* 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.
#define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)
+/*
+ * 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:
*/
union futex_key key;
};
-/*
- * We use this hashed waitqueue instead of a normal wait_queue_t, so
+/**
+ * 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 wakup is always to make the first condition true, then
- * wake up q->waiter, then make the second condition true.
+ * 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;
- /* There can only be a single waiter */
- wait_queue_head_t waiter;
- /* Which hash list lock to use: */
+ struct task_struct *task;
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 */
+ 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
+};
+
/*
- * Split the global futex_lock into every hash list lock.
+ * 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 {
spinlock_t lock;
*/
static inline int match_futex(union futex_key *key1, union futex_key *key2)
{
- return (key1->both.word == key2->both.word
+ return (key1 && key2
+ && key1->both.word == key2->both.word
&& key1->both.ptr == key2->both.ptr
&& key1->both.offset == key2->both.offset);
}
switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
case FUT_OFF_INODE:
- atomic_inc(&key->shared.inode->i_count);
+ ihold(key->shared.inode);
break;
case FUT_OFF_MMSHARED:
atomic_inc(&key->private.mm->mm_count);
*/
static void drop_futex_key_refs(union futex_key *key)
{
- if (!key->both.ptr)
+ 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:
}
/**
- * 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,
- * ¤t->mm->mmap_sem for a PROCESS_SHARED futex
- * @key: address where result is stored.
+ * 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.
*
* Returns a negative error code or 0
* The key words are stored in *key on success.
* 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 ¤t->mm->mmap_sem and
- * caller must have taken the reader lock. but NOT any spinlocks.
+ * 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)
+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;
+ struct page *page, *page_head;
int err;
/*
}
again:
- err = get_user_pages_fast(address, 1, 0, &page);
+ err = get_user_pages_fast(address, 1, 1, &page);
if (err < 0)
return err;
- lock_page(page);
- if (!page->mapping) {
- unlock_page(page);
+#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, 1, &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) {
+ unlock_page(page_head);
+ put_page(page_head);
goto again;
}
* it's a read-only handle, it's expected that futexes attach to
* the object not the particular process.
*/
- if (PageAnon(page)) {
+ if (PageAnon(page_head)) {
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;
+ key->shared.inode = page_head->mapping->host;
+ key->shared.pgoff = page_head->index;
}
get_futex_key_refs(key);
- unlock_page(page);
- put_page(page);
+ unlock_page(page_head);
+ put_page(page_head);
return 0;
}
-static inline
-void put_futex_key(int fshared, union futex_key *key)
+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 = get_user_pages(current, mm, (unsigned long)uaddr,
+ 1, 1, 0, NULL, NULL);
+ 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 u32 cmpxchg_futex_value_locked(u32 __user *uaddr, u32 uval, u32 newval)
{
u32 curval;
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:
* and has cleaned up the pi_state already
*/
if (pi_state->owner) {
- spin_lock_irq(&pi_state->owner->pi_lock);
+ raw_spin_lock_irq(&pi_state->owner->pi_lock);
list_del_init(&pi_state->list);
- spin_unlock_irq(&pi_state->owner->pi_lock);
+ raw_spin_unlock_irq(&pi_state->owner->pi_lock);
rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner);
}
rcu_read_lock();
p = find_task_by_vpid(pid);
- if (!p || ((current->euid != p->euid) && (current->euid != p->uid)))
- p = ERR_PTR(-ESRCH);
- else
+ if (p)
get_task_struct(p);
rcu_read_unlock();
* pi_state_list anymore, but we have to be careful
* versus waiters unqueueing themselves:
*/
- spin_lock_irq(&curr->pi_lock);
+ 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);
- spin_unlock_irq(&curr->pi_lock);
+ raw_spin_unlock_irq(&curr->pi_lock);
spin_lock(&hb->lock);
- spin_lock_irq(&curr->pi_lock);
+ raw_spin_lock_irq(&curr->pi_lock);
/*
* We dropped the pi-lock, so re-check whether this
* task still owns the PI-state:
WARN_ON(list_empty(&pi_state->list));
list_del_init(&pi_state->list);
pi_state->owner = NULL;
- spin_unlock_irq(&curr->pi_lock);
+ raw_spin_unlock_irq(&curr->pi_lock);
rt_mutex_unlock(&pi_state->pi_mutex);
spin_unlock(&hb->lock);
- spin_lock_irq(&curr->pi_lock);
+ raw_spin_lock_irq(&curr->pi_lock);
}
- spin_unlock_irq(&curr->pi_lock);
+ raw_spin_unlock_irq(&curr->pi_lock);
}
static int
*/
pi_state = this->pi_state;
/*
- * Userspace might have messed up non PI and PI futexes
+ * 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);
+
+ /*
+ * When pi_state->owner is NULL then the owner died
+ * and another waiter is on the fly. pi_state->owner
+ * is fixed up by the task which acquires
+ * pi_state->rt_mutex.
+ *
+ * We do not check for pid == 0 which can happen when
+ * the owner died and robust_list_exit() cleared the
+ * TID.
+ */
+ if (pid && pi_state->owner) {
+ /*
+ * Bail out if user space manipulated the
+ * futex value.
+ */
+ if (pid != task_pid_vnr(pi_state->owner))
+ return -EINVAL;
+ }
atomic_inc(&pi_state->refcount);
*ps = pi_state;
if (!pid)
return -ESRCH;
p = futex_find_get_task(pid);
- if (IS_ERR(p))
- return PTR_ERR(p);
+ if (!p)
+ return -ESRCH;
/*
* We need to look at the task state flags to figure out,
* change of the task flags, we do this protected by
* p->pi_lock:
*/
- spin_lock_irq(&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
*/
int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN;
- spin_unlock_irq(&p->pi_lock);
+ raw_spin_unlock_irq(&p->pi_lock);
put_task_struct(p);
return ret;
}
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);
+ raw_spin_unlock_irq(&p->pi_lock);
put_task_struct(p);
return 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)
+ *
+ * Returns:
+ * 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)
+{
+ int lock_taken, ret, ownerdied = 0;
+ u32 uval, newval, curval;
+
+retry:
+ 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(task);
+ if (set_waiters)
+ newval |= FUTEX_WAITERS;
+
+ curval = cmpxchg_futex_value_locked(uaddr, 0, newval);
+
+ if (unlikely(curval == -EFAULT))
+ return -EFAULT;
+
+ /*
+ * Detect deadlocks.
+ */
+ if ((unlikely((curval & FUTEX_TID_MASK) == task_pid_vnr(task))))
+ return -EDEADLK;
+
+ /*
+ * Surprise - we got the lock. Just return to userspace:
+ */
+ if (unlikely(!curval))
+ return 1;
+
+ uval = curval;
+
+ /*
+ * Set the FUTEX_WAITERS flag, so the owner will know it has someone
+ * to wake at the 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(task);
+ ownerdied = 0;
+ lock_taken = 1;
+ }
+
+ curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
+
+ if (unlikely(curval == -EFAULT))
+ return -EFAULT;
+ if (unlikely(curval != uval))
+ goto retry;
+
+ /*
+ * We took the lock due to owner died take over.
+ */
+ if (unlikely(lock_taken))
+ return 1;
+
+ /*
+ * We dont have the lock. Look up the PI state (or create it if
+ * we are the first waiter):
+ */
+ ret = lookup_pi_state(uval, hb, key, ps);
+
+ if (unlikely(ret)) {
+ switch (ret) {
+ case -ESRCH:
+ /*
+ * No owner found for this futex. Check if the
+ * OWNER_DIED bit is set to figure out whether
+ * this is a robust futex or not.
+ */
+ if (get_futex_value_locked(&curval, uaddr))
+ return -EFAULT;
+
+ /*
+ * We simply start over in case of a robust
+ * futex. The code above will take the futex
+ * and return happy.
+ */
+ if (curval & FUTEX_OWNER_DIED) {
+ ownerdied = 1;
+ goto retry;
+ }
+ default:
+ break;
+ }
+ }
+
+ return ret;
+}
+
/*
* 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);
+ struct task_struct *p = q->task;
+
/*
- * The lock in wake_up_all() is a crucial memory barrier after the
- * plist_del() and also before assigning to q->lock_ptr.
+ * We set q->lock_ptr = NULL _before_ we wake up the task. If
+ * a non-futex wake up happens on another CPU then the task
+ * might exit and p would dereference a non-existing task
+ * struct. Prevent this by holding a reference on p across the
+ * wake up.
*/
- wake_up(&q->waiter);
+ get_task_struct(p);
+
+ plist_del(&q->list, &q->list.plist);
/*
- * 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.
+ * 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;
+
+ wake_up_state(p, TASK_NORMAL);
+ put_task_struct(p);
}
static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)
if (!pi_state)
return -EINVAL;
- spin_lock(&pi_state->pi_mutex.wait_lock);
+ /*
+ * 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);
/*
- * 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.
+ * 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;
else if (curval != uval)
ret = -EINVAL;
if (ret) {
- spin_unlock(&pi_state->pi_mutex.wait_lock);
+ raw_spin_unlock(&pi_state->pi_mutex.wait_lock);
return ret;
}
}
- spin_lock_irq(&pi_state->owner->pi_lock);
+ raw_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);
+ raw_spin_unlock_irq(&pi_state->owner->pi_lock);
- spin_lock_irq(&new_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;
- spin_unlock_irq(&new_owner->pi_lock);
+ raw_spin_unlock_irq(&new_owner->pi_lock);
- spin_unlock(&pi_state->pi_mutex.wait_lock);
+ raw_spin_unlock(&pi_state->pi_mutex.wait_lock);
rt_mutex_unlock(&pi_state->pi_mutex);
return 0;
}
}
+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 all waiters hashed on the physical page that is mapped
- * to this virtual address:
+ * Wake up waiters matching bitset queued on this futex (uaddr).
*/
-static int futex_wake(u32 __user *uaddr, int fshared, int nr_wake, u32 bitset)
+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;
if (!bitset)
return -EINVAL;
- ret = get_futex_key(uaddr, fshared, &key);
+ ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key);
if (unlikely(ret != 0))
goto out;
plist_for_each_entry_safe(this, next, head, list) {
if (match_futex (&this->key, &key)) {
- if (this->pi_state) {
+ if (this->pi_state || this->rt_waiter) {
ret = -EINVAL;
break;
}
}
spin_unlock(&hb->lock);
+ put_futex_key(&key);
out:
- put_futex_key(fshared, &key);
return ret;
}
* to this virtual address:
*/
static int
-futex_wake_op(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
+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 plist_head *head;
struct futex_q *this, *next;
- int ret, op_ret, attempt = 0;
+ int ret, op_ret;
-retryfull:
- ret = get_futex_key(uaddr1, fshared, &key1);
+retry:
+ ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1);
if (unlikely(ret != 0))
goto out;
- ret = get_futex_key(uaddr2, fshared, &key2);
+ ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2);
if (unlikely(ret != 0))
- goto out;
+ goto out_put_key1;
hb1 = hash_futex(&key1);
hb2 = hash_futex(&key2);
-retry:
+retry_private:
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);
+ double_unlock_hb(hb1, hb2);
#ifndef CONFIG_MMU
/*
* but we might get them from range checking
*/
ret = op_ret;
- goto out;
+ goto out_put_keys;
#endif
if (unlikely(op_ret != -EFAULT)) {
ret = op_ret;
- goto out;
- }
-
- /*
- * 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;
- goto retry;
+ goto out_put_keys;
}
- ret = get_user(dummy, uaddr2);
+ ret = fault_in_user_writeable(uaddr2);
if (ret)
- return ret;
+ goto out_put_keys;
- goto retryfull;
+ if (!(flags & FLAGS_SHARED))
+ goto retry_private;
+
+ put_futex_key(&key2);
+ put_futex_key(&key1);
+ goto retry;
}
head = &hb1->chain;
ret += op_ret;
}
- spin_unlock(&hb1->lock);
- if (hb1 != hb2)
- spin_unlock(&hb2->lock);
+ double_unlock_hb(hb1, hb2);
+out_put_keys:
+ put_futex_key(&key2);
+out_put_key1:
+ put_futex_key(&key1);
out:
- put_futex_key(fshared, &key2);
- put_futex_key(fshared, &key1);
-
return ret;
}
-/*
- * Requeue all waiters hashed on one physical page to another
- * physical page.
+/**
+ * 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 int futex_requeue(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
- int nr_wake, int nr_requeue, u32 *cmpval)
+static inline
+void requeue_futex(struct futex_q *q, struct futex_hash_bucket *hb1,
+ struct futex_hash_bucket *hb2, union futex_key *key2)
{
- 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;
+ /*
+ * 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);
+ plist_add(&q->list, &hb2->chain);
+ q->lock_ptr = &hb2->lock;
+#ifdef CONFIG_DEBUG_PI_LIST
+ q->list.plist.spinlock = &hb2->lock;
+#endif
+ }
+ get_futex_key_refs(key2);
+ q->key = *key2;
+}
- hb1 = hash_futex(&key1);
- hb2 = hash_futex(&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;
- double_lock_hb(hb1, hb2);
+ WARN_ON(plist_node_empty(&q->list));
+ plist_del(&q->list, &q->list.plist);
- if (likely(cmpval != NULL)) {
- u32 curval;
+ WARN_ON(!q->rt_waiter);
+ q->rt_waiter = NULL;
- ret = get_futex_value_locked(&curval, uaddr1);
+ q->lock_ptr = &hb->lock;
+#ifdef CONFIG_DEBUG_PI_LIST
+ q->list.plist.spinlock = &hb->lock;
+#endif
- if (unlikely(ret)) {
- spin_unlock(&hb1->lock);
- if (hb1 != hb2)
- spin_unlock(&hb2->lock);
+ wake_up_state(q->task, TASK_NORMAL);
+}
- ret = get_user(curval, uaddr1);
+/**
+ * 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.
+ *
+ * Returns:
+ * 0 - failed to acquire the lock atomicly
+ * 1 - acquired the lock
+ * <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;
- if (!ret)
- goto retry;
+ if (get_futex_value_locked(&curval, pifutex))
+ return -EFAULT;
- return ret;
+ /*
+ * 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.
+ */
+ 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 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.
+ *
+ * Returns:
+ * >=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 plist_head *head1;
+ struct futex_q *this, *next;
+ u32 curval2;
+
+ if (requeue_pi) {
+ /*
+ * 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:
+ if (pi_state != NULL) {
+ /*
+ * We will have to lookup the pi_state again, so free this one
+ * to keep the accounting correct.
+ */
+ free_pi_state(pi_state);
+ pi_state = NULL;
+ }
+
+ ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1);
+ if (unlikely(ret != 0))
+ goto out;
+ ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2);
+ if (unlikely(ret != 0))
+ goto out_put_key1;
+
+ hb1 = hash_futex(&key1);
+ hb2 = hash_futex(&key2);
+
+retry_private:
+ 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);
+
+ 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;
}
}
+ 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 (ret == 1) {
+ WARN_ON(pi_state);
+ drop_count++;
+ task_count++;
+ ret = get_futex_value_locked(&curval2, uaddr2);
+ if (!ret)
+ ret = lookup_pi_state(curval2, hb2, &key2,
+ &pi_state);
+ }
+
+ switch (ret) {
+ case 0:
+ break;
+ case -EFAULT:
+ double_unlock_hb(hb1, hb2);
+ put_futex_key(&key2);
+ put_futex_key(&key1);
+ ret = fault_in_user_writeable(uaddr2);
+ if (!ret)
+ goto retry;
+ goto out;
+ case -EAGAIN:
+ /* The owner was exiting, try again. */
+ double_unlock_hb(hb1, hb2);
+ put_futex_key(&key2);
+ put_futex_key(&key1);
+ cond_resched();
+ goto retry;
+ default:
+ goto out_unlock;
+ }
+ }
+
head1 = &hb1->chain;
plist_for_each_entry_safe(this, next, head1, list) {
- if (!match_futex (&this->key, &key1))
+ if (task_count - nr_wake >= nr_requeue)
+ break;
+
+ if (!match_futex(&this->key, &key1))
continue;
- if (++ret <= nr_wake) {
+
+ /*
+ * FUTEX_WAIT_REQEUE_PI and FUTEX_CMP_REQUEUE_PI should always
+ * be paired with each other and no other futex ops.
+ */
+ if ((requeue_pi && !this->rt_waiter) ||
+ (!requeue_pi && this->rt_waiter)) {
+ 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) {
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++;
+ continue;
+ }
- if (ret - nr_wake >= nr_requeue)
- break;
+ /* 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, 1);
+ if (ret == 1) {
+ /* We got the lock. */
+ requeue_pi_wake_futex(this, &key2, hb2);
+ drop_count++;
+ 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:
- spin_unlock(&hb1->lock);
- if (hb1 != hb2)
- spin_unlock(&hb2->lock);
+ double_unlock_hb(hb1, hb2);
- /* drop_futex_key_refs() must be called outside the spinlocks. */
+ /*
+ * 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:
- put_futex_key(fshared, &key2);
- put_futex_key(fshared, &key1);
- return ret;
+ if (pi_state != NULL)
+ free_pi_state(pi_state);
+ 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;
- init_waitqueue_head(&q->waiter);
-
- get_futex_key_refs(&q->key);
hb = hash_futex(&q->key);
q->lock_ptr = &hb->lock;
return hb;
}
+static inline void
+queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb)
+ __releases(&hb->lock)
+{
+ spin_unlock(&hb->lock);
+}
+
+/**
+ * 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;
plist_node_init(&q->list, prio);
#ifdef CONFIG_DEBUG_PI_LIST
- q->list.plist.lock = &hb->lock;
+ q->list.plist.spinlock = &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.
+/**
+ * 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().
+ *
+ * Returns:
+ * 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
*/
-
-/* 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:
+retry:
lock_ptr = q->lock_ptr;
barrier();
if (lock_ptr != NULL) {
* and dropped here.
*/
static void unqueue_me_pi(struct futex_q *q)
+ __releases(q->lock_ptr)
{
WARN_ON(plist_node_empty(&q->list));
plist_del(&q->list, &q->list.plist);
q->pi_state = NULL;
spin_unlock(q->lock_ptr);
-
- drop_futex_key_refs(&q->key);
}
/*
* private futexes.
*/
static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
- struct task_struct *newowner, int fshared)
+ 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, curval, newval;
- int ret, attempt = 0;
+ int ret;
/* Owner died? */
if (!pi_state->owner)
* 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.
+ * 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
* itself.
*/
if (pi_state->owner != NULL) {
- spin_lock_irq(&pi_state->owner->pi_lock);
+ raw_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);
+ raw_spin_unlock_irq(&pi_state->owner->pi_lock);
}
pi_state->owner = newowner;
- spin_lock_irq(&newowner->pi_lock);
+ raw_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);
+ raw_spin_unlock_irq(&newowner->pi_lock);
return 0;
/*
handle_fault:
spin_unlock(q->lock_ptr);
- ret = futex_handle_fault((unsigned long)uaddr, attempt++);
+ ret = fault_in_user_writeable(uaddr);
spin_lock(q->lock_ptr);
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)
+/**
+ * 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.
+ *
+ * Returns:
+ * 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 *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;
+ struct task_struct *owner;
+ int ret = 0;
- if (!bitset)
- return -EINVAL;
+ 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;
+ }
- 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_release_sem;
+ /*
+ * 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;
+ }
- hb = queue_lock(&q);
+ /*
+ * 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. We can access the rt_mutex_owner without
+ * locking, as the other task is now blocked on the hash bucket
+ * lock. Fix the state up.
+ */
+ owner = rt_mutex_owner(&q->pi_state->pi_mutex);
+ ret = fixup_pi_state_owner(uaddr, q, owner);
+ goto out;
+ }
/*
- * Access the page AFTER the futex is queued.
+ * Paranoia check. If we did not take the lock, then we should not be
+ * the owner, nor the pending 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)
+ 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.
+ *
+ * Returns:
+ * 0 - uaddr contains val and hb has been locked
+ * <1 - -EFAULT or -EWOULDBLOCK (uaddr does not contain val) and hb is unlcoked
+ */
+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);
* 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.
*/
+retry:
+ ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q->key);
+ if (unlikely(ret != 0))
+ return ret;
+
+retry_private:
+ *hb = queue_lock(q);
+
ret = get_futex_value_locked(&uval, uaddr);
- if (unlikely(ret)) {
- queue_unlock(&q, hb);
+ if (ret) {
+ queue_unlock(q, *hb);
ret = get_user(uval, uaddr);
+ if (ret)
+ goto out;
- if (!ret)
- goto retry;
- return ret;
- }
- ret = -EWOULDBLOCK;
- if (uval != val)
- goto out_unlock_release_sem;
+ if (!(flags & FLAGS_SHARED))
+ goto retry_private;
- /* Only actually queue if *uaddr contained val. */
- queue_me(&q, hb);
+ put_futex_key(&q->key);
+ goto retry;
+ }
- /*
- * 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.
- */
+ if (uval != val) {
+ queue_unlock(q, *hb);
+ ret = -EWOULDBLOCK;
+ }
- /* 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;
+out:
+ if (ret)
+ put_futex_key(&q->key);
+ return ret;
+}
- /*
- * 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();
+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;
- hrtimer_cancel(&t.timer);
+ if (!bitset)
+ return -EINVAL;
+ q.bitset = bitset;
- /* Flag if a timeout occured */
- rem = (t.task == NULL);
+ if (abs_time) {
+ to = &timeout;
- destroy_hrtimer_on_stack(&t.timer);
- }
+ 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);
}
- __set_current_state(TASK_RUNNING);
+retry:
/*
- * NOTE: we don't remove ourselves from the waitqueue because
- * we are the only user of it.
+ * 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))
- return 0;
- if (rem)
- return -ETIMEDOUT;
+ goto out;
+ ret = -ETIMEDOUT;
+ if (to && !to->task)
+ goto out;
/*
- * We expect signal_pending(current), but another thread may
- * have handled it for us already.
+ * 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)
- return -ERESTARTSYS;
- else {
- struct restart_block *restart;
- restart = ¤t_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;
- }
+ goto out;
- out_unlock_release_sem:
- queue_unlock(&q, hb);
+ restart = ¤t_thread_info()->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;
- out_release_sem:
- put_futex_key(fshared, &q.key);
+ 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 = (u32 __user *)restart->futex.uaddr;
- int fshared = 0;
- ktime_t t;
+ u32 __user *uaddr = restart->futex.uaddr;
+ ktime_t t, *tp = NULL;
- t.tv64 = restart->futex.time;
+ if (restart->futex.flags & FLAGS_HAS_TIMEOUT) {
+ t.tv64 = restart->futex.time;
+ tp = &t;
+ }
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);
+
+ return (long)futex_wait(uaddr, restart->futex.flags,
+ restart->futex.val, tp, restart->futex.bitset);
}
* 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)
+static int futex_lock_pi(u32 __user *uaddr, unsigned int flags, 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;
+ struct futex_q q = futex_q_init;
+ int res, ret;
if (refill_pi_state_cache())
return -ENOMEM;
hrtimer_set_expires(&to->timer, *time);
}
- q.pi_state = NULL;
- retry:
- q.key = FUTEX_KEY_INIT;
- ret = get_futex_key(uaddr, fshared, &q.key);
+retry:
+ ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q.key);
if (unlikely(ret != 0))
- goto out_release_sem;
+ goto out;
- retry_unlocked:
+retry_private:
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_release_sem;
- }
-
- /*
- * Surprise - we got the lock. Just return to userspace:
- */
- if (unlikely(!curval))
- goto out_unlock_release_sem;
-
- 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.
- */
- if (unlikely(lock_taken))
- goto out_unlock_release_sem;
-
- /*
- * We dont have the lock. Look up the PI state (or create it if
- * we are the first waiter):
- */
- ret = lookup_pi_state(uval, hb, &q.key, &q.pi_state);
-
+ 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:
/*
* Task is exiting and we just wait for the
* exit to complete.
*/
queue_unlock(&q, hb);
+ put_futex_key(&q.key);
cond_resched();
goto retry;
-
- case -ESRCH:
- /*
- * No owner found for this futex. Check if the
- * OWNER_DIED bit is set to figure out whether
- * this is a robust futex or not.
- */
- if (get_futex_value_locked(&curval, uaddr))
- goto uaddr_faulted;
-
- /*
- * We simply start over in case of a robust
- * futex. The code above will take the futex
- * and return happy.
- */
- if (curval & FUTEX_OWNER_DIED) {
- ownerdied = 1;
- goto retry_locked;
- }
default:
- goto out_unlock_release_sem;
+ goto out_unlock_put_key;
}
}
}
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 (!ret) {
- /*
- * 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 != curr)
- ret = fixup_pi_state_owner(uaddr, &q, curr, fshared);
- } else {
- /*
- * 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 == curr) {
- /*
- * 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))
- ret = 0;
- else {
- /*
- * 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. We can access the
- * rt_mutex_owner without locking, as
- * the other task is now blocked on
- * the hash bucket lock. Fix the state
- * up.
- */
- struct task_struct *owner;
- int res;
-
- owner = rt_mutex_owner(&q.pi_state->pi_mutex);
- res = fixup_pi_state_owner(uaddr, &q, owner,
- fshared);
-
- /* propagate -EFAULT, if the fixup failed */
- if (res)
- ret = res;
- }
- } else {
- /*
- * Paranoia check. If we did not take the lock
- * in the trylock above, then we should not be
- * the owner of the rtmutex, neither the real
- * nor the pending one:
- */
- if (rt_mutex_owner(&q.pi_state->pi_mutex) == curr)
- printk(KERN_ERR "futex_lock_pi: ret = %d "
- "pi-mutex: %p pi-state %p\n", ret,
- q.pi_state->pi_mutex.owner,
- q.pi_state->owner);
- }
- }
+ /*
+ * 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);
- if (to)
- destroy_hrtimer_on_stack(&to->timer);
- return ret != -EINTR ? ret : -ERESTARTNOINTR;
+ goto out_put_key;
- out_unlock_release_sem:
+out_unlock_put_key:
queue_unlock(&q, hb);
- out_release_sem:
- put_futex_key(fshared, &q.key);
+out_put_key:
+ put_futex_key(&q.key);
+out:
if (to)
destroy_hrtimer_on_stack(&to->timer);
- return ret;
+ return ret != -EINTR ? ret : -ERESTARTNOINTR;
- uaddr_faulted:
- /*
- * We have to r/w *(int __user *)uaddr, 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.
- *
- * ... and hb->lock. :-) --ANK
- */
+uaddr_faulted:
queue_unlock(&q, hb);
- if (attempt++) {
- ret = futex_handle_fault((unsigned long)uaddr, attempt);
- if (ret)
- goto out_release_sem;
- goto retry_unlocked;
- }
+ ret = fault_in_user_writeable(uaddr);
+ if (ret)
+ goto out_put_key;
- ret = get_user(uval, uaddr);
- if (!ret && (uval != -EFAULT))
- goto retry;
+ if (!(flags & FLAGS_SHARED))
+ goto retry_private;
- if (to)
- destroy_hrtimer_on_stack(&to->timer);
- return ret;
+ put_futex_key(&q.key);
+ goto retry;
}
/*
* 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, int fshared)
+static int futex_unlock_pi(u32 __user *uaddr, unsigned int flags)
{
struct futex_hash_bucket *hb;
struct futex_q *this, *next;
u32 uval;
struct plist_head *head;
union futex_key key = FUTEX_KEY_INIT;
- int ret, attempt = 0;
+ int ret;
retry:
if (get_user(uval, uaddr))
if ((uval & FUTEX_TID_MASK) != task_pid_vnr(current))
return -EPERM;
- ret = get_futex_key(uaddr, fshared, &key);
+ ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key);
if (unlikely(ret != 0))
goto out;
hb = hash_futex(&key);
-retry_unlocked:
spin_lock(&hb->lock);
/*
out_unlock:
spin_unlock(&hb->lock);
-out:
- put_futex_key(fshared, &key);
+ put_futex_key(&key);
+out:
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.
+ *
+ * Returns
+ * 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;
+
/*
- * We have to r/w *(int __user *)uaddr, 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.
- *
- * ... and hb->lock. --ANK
+ * 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, &q->list.plist);
+
+ /* 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
+ * @clockrt: whether to use CLOCK_REALTIME (1) or CLOCK_MONOTONIC (0)
+ * @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. 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 wouldn't 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.
+ *
+ * Returns:
+ * 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;
+ union futex_key key2 = FUTEX_KEY_INIT;
+ struct futex_q q = futex_q_init;
+ int res, ret;
+
+ 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.
+ */
+ debug_rt_mutex_init_waiter(&rt_waiter);
+ rt_waiter.task = NULL;
+
+ ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2);
+ 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;
+
+ /* Queue the futex_q, drop the hb lock, wait for wakeup. */
+ futex_wait_queue_me(hb, &q, to);
+
+ spin_lock(&hb->lock);
+ ret = handle_early_requeue_pi_wakeup(hb, &q, &key2, to);
spin_unlock(&hb->lock);
+ if (ret)
+ goto out_put_keys;
- if (attempt++) {
- ret = futex_handle_fault((unsigned long)uaddr, attempt);
- if (ret)
- goto out;
- uval = 0;
- goto retry_unlocked;
+ /*
+ * In order for us to be here, we know our q.key == key2, and since
+ * we took the hb->lock above, we also know that futex_requeue() has
+ * completed and we no longer have to concern ourselves with a wakeup
+ * race with the atomic proxy lock acquisition by the requeue code. The
+ * futex_requeue dropped our key1 reference and incremented our key2
+ * reference count.
+ */
+
+ /* 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(q.lock_ptr);
+ ret = fixup_pi_state_owner(uaddr2, &q, current);
+ spin_unlock(q.lock_ptr);
+ }
+ } 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, 1);
+ debug_rt_mutex_free_waiter(&rt_waiter);
+
+ spin_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);
}
- ret = get_user(uval, uaddr);
- if (!ret && (uval != -EFAULT))
- goto retry;
+ /*
+ * 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 (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;
}
*/
/**
- * 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
+ * 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
*/
-asmlinkage long
-sys_set_robust_list(struct robust_list_head __user *head,
- size_t len)
+SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head,
+ size_t, len)
{
if (!futex_cmpxchg_enabled)
return -ENOSYS;
}
/**
- * 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
+ * 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
*/
-asmlinkage long
-sys_get_robust_list(int pid, struct robust_list_head __user * __user *head_ptr,
- size_t __user *len_ptr)
+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;
+ const struct cred *cred = current_cred(), *pcred;
if (!futex_cmpxchg_enabled)
return -ENOSYS;
if (!p)
goto err_unlock;
ret = -EPERM;
- if ((current->euid != p->euid) && (current->euid != p->uid) &&
- !capable(CAP_SYS_PTRACE))
+ pcred = __task_cred(p);
+ if (cred->euid != pcred->euid &&
+ cred->euid != pcred->uid &&
+ !capable(CAP_SYS_PTRACE))
goto err_unlock;
head = p->robust_list;
rcu_read_unlock();
*/
static inline int fetch_robust_entry(struct robust_list __user **entry,
struct robust_list __user * __user *head,
- int *pi)
+ unsigned int *pi)
{
unsigned long uentry;
{
struct robust_list_head __user *head = curr->robust_list;
struct robust_list __user *entry, *next_entry, *pending;
- unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip;
+ unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
+ unsigned int uninitialized_var(next_pi);
unsigned long futex_offset;
int rc;
long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
u32 __user *uaddr2, u32 val2, u32 val3)
{
- int clockrt, ret = -ENOSYS;
- int cmd = op & FUTEX_CMD_MASK;
- int fshared = 0;
+ int ret = -ENOSYS, cmd = op & FUTEX_CMD_MASK;
+ unsigned int flags = 0;
if (!(op & FUTEX_PRIVATE_FLAG))
- fshared = 1;
+ flags |= FLAGS_SHARED;
- clockrt = op & FUTEX_CLOCK_REALTIME;
- if (clockrt && cmd != FUTEX_WAIT_BITSET)
- return -ENOSYS;
+ if (op & FUTEX_CLOCK_REALTIME) {
+ flags |= FLAGS_CLOCKRT;
+ if (cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI)
+ return -ENOSYS;
+ }
switch (cmd) {
case FUTEX_WAIT:
val3 = FUTEX_BITSET_MATCH_ANY;
case FUTEX_WAIT_BITSET:
- ret = futex_wait(uaddr, fshared, val, timeout, val3, clockrt);
+ ret = futex_wait(uaddr, flags, val, timeout, val3);
break;
case FUTEX_WAKE:
val3 = FUTEX_BITSET_MATCH_ANY;
case FUTEX_WAKE_BITSET:
- ret = futex_wake(uaddr, fshared, val, val3);
+ ret = futex_wake(uaddr, flags, val, val3);
break;
case FUTEX_REQUEUE:
- ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, NULL);
+ ret = futex_requeue(uaddr, flags, uaddr2, val, val2, NULL, 0);
break;
case FUTEX_CMP_REQUEUE:
- ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3);
+ ret = futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 0);
break;
case FUTEX_WAKE_OP:
- ret = futex_wake_op(uaddr, fshared, uaddr2, val, val2, val3);
+ ret = futex_wake_op(uaddr, flags, uaddr2, val, val2, val3);
break;
case FUTEX_LOCK_PI:
if (futex_cmpxchg_enabled)
- ret = futex_lock_pi(uaddr, fshared, val, timeout, 0);
+ ret = futex_lock_pi(uaddr, flags, val, timeout, 0);
break;
case FUTEX_UNLOCK_PI:
if (futex_cmpxchg_enabled)
- ret = futex_unlock_pi(uaddr, fshared);
+ ret = futex_unlock_pi(uaddr, flags);
break;
case FUTEX_TRYLOCK_PI:
if (futex_cmpxchg_enabled)
- ret = futex_lock_pi(uaddr, fshared, 0, timeout, 1);
+ ret = futex_lock_pi(uaddr, flags, 0, timeout, 1);
+ break;
+ case FUTEX_WAIT_REQUEUE_PI:
+ val3 = FUTEX_BITSET_MATCH_ANY;
+ ret = futex_wait_requeue_pi(uaddr, flags, val, timeout, val3,
+ uaddr2);
+ break;
+ case FUTEX_CMP_REQUEUE_PI:
+ ret = futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 1);
break;
default:
ret = -ENOSYS;
}
-asmlinkage long sys_futex(u32 __user *uaddr, int op, u32 val,
- struct timespec __user *utime, u32 __user *uaddr2,
- u32 val3)
+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;
int cmd = op & FUTEX_CMD_MASK;
if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
- cmd == FUTEX_WAIT_BITSET)) {
+ cmd == FUTEX_WAIT_BITSET ||
+ cmd == FUTEX_WAIT_REQUEUE_PI)) {
if (copy_from_user(&ts, utime, sizeof(ts)) != 0)
return -EFAULT;
if (!timespec_valid(&ts))
tp = &t;
}
/*
- * requeue parameter in 'utime' if cmd == FUTEX_REQUEUE.
+ * 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_WAKE_OP)
+ cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP)
val2 = (u32) (unsigned long) utime;
return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
* 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
+ * implementation, the non-functional ones will return
* -ENOSYS.
*/
curval = cmpxchg_futex_value_locked(NULL, 0, 0);
Code Review / linux-2.6.git / blobdiff