--- /dev/null
+/*
+ * 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>
+ *
+ * Requeue-PI support by Darren Hart <dvhltc@us.ibm.com>
+ * Copyright (C) IBM Corporation, 2009
+ * Thanks to Thomas Gleixner for conceptual design and careful reviews.
+ *
+ * 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/export.h>
+#include <linux/magic.h>
+#include <linux/pid.h>
+#include <linux/nsproxy.h>
+#include <linux/ptrace.h>
+#include <linux/sched/rt.h>
+#include <linux/hugetlb.h>
+#include <linux/freezer.h>
+#include <linux/bootmem.h>
+
+#include <asm/futex.h>
+
+#include "locking/rtmutex_common.h"
+
+/*
+ * READ this before attempting to hack on futexes!
+ *
+ * Basic futex operation and ordering guarantees
+ * =============================================
+ *
+ * The waiter reads the futex value in user space and calls
+ * futex_wait(). This function computes the hash bucket and acquires
+ * the hash bucket lock. After that it reads the futex user space value
+ * again and verifies that the data has not changed. If it has not changed
+ * it enqueues itself into the hash bucket, releases the hash bucket lock
+ * and schedules.
+ *
+ * The waker side modifies the user space value of the futex and calls
+ * futex_wake(). This function computes the hash bucket and acquires the
+ * hash bucket lock. Then it looks for waiters on that futex in the hash
+ * bucket and wakes them.
+ *
+ * In futex wake up scenarios where no tasks are blocked on a futex, taking
+ * the hb spinlock can be avoided and simply return. In order for this
+ * optimization to work, ordering guarantees must exist so that the waiter
+ * being added to the list is acknowledged when the list is concurrently being
+ * checked by the waker, avoiding scenarios like the following:
+ *
+ * CPU 0 CPU 1
+ * val = *futex;
+ * sys_futex(WAIT, futex, val);
+ * futex_wait(futex, val);
+ * uval = *futex;
+ * *futex = newval;
+ * sys_futex(WAKE, futex);
+ * futex_wake(futex);
+ * if (queue_empty())
+ * return;
+ * if (uval == val)
+ * lock(hash_bucket(futex));
+ * queue();
+ * unlock(hash_bucket(futex));
+ * schedule();
+ *
+ * This would cause the waiter on CPU 0 to wait forever because it
+ * missed the transition of the user space value from val to newval
+ * and the waker did not find the waiter in the hash bucket queue.
+ *
+ * The correct serialization ensures that a waiter either observes
+ * the changed user space value before blocking or is woken by a
+ * concurrent waker:
+ *
+ * CPU 0 CPU 1
+ * val = *futex;
+ * sys_futex(WAIT, futex, val);
+ * futex_wait(futex, val);
+ *
+ * waiters++; (a)
+ * mb(); (A) <-- paired with -.
+ * |
+ * lock(hash_bucket(futex)); |
+ * |
+ * uval = *futex; |
+ * | *futex = newval;
+ * | sys_futex(WAKE, futex);
+ * | futex_wake(futex);
+ * |
+ * `-------> mb(); (B)
+ * if (uval == val)
+ * queue();
+ * unlock(hash_bucket(futex));
+ * schedule(); if (waiters)
+ * lock(hash_bucket(futex));
+ * else wake_waiters(futex);
+ * waiters--; (b) unlock(hash_bucket(futex));
+ *
+ * Where (A) orders the waiters increment and the futex value read through
+ * atomic operations (see hb_waiters_inc) and where (B) orders the write
+ * to futex and the waiters read -- this is done by the barriers for both
+ * shared and private futexes in get_futex_key_refs().
+ *
+ * This yields the following case (where X:=waiters, Y:=futex):
+ *
+ * X = Y = 0
+ *
+ * w[X]=1 w[Y]=1
+ * MB MB
+ * r[Y]=y r[X]=x
+ *
+ * Which guarantees that x==0 && y==0 is impossible; which translates back into
+ * the guarantee that we cannot both miss the futex variable change and the
+ * enqueue.
+ *
+ * Note that a new waiter is accounted for in (a) even when it is possible that
+ * the wait call can return error, in which case we backtrack from it in (b).
+ * Refer to the comment in queue_lock().
+ *
+ * Similarly, in order to account for waiters being requeued on another
+ * address we always increment the waiters for the destination bucket before
+ * acquiring the lock. It then decrements them again after releasing it -
+ * the code that actually moves the futex(es) between hash buckets (requeue_futex)
+ * will do the additional required waiter count housekeeping. This is done for
+ * double_lock_hb() and double_unlock_hb(), respectively.
+ */
+
+#ifndef CONFIG_HAVE_FUTEX_CMPXCHG
+int __read_mostly futex_cmpxchg_enabled;
+#endif
+
+/*
+ * Futex flags used to encode options to functions and preserve them across
+ * restarts.
+ */
+#define FLAGS_SHARED 0x01
+#define FLAGS_CLOCKRT 0x02
+#define FLAGS_HAS_TIMEOUT 0x04
+
+/*
+ * 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;
+};
+
+/**
+ * struct futex_q - The hashed futex queue entry, one per waiting task
+ * @list: priority-sorted list of tasks waiting on this futex
+ * @task: the task waiting on the futex
+ * @lock_ptr: the hash bucket lock
+ * @key: the key the futex is hashed on
+ * @pi_state: optional priority inheritance state
+ * @rt_waiter: rt_waiter storage for use with requeue_pi
+ * @requeue_pi_key: the requeue_pi target futex key
+ * @bitset: bitset for the optional bitmasked wakeup
+ *
+ * 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 wakeup is always to make the first condition true, then
+ * the second.
+ *
+ * PI futexes are typically woken before they are removed from the hash list via
+ * the rt_mutex code. See unqueue_me_pi().
+ */
+struct futex_q {
+ struct plist_node list;
+
+ struct task_struct *task;
+ spinlock_t *lock_ptr;
+ union futex_key key;
+ struct futex_pi_state *pi_state;
+ struct rt_mutex_waiter *rt_waiter;
+ union futex_key *requeue_pi_key;
+ u32 bitset;
+};
+
+static const struct futex_q futex_q_init = {
+ /* list gets initialized in queue_me()*/
+ .key = FUTEX_KEY_INIT,
+ .bitset = FUTEX_BITSET_MATCH_ANY
+};
+
+/*
+ * Hash buckets are shared by all the futex_keys that hash to the same
+ * location. Each key may have multiple futex_q structures, one for each task
+ * waiting on a futex.
+ */
+struct futex_hash_bucket {
+ atomic_t waiters;
+ spinlock_t lock;
+ struct plist_head chain;
+} ____cacheline_aligned_in_smp;
+
+static unsigned long __read_mostly futex_hashsize;
+
+static struct futex_hash_bucket *futex_queues;
+
+static inline void futex_get_mm(union futex_key *key)
+{
+ atomic_inc(&key->private.mm->mm_count);
+ /*
+ * Ensure futex_get_mm() implies a full barrier such that
+ * get_futex_key() implies a full barrier. This is relied upon
+ * as full barrier (B), see the ordering comment above.
+ */
+ smp_mb__after_atomic();
+}
+
+/*
+ * Reflects a new waiter being added to the waitqueue.
+ */
+static inline void hb_waiters_inc(struct futex_hash_bucket *hb)
+{
+#ifdef CONFIG_SMP
+ atomic_inc(&hb->waiters);
+ /*
+ * Full barrier (A), see the ordering comment above.
+ */
+ smp_mb__after_atomic();
+#endif
+}
+
+/*
+ * Reflects a waiter being removed from the waitqueue by wakeup
+ * paths.
+ */
+static inline void hb_waiters_dec(struct futex_hash_bucket *hb)
+{
+#ifdef CONFIG_SMP
+ atomic_dec(&hb->waiters);
+#endif
+}
+
+static inline int hb_waiters_pending(struct futex_hash_bucket *hb)
+{
+#ifdef CONFIG_SMP
+ return atomic_read(&hb->waiters);
+#else
+ return 1;
+#endif
+}
+
+/*
+ * 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 & (futex_hashsize - 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 && key2
+ && 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:
+ ihold(key->shared.inode); /* implies MB (B) */
+ break;
+ case FUT_OFF_MMSHARED:
+ futex_get_mm(key); /* implies MB (B) */
+ break;
+ default:
+ /*
+ * Private futexes do not hold reference on an inode or
+ * mm, therefore the only purpose of calling get_futex_key_refs
+ * is because we need the barrier for the lockless waiter check.
+ */
+ smp_mb(); /* explicit MB (B) */
+ }
+}
+
+/*
+ * Drop a reference to the resource addressed by a key.
+ * The hash bucket spinlock must not be held. This is
+ * a no-op for private futexes, see comment in the get
+ * counterpart.
+ */
+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
+ * @fshared: 0 for a PROCESS_PRIVATE futex, 1 for PROCESS_SHARED
+ * @key: address where result is stored.
+ * @rw: mapping needs to be read/write (values: VERIFY_READ,
+ * VERIFY_WRITE)
+ *
+ * Return: a negative error code or 0
+ *
+ * The key words are stored in *key on success.
+ *
+ * For shared mappings, it's (page->index, file_inode(vma->vm_file),
+ * offset_within_page). For private mappings, it's (uaddr, current->mm).
+ * We can usually work out the index without swapping in the page.
+ *
+ * lock_page() might sleep, the caller should not hold a spinlock.
+ */
+static int
+get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key, int rw)
+{
+ unsigned long address = (unsigned long)uaddr;
+ struct mm_struct *mm = current->mm;
+ struct page *page, *page_head;
+ int err, ro = 0;
+
+ /*
+ * 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;
+
+ if (unlikely(!access_ok(rw, uaddr, sizeof(u32))))
+ return -EFAULT;
+
+ /*
+ * 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) {
+ key->private.mm = mm;
+ key->private.address = address;
+ get_futex_key_refs(key); /* implies MB (B) */
+ return 0;
+ }
+
+again:
+ err = get_user_pages_fast(address, 1, 1, &page);
+ /*
+ * If write access is not required (eg. FUTEX_WAIT), try
+ * and get read-only access.
+ */
+ if (err == -EFAULT && rw == VERIFY_READ) {
+ err = get_user_pages_fast(address, 1, 0, &page);
+ ro = 1;
+ }
+ if (err < 0)
+ return err;
+ else
+ err = 0;
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+ page_head = page;
+ if (unlikely(PageTail(page))) {
+ put_page(page);
+ /* serialize against __split_huge_page_splitting() */
+ local_irq_disable();
+ if (likely(__get_user_pages_fast(address, 1, !ro, &page) == 1)) {
+ page_head = compound_head(page);
+ /*
+ * page_head is valid pointer but we must pin
+ * it before taking the PG_lock and/or
+ * PG_compound_lock. The moment we re-enable
+ * irqs __split_huge_page_splitting() can
+ * return and the head page can be freed from
+ * under us. We can't take the PG_lock and/or
+ * PG_compound_lock on a page that could be
+ * freed from under us.
+ */
+ if (page != page_head) {
+ get_page(page_head);
+ put_page(page);
+ }
+ local_irq_enable();
+ } else {
+ local_irq_enable();
+ goto again;
+ }
+ }
+#else
+ page_head = compound_head(page);
+ if (page != page_head) {
+ get_page(page_head);
+ put_page(page);
+ }
+#endif
+
+ lock_page(page_head);
+
+ /*
+ * If page_head->mapping is NULL, then it cannot be a PageAnon
+ * page; but it might be the ZERO_PAGE or in the gate area or
+ * in a special mapping (all cases which we are happy to fail);
+ * or it may have been a good file page when get_user_pages_fast
+ * found it, but truncated or holepunched or subjected to
+ * invalidate_complete_page2 before we got the page lock (also
+ * cases which we are happy to fail). And we hold a reference,
+ * so refcount care in invalidate_complete_page's remove_mapping
+ * prevents drop_caches from setting mapping to NULL beneath us.
+ *
+ * The case we do have to guard against is when memory pressure made
+ * shmem_writepage move it from filecache to swapcache beneath us:
+ * an unlikely race, but we do need to retry for page_head->mapping.
+ */
+ if (!page_head->mapping) {
+ int shmem_swizzled = PageSwapCache(page_head);
+ unlock_page(page_head);
+ put_page(page_head);
+ if (shmem_swizzled)
+ goto again;
+ return -EFAULT;
+ }
+
+ /*
+ * 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_head)) {
+ /*
+ * A RO anonymous page will never change and thus doesn't make
+ * sense for futex operations.
+ */
+ if (ro) {
+ err = -EFAULT;
+ goto out;
+ }
+
+ 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_head->mapping->host;
+ key->shared.pgoff = basepage_index(page);
+ }
+
+ get_futex_key_refs(key); /* implies MB (B) */
+
+out:
+ unlock_page(page_head);
+ put_page(page_head);
+ return err;
+}
+
+static inline void put_futex_key(union futex_key *key)
+{
+ drop_futex_key_refs(key);
+}
+
+/**
+ * fault_in_user_writeable() - Fault in user address and verify RW access
+ * @uaddr: pointer to faulting user space address
+ *
+ * Slow path to fixup the fault we just took in the atomic write
+ * access to @uaddr.
+ *
+ * We have no generic implementation of a non-destructive write to the
+ * user address. We know that we faulted in the atomic pagefault
+ * disabled section so we can as well avoid the #PF overhead by
+ * calling get_user_pages() right away.
+ */
+static int fault_in_user_writeable(u32 __user *uaddr)
+{
+ struct mm_struct *mm = current->mm;
+ int ret;
+
+ down_read(&mm->mmap_sem);
+ ret = fixup_user_fault(current, mm, (unsigned long)uaddr,
+ FAULT_FLAG_WRITE);
+ up_read(&mm->mmap_sem);
+
+ return ret < 0 ? ret : 0;
+}
+
+/**
+ * futex_top_waiter() - Return the highest priority waiter on a futex
+ * @hb: the hash bucket the futex_q's reside in
+ * @key: the futex key (to distinguish it from other futex futex_q's)
+ *
+ * Must be called with the hb lock held.
+ */
+static struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb,
+ union futex_key *key)
+{
+ struct futex_q *this;
+
+ plist_for_each_entry(this, &hb->chain, list) {
+ if (match_futex(&this->key, key))
+ return this;
+ }
+ return NULL;
+}
+
+static int cmpxchg_futex_value_locked(u32 *curval, u32 __user *uaddr,
+ u32 uval, u32 newval)
+{
+ int ret;
+
+ pagefault_disable();
+ ret = futex_atomic_cmpxchg_inatomic(curval, uaddr, uval, newval);
+ pagefault_enable();
+
+ return ret;
+}
+
+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;
+}
+
+
+/*
+ * 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;
+}
+
+/*
+ * Must be called with the hb lock held.
+ */
+static void free_pi_state(struct futex_pi_state *pi_state)
+{
+ if (!pi_state)
+ return;
+
+ 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) {
+ raw_spin_lock_irq(&pi_state->owner->pi_lock);
+ list_del_init(&pi_state->list);
+ raw_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;
+
+ rcu_read_lock();
+ p = find_task_by_vpid(pid);
+ if (p)
+ 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:
+ */
+ raw_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);
+ raw_spin_unlock_irq(&curr->pi_lock);
+
+ spin_lock(&hb->lock);
+
+ raw_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) {
+ raw_spin_unlock_irq(&curr->pi_lock);
+ spin_unlock(&hb->lock);
+ raw_spin_lock_irq(&curr->pi_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;
+ raw_spin_unlock_irq(&curr->pi_lock);
+
+ rt_mutex_unlock(&pi_state->pi_mutex);
+
+ spin_unlock(&hb->lock);
+
+ raw_spin_lock_irq(&curr->pi_lock);
+ }
+ raw_spin_unlock_irq(&curr->pi_lock);
+}
+
+/*
+ * We need to check the following states:
+ *
+ * Waiter | pi_state | pi->owner | uTID | uODIED | ?
+ *
+ * [1] NULL | --- | --- | 0 | 0/1 | Valid
+ * [2] NULL | --- | --- | >0 | 0/1 | Valid
+ *
+ * [3] Found | NULL | -- | Any | 0/1 | Invalid
+ *
+ * [4] Found | Found | NULL | 0 | 1 | Valid
+ * [5] Found | Found | NULL | >0 | 1 | Invalid
+ *
+ * [6] Found | Found | task | 0 | 1 | Valid
+ *
+ * [7] Found | Found | NULL | Any | 0 | Invalid
+ *
+ * [8] Found | Found | task | ==taskTID | 0/1 | Valid
+ * [9] Found | Found | task | 0 | 0 | Invalid
+ * [10] Found | Found | task | !=taskTID | 0/1 | Invalid
+ *
+ * [1] Indicates that the kernel can acquire the futex atomically. We
+ * came came here due to a stale FUTEX_WAITERS/FUTEX_OWNER_DIED bit.
+ *
+ * [2] Valid, if TID does not belong to a kernel thread. If no matching
+ * thread is found then it indicates that the owner TID has died.
+ *
+ * [3] Invalid. The waiter is queued on a non PI futex
+ *
+ * [4] Valid state after exit_robust_list(), which sets the user space
+ * value to FUTEX_WAITERS | FUTEX_OWNER_DIED.
+ *
+ * [5] The user space value got manipulated between exit_robust_list()
+ * and exit_pi_state_list()
+ *
+ * [6] Valid state after exit_pi_state_list() which sets the new owner in
+ * the pi_state but cannot access the user space value.
+ *
+ * [7] pi_state->owner can only be NULL when the OWNER_DIED bit is set.
+ *
+ * [8] Owner and user space value match
+ *
+ * [9] There is no transient state which sets the user space TID to 0
+ * except exit_robust_list(), but this is indicated by the
+ * FUTEX_OWNER_DIED bit. See [4]
+ *
+ * [10] There is no transient state which leaves owner and user space
+ * TID out of sync.
+ */
+
+/*
+ * Validate that the existing waiter has a pi_state and sanity check
+ * the pi_state against the user space value. If correct, attach to
+ * it.
+ */
+static int attach_to_pi_state(u32 uval, struct futex_pi_state *pi_state,
+ struct futex_pi_state **ps)
+{
+ pid_t pid = uval & FUTEX_TID_MASK;
+
+ /*
+ * Userspace might have messed up non-PI and PI futexes [3]
+ */
+ if (unlikely(!pi_state))
+ return -EINVAL;
+
+ WARN_ON(!atomic_read(&pi_state->refcount));
+
+ /*
+ * Handle the owner died case:
+ */
+ if (uval & FUTEX_OWNER_DIED) {
+ /*
+ * exit_pi_state_list sets owner to NULL and wakes the
+ * topmost waiter. The task which acquires the
+ * pi_state->rt_mutex will fixup owner.
+ */
+ if (!pi_state->owner) {
+ /*
+ * No pi state owner, but the user space TID
+ * is not 0. Inconsistent state. [5]
+ */
+ if (pid)
+ return -EINVAL;
+ /*
+ * Take a ref on the state and return success. [4]
+ */
+ goto out_state;
+ }
+
+ /*
+ * If TID is 0, then either the dying owner has not
+ * yet executed exit_pi_state_list() or some waiter
+ * acquired the rtmutex in the pi state, but did not
+ * yet fixup the TID in user space.
+ *
+ * Take a ref on the state and return success. [6]
+ */
+ if (!pid)
+ goto out_state;
+ } else {
+ /*
+ * If the owner died bit is not set, then the pi_state
+ * must have an owner. [7]
+ */
+ if (!pi_state->owner)
+ return -EINVAL;
+ }
+
+ /*
+ * Bail out if user space manipulated the futex value. If pi
+ * state exists then the owner TID must be the same as the
+ * user space TID. [9/10]
+ */
+ if (pid != task_pid_vnr(pi_state->owner))
+ return -EINVAL;
+out_state:
+ atomic_inc(&pi_state->refcount);
+ *ps = pi_state;
+ return 0;
+}
+
+/*
+ * Lookup the task for the TID provided from user space and attach to
+ * it after doing proper sanity checks.
+ */
+static int attach_to_pi_owner(u32 uval, union futex_key *key,
+ struct futex_pi_state **ps)
+{
+ pid_t pid = uval & FUTEX_TID_MASK;
+ struct futex_pi_state *pi_state;
+ struct task_struct *p;
+
+ /*
+ * 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 [1]
+ */
+ if (!pid)
+ return -ESRCH;
+ p = futex_find_get_task(pid);
+ if (!p)
+ return -ESRCH;
+
+ if (unlikely(p->flags & PF_KTHREAD)) {
+ put_task_struct(p);
+ return -EPERM;
+ }
+
+ /*
+ * 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:
+ */
+ raw_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;
+
+ raw_spin_unlock_irq(&p->pi_lock);
+ put_task_struct(p);
+ return ret;
+ }
+
+ /*
+ * No existing pi state. First waiter. [2]
+ */
+ 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;
+ raw_spin_unlock_irq(&p->pi_lock);
+
+ put_task_struct(p);
+
+ *ps = pi_state;
+
+ return 0;
+}
+
+static int lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
+ union futex_key *key, struct futex_pi_state **ps)
+{
+ struct futex_q *match = futex_top_waiter(hb, key);
+
+ /*
+ * If there is a waiter on that futex, validate it and
+ * attach to the pi_state when the validation succeeds.
+ */
+ if (match)
+ return attach_to_pi_state(uval, match->pi_state, ps);
+
+ /*
+ * We are the first waiter - try to look up the owner based on
+ * @uval and attach to it.
+ */
+ return attach_to_pi_owner(uval, key, ps);
+}
+
+static int lock_pi_update_atomic(u32 __user *uaddr, u32 uval, u32 newval)
+{
+ u32 uninitialized_var(curval);
+
+ if (unlikely(cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)))
+ return -EFAULT;
+
+ /*If user space value changed, let the caller retry */
+ return curval != uval ? -EAGAIN : 0;
+}
+
+/**
+ * futex_lock_pi_atomic() - Atomic work required to acquire a pi aware futex
+ * @uaddr: the pi futex user address
+ * @hb: the pi futex hash bucket
+ * @key: the futex key associated with uaddr and hb
+ * @ps: the pi_state pointer where we store the result of the
+ * lookup
+ * @task: the task to perform the atomic lock work for. This will
+ * be "current" except in the case of requeue pi.
+ * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0)
+ *
+ * Return:
+ * 0 - ready to wait;
+ * 1 - acquired the lock;
+ * <0 - error
+ *
+ * The hb->lock and futex_key refs shall be held by the caller.
+ */
+static int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb,
+ union futex_key *key,
+ struct futex_pi_state **ps,
+ struct task_struct *task, int set_waiters)
+{
+ u32 uval, newval, vpid = task_pid_vnr(task);
+ struct futex_q *match;
+ int ret;
+
+ /*
+ * Read the user space value first so we can validate a few
+ * things before proceeding further.
+ */
+ if (get_futex_value_locked(&uval, uaddr))
+ return -EFAULT;
+
+ /*
+ * Detect deadlocks.
+ */
+ if ((unlikely((uval & FUTEX_TID_MASK) == vpid)))
+ return -EDEADLK;
+
+ /*
+ * Lookup existing state first. If it exists, try to attach to
+ * its pi_state.
+ */
+ match = futex_top_waiter(hb, key);
+ if (match)
+ return attach_to_pi_state(uval, match->pi_state, ps);
+
+ /*
+ * No waiter and user TID is 0. We are here because the
+ * waiters or the owner died bit is set or called from
+ * requeue_cmp_pi or for whatever reason something took the
+ * syscall.
+ */
+ if (!(uval & FUTEX_TID_MASK)) {
+ /*
+ * We take over the futex. No other waiters and the user space
+ * TID is 0. We preserve the owner died bit.
+ */
+ newval = uval & FUTEX_OWNER_DIED;
+ newval |= vpid;
+
+ /* The futex requeue_pi code can enforce the waiters bit */
+ if (set_waiters)
+ newval |= FUTEX_WAITERS;
+
+ ret = lock_pi_update_atomic(uaddr, uval, newval);
+ /* If the take over worked, return 1 */
+ return ret < 0 ? ret : 1;
+ }
+
+ /*
+ * First waiter. Set the waiters bit before attaching ourself to
+ * the owner. If owner tries to unlock, it will be forced into
+ * the kernel and blocked on hb->lock.
+ */
+ newval = uval | FUTEX_WAITERS;
+ ret = lock_pi_update_atomic(uaddr, uval, newval);
+ if (ret)
+ return ret;
+ /*
+ * If the update of the user space value succeeded, we try to
+ * attach to the owner. If that fails, no harm done, we only
+ * set the FUTEX_WAITERS bit in the user space variable.
+ */
+ return attach_to_pi_owner(uval, key, ps);
+}
+
+/**
+ * __unqueue_futex() - Remove the futex_q from its futex_hash_bucket
+ * @q: The futex_q to unqueue
+ *
+ * The q->lock_ptr must not be NULL and must be held by the caller.
+ */
+static void __unqueue_futex(struct futex_q *q)
+{
+ struct futex_hash_bucket *hb;
+
+ if (WARN_ON_SMP(!q->lock_ptr || !spin_is_locked(q->lock_ptr))
+ || WARN_ON(plist_node_empty(&q->list)))
+ return;
+
+ hb = container_of(q->lock_ptr, struct futex_hash_bucket, lock);
+ plist_del(&q->list, &hb->chain);
+ hb_waiters_dec(hb);
+}
+
+/*
+ * The hash bucket lock must be held when this is called.
+ * Afterwards, the futex_q must not be accessed. Callers
+ * must ensure to later call wake_up_q() for the actual
+ * wakeups to occur.
+ */
+static void mark_wake_futex(struct wake_q_head *wake_q, struct futex_q *q)
+{
+ struct task_struct *p = q->task;
+
+ if (WARN(q->pi_state || q->rt_waiter, "refusing to wake PI futex\n"))
+ return;
+
+ /*
+ * Queue the task for later wakeup for after we've released
+ * the hb->lock. wake_q_add() grabs reference to p.
+ */
+ wake_q_add(wake_q, p);
+ __unqueue_futex(q);
+ /*
+ * The waiting task can free the futex_q as soon as
+ * q->lock_ptr = NULL is written, without taking any locks. A
+ * memory barrier is required here to prevent the following
+ * store to lock_ptr from getting ahead of the plist_del.
+ */
+ smp_wmb();
+ q->lock_ptr = NULL;
+}
+
+static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this,
+ struct futex_hash_bucket *hb)
+{
+ struct task_struct *new_owner;
+ struct futex_pi_state *pi_state = this->pi_state;
+ u32 uninitialized_var(curval), newval;
+ bool deboost;
+ int ret = 0;
+
+ if (!pi_state)
+ return -EINVAL;
+
+ /*
+ * If current does not own the pi_state then the futex is
+ * inconsistent and user space fiddled with the futex value.
+ */
+ if (pi_state->owner != current)
+ return -EINVAL;
+
+ raw_spin_lock(&pi_state->pi_mutex.wait_lock);
+ new_owner = rt_mutex_next_owner(&pi_state->pi_mutex);
+
+ /*
+ * It is possible that the next waiter (the one that brought
+ * this owner to the kernel) timed out and is no longer
+ * waiting on the lock.
+ */
+ 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 cleanup the
+ * owner died bit, because we are the owner.
+ */
+ newval = FUTEX_WAITERS | task_pid_vnr(new_owner);
+
+ if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval))
+ ret = -EFAULT;
+ else if (curval != uval)
+ ret = -EINVAL;
+ if (ret) {
+ raw_spin_unlock(&pi_state->pi_mutex.wait_lock);
+ return ret;
+ }
+
+ raw_spin_lock_irq(&pi_state->owner->pi_lock);
+ WARN_ON(list_empty(&pi_state->list));
+ list_del_init(&pi_state->list);
+ raw_spin_unlock_irq(&pi_state->owner->pi_lock);
+
+ raw_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;
+ raw_spin_unlock_irq(&new_owner->pi_lock);
+
+ raw_spin_unlock(&pi_state->pi_mutex.wait_lock);
+
+ deboost = rt_mutex_futex_unlock(&pi_state->pi_mutex);
+
+ /*
+ * We deboost after dropping hb->lock. That prevents a double
+ * wakeup on RT.
+ */
+ spin_unlock(&hb->lock);
+
+ if (deboost)
+ rt_mutex_adjust_prio(current);
+
+ 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);
+ }
+}
+
+static inline void
+double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
+{
+ spin_unlock(&hb1->lock);
+ if (hb1 != hb2)
+ spin_unlock(&hb2->lock);
+}
+
+/*
+ * Wake up waiters matching bitset queued on this futex (uaddr).
+ */
+static int
+futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset)
+{
+ struct futex_hash_bucket *hb;
+ struct futex_q *this, *next;
+ union futex_key key = FUTEX_KEY_INIT;
+ int ret;
+ WAKE_Q(wake_q);
+
+ if (!bitset)
+ return -EINVAL;
+
+ ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, VERIFY_READ);
+ if (unlikely(ret != 0))
+ goto out;
+
+ hb = hash_futex(&key);
+
+ /* Make sure we really have tasks to wakeup */
+ if (!hb_waiters_pending(hb))
+ goto out_put_key;
+
+ spin_lock(&hb->lock);
+
+ plist_for_each_entry_safe(this, next, &hb->chain, list) {
+ if (match_futex (&this->key, &key)) {
+ if (this->pi_state || this->rt_waiter) {
+ ret = -EINVAL;
+ break;
+ }
+
+ /* Check if one of the bits is set in both bitsets */
+ if (!(this->bitset & bitset))
+ continue;
+
+ mark_wake_futex(&wake_q, this);
+ if (++ret >= nr_wake)
+ break;
+ }
+ }
+
+ spin_unlock(&hb->lock);
+ wake_up_q(&wake_q);
+out_put_key:
+ put_futex_key(&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, unsigned int flags, 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 futex_q *this, *next;
+ int ret, op_ret;
+ WAKE_Q(wake_q);
+
+retry:
+ ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, VERIFY_READ);
+ if (unlikely(ret != 0))
+ goto out;
+ ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, VERIFY_WRITE);
+ if (unlikely(ret != 0))
+ goto out_put_key1;
+
+ hb1 = hash_futex(&key1);
+ hb2 = hash_futex(&key2);
+
+retry_private:
+ double_lock_hb(hb1, hb2);
+ op_ret = futex_atomic_op_inuser(op, uaddr2);
+ if (unlikely(op_ret < 0)) {
+
+ double_unlock_hb(hb1, hb2);
+
+#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;
+ }
+
+ ret = fault_in_user_writeable(uaddr2);
+ if (ret)
+ goto out_put_keys;
+
+ if (!(flags & FLAGS_SHARED))
+ goto retry_private;
+
+ put_futex_key(&key2);
+ put_futex_key(&key1);
+ goto retry;
+ }
+
+ plist_for_each_entry_safe(this, next, &hb1->chain, list) {
+ if (match_futex (&this->key, &key1)) {
+ if (this->pi_state || this->rt_waiter) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
+ mark_wake_futex(&wake_q, this);
+ if (++ret >= nr_wake)
+ break;
+ }
+ }
+
+ if (op_ret > 0) {
+ op_ret = 0;
+ plist_for_each_entry_safe(this, next, &hb2->chain, list) {
+ if (match_futex (&this->key, &key2)) {
+ if (this->pi_state || this->rt_waiter) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
+ mark_wake_futex(&wake_q, this);
+ if (++op_ret >= nr_wake2)
+ break;
+ }
+ }
+ ret += op_ret;
+ }
+
+out_unlock:
+ double_unlock_hb(hb1, hb2);
+ wake_up_q(&wake_q);
+out_put_keys:
+ put_futex_key(&key2);
+out_put_key1:
+ put_futex_key(&key1);
+out:
+ return ret;
+}
+
+/**
+ * requeue_futex() - Requeue a futex_q from one hb to another
+ * @q: the futex_q to requeue
+ * @hb1: the source hash_bucket
+ * @hb2: the target hash_bucket
+ * @key2: the new key for the requeued futex_q
+ */
+static inline
+void requeue_futex(struct futex_q *q, struct futex_hash_bucket *hb1,
+ struct futex_hash_bucket *hb2, union futex_key *key2)
+{
+
+ /*
+ * If key1 and key2 hash to the same bucket, no need to
+ * requeue.
+ */
+ if (likely(&hb1->chain != &hb2->chain)) {
+ plist_del(&q->list, &hb1->chain);
+ hb_waiters_dec(hb1);
+ plist_add(&q->list, &hb2->chain);
+ hb_waiters_inc(hb2);
+ q->lock_ptr = &hb2->lock;
+ }
+ get_futex_key_refs(key2);
+ q->key = *key2;
+}
+
+/**
+ * requeue_pi_wake_futex() - Wake a task that acquired the lock during requeue
+ * @q: the futex_q
+ * @key: the key of the requeue target futex
+ * @hb: the hash_bucket of the requeue target futex
+ *
+ * During futex_requeue, with requeue_pi=1, it is possible to acquire the
+ * target futex if it is uncontended or via a lock steal. Set the futex_q key
+ * to the requeue target futex so the waiter can detect the wakeup on the right
+ * futex, but remove it from the hb and NULL the rt_waiter so it can detect
+ * atomic lock acquisition. Set the q->lock_ptr to the requeue target hb->lock
+ * to protect access to the pi_state to fixup the owner later. Must be called
+ * with both q->lock_ptr and hb->lock held.
+ */
+static inline
+void requeue_pi_wake_futex(struct futex_q *q, union futex_key *key,
+ struct futex_hash_bucket *hb)
+{
+ get_futex_key_refs(key);
+ q->key = *key;
+
+ __unqueue_futex(q);
+
+ WARN_ON(!q->rt_waiter);
+ q->rt_waiter = NULL;
+
+ q->lock_ptr = &hb->lock;
+
+ wake_up_state(q->task, TASK_NORMAL);
+}
+
+/**
+ * futex_proxy_trylock_atomic() - Attempt an atomic lock for the top waiter
+ * @pifutex: the user address of the to futex
+ * @hb1: the from futex hash bucket, must be locked by the caller
+ * @hb2: the to futex hash bucket, must be locked by the caller
+ * @key1: the from futex key
+ * @key2: the to futex key
+ * @ps: address to store the pi_state pointer
+ * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0)
+ *
+ * Try and get the lock on behalf of the top waiter if we can do it atomically.
+ * Wake the top waiter if we succeed. If the caller specified set_waiters,
+ * then direct futex_lock_pi_atomic() to force setting the FUTEX_WAITERS bit.
+ * hb1 and hb2 must be held by the caller.
+ *
+ * Return:
+ * 0 - failed to acquire the lock atomically;
+ * >0 - acquired the lock, return value is vpid of the top_waiter
+ * <0 - error
+ */
+static int futex_proxy_trylock_atomic(u32 __user *pifutex,
+ struct futex_hash_bucket *hb1,
+ struct futex_hash_bucket *hb2,
+ union futex_key *key1, union futex_key *key2,
+ struct futex_pi_state **ps, int set_waiters)
+{
+ struct futex_q *top_waiter = NULL;
+ u32 curval;
+ int ret, vpid;
+
+ if (get_futex_value_locked(&curval, pifutex))
+ return -EFAULT;
+
+ /*
+ * Find the top_waiter and determine if there are additional waiters.
+ * If the caller intends to requeue more than 1 waiter to pifutex,
+ * force futex_lock_pi_atomic() to set the FUTEX_WAITERS bit now,
+ * as we have means to handle the possible fault. If not, don't set
+ * the bit unecessarily as it will force the subsequent unlock to enter
+ * the kernel.
+ */
+ top_waiter = futex_top_waiter(hb1, key1);
+
+ /* There are no waiters, nothing for us to do. */
+ if (!top_waiter)
+ return 0;
+
+ /* Ensure we requeue to the expected futex. */
+ if (!match_futex(top_waiter->requeue_pi_key, key2))
+ return -EINVAL;
+
+ /*
+ * Try to take the lock for top_waiter. Set the FUTEX_WAITERS bit in
+ * the contended case or if set_waiters is 1. The pi_state is returned
+ * in ps in contended cases.
+ */
+ vpid = task_pid_vnr(top_waiter->task);
+ ret = futex_lock_pi_atomic(pifutex, hb2, key2, ps, top_waiter->task,
+ set_waiters);
+ if (ret == 1) {
+ requeue_pi_wake_futex(top_waiter, key2, hb2);
+ return vpid;
+ }
+ return ret;
+}
+
+/**
+ * futex_requeue() - Requeue waiters from uaddr1 to uaddr2
+ * @uaddr1: source futex user address
+ * @flags: futex flags (FLAGS_SHARED, etc.)
+ * @uaddr2: target futex user address
+ * @nr_wake: number of waiters to wake (must be 1 for requeue_pi)
+ * @nr_requeue: number of waiters to requeue (0-INT_MAX)
+ * @cmpval: @uaddr1 expected value (or %NULL)
+ * @requeue_pi: if we are attempting to requeue from a non-pi futex to a
+ * pi futex (pi to pi requeue is not supported)
+ *
+ * Requeue waiters on uaddr1 to uaddr2. In the requeue_pi case, try to acquire
+ * uaddr2 atomically on behalf of the top waiter.
+ *
+ * Return:
+ * >=0 - on success, the number of tasks requeued or woken;
+ * <0 - on error
+ */
+static int futex_requeue(u32 __user *uaddr1, unsigned int flags,
+ u32 __user *uaddr2, int nr_wake, int nr_requeue,
+ u32 *cmpval, int requeue_pi)
+{
+ union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
+ int drop_count = 0, task_count = 0, ret;
+ struct futex_pi_state *pi_state = NULL;
+ struct futex_hash_bucket *hb1, *hb2;
+ struct futex_q *this, *next;
+ WAKE_Q(wake_q);
+
+ if (requeue_pi) {
+ /*
+ * Requeue PI only works on two distinct uaddrs. This
+ * check is only valid for private futexes. See below.
+ */
+ if (uaddr1 == uaddr2)
+ return -EINVAL;
+
+ /*
+ * requeue_pi requires a pi_state, try to allocate it now
+ * without any locks in case it fails.
+ */
+ if (refill_pi_state_cache())
+ return -ENOMEM;
+ /*
+ * requeue_pi must wake as many tasks as it can, up to nr_wake
+ * + nr_requeue, since it acquires the rt_mutex prior to
+ * returning to userspace, so as to not leave the rt_mutex with
+ * waiters and no owner. However, second and third wake-ups
+ * cannot be predicted as they involve race conditions with the
+ * first wake and a fault while looking up the pi_state. Both
+ * pthread_cond_signal() and pthread_cond_broadcast() should
+ * use nr_wake=1.
+ */
+ if (nr_wake != 1)
+ return -EINVAL;
+ }
+
+retry:
+ ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, VERIFY_READ);
+ if (unlikely(ret != 0))
+ goto out;
+ ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2,
+ requeue_pi ? VERIFY_WRITE : VERIFY_READ);
+ if (unlikely(ret != 0))
+ goto out_put_key1;
+
+ /*
+ * The check above which compares uaddrs is not sufficient for
+ * shared futexes. We need to compare the keys:
+ */
+ if (requeue_pi && match_futex(&key1, &key2)) {
+ ret = -EINVAL;
+ goto out_put_keys;
+ }
+
+ hb1 = hash_futex(&key1);
+ hb2 = hash_futex(&key2);
+
+retry_private:
+ hb_waiters_inc(hb2);
+ double_lock_hb(hb1, hb2);
+
+ if (likely(cmpval != NULL)) {
+ u32 curval;
+
+ ret = get_futex_value_locked(&curval, uaddr1);
+
+ if (unlikely(ret)) {
+ double_unlock_hb(hb1, hb2);
+ hb_waiters_dec(hb2);
+
+ ret = get_user(curval, uaddr1);
+ if (ret)
+ goto out_put_keys;
+
+ if (!(flags & FLAGS_SHARED))
+ goto retry_private;
+
+ put_futex_key(&key2);
+ put_futex_key(&key1);
+ goto retry;
+ }
+ if (curval != *cmpval) {
+ ret = -EAGAIN;
+ goto out_unlock;
+ }
+ }
+
+ if (requeue_pi && (task_count - nr_wake < nr_requeue)) {
+ /*
+ * Attempt to acquire uaddr2 and wake the top waiter. If we
+ * intend to requeue waiters, force setting the FUTEX_WAITERS
+ * bit. We force this here where we are able to easily handle
+ * faults rather in the requeue loop below.
+ */
+ ret = futex_proxy_trylock_atomic(uaddr2, hb1, hb2, &key1,
+ &key2, &pi_state, nr_requeue);
+
+ /*
+ * At this point the top_waiter has either taken uaddr2 or is
+ * waiting on it. If the former, then the pi_state will not
+ * exist yet, look it up one more time to ensure we have a
+ * reference to it. If the lock was taken, ret contains the
+ * vpid of the top waiter task.
+ */
+ if (ret > 0) {
+ WARN_ON(pi_state);
+ drop_count++;
+ task_count++;
+ /*
+ * If we acquired the lock, then the user
+ * space value of uaddr2 should be vpid. It
+ * cannot be changed by the top waiter as it
+ * is blocked on hb2 lock if it tries to do
+ * so. If something fiddled with it behind our
+ * back the pi state lookup might unearth
+ * it. So we rather use the known value than
+ * rereading and handing potential crap to
+ * lookup_pi_state.
+ */
+ ret = lookup_pi_state(ret, hb2, &key2, &pi_state);
+ }
+
+ switch (ret) {
+ case 0:
+ break;
+ case -EFAULT:
+ free_pi_state(pi_state);
+ pi_state = NULL;
+ double_unlock_hb(hb1, hb2);
+ hb_waiters_dec(hb2);
+ put_futex_key(&key2);
+ put_futex_key(&key1);
+ ret = fault_in_user_writeable(uaddr2);
+ if (!ret)
+ goto retry;
+ goto out;
+ case -EAGAIN:
+ /*
+ * Two reasons for this:
+ * - Owner is exiting and we just wait for the
+ * exit to complete.
+ * - The user space value changed.
+ */
+ free_pi_state(pi_state);
+ pi_state = NULL;
+ double_unlock_hb(hb1, hb2);
+ hb_waiters_dec(hb2);
+ put_futex_key(&key2);
+ put_futex_key(&key1);
+ cond_resched();
+ goto retry;
+ default:
+ goto out_unlock;
+ }
+ }
+
+ plist_for_each_entry_safe(this, next, &hb1->chain, list) {
+ if (task_count - nr_wake >= nr_requeue)
+ break;
+
+ if (!match_futex(&this->key, &key1))
+ continue;
+
+ /*
+ * FUTEX_WAIT_REQEUE_PI and FUTEX_CMP_REQUEUE_PI should always
+ * be paired with each other and no other futex ops.
+ *
+ * We should never be requeueing a futex_q with a pi_state,
+ * which is awaiting a futex_unlock_pi().
+ */
+ if ((requeue_pi && !this->rt_waiter) ||
+ (!requeue_pi && this->rt_waiter) ||
+ this->pi_state) {
+ ret = -EINVAL;
+ break;
+ }
+
+ /*
+ * Wake nr_wake waiters. For requeue_pi, if we acquired the
+ * lock, we already woke the top_waiter. If not, it will be
+ * woken by futex_unlock_pi().
+ */
+ if (++task_count <= nr_wake && !requeue_pi) {
+ mark_wake_futex(&wake_q, this);
+ continue;
+ }
+
+ /* Ensure we requeue to the expected futex for requeue_pi. */
+ if (requeue_pi && !match_futex(this->requeue_pi_key, &key2)) {
+ ret = -EINVAL;
+ break;
+ }
+
+ /*
+ * Requeue nr_requeue waiters and possibly one more in the case
+ * of requeue_pi if we couldn't acquire the lock atomically.
+ */
+ if (requeue_pi) {
+ /* Prepare the waiter to take the rt_mutex. */
+ atomic_inc(&pi_state->refcount);
+ this->pi_state = pi_state;
+ ret = rt_mutex_start_proxy_lock(&pi_state->pi_mutex,
+ this->rt_waiter,
+ this->task);
+ if (ret == 1) {
+ /* We got the lock. */
+ requeue_pi_wake_futex(this, &key2, hb2);
+ drop_count++;
+ continue;
+ } else if (ret == -EAGAIN) {
+ /*
+ * Waiter was woken by timeout or
+ * signal and has set pi_blocked_on to
+ * PI_WAKEUP_INPROGRESS before we
+ * tried to enqueue it on the rtmutex.
+ */
+ this->pi_state = NULL;
+ free_pi_state(pi_state);
+ continue;
+ } else if (ret) {
+ /* -EDEADLK */
+ this->pi_state = NULL;
+ free_pi_state(pi_state);
+ goto out_unlock;
+ }
+ }
+ requeue_futex(this, hb1, hb2, &key2);
+ drop_count++;
+ }
+
+out_unlock:
+ free_pi_state(pi_state);
+ double_unlock_hb(hb1, hb2);
+ wake_up_q(&wake_q);
+ hb_waiters_dec(hb2);
+
+ /*
+ * drop_futex_key_refs() must be called outside the spinlocks. During
+ * the requeue we moved futex_q's from the hash bucket at key1 to the
+ * one at key2 and updated their key pointer. We no longer need to
+ * hold the references to key1.
+ */
+ while (--drop_count >= 0)
+ drop_futex_key_refs(&key1);
+
+out_put_keys:
+ put_futex_key(&key2);
+out_put_key1:
+ put_futex_key(&key1);
+out:
+ return ret ? ret : task_count;
+}
+
+/* The key must be already stored in q->key. */
+static inline struct futex_hash_bucket *queue_lock(struct futex_q *q)
+ __acquires(&hb->lock)
+{
+ struct futex_hash_bucket *hb;
+
+ hb = hash_futex(&q->key);
+
+ /*
+ * Increment the counter before taking the lock so that
+ * a potential waker won't miss a to-be-slept task that is
+ * waiting for the spinlock. This is safe as all queue_lock()
+ * users end up calling queue_me(). Similarly, for housekeeping,
+ * decrement the counter at queue_unlock() when some error has
+ * occurred and we don't end up adding the task to the list.
+ */
+ hb_waiters_inc(hb);
+
+ q->lock_ptr = &hb->lock;
+
+ spin_lock(&hb->lock); /* implies MB (A) */
+ return hb;
+}
+
+static inline void
+queue_unlock(struct futex_hash_bucket *hb)
+ __releases(&hb->lock)
+{
+ spin_unlock(&hb->lock);
+ hb_waiters_dec(hb);
+}
+
+/**
+ * queue_me() - Enqueue the futex_q on the futex_hash_bucket
+ * @q: The futex_q to enqueue
+ * @hb: The destination hash bucket
+ *
+ * The hb->lock must be held by the caller, and is released here. A call to
+ * queue_me() is typically paired with exactly one call to unqueue_me(). The
+ * exceptions involve the PI related operations, which may use unqueue_me_pi()
+ * or nothing if the unqueue is done as part of the wake process and the unqueue
+ * state is implicit in the state of woken task (see futex_wait_requeue_pi() for
+ * an example).
+ */
+static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb)
+ __releases(&hb->lock)
+{
+ 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);
+ plist_add(&q->list, &hb->chain);
+ q->task = current;
+ spin_unlock(&hb->lock);
+}
+
+/**
+ * unqueue_me() - Remove the futex_q from its futex_hash_bucket
+ * @q: The futex_q to unqueue
+ *
+ * The q->lock_ptr must not be held by the caller. A call to unqueue_me() must
+ * be paired with exactly one earlier call to queue_me().
+ *
+ * Return:
+ * 1 - if the futex_q was still queued (and we removed unqueued it);
+ * 0 - if the futex_q was already removed by the waking thread
+ */
+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;
+ }
+ __unqueue_futex(q);
+
+ 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)
+ __releases(q->lock_ptr)
+{
+ __unqueue_futex(q);
+
+ BUG_ON(!q->pi_state);
+ free_pi_state(q->pi_state);
+ q->pi_state = NULL;
+
+ spin_unlock(q->lock_ptr);
+}
+
+/*
+ * 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)
+{
+ 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, uninitialized_var(curval), newval;
+ int ret;
+
+ /* Owner died? */
+ if (!pi_state->owner)
+ newtid |= FUTEX_OWNER_DIED;
+
+ /*
+ * We are here either because we stole the rtmutex from the
+ * previous highest priority waiter or we are the highest priority
+ * waiter but failed to get the rtmutex the first time.
+ * We have to replace the newowner 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
+ * 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;
+
+ if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval))
+ 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) {
+ raw_spin_lock_irq(&pi_state->owner->pi_lock);
+ WARN_ON(list_empty(&pi_state->list));
+ list_del_init(&pi_state->list);
+ raw_spin_unlock_irq(&pi_state->owner->pi_lock);
+ }
+
+ pi_state->owner = newowner;
+
+ raw_spin_lock_irq(&newowner->pi_lock);
+ WARN_ON(!list_empty(&pi_state->list));
+ list_add(&pi_state->list, &newowner->pi_state_list);
+ raw_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 highest priority
+ * waiter 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 = fault_in_user_writeable(uaddr);
+
+ 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;
+}
+
+static long futex_wait_restart(struct restart_block *restart);
+
+/**
+ * fixup_owner() - Post lock pi_state and corner case management
+ * @uaddr: user address of the futex
+ * @q: futex_q (contains pi_state and access to the rt_mutex)
+ * @locked: if the attempt to take the rt_mutex succeeded (1) or not (0)
+ *
+ * After attempting to lock an rt_mutex, this function is called to cleanup
+ * the pi_state owner as well as handle race conditions that may allow us to
+ * acquire the lock. Must be called with the hb lock held.
+ *
+ * Return:
+ * 1 - success, lock taken;
+ * 0 - success, lock not taken;
+ * <0 - on error (-EFAULT)
+ */
+static int fixup_owner(u32 __user *uaddr, struct futex_q *q, int locked)
+{
+ struct task_struct *owner;
+ int ret = 0;
+
+ if (locked) {
+ /*
+ * Got the lock. We might not be the anticipated owner if we
+ * did a lock-steal - fix up the PI-state in that case:
+ */
+ if (q->pi_state->owner != current)
+ ret = fixup_pi_state_owner(uaddr, q, current);
+ goto out;
+ }
+
+ /*
+ * Catch the rare case, where the lock was released when we were on the
+ * way back before we locked the hash bucket.
+ */
+ if (q->pi_state->owner == current) {
+ /*
+ * Try to get the rt_mutex now. This might fail as some other
+ * task acquired the rt_mutex after we removed ourself from the
+ * rt_mutex waiters list.
+ */
+ if (rt_mutex_trylock(&q->pi_state->pi_mutex)) {
+ locked = 1;
+ goto out;
+ }
+
+ /*
+ * pi_state is incorrect, some other task did a lock steal and
+ * we returned due to timeout or signal without taking the
+ * rt_mutex. Too late.
+ */
+ raw_spin_lock(&q->pi_state->pi_mutex.wait_lock);
+ owner = rt_mutex_owner(&q->pi_state->pi_mutex);
+ if (!owner)
+ owner = rt_mutex_next_owner(&q->pi_state->pi_mutex);
+ raw_spin_unlock(&q->pi_state->pi_mutex.wait_lock);
+ ret = fixup_pi_state_owner(uaddr, q, owner);
+ goto out;
+ }
+
+ /*
+ * Paranoia check. If we did not take the lock, then we should not be
+ * the owner of the rt_mutex.
+ */
+ if (rt_mutex_owner(&q->pi_state->pi_mutex) == current)
+ printk(KERN_ERR "fixup_owner: ret = %d pi-mutex: %p "
+ "pi-state %p\n", ret,
+ q->pi_state->pi_mutex.owner,
+ q->pi_state->owner);
+
+out:
+ return ret ? ret : locked;
+}
+
+/**
+ * futex_wait_queue_me() - queue_me() and wait for wakeup, timeout, or signal
+ * @hb: the futex hash bucket, must be locked by the caller
+ * @q: the futex_q to queue up on
+ * @timeout: the prepared hrtimer_sleeper, or null for no timeout
+ */
+static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q,
+ struct hrtimer_sleeper *timeout)
+{
+ /*
+ * The task state is guaranteed to be set before another task can
+ * wake it. set_current_state() is implemented using set_mb() and
+ * queue_me() calls spin_unlock() upon completion, both serializing
+ * access to the hash list and forcing another memory barrier.
+ */
+ set_current_state(TASK_INTERRUPTIBLE);
+ queue_me(q, hb);
+
+ /* Arm the timer */
+ if (timeout) {
+ hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS);
+ if (!hrtimer_active(&timeout->timer))
+ timeout->task = NULL;
+ }
+
+ /*
+ * If we have been removed from the hash list, then another task
+ * has tried to wake us, and we can skip the call to schedule().
+ */
+ if (likely(!plist_node_empty(&q->list))) {
+ /*
+ * If the timer has already expired, current will already be
+ * flagged for rescheduling. Only call schedule if there
+ * is no timeout, or if it has yet to expire.
+ */
+ if (!timeout || timeout->task)
+ freezable_schedule();
+ }
+ __set_current_state(TASK_RUNNING);
+}
+
+/**
+ * futex_wait_setup() - Prepare to wait on a futex
+ * @uaddr: the futex userspace address
+ * @val: the expected value
+ * @flags: futex flags (FLAGS_SHARED, etc.)
+ * @q: the associated futex_q
+ * @hb: storage for hash_bucket pointer to be returned to caller
+ *
+ * Setup the futex_q and locate the hash_bucket. Get the futex value and
+ * compare it with the expected value. Handle atomic faults internally.
+ * Return with the hb lock held and a q.key reference on success, and unlocked
+ * with no q.key reference on failure.
+ *
+ * Return:
+ * 0 - uaddr contains val and hb has been locked;
+ * <1 - -EFAULT or -EWOULDBLOCK (uaddr does not contain val) and hb is unlocked
+ */
+static int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags,
+ struct futex_q *q, struct futex_hash_bucket **hb)
+{
+ u32 uval;
+ int ret;
+
+ /*
+ * Access the page AFTER the hash-bucket is locked.
+ * 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 locked the hash-bucket after testing *uaddr, that
+ * would open a race condition where we could block indefinitely with
+ * cond(var) false, which would violate the guarantee.
+ *
+ * On the other hand, we insert q and release the hash-bucket only
+ * after testing *uaddr. This guarantees that futex_wait() will NOT
+ * absorb a wakeup if *uaddr does not match the desired values
+ * while the syscall executes.
+ */
+retry:
+ ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q->key, VERIFY_READ);
+ if (unlikely(ret != 0))
+ return ret;
+
+retry_private:
+ *hb = queue_lock(q);
+
+ ret = get_futex_value_locked(&uval, uaddr);
+
+ if (ret) {
+ queue_unlock(*hb);
+
+ ret = get_user(uval, uaddr);
+ if (ret)
+ goto out;
+
+ if (!(flags & FLAGS_SHARED))
+ goto retry_private;
+
+ put_futex_key(&q->key);
+ goto retry;
+ }
+
+ if (uval != val) {
+ queue_unlock(*hb);
+ ret = -EWOULDBLOCK;
+ }
+
+out:
+ if (ret)
+ put_futex_key(&q->key);
+ return ret;
+}
+
+static int futex_wait(u32 __user *uaddr, unsigned int flags, u32 val,
+ ktime_t *abs_time, u32 bitset)
+{
+ struct hrtimer_sleeper timeout, *to = NULL;
+ struct restart_block *restart;
+ struct futex_hash_bucket *hb;
+ struct futex_q q = futex_q_init;
+ int ret;
+
+ if (!bitset)
+ return -EINVAL;
+ q.bitset = bitset;
+
+ if (abs_time) {
+ to = &timeout;
+
+ hrtimer_init_on_stack(&to->timer, (flags & FLAGS_CLOCKRT) ?
+ CLOCK_REALTIME : CLOCK_MONOTONIC,
+ HRTIMER_MODE_ABS);
+ hrtimer_init_sleeper(to, current);
+ hrtimer_set_expires_range_ns(&to->timer, *abs_time,
+ current->timer_slack_ns);
+ }
+
+retry:
+ /*
+ * Prepare to wait on uaddr. On success, holds hb lock and increments
+ * q.key refs.
+ */
+ ret = futex_wait_setup(uaddr, val, flags, &q, &hb);
+ if (ret)
+ goto out;
+
+ /* queue_me and wait for wakeup, timeout, or a signal. */
+ futex_wait_queue_me(hb, &q, to);
+
+ /* If we were woken (and unqueued), we succeeded, whatever. */
+ ret = 0;
+ /* unqueue_me() drops q.key ref */
+ if (!unqueue_me(&q))
+ goto out;
+ ret = -ETIMEDOUT;
+ if (to && !to->task)
+ goto out;
+
+ /*
+ * We expect signal_pending(current), but we might be the
+ * victim of a spurious wakeup as well.
+ */
+ if (!signal_pending(current))
+ goto retry;
+
+ ret = -ERESTARTSYS;
+ if (!abs_time)
+ goto out;
+
+ restart = ¤t->restart_block;
+ restart->fn = futex_wait_restart;
+ restart->futex.uaddr = uaddr;
+ restart->futex.val = val;
+ restart->futex.time = abs_time->tv64;
+ restart->futex.bitset = bitset;
+ restart->futex.flags = flags | FLAGS_HAS_TIMEOUT;
+
+ ret = -ERESTART_RESTARTBLOCK;
+
+out:
+ if (to) {
+ hrtimer_cancel(&to->timer);
+ destroy_hrtimer_on_stack(&to->timer);
+ }
+ return ret;
+}
+
+
+static long futex_wait_restart(struct restart_block *restart)
+{
+ u32 __user *uaddr = restart->futex.uaddr;
+ ktime_t t, *tp = NULL;
+
+ if (restart->futex.flags & FLAGS_HAS_TIMEOUT) {
+ t.tv64 = restart->futex.time;
+ tp = &t;
+ }
+ restart->fn = do_no_restart_syscall;
+
+ return (long)futex_wait(uaddr, restart->futex.flags,
+ restart->futex.val, tp, restart->futex.bitset);
+}
+
+
+/*
+ * 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, unsigned int flags,
+ ktime_t *time, int trylock)
+{
+ struct hrtimer_sleeper timeout, *to = NULL;
+ struct futex_hash_bucket *hb;
+ struct futex_q q = futex_q_init;
+ int res, ret;
+
+ 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);
+ }
+
+retry:
+ ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q.key, VERIFY_WRITE);
+ if (unlikely(ret != 0))
+ goto out;
+
+retry_private:
+ hb = queue_lock(&q);
+
+ ret = futex_lock_pi_atomic(uaddr, hb, &q.key, &q.pi_state, current, 0);
+ if (unlikely(ret)) {
+ switch (ret) {
+ case 1:
+ /* We got the lock. */
+ ret = 0;
+ goto out_unlock_put_key;
+ case -EFAULT:
+ goto uaddr_faulted;
+ case -EAGAIN:
+ /*
+ * Two reasons for this:
+ * - Task is exiting and we just wait for the
+ * exit to complete.
+ * - The user space value changed.
+ */
+ queue_unlock(hb);
+ put_futex_key(&q.key);
+ cond_resched();
+ goto retry;
+ default:
+ goto out_unlock_put_key;
+ }
+ }
+
+ /*
+ * Only actually queue now that the atomic ops are done:
+ */
+ queue_me(&q, hb);
+
+ WARN_ON(!q.pi_state);
+ /*
+ * Block on the PI mutex:
+ */
+ if (!trylock) {
+ ret = rt_mutex_timed_futex_lock(&q.pi_state->pi_mutex, to);
+ } else {
+ ret = rt_mutex_trylock(&q.pi_state->pi_mutex);
+ /* Fixup the trylock return value: */
+ ret = ret ? 0 : -EWOULDBLOCK;
+ }
+
+ spin_lock(q.lock_ptr);
+ /*
+ * Fixup the pi_state owner and possibly acquire the lock if we
+ * haven't already.
+ */
+ res = fixup_owner(uaddr, &q, !ret);
+ /*
+ * If fixup_owner() returned an error, proprogate that. If it acquired
+ * the lock, clear our -ETIMEDOUT or -EINTR.
+ */
+ if (res)
+ ret = (res < 0) ? res : 0;
+
+ /*
+ * If fixup_owner() faulted and was unable to handle the fault, unlock
+ * it and return the fault to userspace.
+ */
+ if (ret && (rt_mutex_owner(&q.pi_state->pi_mutex) == current))
+ rt_mutex_unlock(&q.pi_state->pi_mutex);
+
+ /* Unqueue and drop the lock */
+ unqueue_me_pi(&q);
+
+ goto out_put_key;
+
+out_unlock_put_key:
+ queue_unlock(hb);
+
+out_put_key:
+ put_futex_key(&q.key);
+out:
+ if (to)
+ destroy_hrtimer_on_stack(&to->timer);
+ return ret != -EINTR ? ret : -ERESTARTNOINTR;
+
+uaddr_faulted:
+ queue_unlock(hb);
+
+ ret = fault_in_user_writeable(uaddr);
+ if (ret)
+ goto out_put_key;
+
+ if (!(flags & FLAGS_SHARED))
+ goto retry_private;
+
+ put_futex_key(&q.key);
+ goto retry;
+}
+
+/*
+ * Userspace attempted a TID -> 0 atomic transition, and failed.
+ * This is the in-kernel slowpath: we look up the PI state (if any),
+ * and do the rt-mutex unlock.
+ */
+static int futex_unlock_pi(u32 __user *uaddr, unsigned int flags)
+{
+ u32 uninitialized_var(curval), uval, vpid = task_pid_vnr(current);
+ union futex_key key = FUTEX_KEY_INIT;
+ struct futex_hash_bucket *hb;
+ struct futex_q *match;
+ int ret;
+
+retry:
+ if (get_user(uval, uaddr))
+ return -EFAULT;
+ /*
+ * We release only a lock we actually own:
+ */
+ if ((uval & FUTEX_TID_MASK) != vpid)
+ return -EPERM;
+
+ ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, VERIFY_WRITE);
+ if (ret)
+ return ret;
+
+ hb = hash_futex(&key);
+ spin_lock(&hb->lock);
+
+ /*
+ * Check waiters first. We do not trust user space values at
+ * all and we at least want to know if user space fiddled
+ * with the futex value instead of blindly unlocking.
+ */
+ match = futex_top_waiter(hb, &key);
+ if (match) {
+ ret = wake_futex_pi(uaddr, uval, match, hb);
+
+ /*
+ * In case of success wake_futex_pi dropped the hash
+ * bucket lock.
+ */
+ if (!ret)
+ goto out_putkey;
+
+ /*
+ * The atomic access to the futex value generated a
+ * pagefault, so retry the user-access and the wakeup:
+ */
+ if (ret == -EFAULT)
+ goto pi_faulted;
+
+ /*
+ * wake_futex_pi has detected invalid state. Tell user
+ * space.
+ */
+ goto out_unlock;
+ }
+
+ /*
+ * We have no kernel internal state, i.e. no waiters in the
+ * kernel. Waiters which are about to queue themselves are stuck
+ * on hb->lock. So we can safely ignore them. We do neither
+ * preserve the WAITERS bit not the OWNER_DIED one. We are the
+ * owner.
+ */
+ if (cmpxchg_futex_value_locked(&curval, uaddr, uval, 0))
+ goto pi_faulted;
+
+ /*
+ * If uval has changed, let user space handle it.
+ */
+ ret = (curval == uval) ? 0 : -EAGAIN;
+
+out_unlock:
+ spin_unlock(&hb->lock);
+out_putkey:
+ put_futex_key(&key);
+ return ret;
+
+pi_faulted:
+ spin_unlock(&hb->lock);
+ put_futex_key(&key);
+
+ ret = fault_in_user_writeable(uaddr);
+ if (!ret)
+ goto retry;
+
+ return ret;
+}
+
+/**
+ * handle_early_requeue_pi_wakeup() - Detect early wakeup on the initial futex
+ * @hb: the hash_bucket futex_q was original enqueued on
+ * @q: the futex_q woken while waiting to be requeued
+ * @key2: the futex_key of the requeue target futex
+ * @timeout: the timeout associated with the wait (NULL if none)
+ *
+ * Detect if the task was woken on the initial futex as opposed to the requeue
+ * target futex. If so, determine if it was a timeout or a signal that caused
+ * the wakeup and return the appropriate error code to the caller. Must be
+ * called with the hb lock held.
+ *
+ * Return:
+ * 0 = no early wakeup detected;
+ * <0 = -ETIMEDOUT or -ERESTARTNOINTR
+ */
+static inline
+int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb,
+ struct futex_q *q, union futex_key *key2,
+ struct hrtimer_sleeper *timeout)
+{
+ int ret = 0;
+
+ /*
+ * With the hb lock held, we avoid races while we process the wakeup.
+ * We only need to hold hb (and not hb2) to ensure atomicity as the
+ * wakeup code can't change q.key from uaddr to uaddr2 if we hold hb.
+ * It can't be requeued from uaddr2 to something else since we don't
+ * support a PI aware source futex for requeue.
+ */
+ if (!match_futex(&q->key, key2)) {
+ WARN_ON(q->lock_ptr && (&hb->lock != q->lock_ptr));
+ /*
+ * We were woken prior to requeue by a timeout or a signal.
+ * Unqueue the futex_q and determine which it was.
+ */
+ plist_del(&q->list, &hb->chain);
+ hb_waiters_dec(hb);
+
+ /* Handle spurious wakeups gracefully */
+ ret = -EWOULDBLOCK;
+ if (timeout && !timeout->task)
+ ret = -ETIMEDOUT;
+ else if (signal_pending(current))
+ ret = -ERESTARTNOINTR;
+ }
+ return ret;
+}
+
+/**
+ * futex_wait_requeue_pi() - Wait on uaddr and take uaddr2
+ * @uaddr: the futex we initially wait on (non-pi)
+ * @flags: futex flags (FLAGS_SHARED, FLAGS_CLOCKRT, etc.), they must be
+ * the same type, no requeueing from private to shared, etc.
+ * @val: the expected value of uaddr
+ * @abs_time: absolute timeout
+ * @bitset: 32 bit wakeup bitset set by userspace, defaults to all
+ * @uaddr2: the pi futex we will take prior to returning to user-space
+ *
+ * The caller will wait on uaddr and will be requeued by futex_requeue() to
+ * uaddr2 which must be PI aware and unique from uaddr. Normal wakeup will wake
+ * on uaddr2 and complete the acquisition of the rt_mutex prior to returning to
+ * userspace. This ensures the rt_mutex maintains an owner when it has waiters;
+ * without one, the pi logic would not know which task to boost/deboost, if
+ * there was a need to.
+ *
+ * We call schedule in futex_wait_queue_me() when we enqueue and return there
+ * via the following--
+ * 1) wakeup on uaddr2 after an atomic lock acquisition by futex_requeue()
+ * 2) wakeup on uaddr2 after a requeue
+ * 3) signal
+ * 4) timeout
+ *
+ * If 3, cleanup and return -ERESTARTNOINTR.
+ *
+ * If 2, we may then block on trying to take the rt_mutex and return via:
+ * 5) successful lock
+ * 6) signal
+ * 7) timeout
+ * 8) other lock acquisition failure
+ *
+ * If 6, return -EWOULDBLOCK (restarting the syscall would do the same).
+ *
+ * If 4 or 7, we cleanup and return with -ETIMEDOUT.
+ *
+ * Return:
+ * 0 - On success;
+ * <0 - On error
+ */
+static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
+ u32 val, ktime_t *abs_time, u32 bitset,
+ u32 __user *uaddr2)
+{
+ struct hrtimer_sleeper timeout, *to = NULL;
+ struct rt_mutex_waiter rt_waiter;
+ struct rt_mutex *pi_mutex = NULL;
+ struct futex_hash_bucket *hb, *hb2;
+ union futex_key key2 = FUTEX_KEY_INIT;
+ struct futex_q q = futex_q_init;
+ int res, ret;
+
+ if (uaddr == uaddr2)
+ return -EINVAL;
+
+ if (!bitset)
+ return -EINVAL;
+
+ if (abs_time) {
+ to = &timeout;
+ hrtimer_init_on_stack(&to->timer, (flags & FLAGS_CLOCKRT) ?
+ CLOCK_REALTIME : CLOCK_MONOTONIC,
+ HRTIMER_MODE_ABS);
+ hrtimer_init_sleeper(to, current);
+ hrtimer_set_expires_range_ns(&to->timer, *abs_time,
+ current->timer_slack_ns);
+ }
+
+ /*
+ * The waiter is allocated on our stack, manipulated by the requeue
+ * code while we sleep on uaddr.
+ */
+ rt_mutex_init_waiter(&rt_waiter, false);
+
+ ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, VERIFY_WRITE);
+ if (unlikely(ret != 0))
+ goto out;
+
+ q.bitset = bitset;
+ q.rt_waiter = &rt_waiter;
+ q.requeue_pi_key = &key2;
+
+ /*
+ * Prepare to wait on uaddr. On success, increments q.key (key1) ref
+ * count.
+ */
+ ret = futex_wait_setup(uaddr, val, flags, &q, &hb);
+ if (ret)
+ goto out_key2;
+
+ /*
+ * The check above which compares uaddrs is not sufficient for
+ * shared futexes. We need to compare the keys:
+ */
+ if (match_futex(&q.key, &key2)) {
+ queue_unlock(hb);
+ ret = -EINVAL;
+ goto out_put_keys;
+ }
+
+ /* Queue the futex_q, drop the hb lock, wait for wakeup. */
+ futex_wait_queue_me(hb, &q, to);
+
+ /*
+ * On RT we must avoid races with requeue and trying to block
+ * on two mutexes (hb->lock and uaddr2's rtmutex) by
+ * serializing access to pi_blocked_on with pi_lock.
+ */
+ raw_spin_lock_irq(¤t->pi_lock);
+ if (current->pi_blocked_on) {
+ /*
+ * We have been requeued or are in the process of
+ * being requeued.
+ */
+ raw_spin_unlock_irq(¤t->pi_lock);
+ } else {
+ /*
+ * Setting pi_blocked_on to PI_WAKEUP_INPROGRESS
+ * prevents a concurrent requeue from moving us to the
+ * uaddr2 rtmutex. After that we can safely acquire
+ * (and possibly block on) hb->lock.
+ */
+ current->pi_blocked_on = PI_WAKEUP_INPROGRESS;
+ raw_spin_unlock_irq(¤t->pi_lock);
+
+ spin_lock(&hb->lock);
+
+ /*
+ * Clean up pi_blocked_on. We might leak it otherwise
+ * when we succeeded with the hb->lock in the fast
+ * path.
+ */
+ raw_spin_lock_irq(¤t->pi_lock);
+ current->pi_blocked_on = NULL;
+ raw_spin_unlock_irq(¤t->pi_lock);
+
+ ret = handle_early_requeue_pi_wakeup(hb, &q, &key2, to);
+ spin_unlock(&hb->lock);
+ if (ret)
+ goto out_put_keys;
+ }
+
+ /*
+ * In order to be here, we have either been requeued, are in
+ * the process of being requeued, or requeue successfully
+ * acquired uaddr2 on our behalf. If pi_blocked_on was
+ * non-null above, we may be racing with a requeue. Do not
+ * rely on q->lock_ptr to be hb2->lock until after blocking on
+ * hb->lock or hb2->lock. The futex_requeue dropped our key1
+ * reference and incremented our key2 reference count.
+ */
+ hb2 = hash_futex(&key2);
+
+ /* Check if the requeue code acquired the second futex for us. */
+ if (!q.rt_waiter) {
+ /*
+ * Got the lock. We might not be the anticipated owner if we
+ * did a lock-steal - fix up the PI-state in that case.
+ */
+ if (q.pi_state && (q.pi_state->owner != current)) {
+ spin_lock(&hb2->lock);
+ BUG_ON(&hb2->lock != q.lock_ptr);
+ ret = fixup_pi_state_owner(uaddr2, &q, current);
+ spin_unlock(&hb2->lock);
+ }
+ } else {
+ /*
+ * We have been woken up by futex_unlock_pi(), a timeout, or a
+ * signal. futex_unlock_pi() will not destroy the lock_ptr nor
+ * the pi_state.
+ */
+ WARN_ON(!q.pi_state);
+ pi_mutex = &q.pi_state->pi_mutex;
+ ret = rt_mutex_finish_proxy_lock(pi_mutex, to, &rt_waiter);
+ debug_rt_mutex_free_waiter(&rt_waiter);
+
+ spin_lock(&hb2->lock);
+ BUG_ON(&hb2->lock != q.lock_ptr);
+ /*
+ * Fixup the pi_state owner and possibly acquire the lock if we
+ * haven't already.
+ */
+ res = fixup_owner(uaddr2, &q, !ret);
+ /*
+ * If fixup_owner() returned an error, proprogate that. If it
+ * acquired the lock, clear -ETIMEDOUT or -EINTR.
+ */
+ if (res)
+ ret = (res < 0) ? res : 0;
+
+ /* Unqueue and drop the lock. */
+ unqueue_me_pi(&q);
+ }
+
+ /*
+ * If fixup_pi_state_owner() faulted and was unable to handle the
+ * fault, unlock the rt_mutex and return the fault to userspace.
+ */
+ if (ret == -EFAULT) {
+ if (pi_mutex && rt_mutex_owner(pi_mutex) == current)
+ rt_mutex_unlock(pi_mutex);
+ } else if (ret == -EINTR) {
+ /*
+ * We've already been requeued, but cannot restart by calling
+ * futex_lock_pi() directly. We could restart this syscall, but
+ * it would detect that the user space "val" changed and return
+ * -EWOULDBLOCK. Save the overhead of the restart and return
+ * -EWOULDBLOCK directly.
+ */
+ ret = -EWOULDBLOCK;
+ }
+
+out_put_keys:
+ put_futex_key(&q.key);
+out_key2:
+ put_futex_key(&key2);
+
+out:
+ if (to) {
+ hrtimer_cancel(&to->timer);
+ destroy_hrtimer_on_stack(&to->timer);
+ }
+ return ret;
+}
+
+/*
+ * Support for robust futexes: the kernel cleans up held futexes at
+ * thread exit time.
+ *
+ * Implementation: user-space maintains a per-thread list of locks it
+ * is holding. Upon do_exit(), the kernel carefully walks this list,
+ * and marks all locks that are owned by this thread with the
+ * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is
+ * always manipulated with the lock held, so the list is private and
+ * per-thread. Userspace also maintains a per-thread 'list_op_pending'
+ * field, to allow the kernel to clean up if the thread dies after
+ * acquiring the lock, but just before it could have added itself to
+ * the list. There can only be one such pending lock.
+ */
+
+/**
+ * sys_set_robust_list() - Set the robust-futex list head of a task
+ * @head: pointer to the list-head
+ * @len: length of the list-head, as userspace expects
+ */
+SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head,
+ size_t, len)
+{
+ if (!futex_cmpxchg_enabled)
+ return -ENOSYS;
+ /*
+ * The kernel knows only one size for now:
+ */
+ if (unlikely(len != sizeof(*head)))
+ return -EINVAL;
+
+ current->robust_list = head;
+
+ return 0;
+}
+
+/**
+ * sys_get_robust_list() - Get the robust-futex list head of a task
+ * @pid: pid of the process [zero for current task]
+ * @head_ptr: pointer to a list-head pointer, the kernel fills it in
+ * @len_ptr: pointer to a length field, the kernel fills in the header size
+ */
+SYSCALL_DEFINE3(get_robust_list, int, pid,
+ struct robust_list_head __user * __user *, head_ptr,
+ size_t __user *, len_ptr)
+{
+ struct robust_list_head __user *head;
+ unsigned long ret;
+ struct task_struct *p;
+
+ if (!futex_cmpxchg_enabled)
+ return -ENOSYS;
+
+ rcu_read_lock();
+
+ ret = -ESRCH;
+ if (!pid)
+ p = current;
+ else {
+ p = find_task_by_vpid(pid);
+ if (!p)
+ goto err_unlock;
+ }
+
+ ret = -EPERM;
+ if (!ptrace_may_access(p, PTRACE_MODE_READ))
+ goto err_unlock;
+
+ head = p->robust_list;
+ rcu_read_unlock();
+
+ if (put_user(sizeof(*head), len_ptr))
+ return -EFAULT;
+ return put_user(head, head_ptr);
+
+err_unlock:
+ rcu_read_unlock();
+
+ return ret;
+}
+
+/*
+ * Process a futex-list entry, check whether it's owned by the
+ * dying task, and do notification if so:
+ */
+int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi)
+{
+ u32 uval, uninitialized_var(nval), mval;
+
+retry:
+ if (get_user(uval, uaddr))
+ return -1;
+
+ if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) {
+ /*
+ * Ok, this dying thread is truly holding a futex
+ * of interest. Set the OWNER_DIED bit atomically
+ * via cmpxchg, and if the value had FUTEX_WAITERS
+ * set, wake up a waiter (if any). (We have to do a
+ * futex_wake() even if OWNER_DIED is already set -
+ * to handle the rare but possible case of recursive
+ * thread-death.) The rest of the cleanup is done in
+ * userspace.
+ */
+ mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED;
+ /*
+ * We are not holding a lock here, but we want to have
+ * the pagefault_disable/enable() protection because
+ * we want to handle the fault gracefully. If the
+ * access fails we try to fault in the futex with R/W
+ * verification via get_user_pages. get_user() above
+ * does not guarantee R/W access. If that fails we
+ * give up and leave the futex locked.
+ */
+ if (cmpxchg_futex_value_locked(&nval, uaddr, uval, mval)) {
+ if (fault_in_user_writeable(uaddr))
+ return -1;
+ goto retry;
+ }
+ if (nval != uval)
+ goto retry;
+
+ /*
+ * Wake robust non-PI futexes here. The wakeup of
+ * PI futexes happens in exit_pi_state():
+ */
+ if (!pi && (uval & FUTEX_WAITERS))
+ futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY);
+ }
+ return 0;
+}
+
+/*
+ * Fetch a robust-list pointer. Bit 0 signals PI futexes:
+ */
+static inline int fetch_robust_entry(struct robust_list __user **entry,
+ struct robust_list __user * __user *head,
+ unsigned int *pi)
+{
+ unsigned long uentry;
+
+ if (get_user(uentry, (unsigned long __user *)head))
+ return -EFAULT;
+
+ *entry = (void __user *)(uentry & ~1UL);
+ *pi = uentry & 1;
+
+ return 0;
+}
+
+/*
+ * Walk curr->robust_list (very carefully, it's a userspace list!)
+ * and mark any locks found there dead, and notify any waiters.
+ *
+ * We silently return on any sign of list-walking problem.
+ */
+void exit_robust_list(struct task_struct *curr)
+{
+ struct robust_list_head __user *head = curr->robust_list;
+ struct robust_list __user *entry, *next_entry, *pending;
+ unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
+ unsigned int uninitialized_var(next_pi);
+ unsigned long futex_offset;
+ int rc;
+
+ if (!futex_cmpxchg_enabled)
+ return;
+
+ /*
+ * Fetch the list head (which was registered earlier, via
+ * sys_set_robust_list()):
+ */
+ if (fetch_robust_entry(&entry, &head->list.next, &pi))
+ return;
+ /*
+ * Fetch the relative futex offset:
+ */
+ if (get_user(futex_offset, &head->futex_offset))
+ return;
+ /*
+ * Fetch any possibly pending lock-add first, and handle it
+ * if it exists:
+ */
+ if (fetch_robust_entry(&pending, &head->list_op_pending, &pip))
+ return;
+
+ next_entry = NULL; /* avoid warning with gcc */
+ while (entry != &head->list) {
+ /*
+ * Fetch the next entry in the list before calling
+ * handle_futex_death:
+ */
+ rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi);
+ /*
+ * A pending lock might already be on the list, so
+ * don't process it twice:
+ */
+ if (entry != pending)
+ if (handle_futex_death((void __user *)entry + futex_offset,
+ curr, pi))
+ return;
+ if (rc)
+ return;
+ entry = next_entry;
+ pi = next_pi;
+ /*
+ * Avoid excessively long or circular lists:
+ */
+ if (!--limit)
+ break;
+
+ cond_resched();
+ }
+
+ if (pending)
+ handle_futex_death((void __user *)pending + futex_offset,
+ curr, pip);
+}
+
+long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
+ u32 __user *uaddr2, u32 val2, u32 val3)
+{
+ int cmd = op & FUTEX_CMD_MASK;
+ unsigned int flags = 0;
+
+ if (!(op & FUTEX_PRIVATE_FLAG))
+ flags |= FLAGS_SHARED;
+
+ if (op & FUTEX_CLOCK_REALTIME) {
+ flags |= FLAGS_CLOCKRT;
+ if (cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI)
+ return -ENOSYS;
+ }
+
+ switch (cmd) {
+ case FUTEX_LOCK_PI:
+ case FUTEX_UNLOCK_PI:
+ case FUTEX_TRYLOCK_PI:
+ case FUTEX_WAIT_REQUEUE_PI:
+ case FUTEX_CMP_REQUEUE_PI:
+ if (!futex_cmpxchg_enabled)
+ return -ENOSYS;
+ }
+
+ switch (cmd) {
+ case FUTEX_WAIT:
+ val3 = FUTEX_BITSET_MATCH_ANY;
+ case FUTEX_WAIT_BITSET:
+ return futex_wait(uaddr, flags, val, timeout, val3);
+ case FUTEX_WAKE:
+ val3 = FUTEX_BITSET_MATCH_ANY;
+ case FUTEX_WAKE_BITSET:
+ return futex_wake(uaddr, flags, val, val3);
+ case FUTEX_REQUEUE:
+ return futex_requeue(uaddr, flags, uaddr2, val, val2, NULL, 0);
+ case FUTEX_CMP_REQUEUE:
+ return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 0);
+ case FUTEX_WAKE_OP:
+ return futex_wake_op(uaddr, flags, uaddr2, val, val2, val3);
+ case FUTEX_LOCK_PI:
+ return futex_lock_pi(uaddr, flags, timeout, 0);
+ case FUTEX_UNLOCK_PI:
+ return futex_unlock_pi(uaddr, flags);
+ case FUTEX_TRYLOCK_PI:
+ return futex_lock_pi(uaddr, flags, NULL, 1);
+ case FUTEX_WAIT_REQUEUE_PI:
+ val3 = FUTEX_BITSET_MATCH_ANY;
+ return futex_wait_requeue_pi(uaddr, flags, val, timeout, val3,
+ uaddr2);
+ case FUTEX_CMP_REQUEUE_PI:
+ return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 1);
+ }
+ return -ENOSYS;
+}
+
+
+SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
+ struct timespec __user *, utime, u32 __user *, uaddr2,
+ u32, val3)
+{
+ struct timespec ts;
+ ktime_t t, *tp = NULL;
+ u32 val2 = 0;
+ int cmd = op & FUTEX_CMD_MASK;
+
+ if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
+ cmd == FUTEX_WAIT_BITSET ||
+ cmd == FUTEX_WAIT_REQUEUE_PI)) {
+ if (copy_from_user(&ts, utime, sizeof(ts)) != 0)
+ return -EFAULT;
+ if (!timespec_valid(&ts))
+ return -EINVAL;
+
+ t = timespec_to_ktime(ts);
+ if (cmd == FUTEX_WAIT)
+ t = ktime_add_safe(ktime_get(), t);
+ tp = &t;
+ }
+ /*
+ * requeue parameter in 'utime' if cmd == FUTEX_*_REQUEUE_*.
+ * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP.
+ */
+ if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
+ cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP)
+ val2 = (u32) (unsigned long) utime;
+
+ return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
+}
+
+static void __init futex_detect_cmpxchg(void)
+{
+#ifndef CONFIG_HAVE_FUTEX_CMPXCHG
+ u32 curval;
+
+ /*
+ * This will fail and we want it. Some arch implementations do
+ * runtime detection of the futex_atomic_cmpxchg_inatomic()
+ * functionality. We want to know that before we call in any
+ * of the complex code paths. Also we want to prevent
+ * registration of robust lists in that case. NULL is
+ * guaranteed to fault and we get -EFAULT on functional
+ * implementation, the non-functional ones will return
+ * -ENOSYS.
+ */
+ if (cmpxchg_futex_value_locked(&curval, NULL, 0, 0) == -EFAULT)
+ futex_cmpxchg_enabled = 1;
+#endif
+}
+
+static int __init futex_init(void)
+{
+ unsigned int futex_shift;
+ unsigned long i;
+
+#if CONFIG_BASE_SMALL
+ futex_hashsize = 16;
+#else
+ futex_hashsize = roundup_pow_of_two(256 * num_possible_cpus());
+#endif
+
+ futex_queues = alloc_large_system_hash("futex", sizeof(*futex_queues),
+ futex_hashsize, 0,
+ futex_hashsize < 256 ? HASH_SMALL : 0,
+ &futex_shift, NULL,
+ futex_hashsize, futex_hashsize);
+ futex_hashsize = 1UL << futex_shift;
+
+ futex_detect_cmpxchg();
+
+ for (i = 0; i < futex_hashsize; i++) {
+ atomic_set(&futex_queues[i].waiters, 0);
+ plist_head_init(&futex_queues[i].chain);
+ spin_lock_init(&futex_queues[i].lock);
+ }
+
+ return 0;
+}
+__initcall(futex_init);
Code Review / kvmfornfv.git / blobdiff