drivers/input/touchscreen/gunze.c


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204

/*
 *  Copyright (c) 2000-2001 Vojtech Pavlik
 */

/*
 * Gunze AHL-51S touchscreen driver for Linux
 */

/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 * Should you need to contact me, the author, you can do so either by
 * e-mail - mail your message to <vojtech@ucw.cz>, or by paper mail:
 * Vojtech Pavlik, Simunkova 1594, Prague 8, 182 00 Czech Republic
 */

#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/input.h>
#include <linux/serio.h>
#include <linux/init.h>

#define DRIVER_DESC	"Gunze AHL-51S touchscreen driver"

MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE("GPL");

/*
 * Definitions & global arrays.
 */

#define	GUNZE_MAX_LENGTH	10

/*
 * Per-touchscreen data.
 */

struct gunze {
	struct input_dev *dev;
	struct serio *serio;
	int idx;
	unsigned char data[GUNZE_MAX_LENGTH];
	char phys[32];
};

static void gunze_process_packet(struct gunze* gunze)
{
	struct input_dev *dev = gunze->dev;

	if (gunze->idx != GUNZE_MAX_LENGTH || gunze->data[5] != ',' ||
		(gunze->data[0] != 'T' && gunze->data[0] != 'R')) {
		printk(KERN_WARNING "gunze.c: bad packet: >%.*s<\n", GUNZE_MAX_LENGTH, gunze->data);
		return;
	}

	input_report_abs(dev, ABS_X, simple_strtoul(gunze->data + 1, NULL, 10));
	input_report_abs(dev, ABS_Y, 1024 - simple_strtoul(gunze->data + 6, NULL, 10));
	input_report_key(dev, BTN_TOUCH, gunze->data[0] == 'T');
	input_sync(dev);
}

static irqreturn_t gunze_interrupt(struct serio *serio,
		unsigned char data, unsigned int flags)
{
	struct gunze* gunze = serio_get_drvdata(serio);

	if (data == '\r') {
		gunze_process_packet(gunze);
		gunze->idx = 0;
	} else {
		if (gunze->idx < GUNZE_MAX_LENGTH)
			gunze->data[gunze->idx++] = data;
	}
	return IRQ_HANDLED;
}

/*
 * gunze_disconnect() is the opposite of gunze_connect()
 */

static void gunze_disconnect(struct serio *serio)
{
	struct gunze *gunze = serio_get_drvdata(serio);

	input_get_device(gunze->dev);
	input_unregister_device(gunze->dev);
	serio_close(serio);
	serio_set_drvdata(serio, NULL);
	input_put_device(gunze->dev);
	kfree(gunze);
}

/*
 * gunze_connect() is the routine that is called when someone adds a
 * new serio device that supports Gunze protocol and registers it as
 * an input device.
 */

static int gunze_connect(struct serio *serio, struct serio_driver *drv)
{
	struct gunze *gunze;
	struct input_dev *input_dev;
	int err;

	gunze = kzalloc(sizeof(struct gunze), GFP_KERNEL);
	input_dev = input_allocate_device();
	if (!gunze || !input_dev) {
		err = -ENOMEM;
		goto fail1;
	}

	gunze->serio = serio;
	gunze->dev = input_dev;
	snprintf(gunze->phys, sizeof(serio->phys), "%s/input0", serio->phys);

	input_dev->name = "Gunze AHL-51S TouchScreen";
	input_dev->phys = gunze->phys;
	input_dev->id.bustype = BUS_RS232;
	input_dev->id.vendor = SERIO_GUNZE;
	input_dev->id.product = 0x0051;
	input_dev->id.version = 0x0100;
	input_dev->dev.parent = &serio->dev;
	input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
	input_dev->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);
	input_set_abs_params(input_dev, ABS_X, 24, 1000, 0, 0);
	input_set_abs_params(input_dev, ABS_Y, 24, 1000, 0, 0);

	serio_set_drvdata(serio, gunze);

	err = serio_open(serio, drv);
	if (err)
		goto fail2;

	err = input_register_device(gunze->dev);
	if (err)
		goto fail3;

	return 0;

 fail3:	serio_close(serio);
 fail2:	serio_set_drvdata(serio, NULL);
 fail1:	input_free_device(input_dev);
	kfree(gunze);
	return err;
}

/*
 * The serio driver structure.
 */

static struct serio_device_id gunze_serio_ids[] = {
	{
		.type	= SERIO_RS232,
		.proto	= SERIO_GUNZE,
		.id	= SERIO_ANY,
		.extra	= SERIO_ANY,
	},
	{ 0 }
};

MODULE_DEVICE_TABLE(serio, gunze_serio_ids);

static struct serio_driver gunze_drv = {
	.driver		= {
		.name	= "gunze",
	},
	.description	= DRIVER_DESC,
	.id_table	= gunze_serio_ids,
	.interrupt	= gunze_interrupt,
	.connect	= gunze_connect,
	.disconnect	= gunze_disconnect,
};

/*
 * The functions for inserting/removing us as a module.
 */

static int __init gunze_init(void)
{
	return serio_register_driver(&gunze_drv);
}

static void __exit gunze_exit(void)
{
	serio_unregister_driver(&gunze_drv);
}

module_init(gunze_init);
module_exit(gunze_exit);
/*
 *  Fast Userspace Mutexes (which I call "Futexes!").
 *  (C) Rusty Russell, IBM 2002
 *
 *  Generalized futexes, futex requeueing, misc fixes by Ingo Molnar
 *  (C) Copyright 2003 Red Hat Inc, All Rights Reserved
 *
 *  Removed page pinning, fix privately mapped COW pages and other cleanups
 *  (C) Copyright 2003, 2004 Jamie Lokier
 *
 *  Robust futex support started by Ingo Molnar
 *  (C) Copyright 2006 Red Hat Inc, All Rights Reserved
 *  Thanks to Thomas Gleixner for suggestions, analysis and fixes.
 *
 *  PI-futex support started by Ingo Molnar and Thomas Gleixner
 *  Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *  Copyright (C) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com>
 *
 *  PRIVATE futexes by Eric Dumazet
 *  Copyright (C) 2007 Eric Dumazet <dada1@cosmosbay.com>
 *
 *  Thanks to Ben LaHaise for yelling "hashed waitqueues" loudly
 *  enough at me, Linus for the original (flawed) idea, Matthew
 *  Kirkwood for proof-of-concept implementation.
 *
 *  "The futexes are also cursed."
 *  "But they come in a choice of three flavours!"
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
#include <linux/slab.h>
#include <linux/poll.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/jhash.h>
#include <linux/init.h>
#include <linux/futex.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
#include <linux/syscalls.h>
#include <linux/signal.h>
#include <linux/module.h>
#include <linux/magic.h>
#include <linux/pid.h>
#include <linux/nsproxy.h>

#include <asm/futex.h>

#include "rtmutex_common.h"

int __read_mostly futex_cmpxchg_enabled;

#define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)

/*
 * Priority Inheritance state:
 */
struct futex_pi_state {
	/*
	 * list of 'owned' pi_state instances - these have to be
	 * cleaned up in do_exit() if the task exits prematurely:
	 */
	struct list_head list;

	/*
	 * The PI object:
	 */
	struct rt_mutex pi_mutex;

	struct task_struct *owner;
	atomic_t refcount;

	union futex_key key;
};

/*
 * We use this hashed waitqueue instead of a normal wait_queue_t, so
 * we can wake only the relevant ones (hashed queues may be shared).
 *
 * A futex_q has a woken state, just like tasks have TASK_RUNNING.
 * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0.
 * The order of wakup is always to make the first condition true, then
 * wake up q->waiter, then make the second condition true.
 */
struct futex_q {
	struct plist_node list;
	/* There can only be a single waiter */
	wait_queue_head_t waiter;

	/* Which hash list lock to use: */
	spinlock_t *lock_ptr;

	/* Key which the futex is hashed on: */
	union futex_key key;

	/* Optional priority inheritance state: */
	struct futex_pi_state *pi_state;
	struct task_struct *task;

	/* Bitset for the optional bitmasked wakeup */
	u32 bitset;
};

/*
 * Split the global futex_lock into every hash list lock.
 */
struct futex_hash_bucket {
	spinlock_t lock;
	struct plist_head chain;
};

static struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS];

/*
 * We hash on the keys returned from get_futex_key (see below).
 */
static struct futex_hash_bucket *hash_futex(union futex_key *key)
{
	u32 hash = jhash2((u32*)&key->both.word,
			  (sizeof(key->both.word)+sizeof(key->both.ptr))/4,
			  key->both.offset);
	return &futex_queues[hash & ((1 << FUTEX_HASHBITS)-1)];
}

/*
 * Return 1 if two futex_keys are equal, 0 otherwise.
 */
static inline int match_futex(union futex_key *key1, union futex_key *key2)
{
	return (key1->both.word == key2->both.word
		&& key1->both.ptr == key2->both.ptr
		&& key1->both.offset == key2->both.offset);
}

/*
 * Take a reference to the resource addressed by a key.
 * Can be called while holding spinlocks.
 *
 */
static void get_futex_key_refs(union futex_key *key)
{
	if (!key->both.ptr)
		return;

	switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
	case FUT_OFF_INODE:
		atomic_inc(&key->shared.inode->i_count);
		break;
	case FUT_OFF_MMSHARED:
		atomic_inc(&key->private.mm->mm_count);
		break;
	}
}

/*
 * Drop a reference to the resource addressed by a key.
 * The hash bucket spinlock must not be held.
 */
static void drop_futex_key_refs(union futex_key *key)
{
	if (!key->both.ptr) {
		/* If we're here then we tried to put a key we failed to get */
		WARN_ON_ONCE(1);
		return;
	}

	switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
	case FUT_OFF_INODE:
		iput(key->shared.inode);
		break;
	case FUT_OFF_MMSHARED:
		mmdrop(key->private.mm);
		break;
	}
}

/**
 * get_futex_key - Get parameters which are the keys for a futex.
 * @uaddr: virtual address of the futex
 * @shared: NULL for a PROCESS_PRIVATE futex,
 *	&current->mm->mmap_sem for a PROCESS_SHARED futex
 * @key: address where result is stored.
 *
 * Returns a negative error code or 0
 * The key words are stored in *key on success.
 *
 * For shared mappings, it's (page->index, vma->vm_file->f_path.dentry->d_inode,
 * offset_within_page).  For private mappings, it's (uaddr, current->mm).
 * We can usually work out the index without swapping in the page.
 *
 * fshared is NULL for PROCESS_PRIVATE futexes
 * For other futexes, it points to &current->mm->mmap_sem and
 * caller must have taken the reader lock. but NOT any spinlocks.
 */
static int get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key)
{
	unsigned long address = (unsigned long)uaddr;
	struct mm_struct *mm = current->mm;
	struct page *page;
	int err;

	/*
	 * The futex address must be "naturally" aligned.
	 */
	key->both.offset = address % PAGE_SIZE;
	if (unlikely((address % sizeof(u32)) != 0))
		return -EINVAL;
	address -= key->both.offset;

	/*
	 * PROCESS_PRIVATE futexes are fast.
	 * As the mm cannot disappear under us and the 'key' only needs
	 * virtual address, we dont even have to find the underlying vma.
	 * Note : We do have to check 'uaddr' is a valid user address,
	 *        but access_ok() should be faster than find_vma()
	 */
	if (!fshared) {
		if (unlikely(!access_ok(VERIFY_WRITE, uaddr, sizeof(u32))))
			return -EFAULT;
		key->private.mm = mm;
		key->private.address = address;
		get_futex_key_refs(key);
		return 0;
	}

again:
	err = get_user_pages_fast(address, 1, 0, &page);
	if (err < 0)
		return err;

	lock_page(page);
	if (!page->mapping) {
		unlock_page(page);
		put_page(page);
		goto again;
	}

	/*
	 * Private mappings are handled in a simple way.
	 *
	 * NOTE: When userspace waits on a MAP_SHARED mapping, even if
	 * it's a read-only handle, it's expected that futexes attach to
	 * the object not the particular process.
	 */
	if (PageAnon(page)) {
		key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */
		key->private.mm = mm;
		key->private.address = address;
	} else {
		key->both.offset |= FUT_OFF_INODE; /* inode-based key */
		key->shared.inode = page->mapping->host;
		key->shared.pgoff = page->index;
	}

	get_futex_key_refs(key);

	unlock_page(page);
	put_page(page);
	return 0;
}

static inline
void put_futex_key(int fshared, union futex_key *key)
{
	drop_futex_key_refs(key);
}

static u32 cmpxchg_futex_value_locked(u32 __user *uaddr, u32 uval, u32 newval)
{
	u32 curval;

	pagefault_disable();
	curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval);
	pagefault_enable();

	return curval;
}

static int get_futex_value_locked(u32 *dest, u32 __user *from)
{
	int ret;

	pagefault_disable();
	ret = __copy_from_user_inatomic(dest, from, sizeof(u32));
	pagefault_enable();

	return ret ? -EFAULT : 0;
}

/*
 * Fault handling.
 */
static int futex_handle_fault(unsigned long address, int attempt)
{
	struct vm_area_struct * vma;
	struct mm_struct *mm = current->mm;
	int ret = -EFAULT;

	if (attempt > 2)
		return ret;

	down_read(&mm->mmap_sem);
	vma = find_vma(mm, address);
	if (vma && address >= vma->vm_start &&
	    (vma->vm_flags & VM_WRITE)) {
		int fault;
		fault = handle_mm_fault(mm, vma, address, 1);
		if (unlikely((fault & VM_FAULT_ERROR))) {
#if 0
			/* XXX: let's do this when we verify it is OK */
			if (ret & VM_FAULT_OOM)
				ret = -ENOMEM;
#endif
		} else {
			ret = 0;
			if (fault & VM_FAULT_MAJOR)
				current->maj_flt++;
			else
				current->min_flt++;
		}
	}
	up_read(&mm->mmap_sem);
	return ret;
}

/*
 * PI code:
 */
static int refill_pi_state_cache(void)
{
	struct futex_pi_state *pi_state;

	if (likely(current->pi_state_cache))
		return 0;

	pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL);

	if (!pi_state)
		return -ENOMEM;

	INIT_LIST_HEAD(&pi_state->list);
	/* pi_mutex gets initialized later */
	pi_state->owner = NULL;
	atomic_set(&pi_state->refcount, 1);
	pi_state->key = FUTEX_KEY_INIT;

	current->pi_state_cache = pi_state;

	return 0;
}

static struct futex_pi_state * alloc_pi_state(void)
{
	struct futex_pi_state *pi_state = current->pi_state_cache;

	WARN_ON(!pi_state);
	current->pi_state_cache = NULL;

	return pi_state;
}

static void free_pi_state(struct futex_pi_state *pi_state)
{
	if (!atomic_dec_and_test(&pi_state->refcount))
		return;

	/*
	 * If pi_state->owner is NULL, the owner is most probably dying
	 * and has cleaned up the pi_state already
	 */
	if (pi_state->owner) {
		spin_lock_irq(&pi_state->owner->pi_lock);
		list_del_init(&pi_state->list);
		spin_unlock_irq(&pi_state->owner->pi_lock);

		rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner);
	}

	if (current->pi_state_cache)
		kfree(pi_state);
	else {
		/*
		 * pi_state->list is already empty.
		 * clear pi_state->owner.
		 * refcount is at 0 - put it back to 1.
		 */
		pi_state->owner = NULL;
		atomic_set(&pi_state->refcount, 1);
		current->pi_state_cache = pi_state;
	}
}

/*
 * Look up the task based on what TID userspace gave us.
 * We dont trust it.
 */
static struct task_struct * futex_find_get_task(pid_t pid)
{
	struct task_struct *p;
	const struct cred *cred = current_cred(), *pcred;

	rcu_read_lock();
	p = find_task_by_vpid(pid);
	if (!p) {
		p = ERR_PTR(-ESRCH);
	} else {
		pcred = __task_cred(p);
		if (cred->euid != pcred->euid &&
		    cred->euid != pcred->uid)
			p = ERR_PTR(-ESRCH);
		else
			get_task_struct(p);
	}

	rcu_read_unlock();

	return p;
}

/*
 * This task is holding PI mutexes at exit time => bad.
 * Kernel cleans up PI-state, but userspace is likely hosed.
 * (Robust-futex cleanup is separate and might save the day for userspace.)
 */
void exit_pi_state_list(struct task_struct *curr)
{
	struct list_head *next, *head = &curr->pi_state_list;
	struct futex_pi_state *pi_state;
	struct futex_hash_bucket *hb;
	union futex_key key = FUTEX_KEY_INIT;

	if (!futex_cmpxchg_enabled)
		return;
	/*
	 * We are a ZOMBIE and nobody can enqueue itself on
	 * pi_state_list anymore, but we have to be careful
	 * versus waiters unqueueing themselves:
	 */
	spin_lock_irq(&curr->pi_lock);
	while (!list_empty(head)) {

		next = head->next;
		pi_state = list_entry(next, struct futex_pi_state, list);
		key = pi_state->key;
		hb = hash_futex(&key);
		spin_unlock_irq(&curr->pi_lock);

		spin_lock(&hb->lock);

		spin_lock_irq(&curr->pi_lock);
		/*
		 * We dropped the pi-lock, so re-check whether this
		 * task still owns the PI-state:
		 */
		if (head->next != next) {
			spin_unlock(&hb->lock);
			continue;
		}

		WARN_ON(pi_state->owner != curr);
		WARN_ON(list_empty(&pi_state->list));
		list_del_init(&pi_state->list);
		pi_state->owner = NULL;
		spin_unlock_irq(&curr->pi_lock);

		rt_mutex_unlock(&pi_state->pi_mutex);

		spin_unlock(&hb->lock);

		spin_lock_irq(&curr->pi_lock);
	}
	spin_unlock_irq(&curr->pi_lock);
}

static int
lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
		union futex_key *key, struct futex_pi_state **ps)
{
	struct futex_pi_state *pi_state = NULL;
	struct futex_q *this, *next;
	struct plist_head *head;
	struct task_struct *p;
	pid_t pid = uval & FUTEX_TID_MASK;

	head = &hb->chain;

	plist_for_each_entry_safe(this, next, head, list) {
		if (match_futex(&this->key, key)) {
			/*
			 * Another waiter already exists - bump up
			 * the refcount and return its pi_state:
			 */
			pi_state = this->pi_state;
			/*
			 * Userspace might have messed up non PI and PI futexes
			 */
			if (unlikely(!pi_state))
				return -EINVAL;

			WARN_ON(!atomic_read(&pi_state->refcount));
			WARN_ON(pid && pi_state->owner &&
				pi_state->owner->pid != pid);

			atomic_inc(&pi_state->refcount);
			*ps = pi_state;

			return 0;
		}
	}

	/*
	 * We are the first waiter - try to look up the real owner and attach
	 * the new pi_state to it, but bail out when TID = 0
	 */
	if (!pid)
		return -ESRCH;
	p = futex_find_get_task(pid);
	if (IS_ERR(p))
		return PTR_ERR(p);

	/*
	 * We need to look at the task state flags to figure out,
	 * whether the task is exiting. To protect against the do_exit
	 * change of the task flags, we do this protected by
	 * p->pi_lock:
	 */
	spin_lock_irq(&p->pi_lock);
	if (unlikely(p->flags & PF_EXITING)) {
		/*
		 * The task is on the way out. When PF_EXITPIDONE is
		 * set, we know that the task has finished the
		 * cleanup:
		 */
		int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN;

		spin_unlock_irq(&p->pi_lock);
		put_task_struct(p);
		return ret;
	}

	pi_state = alloc_pi_state();

	/*
	 * Initialize the pi_mutex in locked state and make 'p'
	 * the owner of it:
	 */
	rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p);

	/* Store the key for possible exit cleanups: */
	pi_state->key = *key;

	WARN_ON(!list_empty(&pi_state->list));
	list_add(&pi_state->list, &p->pi_state_list);
	pi_state->owner = p;
	spin_unlock_irq(&p->pi_lock);

	put_task_struct(p);

	*ps = pi_state;

	return 0;
}

/*
 * The hash bucket lock must be held when this is called.
 * Afterwards, the futex_q must not be accessed.
 */
static void wake_futex(struct futex_q *q)
{
	plist_del(&q->list, &q->list.plist);
	/*
	 * The lock in wake_up_all() is a crucial memory barrier after the
	 * plist_del() and also before assigning to q->lock_ptr.
	 */
	wake_up(&q->waiter);
	/*
	 * The waiting task can free the futex_q as soon as this is written,
	 * without taking any locks.  This must come last.
	 *
	 * A memory barrier is required here to prevent the following store
	 * to lock_ptr from getting ahead of the wakeup. Clearing the lock
	 * at the end of wake_up_all() does not prevent this store from
	 * moving.
	 */
	smp_wmb();
	q->lock_ptr = NULL;
}

static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)
{
	struct task_struct *new_owner;
	struct futex_pi_state *pi_state = this->pi_state;
	u32 curval, newval;

	if (!pi_state)
		return -EINVAL;

	spin_lock(&pi_state->pi_mutex.wait_lock);
	new_owner = rt_mutex_next_owner(&pi_state->pi_mutex);

	/*
	 * This happens when we have stolen the lock and the original
	 * pending owner did not enqueue itself back on the rt_mutex.
	 * Thats not a tragedy. We know that way, that a lock waiter
	 * is on the fly. We make the futex_q waiter the pending owner.
	 */
	if (!new_owner)
		new_owner = this->task;

	/*
	 * We pass it to the next owner. (The WAITERS bit is always
	 * kept enabled while there is PI state around. We must also
	 * preserve the owner died bit.)
	 */
	if (!(uval & FUTEX_OWNER_DIED)) {
		int ret = 0;

		newval = FUTEX_WAITERS | task_pid_vnr(new_owner);

		curval = cmpxchg_futex_value_locked(uaddr, uval, newval);

		if (curval == -EFAULT)
			ret = -EFAULT;
		else if (curval != uval)
			ret = -EINVAL;
		if (ret) {
			spin_unlock(&pi_state->pi_mutex.wait_lock);
			return ret;
		}
	}

	spin_lock_irq(&pi_state->owner->pi_lock);
	WARN_ON(list_empty(&pi_state->list));
	list_del_init(&pi_state->list);
	spin_unlock_irq(&pi_state->owner->pi_lock);

	spin_lock_irq(&new_owner->pi_lock);
	WARN_ON(!list_empty(&pi_state->list));
	list_add(&pi_state->list, &new_owner->pi_state_list);
	pi_state->owner = new_owner;
	spin_unlock_irq(&new_owner->pi_lock);

	spin_unlock(&pi_state->pi_mutex.wait_lock);
	rt_mutex_unlock(&pi_state->pi_mutex);

	return 0;
}

static int unlock_futex_pi(u32 __user *uaddr, u32 uval)
{
	u32 oldval;

	/*
	 * There is no waiter, so we unlock the futex. The owner died
	 * bit has not to be preserved here. We are the owner:
	 */
	oldval = cmpxchg_futex_value_locked(uaddr, uval, 0);

	if (oldval == -EFAULT)
		return oldval;
	if (oldval != uval)
		return -EAGAIN;

	return 0;
}

/*
 * Express the locking dependencies for lockdep:
 */
static inline void
double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
{
	if (hb1 <= hb2) {
		spin_lock(&hb1->lock);
		if (hb1 < hb2)
			spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING);
	} else { /* hb1 > hb2 */
		spin_lock(&hb2->lock);
		spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING);
	}
}

/*
 * Wake up all waiters hashed on the physical page that is mapped
 * to this virtual address:
 */
static int futex_wake(u32 __user *uaddr, int fshared, int nr_wake, u32 bitset)
{
	struct futex_hash_bucket *hb;
	struct futex_q *this, *next;
	struct plist_head *head;
	union futex_key key = FUTEX_KEY_INIT;
	int ret;

	if (!bitset)
		return -EINVAL;

	ret = get_futex_key(uaddr, fshared, &key);
	if (unlikely(ret != 0))
		goto out;

	hb = hash_futex(&key);
	spin_lock(&hb->lock);
	head = &hb->chain;

	plist_for_each_entry_safe(this, next, head, list) {
		if (match_futex (&this->key, &key)) {
			if (this->pi_state) {
				ret = -EINVAL;
				break;
			}

			/* Check if one of the bits is set in both bitsets */
			if (!(this->bitset & bitset))
				continue;

			wake_futex(this);
			if (++ret >= nr_wake)
				break;
		}
	}

	spin_unlock(&hb->lock);
	put_futex_key(fshared, &key);
out:
	return ret;
}

/*
 * Wake up all waiters hashed on the physical page that is mapped
 * to this virtual address:
 */
static int
futex_wake_op(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
	      int nr_wake, int nr_wake2, int op)
{
	union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
	struct futex_hash_bucket *hb1, *hb2;
	struct plist_head *head;
	struct futex_q *this, *next;
	int ret, op_ret, attempt = 0;

retryfull:
	ret = get_futex_key(uaddr1, fshared, &key1);
	if (unlikely(ret != 0))
		goto out;
	ret = get_futex_key(uaddr2, fshared, &key2);
	if (unlikely(ret != 0))
		goto out_put_key1;

	hb1 = hash_futex(&key1);
	hb2 = hash_futex(&key2);

retry:
	double_lock_hb(hb1, hb2);

	op_ret = futex_atomic_op_inuser(op, uaddr2);
	if (unlikely(op_ret < 0)) {
		u32 dummy;

		spin_unlock(&hb1->lock);
		if (hb1 != hb2)
			spin_unlock(&hb2->lock);

#ifndef CONFIG_MMU
		/*
		 * we don't get EFAULT from MMU faults if we don't have an MMU,
		 * but we might get them from range checking
		 */
		ret = op_ret;
		goto out_put_keys;
#endif

		if (unlikely(op_ret != -EFAULT)) {
			ret = op_ret;
			goto out_put_keys;
		}

		/*
		 * futex_atomic_op_inuser needs to both read and write
		 * *(int __user *)uaddr2, but we can't modify it
		 * non-atomically.  Therefore, if get_user below is not
		 * enough, we need to handle the fault ourselves, while
		 * still holding the mmap_sem.
		 */
		if (attempt++) {
			ret = futex_handle_fault((unsigned long)uaddr2,
						 attempt);
			if (ret)
				goto out_put_keys;
			goto retry;
		}

		ret = get_user(dummy, uaddr2);
		if (ret)
			return ret;

		goto retryfull;
	}

	head = &hb1->chain;

	plist_for_each_entry_safe(this, next, head, list) {
		if (match_futex (&this->key, &key1)) {
			wake_futex(this);
			if (++ret >= nr_wake)
				break;
		}
	}

	if (op_ret > 0) {
		head = &hb2->chain;

		op_ret = 0;
		plist_for_each_entry_safe(this, next, head, list) {
			if (match_futex (&this->key, &key2)) {
				wake_futex(this);
				if (++op_ret >= nr_wake2)
					break;
			}
		}
		ret += op_ret;
	}

	spin_unlock(&hb1->lock);
	if (hb1 != hb2)
		spin_unlock(&hb2->lock);
out_put_keys:
	put_futex_key(fshared, &key2);
out_put_key1:
	put_futex_key(fshared, &key1);
out:
	return ret;
}

/*
 * Requeue all waiters hashed on one physical page to another
 * physical page.
 */
static int futex_requeue(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
			 int nr_wake, int nr_requeue, u32 *cmpval)
{
	union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
	struct futex_hash_bucket *hb1, *hb2;
	struct plist_head *head1;
	struct futex_q *this, *next;
	int ret, drop_count = 0;

retry:
	ret = get_futex_key(uaddr1, fshared, &key1);
	if (unlikely(ret != 0))
		goto out;
	ret = get_futex_key(uaddr2, fshared, &key2);
	if (unlikely(ret != 0))
		goto out_put_key1;

	hb1 = hash_futex(&key1);
	hb2 = hash_futex(&key2);

	double_lock_hb(hb1, hb2);

	if (likely(cmpval != NULL)) {
		u32 curval;

		ret = get_futex_value_locked(&curval, uaddr1);

		if (unlikely(ret)) {
			spin_unlock(&hb1->lock);
			if (hb1 != hb2)
				spin_unlock(&hb2->lock);

			ret = get_user(curval, uaddr1);

			if (!ret)
				goto retry;

			goto out_put_keys;
		}
		if (curval != *cmpval) {
			ret = -EAGAIN;
			goto out_unlock;
		}
	}

	head1 = &hb1->chain;
	plist_for_each_entry_safe(this, next, head1, list) {
		if (!match_futex (&this->key, &key1))
			continue;
		if (++ret <= nr_wake) {
			wake_futex(this);
		} else {
			/*
			 * If key1 and key2 hash to the same bucket, no need to
			 * requeue.
			 */
			if (likely(head1 != &hb2->chain)) {
				plist_del(&this->list, &hb1->chain);
				plist_add(&this->list, &hb2->chain);
				this->lock_ptr = &hb2->lock;
#ifdef CONFIG_DEBUG_PI_LIST
				this->list.plist.lock = &hb2->lock;
#endif
			}
			this->key = key2;
			get_futex_key_refs(&key2);
			drop_count++;

			if (ret - nr_wake >= nr_requeue)
				break;
		}
	}

out_unlock:
	spin_unlock(&hb1->lock);
	if (hb1 != hb2)
		spin_unlock(&hb2->lock);

	/* drop_futex_key_refs() must be called outside the spinlocks. */
	while (--drop_count >= 0)
		drop_futex_key_refs(&key1);

out_put_keys:
	put_futex_key(fshared, &key2);
out_put_key1:
	put_futex_key(fshared, &key1);
out:
	return ret;
}

/* The key must be already stored in q->key. */
static inline struct futex_hash_bucket *queue_lock(struct futex_q *q)
{
	struct futex_hash_bucket *hb;

	init_waitqueue_head(&q->waiter);

	get_futex_key_refs(&q->key);
	hb = hash_futex(&q->key);
	q->lock_ptr = &hb->lock;

	spin_lock(&hb->lock);
	return hb;
}

static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb)
{
	int prio;

	/*
	 * The priority used to register this element is
	 * - either the real thread-priority for the real-time threads
	 * (i.e. threads with a priority lower than MAX_RT_PRIO)
	 * - or MAX_RT_PRIO for non-RT threads.
	 * Thus, all RT-threads are woken first in priority order, and
	 * the others are woken last, in FIFO order.
	 */
	prio = min(current->normal_prio, MAX_RT_PRIO);

	plist_node_init(&q->list, prio);
#ifdef CONFIG_DEBUG_PI_LIST
	q->list.plist.lock = &hb->lock;
#endif
	plist_add(&q->list, &hb->chain);
	q->task = current;
	spin_unlock(&hb->lock);
}

static inline void
queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb)
{
	spin_unlock(&hb->lock);
	drop_futex_key_refs(&q->key);
}

/*
 * queue_me and unqueue_me must be called as a pair, each
 * exactly once.  They are called with the hashed spinlock held.
 */

/* Return 1 if we were still queued (ie. 0 means we were woken) */
static int unqueue_me(struct futex_q *q)
{
	spinlock_t *lock_ptr;
	int ret = 0;

	/* In the common case we don't take the spinlock, which is nice. */
retry:
	lock_ptr = q->lock_ptr;
	barrier();
	if (lock_ptr != NULL) {
		spin_lock(lock_ptr);
		/*
		 * q->lock_ptr can change between reading it and
		 * spin_lock(), causing us to take the wrong lock.  This
		 * corrects the race condition.
		 *
		 * Reasoning goes like this: if we have the wrong lock,
		 * q->lock_ptr must have changed (maybe several times)
		 * between reading it and the spin_lock().  It can
		 * change again after the spin_lock() but only if it was
		 * already changed before the spin_lock().  It cannot,
		 * however, change back to the original value.  Therefore
		 * we can detect whether we acquired the correct lock.
		 */
		if (unlikely(lock_ptr != q->lock_ptr)) {
			spin_unlock(lock_ptr);
			goto retry;
		}
		WARN_ON(plist_node_empty(&q->list));
		plist_del(&q->list, &q->list.plist);

		BUG_ON(q->pi_state);

		spin_unlock(lock_ptr);
		ret = 1;
	}

	drop_futex_key_refs(&q->key);
	return ret;
}

/*
 * PI futexes can not be requeued and must remove themself from the
 * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry
 * and dropped here.
 */
static void unqueue_me_pi(struct futex_q *q)
{
	WARN_ON(plist_node_empty(&q->list));
	plist_del(&q->list, &q->list.plist);

	BUG_ON(!q->pi_state);
	free_pi_state(q->pi_state);
	q->pi_state = NULL;

	spin_unlock(q->lock_ptr);

	drop_futex_key_refs(&q->key);
}

/*
 * Fixup the pi_state owner with the new owner.
 *
 * Must be called with hash bucket lock held and mm->sem held for non
 * private futexes.
 */
static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
				struct task_struct *newowner, int fshared)
{
	u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS;
	struct futex_pi_state *pi_state = q->pi_state;
	struct task_struct *oldowner = pi_state->owner;
	u32 uval, curval, newval;
	int ret, attempt = 0;

	/* Owner died? */
	if (!pi_state->owner)
		newtid |= FUTEX_OWNER_DIED;

	/*
	 * We are here either because we stole the rtmutex from the
	 * pending owner or we are the pending owner which failed to
	 * get the rtmutex. We have to replace the pending owner TID
	 * in the user space variable. This must be atomic as we have
	 * to preserve the owner died bit here.
	 *
	 * Note: We write the user space value _before_ changing the
	 * pi_state because we can fault here. Imagine swapped out
	 * pages or a fork, which was running right before we acquired
	 * mmap_sem, that marked all the anonymous memory readonly for
	 * cow.
	 *
	 * Modifying pi_state _before_ the user space value would
	 * leave the pi_state in an inconsistent state when we fault
	 * here, because we need to drop the hash bucket lock to
	 * handle the fault. This might be observed in the PID check
	 * in lookup_pi_state.
	 */
retry:
	if (get_futex_value_locked(&uval, uaddr))
		goto handle_fault;

	while (1) {
		newval = (uval & FUTEX_OWNER_DIED) | newtid;

		curval = cmpxchg_futex_value_locked(uaddr, uval, newval);

		if (curval == -EFAULT)
			goto handle_fault;
		if (curval == uval)
			break;
		uval = curval;
	}

	/*
	 * We fixed up user space. Now we need to fix the pi_state
	 * itself.
	 */
	if (pi_state->owner != NULL) {
		spin_lock_irq(&pi_state->owner->pi_lock);
		WARN_ON(list_empty(&pi_state->list));
		list_del_init(&pi_state->list);
		spin_unlock_irq(&pi_state->owner->pi_lock);
	}

	pi_state->owner = newowner;

	spin_lock_irq(&newowner->pi_lock);
	WARN_ON(!list_empty(&pi_state->list));
	list_add(&pi_state->list, &newowner->pi_state_list);
	spin_unlock_irq(&newowner->pi_lock);
	return 0;

	/*
	 * To handle the page fault we need to drop the hash bucket
	 * lock here. That gives the other task (either the pending
	 * owner itself or the task which stole the rtmutex) the
	 * chance to try the fixup of the pi_state. So once we are
	 * back from handling the fault we need to check the pi_state
	 * after reacquiring the hash bucket lock and before trying to
	 * do another fixup. When the fixup has been done already we
	 * simply return.
	 */
handle_fault:
	spin_unlock(q->lock_ptr);

	ret = futex_handle_fault((unsigned long)uaddr, attempt++);

	spin_lock(q->lock_ptr);

	/*
	 * Check if someone else fixed it for us:
	 */
	if (pi_state->owner != oldowner)
		return 0;

	if (ret)
		return ret;

	goto retry;
}

/*
 * In case we must use restart_block to restart a futex_wait,
 * we encode in the 'flags' shared capability
 */
#define FLAGS_SHARED		0x01
#define FLAGS_CLOCKRT		0x02

static long futex_wait_restart(struct restart_block *restart);

static int futex_wait(u32 __user *uaddr, int fshared,
		      u32 val, ktime_t *abs_time, u32 bitset, int clockrt)
{
	struct task_struct *curr = current;
	DECLARE_WAITQUEUE(wait, curr);
	struct futex_hash_bucket *hb;
	struct futex_q q;
	u32 uval;
	int ret;
	struct hrtimer_sleeper t;
	int rem = 0;

	if (!bitset)
		return -EINVAL;

	q.pi_state = NULL;
	q.bitset = bitset;
retry:
	q.key = FUTEX_KEY_INIT;
	ret = get_futex_key(uaddr, fshared, &q.key);
	if (unlikely(ret != 0))
		goto out;

	hb = queue_lock(&q);

	/*
	 * Access the page AFTER the futex is queued.
	 * Order is important:
	 *
	 *   Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val);
	 *   Userspace waker:  if (cond(var)) { var = new; futex_wake(&var); }
	 *
	 * The basic logical guarantee of a futex is that it blocks ONLY
	 * if cond(var) is known to be true at the time of blocking, for
	 * any cond.  If we queued after testing *uaddr, that would open
	 * a race condition where we could block indefinitely with
	 * cond(var) false, which would violate the guarantee.
	 *
	 * A consequence is that futex_wait() can return zero and absorb
	 * a wakeup when *uaddr != val on entry to the syscall.  This is
	 * rare, but normal.
	 *
	 * for shared futexes, we hold the mmap semaphore, so the mapping
	 * cannot have changed since we looked it up in get_futex_key.
	 */
	ret = get_futex_value_locked(&uval, uaddr);

	if (unlikely(ret)) {
		queue_unlock(&q, hb);
		put_futex_key(fshared, &q.key);

		ret = get_user(uval, uaddr);

		if (!ret)
			goto retry;
		return ret;
	}
	ret = -EWOULDBLOCK;
	if (uval != val)
		goto out_unlock_put_key;

	/* Only actually queue if *uaddr contained val.  */
	queue_me(&q, hb);

	/*
	 * There might have been scheduling since the queue_me(), as we
	 * cannot hold a spinlock across the get_user() in case it
	 * faults, and we cannot just set TASK_INTERRUPTIBLE state when
	 * queueing ourselves into the futex hash.  This code thus has to
	 * rely on the futex_wake() code removing us from hash when it
	 * wakes us up.
	 */

	/* add_wait_queue is the barrier after __set_current_state. */
	__set_current_state(TASK_INTERRUPTIBLE);
	add_wait_queue(&q.waiter, &wait);
	/*
	 * !plist_node_empty() is safe here without any lock.
	 * q.lock_ptr != 0 is not safe, because of ordering against wakeup.
	 */
	if (likely(!plist_node_empty(&q.list))) {
		if (!abs_time)
			schedule();
		else {
			unsigned long slack;
			slack = current->timer_slack_ns;
			if (rt_task(current))
				slack = 0;
			hrtimer_init_on_stack(&t.timer,
					      clockrt ? CLOCK_REALTIME :
					      CLOCK_MONOTONIC,
					      HRTIMER_MODE_ABS);
			hrtimer_init_sleeper(&t, current);
			hrtimer_set_expires_range_ns(&t.timer, *abs_time, slack);

			hrtimer_start_expires(&t.timer, HRTIMER_MODE_ABS);
			if (!hrtimer_active(&t.timer))
				t.task = NULL;

			/*
			 * the timer could have already expired, in which
			 * case current would be flagged for rescheduling.
			 * Don't bother calling schedule.
			 */
			if (likely(t.task))
				schedule();

			hrtimer_cancel(&t.timer);

			/* Flag if a timeout occured */
			rem = (t.task == NULL);

			destroy_hrtimer_on_stack(&t.timer);
		}
	}
	__set_current_state(TASK_RUNNING);

	/*
	 * NOTE: we don't remove ourselves from the waitqueue because
	 * we are the only user of it.
	 */

	/* If we were woken (and unqueued), we succeeded, whatever. */
	if (!unqueue_me(&q))
		return 0;
	if (rem)
		return -ETIMEDOUT;

	/*
	 * We expect signal_pending(current), but another thread may
	 * have handled it for us already.
	 */
	if (!abs_time)
		return -ERESTARTSYS;
	else {
		struct restart_block *restart;
		restart = &current_thread_info()->restart_block;
		restart->fn = futex_wait_restart;
		restart->futex.uaddr = (u32 *)uaddr;
		restart->futex.val = val;
		restart->futex.time = abs_time->tv64;
		restart->futex.bitset = bitset;
		restart->futex.flags = 0;

		if (fshared)
			restart->futex.flags |= FLAGS_SHARED;
		if (clockrt)
			restart->futex.flags |= FLAGS_CLOCKRT;
		return -ERESTART_RESTARTBLOCK;
	}

out_unlock_put_key:
	queue_unlock(&q, hb);
	put_futex_key(fshared, &q.key);

out:
	return ret;
}


static long futex_wait_restart(struct restart_block *restart)
{
	u32 __user *uaddr = (u32 __user *)restart->futex.uaddr;
	int fshared = 0;
	ktime_t t;

	t.tv64 = restart->futex.time;
	restart->fn = do_no_restart_syscall;
	if (restart->futex.flags & FLAGS_SHARED)
		fshared = 1;
	return (long)futex_wait(uaddr, fshared, restart->futex.val, &t,
				restart->futex.bitset,
				restart->futex.flags & FLAGS_CLOCKRT);
}


/*
 * Userspace tried a 0 -> TID atomic transition of the futex value
 * and failed. The kernel side here does the whole locking operation:
 * if there are waiters then it will block, it does PI, etc. (Due to
 * races the kernel might see a 0 value of the futex too.)
 */
static int futex_lock_pi(u32 __user *uaddr, int fshared,
			 int detect, ktime_t *time, int trylock)
{
	struct hrtimer_sleeper timeout, *to = NULL;
	struct task_struct *curr = current;
	struct futex_hash_bucket *hb;
	u32 uval, newval, curval;
	struct futex_q q;
	int ret, lock_taken, ownerdied = 0, attempt = 0;

	if (refill_pi_state_cache())
		return -ENOMEM;

	if (time) {
		to = &timeout;
		hrtimer_init_on_stack(&to->timer, CLOCK_REALTIME,
				      HRTIMER_MODE_ABS);
		hrtimer_init_sleeper(to, current);
		hrtimer_set_expires(&to->timer, *time);
	}

	q.pi_state = NULL;
retry:
	q.key = FUTEX_KEY_INIT;
	ret = get_futex_key(uaddr, fshared, &q.key);
	if (unlikely(ret != 0))
		goto out;

retry_unlocked:
	hb = queue_lock(&q);

retry_locked:
	ret = lock_taken = 0;

	/*
	 * To avoid races, we attempt to take the lock here again
	 * (by doing a 0 -> TID atomic cmpxchg), while holding all
	 * the locks. It will most likely not succeed.
	 */
	newval = task_pid_vnr(current);

	curval = cmpxchg_futex_value_locked(uaddr, 0, newval);

	if (unlikely(curval == -EFAULT))
		goto uaddr_faulted;

	/*
	 * Detect deadlocks. In case of REQUEUE_PI this is a valid
	 * situation and we return success to user space.
	 */
	if (unlikely((curval & FUTEX_TID_MASK) == task_pid_vnr(current))) {
		ret = -EDEADLK;
		goto out_unlock_put_key;
	}

	/*
	 * Surprise - we got the lock. Just return to userspace:
	 */
	if (unlikely(!curval))
		goto out_unlock_put_key;

	uval = curval;

	/*
	 * Set the WAITERS flag, so the owner will know it has someone
	 * to wake at next unlock
	 */
	newval = curval | FUTEX_WAITERS;

	/*
	 * There are two cases, where a futex might have no owner (the
	 * owner TID is 0): OWNER_DIED. We take over the futex in this
	 * case. We also do an unconditional take over, when the owner
	 * of the futex died.
	 *
	 * This is safe as we are protected by the hash bucket lock !
	 */
	if (unlikely(ownerdied || !(curval & FUTEX_TID_MASK))) {
		/* Keep the OWNER_DIED bit */
		newval = (curval & ~FUTEX_TID_MASK) | task_pid_vnr(current);
		ownerdied = 0;
		lock_taken = 1;
	}

	curval = cmpxchg_futex_value_locked(uaddr, uval, newval);

	if (unlikely(curval == -EFAULT))
		goto uaddr_faulted;
	if (unlikely(curval != uval))
		goto retry_locked;

	/*
	 * We took the lock due to owner died take over.
	 */