore *fshared,
188 union futex_key *key)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700189{
Ingo Molnare2970f22006-06-27 02:54:47 -0700190 unsigned long address = (unsigned long)uaddr;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700191 struct mm_struct *mm = current->mm;
192 struct vm_area_struct *vma;
193 struct page *page;
194 int err;
195
196 /*
197 * The futex address must be "naturally" aligned.
198 */
Ingo Molnare2970f22006-06-27 02:54:47 -0700199 key->both.offset = address % PAGE_SIZE;
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700200 if (unlikely((address % sizeof(u32)) != 0))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700201 return -EINVAL;
Ingo Molnare2970f22006-06-27 02:54:47 -0700202 address -= key->both.offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700203
204 /*
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700205 * PROCESS_PRIVATE futexes are fast.
206 * As the mm cannot disappear under us and the 'key' only needs
207 * virtual address, we dont even have to find the underlying vma.
208 * Note : We do have to check 'uaddr' is a valid user address,
209 * but access_ok() should be faster than find_vma()
210 */
211 if (!fshared) {
212 if (unlikely(!access_ok(VERIFY_WRITE, uaddr, sizeof(u32))))
213 return -EFAULT;
214 key->private.mm = mm;
215 key->private.address = address;
216 return 0;
217 }
218 /*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700219 * The futex is hashed differently depending on whether
220 * it's in a shared or private mapping. So check vma first.
221 */
Ingo Molnare2970f22006-06-27 02:54:47 -0700222 vma = find_extend_vma(mm, address);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700223 if (unlikely(!vma))
224 return -EFAULT;
225
226 /*
227 * Permissions.
228 */
229 if (unlikely((vma->vm_flags & (VM_IO|VM_READ)) != VM_READ))
230 return (vma->vm_flags & VM_IO) ? -EPERM : -EACCES;
231
232 /*
233 * Private mappings are handled in a simple way.
234 *
235 * NOTE: When userspace waits on a MAP_SHARED mapping, even if
236 * it's a read-only handle, it's expected that futexes attach to
237 * the object not the particular process. Therefore we use
238 * VM_MAYSHARE here, not VM_SHARED which is restricted to shared
239 * mappings of _writable_ handles.
240 */
241 if (likely(!(vma->vm_flags & VM_MAYSHARE))) {
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700242 key->both.offset |= FUT_OFF_MMSHARED; /* reference taken on mm */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700243 key->private.mm = mm;
Ingo Molnare2970f22006-06-27 02:54:47 -0700244 key->private.address = address;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700245 return 0;
246 }
247
248 /*
249 * Linear file mappings are also simple.
250 */
Josef "Jeff" Sipekf3a43f32006-12-08 02:36:43 -0800251 key->shared.inode = vma->vm_file->f_path.dentry->d_inode;
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700252 key->both.offset |= FUT_OFF_INODE; /* inode-based key. */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700253 if (likely(!(vma->vm_flags & VM_NONLINEAR))) {
Ingo Molnare2970f22006-06-27 02:54:47 -0700254 key->shared.pgoff = (((address - vma->vm_start) >> PAGE_SHIFT)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700255 + vma->vm_pgoff);
256 return 0;
257 }
258
259 /*
260 * We could walk the page table to read the non-linear
261 * pte, and get the page index without fetching the page
262 * from swap. But that's a lot of code to duplicate here
263 * for a rare case, so we simply fetch the page.
264 */
Ingo Molnare2970f22006-06-27 02:54:47 -0700265 err = get_user_pages(current, mm, address, 1, 0, 0, &page, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700266 if (err >= 0) {
267 key->shared.pgoff =
268 page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
269 put_page(page);
270 return 0;
271 }
272 return err;
273}
274
275/*
276 * Take a reference to the resource addressed by a key.
277 * Can be called while holding spinlocks.
278 *
Linus Torvalds1da177e2005-04-16 15:20:36 -0700279 */
Adrian Bunkfad23fc2007-11-02 16:43:22 +0100280static void get_futex_key_refs(union futex_key *key)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700281{
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700282 if (key->both.ptr == 0)
283 return;
284 switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
285 case FUT_OFF_INODE:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700286 atomic_inc(&key->shared.inode->i_count);
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700287 break;
288 case FUT_OFF_MMSHARED:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700289 atomic_inc(&key->private.mm->mm_count);
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700290 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700291 }
292}
293
294/*
295 * Drop a reference to the resource addressed by a key.
296 * The hash bucket spinlock must not be held.
297 */
Adrian Bunkfad23fc2007-11-02 16:43:22 +0100298static void drop_futex_key_refs(union futex_key *key)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700299{
Stephen Hemmingerc80544d2007-10-18 03:07:05 -0700300 if (!key->both.ptr)
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700301 return;
302 switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
303 case FUT_OFF_INODE:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700304 iput(key->shared.inode);
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700305 break;
306 case FUT_OFF_MMSHARED:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700307 mmdrop(key->private.mm);
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700308 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700309 }
310}
311
Thomas Gleixner36cf3b52007-07-15 23:41:20 -0700312static u32 cmpxchg_futex_value_locked(u32 __user *uaddr, u32 uval, u32 newval)
313{
314 u32 curval;
315
316 pagefault_disable();
317 curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval);
318 pagefault_enable();
319
320 return curval;
321}
322
323static int get_futex_value_locked(u32 *dest, u32 __user *from)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700324{
325 int ret;
326
Peter Zijlstraa8663742006-12-06 20:32:20 -0800327 pagefault_disable();
Ingo Molnare2970f22006-06-27 02:54:47 -0700328 ret = __copy_from_user_inatomic(dest, from, sizeof(u32));
Peter Zijlstraa8663742006-12-06 20:32:20 -0800329 pagefault_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700330
331 return ret ? -EFAULT : 0;
332}
333
334/*
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700335 * Fault handling.
336 * if fshared is non NULL, current->mm->mmap_sem is already held
Ingo Molnarc87e2832006-06-27 02:54:58 -0700337 */
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700338static int futex_handle_fault(unsigned long address,
339 struct rw_semaphore *fshared, int attempt)
Ingo Molnarc87e2832006-06-27 02:54:58 -0700340{
341 struct vm_area_struct * vma;
342 struct mm_struct *mm = current->mm;
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700343 int ret = -EFAULT;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700344
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700345 if (attempt > 2)
346 return ret;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700347
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700348 if (!fshared)
349 down_read(&mm->mmap_sem);
350 vma = find_vma(mm, address);
351 if (vma && address >= vma->vm_start &&
352 (vma->vm_flags & VM_WRITE)) {
Nick Piggin83c54072007-07-19 01:47:05 -0700353 int fault;
354 fault = handle_mm_fault(mm, vma, address, 1);
355 if (unlikely((fault & VM_FAULT_ERROR))) {
356#if 0
357 /* XXX: let's do this when we verify it is OK */
358 if (ret & VM_FAULT_OOM)
359 ret = -ENOMEM;
360#endif
361 } else {
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700362 ret = 0;
Nick Piggin83c54072007-07-19 01:47:05 -0700363 if (fault & VM_FAULT_MAJOR)
364 current->maj_flt++;
365 else
366 current->min_flt++;
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700367 }
Ingo Molnarc87e2832006-06-27 02:54:58 -0700368 }
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700369 if (!fshared)
370 up_read(&mm->mmap_sem);
371 return ret;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700372}
373
374/*
375 * PI code:
376 */
377static int refill_pi_state_cache(void)
378{
379 struct futex_pi_state *pi_state;
380
381 if (likely(current->pi_state_cache))
382 return 0;
383
Burman Yan4668edc2006-12-06 20:38:51 -0800384 pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700385
386 if (!pi_state)
387 return -ENOMEM;
388
Ingo Molnarc87e2832006-06-27 02:54:58 -0700389 INIT_LIST_HEAD(&pi_state->list);
390 /* pi_mutex gets initialized later */
391 pi_state->owner = NULL;
392 atomic_set(&pi_state->refcount, 1);
393
394 current->pi_state_cache = pi_state;
395
396 return 0;
397}
398
399static struct futex_pi_state * alloc_pi_state(void)
400{
401 struct futex_pi_state *pi_state = current->pi_state_cache;
402
403 WARN_ON(!pi_state);
404 current->pi_state_cache = NULL;
405
406 return pi_state;
407}
408
409static void free_pi_state(struct futex_pi_state *pi_state)
410{
411 if (!atomic_dec_and_test(&pi_state->refcount))
412 return;
413
414 /*
415 * If pi_state->owner is NULL, the owner is most probably dying
416 * and has cleaned up the pi_state already
417 */
418 if (pi_state->owner) {
419 spin_lock_irq(&pi_state->owner->pi_lock);
420 list_del_init(&pi_state->list);
421 spin_unlock_irq(&pi_state->owner->pi_lock);
422
423 rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner);
424 }
425
426 if (current->pi_state_cache)
427 kfree(pi_state);
428 else {
429 /*
430 * pi_state->list is already empty.
431 * clear pi_state->owner.
432 * refcount is at 0 - put it back to 1.
433 */
434 pi_state->owner = NULL;
435 atomic_set(&pi_state->refcount, 1);
436 current->pi_state_cache = pi_state;
437 }
438}
439
440/*
441 * Look up the task based on what TID userspace gave us.
442 * We dont trust it.
443 */
444static struct task_struct * futex_find_get_task(pid_t pid)
445{
446 struct task_struct *p;
447
Oleg Nesterovd359b542006-09-29 02:00:55 -0700448 rcu_read_lock();
Pavel Emelyanov228ebcb2007-10-18 23:40:16 -0700449 p = find_task_by_vpid(pid);
Thomas Gleixnera06381f2007-06-23 11:48:40 +0200450 if (!p || ((current->euid != p->euid) && (current->euid != p->uid)))
451 p = ERR_PTR(-ESRCH);
452 else
453 get_task_struct(p);
454
Oleg Nesterovd359b542006-09-29 02:00:55 -0700455 rcu_read_unlock();
Ingo Molnarc87e2832006-06-27 02:54:58 -0700456
457 return p;
458}
459
460/*
461 * This task is holding PI mutexes at exit time => bad.
462 * Kernel cleans up PI-state, but userspace is likely hosed.
463 * (Robust-futex cleanup is separate and might save the day for userspace.)
464 */
465void exit_pi_state_list(struct task_struct *curr)
466{
Ingo Molnarc87e2832006-06-27 02:54:58 -0700467 struct list_head *next, *head = &curr->pi_state_list;
468 struct futex_pi_state *pi_state;
Ingo Molnar627371d2006-07-29 05:16:20 +0200469 struct futex_hash_bucket *hb;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700470 union futex_key key;
471
472 /*
473 * We are a ZOMBIE and nobody can enqueue itself on
474 * pi_state_list anymore, but we have to be careful
Ingo Molnar627371d2006-07-29 05:16:20 +0200475 * versus waiters unqueueing themselves:
Ingo Molnarc87e2832006-06-27 02:54:58 -0700476 */
477 spin_lock_irq(&curr->pi_lock);
478 while (!list_empty(head)) {
479
480 next = head->next;
481 pi_state = list_entry(next, struct futex_pi_state, list);
482 key = pi_state->key;
Ingo Molnar627371d2006-07-29 05:16:20 +0200483 hb = hash_futex(&key);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700484 spin_unlock_irq(&curr->pi_lock);
485
Ingo Molnarc87e2832006-06-27 02:54:58 -0700486 spin_lock(&hb->lock);
487
488 spin_lock_irq(&curr->pi_lock);
Ingo Molnar627371d2006-07-29 05:16:20 +0200489 /*
490 * We dropped the pi-lock, so re-check whether this
491 * task still owns the PI-state:
492 */
Ingo Molnarc87e2832006-06-27 02:54:58 -0700493 if (head->next != next) {
494 spin_unlock(&hb->lock);
495 continue;
496 }
497
Ingo Molnarc87e2832006-06-27 02:54:58 -0700498 WARN_ON(pi_state->owner != curr);
Ingo Molnar627371d2006-07-29 05:16:20 +0200499 WARN_ON(list_empty(&pi_state->list));
500 list_del_init(&pi_state->list);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700501 pi_state->owner = NULL;
502 spin_unlock_irq(&curr->pi_lock);
503
504 rt_mutex_unlock(&pi_state->pi_mutex);
505
506 spin_unlock(&hb->lock);
507
508 spin_lock_irq(&curr->pi_lock);
509 }
510 spin_unlock_irq(&curr->pi_lock);
511}
512
513static int
Pierre Peifferd0aa7a72007-05-09 02:35:02 -0700514lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
515 union futex_key *key, struct futex_pi_state **ps)
Ingo Molnarc87e2832006-06-27 02:54:58 -0700516{
517 struct futex_pi_state *pi_state = NULL;
518 struct futex_q *this, *next;
Pierre Peifferec92d082007-05-09 02:35:00 -0700519 struct plist_head *head;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700520 struct task_struct *p;
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700521 pid_t pid = uval & FUTEX_TID_MASK;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700522
523 head = &hb->chain;
524
Pierre Peifferec92d082007-05-09 02:35:00 -0700525 plist_for_each_entry_safe(this, next, head, list) {
Pierre Peifferd0aa7a72007-05-09 02:35:02 -0700526 if (match_futex(&this->key, key)) {
Ingo Molnarc87e2832006-06-27 02:54:58 -0700527 /*
528 * Another waiter already exists - bump up
529 * the refcount and return its pi_state:
530 */
531 pi_state = this->pi_state;
Thomas Gleixner06a9ec22006-07-10 04:44:30 -0700532 /*
533 * Userspace might have messed up non PI and PI futexes
534 */
535 if (unlikely(!pi_state))
536 return -EINVAL;
537
Ingo Molnar627371d2006-07-29 05:16:20 +0200538 WARN_ON(!atomic_read(&pi_state->refcount));
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700539 WARN_ON(pid && pi_state->owner &&
540 pi_state->owner->pid != pid);
Ingo Molnar627371d2006-07-29 05:16:20 +0200541
Ingo Molnarc87e2832006-06-27 02:54:58 -0700542 atomic_inc(&pi_state->refcount);
Pierre Peifferd0aa7a72007-05-09 02:35:02 -0700543 *ps = pi_state;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700544
545 return 0;
546 }
547 }
548
549 /*
Ingo Molnare3f2dde2006-07-29 05:17:57 +0200550 * We are the first waiter - try to look up the real owner and attach
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700551 * the new pi_state to it, but bail out when TID = 0
Ingo Molnarc87e2832006-06-27 02:54:58 -0700552 */
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700553 if (!pid)
Ingo Molnare3f2dde2006-07-29 05:17:57 +0200554 return -ESRCH;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700555 p = futex_find_get_task(pid);
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700556 if (IS_ERR(p))
557 return PTR_ERR(p);
558
559 /*
560 * We need to look at the task state flags to figure out,
561 * whether the task is exiting. To protect against the do_exit
562 * change of the task flags, we do this protected by
563 * p->pi_lock:
564 */
565 spin_lock_irq(&p->pi_lock);
566 if (unlikely(p->flags & PF_EXITING)) {
567 /*
568 * The task is on the way out. When PF_EXITPIDONE is
569 * set, we know that the task has finished the
570 * cleanup:
571 */
572 int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN;
573
574 spin_unlock_irq(&p->pi_lock);
575 put_task_struct(p);
576 return ret;
577 }
Ingo Molnarc87e2832006-06-27 02:54:58 -0700578
579 pi_state = alloc_pi_state();
580
581 /*
582 * Initialize the pi_mutex in locked state and make 'p'
583 * the owner of it:
584 */
585 rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p);
586
587 /* Store the key for possible exit cleanups: */
Pierre Peifferd0aa7a72007-05-09 02:35:02 -0700588 pi_state->key = *key;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700589
Ingo Molnar627371d2006-07-29 05:16:20 +0200590 WARN_ON(!list_empty(&pi_state->list));
Ingo Molnarc87e2832006-06-27 02:54:58 -0700591 list_add(&pi_state->list, &p->pi_state_list);
592 pi_state->owner = p;
593 spin_unlock_irq(&p->pi_lock);
594
595 put_task_struct(p);
596
Pierre Peifferd0aa7a72007-05-09 02:35:02 -0700597 *ps = pi_state;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700598
599 return 0;
600}
601
602/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700603 * The hash bucket lock must be held when this is called.
604 * Afterwards, the futex_q must not be accessed.
605 */
606static void wake_futex(struct futex_q *q)
607{
Pierre Peifferec92d082007-05-09 02:35:00 -0700608 plist_del(&q->list, &q->list.plist);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700609 if (q->filp)
610 send_sigio(&q->filp->f_owner, q->fd, POLL_IN);
611 /*
612 * The lock in wake_up_all() is a crucial memory barrier after the
Pierre Peifferec92d082007-05-09 02:35:00 -0700613 * plist_del() and also before assigning to q->lock_ptr.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700614 */
615 wake_up_all(&q->waiters);
616 /*
617 * The waiting task can free the futex_q as soon as this is written,
618 * without taking any locks. This must come last.
Andrew Morton8e311082005-12-23 19:54:46 -0800619 *
620 * A memory barrier is required here to prevent the following store
621 * to lock_ptr from getting ahead of the wakeup. Clearing the lock
622 * at the end of wake_up_all() does not prevent this store from
623 * moving.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700624 */
Ralf Baechleccdea2f2006-12-06 20:40:26 -0800625 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700626 q->lock_ptr = NULL;
627}
628
Ingo Molnarc87e2832006-06-27 02:54:58 -0700629static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)
630{
631 struct task_struct *new_owner;
632 struct futex_pi_state *pi_state = this->pi_state;
633 u32 curval, newval;
634
635 if (!pi_state)
636 return -EINVAL;
637
Ingo Molnar217788672007-03-16 13:38:31 -0800638 spin_lock(&pi_state->pi_mutex.wait_lock);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700639 new_owner = rt_mutex_next_owner(&pi_state->pi_mutex);
640
641 /*
642 * This happens when we have stolen the lock and the original
643 * pending owner did not enqueue itself back on the rt_mutex.
644 * Thats not a tragedy. We know that way, that a lock waiter
645 * is on the fly. We make the futex_q waiter the pending owner.
646 */
647 if (!new_owner)
648 new_owner = this->task;
649
650 /*
651 * We pass it to the next owner. (The WAITERS bit is always
652 * kept enabled while there is PI state around. We must also
653 * preserve the owner died bit.)
654 */
Ingo Molnare3f2dde2006-07-29 05:17:57 +0200655 if (!(uval & FUTEX_OWNER_DIED)) {
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700656 int ret = 0;
657
Pavel Emelyanovb4888932007-10-18 23:40:14 -0700658 newval = FUTEX_WAITERS | task_pid_vnr(new_owner);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700659
Thomas Gleixner36cf3b52007-07-15 23:41:20 -0700660 curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700661
Ingo Molnare3f2dde2006-07-29 05:17:57 +0200662 if (curval == -EFAULT)
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700663 ret = -EFAULT;
Thomas Gleixnercde898f2007-12-05 15:46:09 +0100664 else if (curval != uval)
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700665 ret = -EINVAL;
666 if (ret) {
667 spin_unlock(&pi_state->pi_mutex.wait_lock);
668 return ret;
669 }
Ingo Molnare3f2dde2006-07-29 05:17:57 +0200670 }
Ingo Molnarc87e2832006-06-27 02:54:58 -0700671
Ingo Molnar627371d2006-07-29 05:16:20 +0200672 spin_lock_irq(&pi_state->owner->pi_lock);
673 WARN_ON(list_empty(&pi_state->list));
674 list_del_init(&pi_state->list);
675 spin_unlock_irq(&pi_state->owner->pi_lock);
676
677 spin_lock_irq(&new_owner->pi_lock);
678 WARN_ON(!list_empty(&pi_state->list));
Ingo Molnarc87e2832006-06-27 02:54:58 -0700679 list_add(&pi_state->list, &new_owner->pi_state_list);
680 pi_state->owner = new_owner;
Ingo Molnar627371d2006-07-29 05:16:20 +0200681 spin_unlock_irq(&new_owner->pi_lock);
682
Ingo Molnar217788672007-03-16 13:38:31 -0800683 spin_unlock(&pi_state->pi_mutex.wait_lock);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700684 rt_mutex_unlock(&pi_state->pi_mutex);
685
686 return 0;
687}
688
689static int unlock_futex_pi(u32 __user *uaddr, u32 uval)
690{
691 u32 oldval;
692
693 /*
694 * There is no waiter, so we unlock the futex. The owner died
695 * bit has not to be preserved here. We are the owner:
696 */
Thomas Gleixner36cf3b52007-07-15 23:41:20 -0700697 oldval = cmpxchg_futex_value_locked(uaddr, uval, 0);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700698
699 if (oldval == -EFAULT)
700 return oldval;
701 if (oldval != uval)
702 return -EAGAIN;
703
704 return 0;
705}
706
Linus Torvalds1da177e2005-04-16 15:20:36 -0700707/*
Ingo Molnar8b8f3192006-07-03 00:25:05 -0700708 * Express the locking dependencies for lockdep:
709 */
710static inline void
711double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
712{
713 if (hb1 <= hb2) {
714 spin_lock(&hb1->lock);
715 if (hb1 < hb2)
716 spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING);
717 } else { /* hb1 > hb2 */
718 spin_lock(&hb2->lock);
719 spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING);
720 }
721}
722
723/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700724 * Wake up all waiters hashed on the physical page that is mapped
725 * to this virtual address:
726 */
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700727static int futex_wake(u32 __user *uaddr, struct rw_semaphore *fshared,
Thomas Gleixnercd689982008-02-01 17:45:14 +0100728 int nr_wake, u32 bitset)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700729{
Ingo Molnare2970f22006-06-27 02:54:47 -0700730 struct futex_hash_bucket *hb;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700731 struct futex_q *this, *next;
Pierre Peifferec92d082007-05-09 02:35:00 -0700732 struct plist_head *head;
Ingo Molnare2970f22006-06-27 02:54:47 -0700733 union futex_key key;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700734 int ret;
735
Thomas Gleixnercd689982008-02-01 17:45:14 +0100736 if (!bitset)
737 return -EINVAL;
738
Thomas Gleixner36cf3b52007-07-15 23:41:20 -0700739 futex_lock_mm(fshared);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700740
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700741 ret = get_futex_key(uaddr, fshared, &key);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700742 if (unlikely(ret != 0))
743 goto out;
744
Ingo Molnare2970f22006-06-27 02:54:47 -0700745 hb = hash_futex(&key);
746 spin_lock(&hb->lock);
747 head = &hb->chain;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700748
Pierre Peifferec92d082007-05-09 02:35:00 -0700749 plist_for_each_entry_safe(this, next, head, list) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700750 if (match_futex (&this->key, &key)) {
Ingo Molnared6f7b12006-07-01 04:35:46 -0700751 if (this->pi_state) {
752 ret = -EINVAL;
753 break;
754 }
Thomas Gleixnercd689982008-02-01 17:45:14 +0100755
756 /* Check if one of the bits is set in both bitsets */
757 if (!(this->bitset & bitset))
758 continue;
759
Linus Torvalds1da177e2005-04-16 15:20:36 -0700760 wake_futex(this);
761 if (++ret >= nr_wake)
762 break;
763 }
764 }
765
Ingo Molnare2970f22006-06-27 02:54:47 -0700766 spin_unlock(&hb->lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700767out:
Thomas Gleixner36cf3b52007-07-15 23:41:20 -0700768 futex_unlock_mm(fshared);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700769 return ret;
770}
771
772/*
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700773 * Wake up all waiters hashed on the physical page that is mapped
774 * to this virtual address:
775 */
Ingo Molnare2970f22006-06-27 02:54:47 -0700776static int
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700777futex_wake_op(u32 __user *uaddr1, struct rw_semaphore *fshared,
778 u32 __user *uaddr2,
Ingo Molnare2970f22006-06-27 02:54:47 -0700779 int nr_wake, int nr_wake2, int op)
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700780{
781 union futex_key key1, key2;
Ingo Molnare2970f22006-06-27 02:54:47 -0700782 struct futex_hash_bucket *hb1, *hb2;
Pierre Peifferec92d082007-05-09 02:35:00 -0700783 struct plist_head *head;
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700784 struct futex_q *this, *next;
785 int ret, op_ret, attempt = 0;
786
787retryfull:
Thomas Gleixner36cf3b52007-07-15 23:41:20 -0700788 futex_lock_mm(fshared);
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700789
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700790 ret = get_futex_key(uaddr1, fshared, &key1);
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700791 if (unlikely(ret != 0))
792 goto out;
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700793 ret = get_futex_key(uaddr2, fshared, &key2);
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700794 if (unlikely(ret != 0))
795 goto out;
796
Ingo Molnare2970f22006-06-27 02:54:47 -0700797 hb1 = hash_futex(&key1);
798 hb2 = hash_futex(&key2);
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700799
800retry:
Ingo Molnar8b8f3192006-07-03 00:25:05 -0700801 double_lock_hb(hb1, hb2);
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700802
Ingo Molnare2970f22006-06-27 02:54:47 -0700803 op_ret = futex_atomic_op_inuser(op, uaddr2);
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700804 if (unlikely(op_ret < 0)) {
Ingo Molnare2970f22006-06-27 02:54:47 -0700805 u32 dummy;
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700806
Ingo Molnare2970f22006-06-27 02:54:47 -0700807 spin_unlock(&hb1->lock);
808 if (hb1 != hb2)
809 spin_unlock(&hb2->lock);
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700810
David Howells7ee1dd32006-01-06 00:11:44 -0800811#ifndef CONFIG_MMU
Ingo Molnare2970f22006-06-27 02:54:47 -0700812 /*
813 * we don't get EFAULT from MMU faults if we don't have an MMU,
814 * but we might get them from range checking
815 */
David Howells7ee1dd32006-01-06 00:11:44 -0800816 ret = op_ret;
817 goto out;
818#endif
819
David Gibson796f8d92005-11-07 00:59:33 -0800820 if (unlikely(op_ret != -EFAULT)) {
821 ret = op_ret;
822 goto out;
823 }
824
Ingo Molnare2970f22006-06-27 02:54:47 -0700825 /*
826 * futex_atomic_op_inuser needs to both read and write
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700827 * *(int __user *)uaddr2, but we can't modify it
828 * non-atomically. Therefore, if get_user below is not
829 * enough, we need to handle the fault ourselves, while
Ingo Molnare2970f22006-06-27 02:54:47 -0700830 * still holding the mmap_sem.
831 */
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700832 if (attempt++) {
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700833 ret = futex_handle_fault((unsigned long)uaddr2,
Thomas Gleixner36cf3b52007-07-15 23:41:20 -0700834 fshared, attempt);
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700835 if (ret)
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700836 goto out;
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700837 goto retry;
838 }
839
Ingo Molnare2970f22006-06-27 02:54:47 -0700840 /*
841 * If we would have faulted, release mmap_sem,
842 * fault it in and start all over again.
843 */
Thomas Gleixner36cf3b52007-07-15 23:41:20 -0700844 futex_unlock_mm(fshared);
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700845
Ingo Molnare2970f22006-06-27 02:54:47 -0700846 ret = get_user(dummy, uaddr2);
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700847 if (ret)
848 return ret;
849
850 goto retryfull;
851 }
852
Ingo Molnare2970f22006-06-27 02:54:47 -0700853 head = &hb1->chain;
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700854
Pierre Peifferec92d082007-05-09 02:35:00 -0700855 plist_for_each_entry_safe(this, next, head, list) {
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700856 if (match_futex (&this->key, &key1)) {
857 wake_futex(this);
858 if (++ret >= nr_wake)
859 break;
860 }
861 }
862
863 if (op_ret > 0) {
Ingo Molnare2970f22006-06-27 02:54:47 -0700864 head = &hb2->chain;
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700865
866 op_ret = 0;
Pierre Peifferec92d082007-05-09 02:35:00 -0700867 plist_for_each_entry_safe(this, next, head, list) {
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700868 if (match_futex (&this->key, &key2)) {
869 wake_futex(this);
870 if (++op_ret >= nr_wake2)
871 break;
872 }
873 }
874 ret += op_ret;
875 }
876
Ingo Molnare2970f22006-06-27 02:54:47 -0700877 spin_unlock(&hb1->lock);
878 if (hb1 != hb2)
879 spin_unlock(&hb2->lock);
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700880out:
Thomas Gleixner36cf3b52007-07-15 23:41:20 -0700881 futex_unlock_mm(fshared);
882
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700883 return ret;
884}
885
886/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700887 * Requeue all waiters hashed on one physical page to another
888 * physical page.
889 */
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700890static int futex_requeue(u32 __user *uaddr1, struct rw_semaphore *fshared,
891 u32 __user *uaddr2,
Ingo Molnare2970f22006-06-27 02:54:47 -0700892 int nr_wake, int nr_requeue, u32 *cmpval)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700893{
894 union futex_key key1, key2;
Ingo Molnare2970f22006-06-27 02:54:47 -0700895 struct futex_hash_bucket *hb1, *hb2;
Pierre Peifferec92d082007-05-09 02:35:00 -0700896 struct plist_head *head1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700897 struct futex_q *this, *next;
898 int ret, drop_count = 0;
899
900 retry:
Thomas Gleixner36cf3b52007-07-15 23:41:20 -0700901 futex_lock_mm(fshared);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700902
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700903 ret = get_futex_key(uaddr1, fshared, &key1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700904 if (unlikely(ret != 0))
905 goto out;
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700906 ret = get_futex_key(uaddr2, fshared, &key2);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700907 if (unlikely(ret != 0))
908 goto out;
909
Ingo Molnare2970f22006-06-27 02:54:47 -0700910 hb1 = hash_futex(&key1);
911 hb2 = hash_futex(&key2);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700912
Ingo Molnar8b8f3192006-07-03 00:25:05 -0700913 double_lock_hb(hb1, hb2);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700914
Ingo Molnare2970f22006-06-27 02:54:47 -0700915 if (likely(cmpval != NULL)) {
916 u32 curval;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700917
Ingo Molnare2970f22006-06-27 02:54:47 -0700918 ret = get_futex_value_locked(&curval, uaddr1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700919
920 if (unlikely(ret)) {
Ingo Molnare2970f22006-06-27 02:54:47 -0700921 spin_unlock(&hb1->lock);
922 if (hb1 != hb2)
923 spin_unlock(&hb2->lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700924
Ingo Molnare2970f22006-06-27 02:54:47 -0700925 /*
926 * If we would have faulted, release mmap_sem, fault
Linus Torvalds1da177e2005-04-16 15:20:36 -0700927 * it in and start all over again.
928 */
Thomas Gleixner36cf3b52007-07-15 23:41:20 -0700929 futex_unlock_mm(fshared);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700930
Ingo Molnare2970f22006-06-27 02:54:47 -0700931 ret = get_user(curval, uaddr1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700932
933 if (!ret)
934 goto retry;
935
936 return ret;
937 }
Ingo Molnare2970f22006-06-27 02:54:47 -0700938 if (curval != *cmpval) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700939 ret = -EAGAIN;
940 goto out_unlock;
941 }
942 }
943
Ingo Molnare2970f22006-06-27 02:54:47 -0700944 head1 = &hb1->chain;
Pierre Peifferec92d082007-05-09 02:35:00 -0700945 plist_for_each_entry_safe(this, next, head1, list) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700946 if (!match_futex (&this->key, &key1))
947 continue;
948 if (++ret <= nr_wake) {
949 wake_futex(this);
950 } else {
Sebastien Dugue59e0e0a2006-06-27 02:55:03 -0700951 /*
952 * If key1 and key2 hash to the same bucket, no need to
953 * requeue.
954 */
955 if (likely(head1 != &hb2->chain)) {
Pierre Peifferec92d082007-05-09 02:35:00 -0700956 plist_del(&this->list, &hb1->chain);
957 plist_add(&this->list, &hb2->chain);
Sebastien Dugue59e0e0a2006-06-27 02:55:03 -0700958 this->lock_ptr = &hb2->lock;
Pierre Peifferec92d082007-05-09 02:35:00 -0700959#ifdef CONFIG_DEBUG_PI_LIST
960 this->list.plist.lock = &hb2->lock;
961#endif
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700962 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700963 this->key = key2;
Rusty Russell9adef582007-05-08 00:26:42 -0700964 get_futex_key_refs(&key2);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700965 drop_count++;
966
967 if (ret - nr_wake >= nr_requeue)
968 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700969 }
970 }
971
972out_unlock:
Ingo Molnare2970f22006-06-27 02:54:47 -0700973 spin_unlock(&hb1->lock);
974 if (hb1 != hb2)
975 spin_unlock(&hb2->lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700976
Rusty Russell9adef582007-05-08 00:26:42 -0700977 /* drop_futex_key_refs() must be called outside the spinlocks. */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700978 while (--drop_count >= 0)
Rusty Russell9adef582007-05-08 00:26:42 -0700979 drop_futex_key_refs(&key1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700980
981out:
Thomas Gleixner36cf3b52007-07-15 23:41:20 -0700982 futex_unlock_mm(fshared);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700983 return ret;
984}
985
986/* The key must be already stored in q->key. */
987static inline struct futex_hash_bucket *
988queue_lock(struct futex_q *q, int fd, struct file *filp)
989{
Ingo Molnare2970f22006-06-27 02:54:47 -0700990 struct futex_hash_bucket *hb;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700991
992 q->fd = fd;
993 q->filp = filp;
994
995 init_waitqueue_head(&q->waiters);
996
Rusty Russell9adef582007-05-08 00:26:42 -0700997 get_futex_key_refs(&q->key);
Ingo Molnare2970f22006-06-27 02:54:47 -0700998 hb = hash_futex(&q->key);
999 q->lock_ptr = &hb->lock;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001000
Ingo Molnare2970f22006-06-27 02:54:47 -07001001 spin_lock(&hb->lock);
1002 return hb;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001003}
1004
Ingo Molnare2970f22006-06-27 02:54:47 -07001005static inline void __queue_me(struct futex_q *q, struct futex_hash_bucket *hb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001006{
Pierre Peifferec92d082007-05-09 02:35:00 -07001007 int prio;
1008
1009 /*
1010 * The priority used to register this element is
1011 * - either the real thread-priority for the real-time threads
1012 * (i.e. threads with a priority lower than MAX_RT_PRIO)
1013 * - or MAX_RT_PRIO for non-RT threads.
1014 * Thus, all RT-threads are woken first in priority order, and
1015 * the others are woken last, in FIFO order.
1016 */
1017 prio = min(current->normal_prio, MAX_RT_PRIO);
1018
1019 plist_node_init(&q->list, prio);
1020#ifdef CONFIG_DEBUG_PI_LIST
1021 q->list.plist.lock = &hb->lock;
1022#endif
1023 plist_add(&q->list, &hb->chain);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001024 q->task = current;
Ingo Molnare2970f22006-06-27 02:54:47 -07001025 spin_unlock(&hb->lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001026}
1027
1028static inline void
Ingo Molnare2970f22006-06-27 02:54:47 -07001029queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001030{
Ingo Molnare2970f22006-06-27 02:54:47 -07001031 spin_unlock(&hb->lock);
Rusty Russell9adef582007-05-08 00:26:42 -07001032 drop_futex_key_refs(&q->key);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001033}
1034
1035/*
1036 * queue_me and unqueue_me must be called as a pair, each
1037 * exactly once. They are called with the hashed spinlock held.
1038 */
1039
1040/* The key must be already stored in q->key. */
1041static void queue_me(struct futex_q *q, int fd, struct file *filp)
1042{
Ingo Molnare2970f22006-06-27 02:54:47 -07001043 struct futex_hash_bucket *hb;
1044
1045 hb = queue_lock(q, fd, filp);
1046 __queue_me(q, hb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001047}
1048
1049/* Return 1 if we were still queued (ie. 0 means we were woken) */
1050static int unqueue_me(struct futex_q *q)
1051{
Linus Torvalds1da177e2005-04-16 15:20:36 -07001052 spinlock_t *lock_ptr;
Ingo Molnare2970f22006-06-27 02:54:47 -07001053 int ret = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001054
1055 /* In the common case we don't take the spinlock, which is nice. */
1056 retry:
1057 lock_ptr = q->lock_ptr;
Christian Borntraegere91467e2006-08-05 12:13:52 -07001058 barrier();
Stephen Hemmingerc80544d2007-10-18 03:07:05 -07001059 if (lock_ptr != NULL) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001060 spin_lock(lock_ptr);
1061 /*
1062 * q->lock_ptr can change between reading it and
1063 * spin_lock(), causing us to take the wrong lock. This
1064 * corrects the race condition.
1065 *
1066 * Reasoning goes like this: if we have the wrong lock,
1067 * q->lock_ptr must have changed (maybe several times)
1068 * between reading it and the spin_lock(). It can
1069 * change again after the spin_lock() but only if it was
1070 * already changed before the spin_lock(). It cannot,
1071 * however, change back to the original value. Therefore
1072 * we can detect whether we acquired the correct lock.
1073 */
1074 if (unlikely(lock_ptr != q->lock_ptr)) {
1075 spin_unlock(lock_ptr);
1076 goto retry;
1077 }
Pierre Peifferec92d082007-05-09 02:35:00 -07001078 WARN_ON(plist_node_empty(&q->list));
1079 plist_del(&q->list, &q->list.plist);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001080
1081 BUG_ON(q->pi_state);
1082
Linus Torvalds1da177e2005-04-16 15:20:36 -07001083 spin_unlock(lock_ptr);
1084 ret = 1;
1085 }
1086
Rusty Russell9adef582007-05-08 00:26:42 -07001087 drop_futex_key_refs(&q->key);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001088 return ret;
1089}
1090
Ingo Molnarc87e2832006-06-27 02:54:58 -07001091/*
1092 * PI futexes can not be requeued and must remove themself from the
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001093 * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry
1094 * and dropped here.
Ingo Molnarc87e2832006-06-27 02:54:58 -07001095 */
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001096static void unqueue_me_pi(struct futex_q *q)
Ingo Molnarc87e2832006-06-27 02:54:58 -07001097{
Pierre Peifferec92d082007-05-09 02:35:00 -07001098 WARN_ON(plist_node_empty(&q->list));
1099 plist_del(&q->list, &q->list.plist);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001100
1101 BUG_ON(!q->pi_state);
1102 free_pi_state(q->pi_state);
1103 q->pi_state = NULL;
1104
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001105 spin_unlock(q->lock_ptr);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001106
Rusty Russell9adef582007-05-08 00:26:42 -07001107 drop_futex_key_refs(&q->key);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001108}
1109
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001110/*
Thomas Gleixnercdf71a12008-01-08 19:47:38 +01001111 * Fixup the pi_state owner with the new owner.
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001112 *
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001113 * Must be called with hash bucket lock held and mm->sem held for non
1114 * private futexes.
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001115 */
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001116static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
Thomas Gleixnercdf71a12008-01-08 19:47:38 +01001117 struct task_struct *newowner)
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001118{
Thomas Gleixnercdf71a12008-01-08 19:47:38 +01001119 u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS;
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001120 struct futex_pi_state *pi_state = q->pi_state;
1121 u32 uval, curval, newval;
1122 int ret;
1123
1124 /* Owner died? */
1125 if (pi_state->owner != NULL) {
1126 spin_lock_irq(&pi_state->owner->pi_lock);
1127 WARN_ON(list_empty(&pi_state->list));
1128 list_del_init(&pi_state->list);
1129 spin_unlock_irq(&pi_state->owner->pi_lock);
1130 } else
1131 newtid |= FUTEX_OWNER_DIED;
1132
Thomas Gleixnercdf71a12008-01-08 19:47:38 +01001133 pi_state->owner = newowner;
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001134
Thomas Gleixnercdf71a12008-01-08 19:47:38 +01001135 spin_lock_irq(&newowner->pi_lock);
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001136 WARN_ON(!list_empty(&pi_state->list));
Thomas Gleixnercdf71a12008-01-08 19:47:38 +01001137 list_add(&pi_state->list, &newowner->pi_state_list);
1138 spin_unlock_irq(&newowner->pi_lock);
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001139
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001140 /*
1141 * We own it, so we have to replace the pending owner
1142 * TID. This must be atomic as we have preserve the
1143 * owner died bit here.
1144 */
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001145 ret = get_futex_value_locked(&uval, uaddr);
1146
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001147 while (!ret) {
1148 newval = (uval & FUTEX_OWNER_DIED) | newtid;
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001149
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001150 curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001151
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001152 if (curval == -EFAULT)
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001153 ret = -EFAULT;
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001154 if (curval == uval)
1155 break;
1156 uval = curval;
1157 }
1158 return ret;
1159}
1160
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001161/*
1162 * In case we must use restart_block to restart a futex_wait,
Steven Rostedtce6bd422007-12-05 15:46:09 +01001163 * we encode in the 'flags' shared capability
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001164 */
Steven Rostedtce6bd422007-12-05 15:46:09 +01001165#define FLAGS_SHARED 1
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001166
Nick Piggin72c1bbf2007-05-08 00:26:43 -07001167static long futex_wait_restart(struct restart_block *restart);
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001168
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001169static int futex_wait(u32 __user *uaddr, struct rw_semaphore *fshared,
Thomas Gleixnercd689982008-02-01 17:45:14 +01001170 u32 val, ktime_t *abs_time, u32 bitset)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001171{
Ingo Molnarc87e2832006-06-27 02:54:58 -07001172 struct task_struct *curr = current;
1173 DECLARE_WAITQUEUE(wait, curr);
Ingo Molnare2970f22006-06-27 02:54:47 -07001174 struct futex_hash_bucket *hb;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001175 struct futex_q q;
Ingo Molnare2970f22006-06-27 02:54:47 -07001176 u32 uval;
1177 int ret;
Thomas Gleixnerbd197232007-06-17 21:11:10 +02001178 struct hrtimer_sleeper t;
Pierre Peifferc19384b2007-05-09 02:35:02 -07001179 int rem = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001180
Thomas Gleixnercd689982008-02-01 17:45:14 +01001181 if (!bitset)
1182 return -EINVAL;
1183
Ingo Molnarc87e2832006-06-27 02:54:58 -07001184 q.pi_state = NULL;
Thomas Gleixnercd689982008-02-01 17:45:14 +01001185 q.bitset = bitset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001186 retry:
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001187 futex_lock_mm(fshared);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001188
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001189 ret = get_futex_key(uaddr, fshared, &q.key);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001190 if (unlikely(ret != 0))
1191 goto out_release_sem;
1192
Ingo Molnare2970f22006-06-27 02:54:47 -07001193 hb = queue_lock(&q, -1, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001194
1195 /*
1196 * Access the page AFTER the futex is queued.
1197 * Order is important:
1198 *
1199 * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val);
1200 * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); }
1201 *
1202 * The basic logical guarantee of a futex is that it blocks ONLY
1203 * if cond(var) is known to be true at the time of blocking, for
1204 * any cond. If we queued after testing *uaddr, that would open
1205 * a race condition where we could block indefinitely with
1206 * cond(var) false, which would violate the guarantee.
1207 *
1208 * A consequence is that futex_wait() can return zero and absorb
1209 * a wakeup when *uaddr != val on entry to the syscall. This is
1210 * rare, but normal.
1211 *
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001212 * for shared futexes, we hold the mmap semaphore, so the mapping
1213 * cannot have changed since we looked it up in get_futex_key.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001214 */
Ingo Molnare2970f22006-06-27 02:54:47 -07001215 ret = get_futex_value_locked(&uval, uaddr);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001216
1217 if (unlikely(ret)) {
Ingo Molnare2970f22006-06-27 02:54:47 -07001218 queue_unlock(&q, hb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001219
Ingo Molnare2970f22006-06-27 02:54:47 -07001220 /*
1221 * If we would have faulted, release mmap_sem, fault it in and
Linus Torvalds1da177e2005-04-16 15:20:36 -07001222 * start all over again.
1223 */
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001224 futex_unlock_mm(fshared);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001225
Ingo Molnare2970f22006-06-27 02:54:47 -07001226 ret = get_user(uval, uaddr);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001227
1228 if (!ret)
1229 goto retry;
1230 return ret;
1231 }
Ingo Molnarc87e2832006-06-27 02:54:58 -07001232 ret = -EWOULDBLOCK;
1233 if (uval != val)
1234 goto out_unlock_release_sem;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001235
1236 /* Only actually queue if *uaddr contained val. */
Ingo Molnare2970f22006-06-27 02:54:47 -07001237 __queue_me(&q, hb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001238
1239 /*
1240 * Now the futex is queued and we have checked the data, we
1241 * don't want to hold mmap_sem while we sleep.
Ingo Molnarc87e2832006-06-27 02:54:58 -07001242 */
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001243 futex_unlock_mm(fshared);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001244
1245 /*
1246 * There might have been scheduling since the queue_me(), as we
1247 * cannot hold a spinlock across the get_user() in case it
1248 * faults, and we cannot just set TASK_INTERRUPTIBLE state when
1249 * queueing ourselves into the futex hash. This code thus has to
1250 * rely on the futex_wake() code removing us from hash when it
1251 * wakes us up.
1252 */
1253
1254 /* add_wait_queue is the barrier after __set_current_state. */
1255 __set_current_state(TASK_INTERRUPTIBLE);
1256 add_wait_queue(&q.waiters, &wait);
1257 /*
Pierre Peifferec92d082007-05-09 02:35:00 -07001258 * !plist_node_empty() is safe here without any lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001259 * q.lock_ptr != 0 is not safe, because of ordering against wakeup.
1260 */
Pierre Peifferec92d082007-05-09 02:35:00 -07001261 if (likely(!plist_node_empty(&q.list))) {
Pierre Peifferc19384b2007-05-09 02:35:02 -07001262 if (!abs_time)
1263 schedule();
1264 else {
1265 hrtimer_init(&t.timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
1266 hrtimer_init_sleeper(&t, current);
1267 t.timer.expires = *abs_time;
Nick Piggin72c1bbf2007-05-08 00:26:43 -07001268
Pierre Peifferc19384b2007-05-09 02:35:02 -07001269 hrtimer_start(&t.timer, t.timer.expires, HRTIMER_MODE_ABS);
Peter Zijlstra3588a082008-02-01 17:45:13 +01001270 if (!hrtimer_active(&t.timer))
1271 t.task = NULL;
Nick Piggin72c1bbf2007-05-08 00:26:43 -07001272
Pierre Peifferc19384b2007-05-09 02:35:02 -07001273 /*
1274 * the timer could have already expired, in which
1275 * case current would be flagged for rescheduling.
1276 * Don't bother calling schedule.
1277 */
1278 if (likely(t.task))
1279 schedule();
1280
1281 hrtimer_cancel(&t.timer);
1282
1283 /* Flag if a timeout occured */
1284 rem = (t.task == NULL);
1285 }
Nick Piggin72c1bbf2007-05-08 00:26:43 -07001286 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001287 __set_current_state(TASK_RUNNING);
1288
1289 /*
1290 * NOTE: we don't remove ourselves from the waitqueue because
1291 * we are the only user of it.
1292 */
1293
1294 /* If we were woken (and unqueued), we succeeded, whatever. */
1295 if (!unqueue_me(&q))
1296 return 0;
Pierre Peifferc19384b2007-05-09 02:35:02 -07001297 if (rem)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001298 return -ETIMEDOUT;
Nick Piggin72c1bbf2007-05-08 00:26:43 -07001299
Ingo Molnare2970f22006-06-27 02:54:47 -07001300 /*
1301 * We expect signal_pending(current), but another thread may
1302 * have handled it for us already.
1303 */
Pierre Peifferc19384b2007-05-09 02:35:02 -07001304 if (!abs_time)
Nick Piggin72c1bbf2007-05-08 00:26:43 -07001305 return -ERESTARTSYS;
1306 else {
1307 struct restart_block *restart;
1308 restart = &current_thread_info()->restart_block;
1309 restart->fn = futex_wait_restart;
Steven Rostedtce6bd422007-12-05 15:46:09 +01001310 restart->futex.uaddr = (u32 *)uaddr;
1311 restart->futex.val = val;
1312 restart->futex.time = abs_time->tv64;
Thomas Gleixnercd689982008-02-01 17:45:14 +01001313 restart->futex.bitset = bitset;
Steven Rostedtce6bd422007-12-05 15:46:09 +01001314 restart->futex.flags = 0;
1315
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001316 if (fshared)
Steven Rostedtce6bd422007-12-05 15:46:09 +01001317 restart->futex.flags |= FLAGS_SHARED;
Nick Piggin72c1bbf2007-05-08 00:26:43 -07001318 return -ERESTART_RESTARTBLOCK;
1319 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001320
Ingo Molnarc87e2832006-06-27 02:54:58 -07001321 out_unlock_release_sem:
1322 queue_unlock(&q, hb);
1323
Linus Torvalds1da177e2005-04-16 15:20:36 -07001324 out_release_sem:
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001325 futex_unlock_mm(fshared);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001326 return ret;
1327}
1328
Nick Piggin72c1bbf2007-05-08 00:26:43 -07001329
1330static long futex_wait_restart(struct restart_block *restart)
1331{
Steven Rostedtce6bd422007-12-05 15:46:09 +01001332 u32 __user *uaddr = (u32 __user *)restart->futex.uaddr;
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001333 struct rw_semaphore *fshared = NULL;
Steven Rostedtce6bd422007-12-05 15:46:09 +01001334 ktime_t t;
Nick Piggin72c1bbf2007-05-08 00:26:43 -07001335
Steven Rostedtce6bd422007-12-05 15:46:09 +01001336 t.tv64 = restart->futex.time;
Nick Piggin72c1bbf2007-05-08 00:26:43 -07001337 restart->fn = do_no_restart_syscall;
Steven Rostedtce6bd422007-12-05 15:46:09 +01001338 if (restart->futex.flags & FLAGS_SHARED)
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001339 fshared = &current->mm->mmap_sem;
Thomas Gleixnercd689982008-02-01 17:45:14 +01001340 return (long)futex_wait(uaddr, fshared, restart->futex.val, &t,
1341 restart->futex.bitset);
Nick Piggin72c1bbf2007-05-08 00:26:43 -07001342}
1343
1344
Ingo Molnarc87e2832006-06-27 02:54:58 -07001345/*
1346 * Userspace tried a 0 -> TID atomic transition of the futex value
1347 * and failed. The kernel side here does the whole locking operation:
1348 * if there are waiters then it will block, it does PI, etc. (Due to
1349 * races the kernel might see a 0 value of the futex too.)
1350 */
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001351static int futex_lock_pi(u32 __user *uaddr, struct rw_semaphore *fshared,
1352 int detect, ktime_t *time, int trylock)
Ingo Molnarc87e2832006-06-27 02:54:58 -07001353{
Thomas Gleixnerc5780e92006-09-08 09:47:15 -07001354 struct hrtimer_sleeper timeout, *to = NULL;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001355 struct task_struct *curr = current;
1356 struct futex_hash_bucket *hb;
1357 u32 uval, newval, curval;
1358 struct futex_q q;
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001359 int ret, lock_taken, ownerdied = 0, attempt = 0;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001360
1361 if (refill_pi_state_cache())
1362 return -ENOMEM;
1363
Pierre Peifferc19384b2007-05-09 02:35:02 -07001364 if (time) {
Thomas Gleixnerc5780e92006-09-08 09:47:15 -07001365 to = &timeout;
Thomas Gleixnerc9cb2e32007-02-16 01:27:49 -08001366 hrtimer_init(&to->timer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
Thomas Gleixnerc5780e92006-09-08 09:47:15 -07001367 hrtimer_init_sleeper(to, current);
Pierre Peifferc19384b2007-05-09 02:35:02 -07001368 to->timer.expires = *time;
Thomas Gleixnerc5780e92006-09-08 09:47:15 -07001369 }
1370
Ingo Molnarc87e2832006-06-27 02:54:58 -07001371 q.pi_state = NULL;
1372 retry:
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001373 futex_lock_mm(fshared);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001374
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001375 ret = get_futex_key(uaddr, fshared, &q.key);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001376 if (unlikely(ret != 0))
1377 goto out_release_sem;
1378
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001379 retry_unlocked:
Ingo Molnarc87e2832006-06-27 02:54:58 -07001380 hb = queue_lock(&q, -1, NULL);
1381
1382 retry_locked:
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001383 ret = lock_taken = 0;
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001384
Ingo Molnarc87e2832006-06-27 02:54:58 -07001385 /*
1386 * To avoid races, we attempt to take the lock here again
1387 * (by doing a 0 -> TID atomic cmpxchg), while holding all
1388 * the locks. It will most likely not succeed.
1389 */
Pavel Emelyanovb4888932007-10-18 23:40:14 -07001390 newval = task_pid_vnr(current);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001391
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001392 curval = cmpxchg_futex_value_locked(uaddr, 0, newval);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001393
1394 if (unlikely(curval == -EFAULT))
1395 goto uaddr_faulted;
1396
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001397 /*
1398 * Detect deadlocks. In case of REQUEUE_PI this is a valid
1399 * situation and we return success to user space.
1400 */
Pavel Emelyanovb4888932007-10-18 23:40:14 -07001401 if (unlikely((curval & FUTEX_TID_MASK) == task_pid_vnr(current))) {
Thomas Gleixnerbd197232007-06-17 21:11:10 +02001402 ret = -EDEADLK;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001403 goto out_unlock_release_sem;
1404 }
1405
1406 /*
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001407 * Surprise - we got the lock. Just return to userspace:
Ingo Molnarc87e2832006-06-27 02:54:58 -07001408 */
1409 if (unlikely(!curval))
1410 goto out_unlock_release_sem;
1411
1412 uval = curval;
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001413
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001414 /*
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001415 * Set the WAITERS flag, so the owner will know it has someone
1416 * to wake at next unlock
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001417 */
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001418 newval = curval | FUTEX_WAITERS;
1419
1420 /*
1421 * There are two cases, where a futex might have no owner (the
Thomas Gleixnerbd197232007-06-17 21:11:10 +02001422 * owner TID is 0): OWNER_DIED. We take over the futex in this
1423 * case. We also do an unconditional take over, when the owner
1424 * of the futex died.
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001425 *
1426 * This is safe as we are protected by the hash bucket lock !
1427 */
1428 if (unlikely(ownerdied || !(curval & FUTEX_TID_MASK))) {
Thomas Gleixnerbd197232007-06-17 21:11:10 +02001429 /* Keep the OWNER_DIED bit */
Pavel Emelyanovb4888932007-10-18 23:40:14 -07001430 newval = (curval & ~FUTEX_TID_MASK) | task_pid_vnr(current);
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001431 ownerdied = 0;
1432 lock_taken = 1;
1433 }
Ingo Molnarc87e2832006-06-27 02:54:58 -07001434
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001435 curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001436
1437 if (unlikely(curval == -EFAULT))
1438 goto uaddr_faulted;
1439 if (unlikely(curval != uval))
1440 goto retry_locked;
1441
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001442 /*
Thomas Gleixnerbd197232007-06-17 21:11:10 +02001443 * We took the lock due to owner died take over.
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001444 */
Thomas Gleixnerbd197232007-06-17 21:11:10 +02001445 if (unlikely(lock_taken))
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001446 goto out_unlock_release_sem;
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001447
Ingo Molnarc87e2832006-06-27 02:54:58 -07001448 /*
1449 * We dont have the lock. Look up the PI state (or create it if
1450 * we are the first waiter):
1451 */
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001452 ret = lookup_pi_state(uval, hb, &q.key, &q.pi_state);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001453
1454 if (unlikely(ret)) {
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001455 switch (ret) {
Ingo Molnarc87e2832006-06-27 02:54:58 -07001456
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001457 case -EAGAIN:
1458 /*
1459 * Task is exiting and we just wait for the
1460 * exit to complete.
1461 */
1462 queue_unlock(&q, hb);
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001463 futex_unlock_mm(fshared);
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001464 cond_resched();
1465 goto retry;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001466
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001467 case -ESRCH:
1468 /*
1469 * No owner found for this futex. Check if the
1470 * OWNER_DIED bit is set to figure out whether
1471 * this is a robust futex or not.
1472 */
1473 if (get_futex_value_locked(&curval, uaddr))
Ingo Molnarc87e2832006-06-27 02:54:58 -07001474 goto uaddr_faulted;
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001475
1476 /*
1477 * We simply start over in case of a robust
1478 * futex. The code above will take the futex
1479 * and return happy.
1480 */
1481 if (curval & FUTEX_OWNER_DIED) {
1482 ownerdied = 1;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001483 goto retry_locked;
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001484 }
1485 default:
1486 goto out_unlock_release_sem;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001487 }
Ingo Molnarc87e2832006-06-27 02:54:58 -07001488 }
1489
1490 /*
1491 * Only actually queue now that the atomic ops are done:
1492 */
1493 __queue_me(&q, hb);
1494
1495 /*
1496 * Now the futex is queued and we have checked the data, we
1497 * don't want to hold mmap_sem while we sleep.
1498 */
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001499 futex_unlock_mm(fshared);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001500
1501 WARN_ON(!q.pi_state);
1502 /*
1503 * Block on the PI mutex:
1504 */
1505 if (!trylock)
1506 ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1);
1507 else {
1508 ret = rt_mutex_trylock(&q.pi_state->pi_mutex);
1509 /* Fixup the trylock return value: */
1510 ret = ret ? 0 : -EWOULDBLOCK;
1511 }
1512
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001513 futex_lock_mm(fshared);
Vernon Mauerya99e4e42006-07-01 04:35:42 -07001514 spin_lock(q.lock_ptr);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001515
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001516 if (!ret) {
1517 /*
1518 * Got the lock. We might not be the anticipated owner
1519 * if we did a lock-steal - fix up the PI-state in
1520 * that case:
1521 */
1522 if (q.pi_state->owner != curr)
1523 ret = fixup_pi_state_owner(uaddr, &q, curr);
1524 } else {
Ingo Molnarc87e2832006-06-27 02:54:58 -07001525 /*
1526 * Catch the rare case, where the lock was released
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001527 * when we were on the way back before we locked the
1528 * hash bucket.
Ingo Molnarc87e2832006-06-27 02:54:58 -07001529 */
Thomas Gleixnercdf71a12008-01-08 19:47:38 +01001530 if (q.pi_state->owner == curr) {
1531 /*
1532 * Try to get the rt_mutex now. This might
1533 * fail as some other task acquired the
1534 * rt_mutex after we removed ourself from the
1535 * rt_mutex waiters list.
1536 */
1537 if (rt_mutex_trylock(&q.pi_state->pi_mutex))
1538 ret = 0;
1539 else {
1540 /*
1541 * pi_state is incorrect, some other
1542 * task did a lock steal and we
1543 * returned due to timeout or signal
1544 * without taking the rt_mutex. Too
1545 * late. We can access the
1546 * rt_mutex_owner without locking, as
1547 * the other task is now blocked on
1548 * the hash bucket lock. Fix the state
1549 * up.
1550 */
1551 struct task_struct *owner;
1552 int res;
1553
1554 owner = rt_mutex_owner(&q.pi_state->pi_mutex);
1555 res = fixup_pi_state_owner(uaddr, &q, owner);
1556
Thomas Gleixnercdf71a12008-01-08 19:47:38 +01001557 /* propagate -EFAULT, if the fixup failed */
1558 if (res)
1559 ret = res;
1560 }
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001561 } else {
1562 /*
1563 * Paranoia check. If we did not take the lock
1564 * in the trylock above, then we should not be
1565 * the owner of the rtmutex, neither the real
1566 * nor the pending one:
1567 */
1568 if (rt_mutex_owner(&q.pi_state->pi_mutex) == curr)
1569 printk(KERN_ERR "futex_lock_pi: ret = %d "
1570 "pi-mutex: %p pi-state %p\n", ret,
1571 q.pi_state->pi_mutex.owner,
1572 q.pi_state->owner);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001573 }
Ingo Molnarc87e2832006-06-27 02:54:58 -07001574 }
1575
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001576 /* Unqueue and drop the lock */
1577 unqueue_me_pi(&q);
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001578 futex_unlock_mm(fshared);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001579
Thomas Gleixnerc5780e92006-09-08 09:47:15 -07001580 return ret != -EINTR ? ret : -ERESTARTNOINTR;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001581
1582 out_unlock_release_sem:
1583 queue_unlock(&q, hb);
1584
1585 out_release_sem:
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001586 futex_unlock_mm(fshared);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001587 return ret;
1588
1589 uaddr_faulted:
1590 /*
1591 * We have to r/w *(int __user *)uaddr, but we can't modify it
1592 * non-atomically. Therefore, if get_user below is not
1593 * enough, we need to handle the fault ourselves, while
1594 * still holding the mmap_sem.
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001595 *
1596 * ... and hb->lock. :-) --ANK
Ingo Molnarc87e2832006-06-27 02:54:58 -07001597 */
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001598 queue_unlock(&q, hb);
1599
Ingo Molnarc87e2832006-06-27 02:54:58 -07001600 if (attempt++) {
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001601 ret = futex_handle_fault((unsigned long)uaddr, fshared,
1602 attempt);
1603 if (ret)
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001604 goto out_release_sem;
1605 goto retry_unlocked;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001606 }
1607
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001608 futex_unlock_mm(fshared);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001609
1610 ret = get_user(uval, uaddr);
1611 if (!ret && (uval != -EFAULT))
1612 goto retry;
1613
1614 return ret;
1615}
1616
1617/*
Ingo Molnarc87e2832006-06-27 02:54:58 -07001618 * Userspace attempted a TID -> 0 atomic transition, and failed.
1619 * This is the in-kernel slowpath: we look up the PI state (if any),
1620 * and do the rt-mutex unlock.
1621 */
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001622static int futex_unlock_pi(u32 __user *uaddr, struct rw_semaphore *fshared)
Ingo Molnarc87e2832006-06-27 02:54:58 -07001623{
1624 struct futex_hash_bucket *hb;
1625 struct futex_q *this, *next;
1626 u32 uval;
Pierre Peifferec92d082007-05-09 02:35:00 -07001627 struct plist_head *head;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001628 union futex_key key;
1629 int ret, attempt = 0;
1630
1631retry:
1632 if (get_user(uval, uaddr))
1633 return -EFAULT;
1634 /*
1635 * We release only a lock we actually own:
1636 */
Pavel Emelyanovb4888932007-10-18 23:40:14 -07001637 if ((uval & FUTEX_TID_MASK) != task_pid_vnr(current))
Ingo Molnarc87e2832006-06-27 02:54:58 -07001638 return -EPERM;
1639 /*
1640 * First take all the futex related locks:
1641 */
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001642 futex_lock_mm(fshared);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001643
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001644 ret = get_futex_key(uaddr, fshared, &key);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001645 if (unlikely(ret != 0))
1646 goto out;
1647
1648 hb = hash_futex(&key);
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001649retry_unlocked:
Ingo Molnarc87e2832006-06-27 02:54:58 -07001650 spin_lock(&hb->lock);
1651
Ingo Molnarc87e2832006-06-27 02:54:58 -07001652 /*
1653 * To avoid races, try to do the TID -> 0 atomic transition
1654 * again. If it succeeds then we can return without waking
1655 * anyone else up:
1656 */
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001657 if (!(uval & FUTEX_OWNER_DIED))
Pavel Emelyanovb4888932007-10-18 23:40:14 -07001658 uval = cmpxchg_futex_value_locked(uaddr, task_pid_vnr(current), 0);
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001659
Ingo Molnarc87e2832006-06-27 02:54:58 -07001660
1661 if (unlikely(uval == -EFAULT))
1662 goto pi_faulted;
1663 /*
1664 * Rare case: we managed to release the lock atomically,
1665 * no need to wake anyone else up:
1666 */
Pavel Emelyanovb4888932007-10-18 23:40:14 -07001667 if (unlikely(uval == task_pid_vnr(current)))
Ingo Molnarc87e2832006-06-27 02:54:58 -07001668 goto out_unlock;
1669
1670 /*
1671 * Ok, other tasks may need to be woken up - check waiters
1672 * and do the wakeup if necessary:
1673 */
1674 head = &hb->chain;
1675
Pierre Peifferec92d082007-05-09 02:35:00 -07001676 plist_for_each_entry_safe(this, next, head, list) {
Ingo Molnarc87e2832006-06-27 02:54:58 -07001677 if (!match_futex (&this->key, &key))
1678 continue;
1679 ret = wake_futex_pi(uaddr, uval, this);
1680 /*
1681 * The atomic access to the futex value
1682 * generated a pagefault, so retry the
1683 * user-access and the wakeup:
1684 */
1685 if (ret == -EFAULT)
1686 goto pi_faulted;
1687 goto out_unlock;
1688 }
1689 /*
1690 * No waiters - kernel unlocks the futex:
1691 */
Ingo Molnare3f2dde2006-07-29 05:17:57 +02001692 if (!(uval & FUTEX_OWNER_DIED)) {
1693 ret = unlock_futex_pi(uaddr, uval);
1694 if (ret == -EFAULT)
1695 goto pi_faulted;
1696 }
Ingo Molnarc87e2832006-06-27 02:54:58 -07001697
1698out_unlock:
1699 spin_unlock(&hb->lock);
1700out:
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001701 futex_unlock_mm(fshared);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001702
1703 return ret;
1704
1705pi_faulted:
1706 /*
1707 * We have to r/w *(int __user *)uaddr, but we can't modify it
1708 * non-atomically. Therefore, if get_user below is not
1709 * enough, we need to handle the fault ourselves, while
1710 * still holding the mmap_sem.
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001711 *
1712 * ... and hb->lock. --ANK
Ingo Molnarc87e2832006-06-27 02:54:58 -07001713 */
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001714 spin_unlock(&hb->lock);
1715
Ingo Molnarc87e2832006-06-27 02:54:58 -07001716 if (attempt++) {
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001717 ret = futex_handle_fault((unsigned long)uaddr, fshared,
1718 attempt);
1719 if (ret)
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001720 goto out;
john stultz187226f2007-08-22 14:01:10 -07001721 uval = 0;
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001722 goto retry_unlocked;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001723 }
1724
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001725 futex_unlock_mm(fshared);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001726
1727 ret = get_user(uval, uaddr);
1728 if (!ret && (uval != -EFAULT))
1729 goto retry;
1730
Linus Torvalds1da177e2005-04-16 15:20:36 -07001731 return ret;
1732}
1733
1734static int futex_close(struct inode *inode, struct file *filp)
1735{
1736 struct futex_q *q = filp->private_data;
1737
1738 unqueue_me(q);
1739 kfree(q);
Ingo Molnare2970f22006-06-27 02:54:47 -07001740
Linus Torvalds1da177e2005-04-16 15:20:36 -07001741 return 0;
1742}
1743
1744/* This is one-shot: once it's gone off you need a new fd */
1745static unsigned int futex_poll(struct file *filp,
1746 struct poll_table_struct *wait)
1747{
1748 struct futex_q *q = filp->private_data;
1749 int ret = 0;
1750
1751 poll_wait(filp, &q->waiters, wait);
1752
1753 /*
Pierre Peifferec92d082007-05-09 02:35:00 -07001754 * plist_node_empty() is safe here without any lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001755 * q->lock_ptr != 0 is not safe, because of ordering against wakeup.
1756 */
Pierre Peifferec92d082007-05-09 02:35:00 -07001757 if (plist_node_empty(&q->list))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001758 ret = POLLIN | POLLRDNORM;
1759
1760 return ret;
1761}
1762
Helge Deller15ad7cd2006-12-06 20:40:36 -08001763static const struct file_operations futex_fops = {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001764 .release = futex_close,
1765 .poll = futex_poll,
1766};
1767
1768/*
1769 * Signal allows caller to avoid the race which would occur if they
1770 * set the sigio stuff up afterwards.
1771 */
Ingo Molnare2970f22006-06-27 02:54:47 -07001772static int futex_fd(u32 __user *uaddr, int signal)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001773{
1774 struct futex_q *q;
1775 struct file *filp;
1776 int ret, err;
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001777 struct rw_semaphore *fshared;
Andrew Morton19c6b6e2006-11-02 22:07:17 -08001778 static unsigned long printk_interval;
1779
1780 if (printk_timed_ratelimit(&printk_interval, 60 * 60 * 1000)) {
1781 printk(KERN_WARNING "Process `%s' used FUTEX_FD, which "
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001782 "will be removed from the kernel in June 2007\n",
1783 current->comm);
Andrew Morton19c6b6e2006-11-02 22:07:17 -08001784 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001785
1786 ret = -EINVAL;
Jesper Juhl7ed20e12005-05-01 08:59:14 -07001787 if (!valid_signal(signal))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001788 goto out;
1789
1790 ret = get_unused_fd();
1791 if (ret < 0)
1792 goto out;
1793 filp = get_empty_filp();
1794 if (!filp) {
1795 put_unused_fd(ret);
1796 ret = -ENFILE;
1797 goto out;
1798 }
1799 filp->f_op = &futex_fops;
Josef "Jeff" Sipekf3a43f32006-12-08 02:36:43 -08001800 filp->f_path.mnt = mntget(futex_mnt);
1801 filp->f_path.dentry = dget(futex_mnt->mnt_root);
1802 filp->f_mapping = filp->f_path.dentry->d_inode->i_mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001803
1804 if (signal) {
Eric W. Biederman609d7fa2006-10-02 02:17:15 -07001805 err = __f_setown(filp, task_pid(current), PIDTYPE_PID, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001806 if (err < 0) {
Pekka Enberg39ed3fd2005-09-06 15:17:44 -07001807 goto error;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001808 }
1809 filp->f_owner.signum = signal;
1810 }
1811
1812 q = kmalloc(sizeof(*q), GFP_KERNEL);
1813 if (!q) {
Pekka Enberg39ed3fd2005-09-06 15:17:44 -07001814 err = -ENOMEM;
1815 goto error;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001816 }
Ingo Molnarc87e2832006-06-27 02:54:58 -07001817 q->pi_state = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001818
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001819 fshared = &current->mm->mmap_sem;
1820 down_read(fshared);
1821 err = get_futex_key(uaddr, fshared, &q->key);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001822
1823 if (unlikely(err != 0)) {
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001824 up_read(fshared);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001825 kfree(q);
Pekka Enberg39ed3fd2005-09-06 15:17:44 -07001826 goto error;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001827 }
1828
1829 /*
1830 * queue_me() must be called before releasing mmap_sem, because
1831 * key->shared.inode needs to be referenced while holding it.
1832 */
1833 filp->private_data = q;
1834
1835 queue_me(q, ret, filp);
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001836 up_read(fshared);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001837
1838 /* Now we map fd to filp, so userspace can access it */
1839 fd_install(ret, filp);
1840out:
1841 return ret;
Pekka Enberg39ed3fd2005-09-06 15:17:44 -07001842error:
1843 put_unused_fd(ret);
1844 put_filp(filp);
1845 ret = err;
1846 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001847}
1848
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001849/*
1850 * Support for robust futexes: the kernel cleans up held futexes at
1851 * thread exit time.
1852 *
1853 * Implementation: user-space maintains a per-thread list of locks it
1854 * is holding. Upon do_exit(), the kernel carefully walks this list,
1855 * and marks all locks that are owned by this thread with the
Ingo Molnarc87e2832006-06-27 02:54:58 -07001856 * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001857 * always manipulated with the lock held, so the list is private and
1858 * per-thread. Userspace also maintains a per-thread 'list_op_pending'
1859 * field, to allow the kernel to clean up if the thread dies after
1860 * acquiring the lock, but just before it could have added itself to
1861 * the list. There can only be one such pending lock.
1862 */
1863
1864/**
1865 * sys_set_robust_list - set the robust-futex list head of a task
1866 * @head: pointer to the list-head
1867 * @len: length of the list-head, as userspace expects
1868 */
1869asmlinkage long
1870sys_set_robust_list(struct robust_list_head __user *head,
1871 size_t len)
1872{
1873 /*
1874 * The kernel knows only one size for now:
1875 */
1876 if (unlikely(len != sizeof(*head)))
1877 return -EINVAL;
1878
1879 current->robust_list = head;
1880
1881 return 0;
1882}
1883
1884/**
1885 * sys_get_robust_list - get the robust-futex list head of a task
1886 * @pid: pid of the process [zero for current task]
1887 * @head_ptr: pointer to a list-head pointer, the kernel fills it in
1888 * @len_ptr: pointer to a length field, the kernel fills in the header size
1889 */
1890asmlinkage long
Al Viroba46df92006-10-10 22:46:07 +01001891sys_get_robust_list(int pid, struct robust_list_head __user * __user *head_ptr,
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001892 size_t __user *len_ptr)
1893{
Al Viroba46df92006-10-10 22:46:07 +01001894 struct robust_list_head __user *head;
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001895 unsigned long ret;
1896
1897 if (!pid)
1898 head = current->robust_list;
1899 else {
1900 struct task_struct *p;
1901
1902 ret = -ESRCH;
Oleg Nesterovaaa2a972006-09-29 02:00:55 -07001903 rcu_read_lock();
Pavel Emelyanov228ebcb2007-10-18 23:40:16 -07001904 p = find_task_by_vpid(pid);
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001905 if (!p)
1906 goto err_unlock;
1907 ret = -EPERM;
1908 if ((current->euid != p->euid) && (current->euid != p->uid) &&
1909 !capable(CAP_SYS_PTRACE))
1910 goto err_unlock;
1911 head = p->robust_list;
Oleg Nesterovaaa2a972006-09-29 02:00:55 -07001912 rcu_read_unlock();
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001913 }
1914
1915 if (put_user(sizeof(*head), len_ptr))
1916 return -EFAULT;
1917 return put_user(head, head_ptr);
1918
1919err_unlock:
Oleg Nesterovaaa2a972006-09-29 02:00:55 -07001920 rcu_read_unlock();
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001921
1922 return ret;
1923}
1924
1925/*
1926 * Process a futex-list entry, check whether it's owned by the
1927 * dying task, and do notification if so:
1928 */
Ingo Molnare3f2dde2006-07-29 05:17:57 +02001929int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi)
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001930{
Ingo Molnare3f2dde2006-07-29 05:17:57 +02001931 u32 uval, nval, mval;
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001932
Ingo Molnar8f17d3a2006-03-27 01:16:27 -08001933retry:
1934 if (get_user(uval, uaddr))
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001935 return -1;
1936
Pavel Emelyanovb4888932007-10-18 23:40:14 -07001937 if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) {
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001938 /*
1939 * Ok, this dying thread is truly holding a futex
1940 * of interest. Set the OWNER_DIED bit atomically
1941 * via cmpxchg, and if the value had FUTEX_WAITERS
1942 * set, wake up a waiter (if any). (We have to do a
1943 * futex_wake() even if OWNER_DIED is already set -
1944 * to handle the rare but possible case of recursive
1945 * thread-death.) The rest of the cleanup is done in
1946 * userspace.
1947 */
Ingo Molnare3f2dde2006-07-29 05:17:57 +02001948 mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED;
1949 nval = futex_atomic_cmpxchg_inatomic(uaddr, uval, mval);
1950
Ingo Molnarc87e2832006-06-27 02:54:58 -07001951 if (nval == -EFAULT)
1952 return -1;
1953
1954 if (nval != uval)
Ingo Molnar8f17d3a2006-03-27 01:16:27 -08001955 goto retry;
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001956
Ingo Molnare3f2dde2006-07-29 05:17:57 +02001957 /*
1958 * Wake robust non-PI futexes here. The wakeup of
1959 * PI futexes happens in exit_pi_state():
1960 */
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001961 if (!pi && (uval & FUTEX_WAITERS))
Thomas Gleixnercd689982008-02-01 17:45:14 +01001962 futex_wake(uaddr, &curr->mm->mmap_sem, 1,
1963 FUTEX_BITSET_MATCH_ANY);
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001964 }
1965 return 0;
1966}
1967
1968/*
Ingo Molnare3f2dde2006-07-29 05:17:57 +02001969 * Fetch a robust-list pointer. Bit 0 signals PI futexes:
1970 */
1971static inline int fetch_robust_entry(struct robust_list __user **entry,
Al Viroba46df92006-10-10 22:46:07 +01001972 struct robust_list __user * __user *head,
1973 int *pi)
Ingo Molnare3f2dde2006-07-29 05:17:57 +02001974{
1975 unsigned long uentry;
1976
Al Viroba46df92006-10-10 22:46:07 +01001977 if (get_user(uentry, (unsigned long __user *)head))
Ingo Molnare3f2dde2006-07-29 05:17:57 +02001978 return -EFAULT;
1979
Al Viroba46df92006-10-10 22:46:07 +01001980 *entry = (void __user *)(uentry & ~1UL);
Ingo Molnare3f2dde2006-07-29 05:17:57 +02001981 *pi = uentry & 1;
1982
1983 return 0;
1984}
1985
1986/*
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001987 * Walk curr->robust_list (very carefully, it's a userspace list!)
1988 * and mark any locks found there dead, and notify any waiters.
1989 *
1990 * We silently return on any sign of list-walking problem.
1991 */
1992void exit_robust_list(struct task_struct *curr)
1993{
1994 struct robust_list_head __user *head = curr->robust_list;
Martin Schwidefsky9f96cb12007-10-01 01:20:13 -07001995 struct robust_list __user *entry, *next_entry, *pending;
1996 unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip;
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001997 unsigned long futex_offset;
Martin Schwidefsky9f96cb12007-10-01 01:20:13 -07001998 int rc;
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001999
2000 /*
2001 * Fetch the list head (which was registered earlier, via
2002 * sys_set_robust_list()):
2003 */
Ingo Molnare3f2dde2006-07-29 05:17:57 +02002004 if (fetch_robust_entry(&entry, &head->list.next, &pi))
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002005 return;
2006 /*
2007 * Fetch the relative futex offset:
2008 */
2009 if (get_user(futex_offset, &head->futex_offset))
2010 return;
2011 /*
2012 * Fetch any possibly pending lock-add first, and handle it
2013 * if it exists:
2014 */
Ingo Molnare3f2dde2006-07-29 05:17:57 +02002015 if (fetch_robust_entry(&pending, &head->list_op_pending, &pip))
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002016 return;
Ingo Molnare3f2dde2006-07-29 05:17:57 +02002017
Martin Schwidefsky9f96cb12007-10-01 01:20:13 -07002018 next_entry = NULL; /* avoid warning with gcc */
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002019 while (entry != &head->list) {
2020 /*
Martin Schwidefsky9f96cb12007-10-01 01:20:13 -07002021 * Fetch the next entry in the list before calling
2022 * handle_futex_death:
2023 */
2024 rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi);
2025 /*
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002026 * A pending lock might already be on the list, so
Ingo Molnarc87e2832006-06-27 02:54:58 -07002027 * don't process it twice:
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002028 */
2029 if (entry != pending)
Al Viroba46df92006-10-10 22:46:07 +01002030 if (handle_futex_death((void __user *)entry + futex_offset,
Ingo Molnare3f2dde2006-07-29 05:17:57 +02002031 curr, pi))
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002032 return;
Martin Schwidefsky9f96cb12007-10-01 01:20:13 -07002033 if (rc)
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002034 return;
Martin Schwidefsky9f96cb12007-10-01 01:20:13 -07002035 entry = next_entry;
2036 pi = next_pi;
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002037 /*
2038 * Avoid excessively long or circular lists:
2039 */
2040 if (!--limit)
2041 break;
2042
2043 cond_resched();
2044 }
Martin Schwidefsky9f96cb12007-10-01 01:20:13 -07002045
2046 if (pending)
2047 handle_futex_death((void __user *)pending + futex_offset,
2048 curr, pip);
Ingo Molnar0771dfe2006-03-27 01:16:22 -08002049}
2050
Pierre Peifferc19384b2007-05-09 02:35:02 -07002051long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
Ingo Molnare2970f22006-06-27 02:54:47 -07002052 u32 __user *uaddr2, u32 val2, u32 val3)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002053{
2054 int ret;
Eric Dumazet34f01cc2007-05-09 02:35:04 -07002055 int cmd = op & FUTEX_CMD_MASK;
2056 struct rw_semaphore *fshared = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002057
Eric Dumazet34f01cc2007-05-09 02:35:04 -07002058 if (!(op & FUTEX_PRIVATE_FLAG))
2059 fshared = &current->mm->mmap_sem;
2060
2061 switch (cmd) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002062 case FUTEX_WAIT:
Thomas Gleixnercd689982008-02-01 17:45:14 +01002063 val3 = FUTEX_BITSET_MATCH_ANY;
2064 case FUTEX_WAIT_BITSET:
2065 ret = futex_wait(uaddr, fshared, val, timeout, val3);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002066 break;
2067 case FUTEX_WAKE:
Thomas Gleixnercd689982008-02-01 17:45:14 +01002068 val3 = FUTEX_BITSET_MATCH_ANY;
2069 case FUTEX_WAKE_BITSET:
2070 ret = futex_wake(uaddr, fshared, val, val3);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002071 break;
2072 case FUTEX_FD:
2073 /* non-zero val means F_SETOWN(getpid()) & F_SETSIG(val) */
2074 ret = futex_fd(uaddr, val);
2075 break;
2076 case FUTEX_REQUEUE:
Eric Dumazet34f01cc2007-05-09 02:35:04 -07002077 ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002078 break;
2079 case FUTEX_CMP_REQUEUE:
Eric Dumazet34f01cc2007-05-09 02:35:04 -07002080 ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002081 break;
Jakub Jelinek4732efb2005-09-06 15:16:25 -07002082 case FUTEX_WAKE_OP:
Eric Dumazet34f01cc2007-05-09 02:35:04 -07002083 ret = futex_wake_op(uaddr, fshared, uaddr2, val, val2, val3);
Jakub Jelinek4732efb2005-09-06 15:16:25 -07002084 break;
Ingo Molnarc87e2832006-06-27 02:54:58 -07002085 case FUTEX_LOCK_PI:
Eric Dumazet34f01cc2007-05-09 02:35:04 -07002086 ret = futex_lock_pi(uaddr, fshared, val, timeout, 0);
Ingo Molnarc87e2832006-06-27 02:54:58 -07002087 break;
2088 case FUTEX_UNLOCK_PI:
Eric Dumazet34f01cc2007-05-09 02:35:04 -07002089 ret = futex_unlock_pi(uaddr, fshared);
Ingo Molnarc87e2832006-06-27 02:54:58 -07002090 break;
2091 case FUTEX_TRYLOCK_PI:
Eric Dumazet34f01cc2007-05-09 02:35:04 -07002092 ret = futex_lock_pi(uaddr, fshared, 0, timeout, 1);
Ingo Molnarc87e2832006-06-27 02:54:58 -07002093 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002094 default:
2095 ret = -ENOSYS;
2096 }
2097 return ret;
2098}
2099
2100
Ingo Molnare2970f22006-06-27 02:54:47 -07002101asmlinkage long sys_futex(u32 __user *uaddr, int op, u32 val,
Linus Torvalds1da177e2005-04-16 15:20:36 -07002102 struct timespec __user *utime, u32 __user *uaddr2,
Ingo Molnare2970f22006-06-27 02:54:47 -07002103 u32 val3)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002104{
Pierre Peifferc19384b2007-05-09 02:35:02 -07002105 struct timespec ts;
2106 ktime_t t, *tp = NULL;
Ingo Molnare2970f22006-06-27 02:54:47 -07002107 u32 val2 = 0;
Eric Dumazet34f01cc2007-05-09 02:35:04 -07002108 int cmd = op & FUTEX_CMD_MASK;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002109
Thomas Gleixnercd689982008-02-01 17:45:14 +01002110 if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
2111 cmd == FUTEX_WAIT_BITSET)) {
Pierre Peifferc19384b2007-05-09 02:35:02 -07002112 if (copy_from_user(&ts, utime, sizeof(ts)) != 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002113 return -EFAULT;
Pierre Peifferc19384b2007-05-09 02:35:02 -07002114 if (!timespec_valid(&ts))
Thomas Gleixner9741ef962006-03-31 02:31:32 -08002115 return -EINVAL;
Pierre Peifferc19384b2007-05-09 02:35:02 -07002116
2117 t = timespec_to_ktime(ts);
Eric Dumazet34f01cc2007-05-09 02:35:04 -07002118 if (cmd == FUTEX_WAIT)
Pierre Peifferc19384b2007-05-09 02:35:02 -07002119 t = ktime_add(ktime_get(), t);
2120 tp = &t;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002121 }
2122 /*
Eric Dumazet34f01cc2007-05-09 02:35:04 -07002123 * requeue parameter in 'utime' if cmd == FUTEX_REQUEUE.
Andreas Schwabf54f0982007-07-31 00:38:51 -07002124 * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002125 */
Andreas Schwabf54f0982007-07-31 00:38:51 -07002126 if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
2127 cmd == FUTEX_WAKE_OP)
Ingo Molnare2970f22006-06-27 02:54:47 -07002128 val2 = (u32) (unsigned long) utime;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002129
Pierre Peifferc19384b2007-05-09 02:35:02 -07002130 return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002131}
2132
David Howells454e2392006-06-23 02:02:57 -07002133static int futexfs_get_sb(struct file_system_type *fs_type,
2134 int flags, const char *dev_name, void *data,
2135 struct vfsmount *mnt)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002136{
Andrey Mirkinfd5eea42007-10-16 23:30:13 -07002137 return get_sb_pseudo(fs_type, "futex", NULL, FUTEXFS_SUPER_MAGIC, mnt);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002138}
2139
2140static struct file_system_type futex_fs_type = {
2141 .name = "futexfs",
2142 .get_sb = futexfs_get_sb,
2143 .kill_sb = kill_anon_super,
2144};
2145
2146static int __init init(void)
2147{
Akinobu Mita95362fa2006-12-06 20:39:03 -08002148 int i = register_filesystem(&futex_fs_type);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002149
Akinobu Mita95362fa2006-12-06 20:39:03 -08002150 if (i)
2151 return i;
2152
Linus Torvalds1da177e2005-04-16 15:20:36 -07002153 futex_mnt = kern_mount(&futex_fs_type);
Akinobu Mita95362fa2006-12-06 20:39:03 -08002154 if (IS_ERR(futex_mnt)) {
2155 unregister_filesystem(&futex_fs_type);
2156 return PTR_ERR(futex_mnt);
2157 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002158
2159 for (i = 0; i < ARRAY_SIZE(futex_queues); i++) {
Pierre Peifferec92d082007-05-09 02:35:00 -07002160 plist_head_init(&futex_queues[i].chain, &futex_queues[i].lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002161 spin_lock_init(&futex_queues[i].lock);
2162 }
2163 return 0;
2164}
2165__initcall(init);