* 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->waiters, then make the second condition true.
+ * wake up q->waiter, then make the second condition true.
*/
struct futex_q {
struct plist_node list;
- wait_queue_head_t waiters;
+ /* There can only be a single waiter */
+ wait_queue_head_t waiter;
/* Which hash list lock to use: */
spinlock_t *lock_ptr;
/* Key which the futex is hashed on: */
union futex_key key;
- /* For fd, sigio sent using these: */
- int fd;
- struct file *filp;
-
/* Optional priority inheritance state: */
struct futex_pi_state *pi_state;
struct task_struct *task;
};
/*
- * 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 struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS];
-/* Futex-fs vfsmount entry: */
-static struct vfsmount *futex_mnt;
-
-/*
- * Take mm->mmap_sem, when futex is shared
- */
-static inline void futex_lock_mm(struct rw_semaphore *fshared)
-{
- if (fshared)
- down_read(fshared);
-}
-
-/*
- * Release mm->mmap_sem, when the futex is shared
- */
-static inline void futex_unlock_mm(struct rw_semaphore *fshared)
-{
- if (fshared)
- up_read(fshared);
-}
-
/*
* We hash on the keys returned from get_futex_key (see below).
*/
&& key1->both.offset == key2->both.offset);
}
+/*
+ * Take a reference to the resource addressed by a key.
+ * Can be called while holding spinlocks.
+ *
+ */
+static void get_futex_key_refs(union futex_key *key)
+{
+ if (!key->both.ptr)
+ return;
+
+ switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
+ case FUT_OFF_INODE:
+ atomic_inc(&key->shared.inode->i_count);
+ break;
+ case FUT_OFF_MMSHARED:
+ atomic_inc(&key->private.mm->mm_count);
+ break;
+ }
+}
+
+/*
+ * Drop a reference to the resource addressed by a key.
+ * The hash bucket spinlock must not be held.
+ */
+static void drop_futex_key_refs(union futex_key *key)
+{
+ if (!key->both.ptr) {
+ /* If we're here then we tried to put a key we failed to get */
+ WARN_ON_ONCE(1);
+ return;
+ }
+
+ switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
+ case FUT_OFF_INODE:
+ iput(key->shared.inode);
+ break;
+ case FUT_OFF_MMSHARED:
+ mmdrop(key->private.mm);
+ break;
+ }
+}
+
/**
* get_futex_key - Get parameters which are the keys for a futex.
* @uaddr: virtual address of the futex
- * @shared: NULL for a PROCESS_PRIVATE futex,
- * ¤t->mm->mmap_sem for a PROCESS_SHARED 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)
*
* 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, struct rw_semaphore *fshared,
- union futex_key *key)
+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 vm_area_struct *vma;
struct page *page;
int err;
* but access_ok() should be faster than find_vma()
*/
if (!fshared) {
- if (unlikely(!access_ok(VERIFY_WRITE, uaddr, sizeof(u32))))
+ if (unlikely(!access_ok(rw, uaddr, sizeof(u32))))
return -EFAULT;
key->private.mm = mm;
key->private.address = address;
+ get_futex_key_refs(key);
return 0;
}
- /*
- * The futex is hashed differently depending on whether
- * it's in a shared or private mapping. So check vma first.
- */
- vma = find_extend_vma(mm, address);
- if (unlikely(!vma))
- return -EFAULT;
- /*
- * Permissions.
- */
- if (unlikely((vma->vm_flags & (VM_IO|VM_READ)) != VM_READ))
- return (vma->vm_flags & VM_IO) ? -EPERM : -EACCES;
+again:
+ err = get_user_pages_fast(address, 1, rw == VERIFY_WRITE, &page);
+ if (err < 0)
+ return err;
+
+ lock_page(page);
+ if (!page->mapping) {
+ unlock_page(page);
+ put_page(page);
+ goto again;
+ }
/*
* Private mappings are handled in a simple way.
*
* NOTE: When userspace waits on a MAP_SHARED mapping, even if
* it's a read-only handle, it's expected that futexes attach to
- * the object not the particular process. Therefore we use
- * VM_MAYSHARE here, not VM_SHARED which is restricted to shared
- * mappings of _writable_ handles.
+ * the object not the particular process.
*/
- if (likely(!(vma->vm_flags & VM_MAYSHARE))) {
- key->both.offset |= FUT_OFF_MMSHARED; /* reference taken on mm */
+ if (PageAnon(page)) {
+ key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */
key->private.mm = mm;
key->private.address = address;
- return 0;
+ } else {
+ key->both.offset |= FUT_OFF_INODE; /* inode-based key */
+ key->shared.inode = page->mapping->host;
+ key->shared.pgoff = page->index;
}
- /*
- * Linear file mappings are also simple.
- */
- key->shared.inode = vma->vm_file->f_path.dentry->d_inode;
- key->both.offset |= FUT_OFF_INODE; /* inode-based key. */
- if (likely(!(vma->vm_flags & VM_NONLINEAR))) {
- key->shared.pgoff = (((address - vma->vm_start) >> PAGE_SHIFT)
- + vma->vm_pgoff);
- return 0;
- }
+ get_futex_key_refs(key);
- /*
- * We could walk the page table to read the non-linear
- * pte, and get the page index without fetching the page
- * from swap. But that's a lot of code to duplicate here
- * for a rare case, so we simply fetch the page.
- */
- err = get_user_pages(current, mm, address, 1, 0, 0, &page, NULL);
- if (err >= 0) {
- key->shared.pgoff =
- page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
- put_page(page);
- return 0;
- }
- return err;
+ unlock_page(page);
+ put_page(page);
+ return 0;
}
-/*
- * 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)
+static inline
+void put_futex_key(int fshared, union futex_key *key)
{
- if (key->both.ptr == NULL)
- return;
- switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
- case FUT_OFF_INODE:
- atomic_inc(&key->shared.inode->i_count);
- break;
- case FUT_OFF_MMSHARED:
- atomic_inc(&key->private.mm->mm_count);
- break;
- }
-}
-
-/*
- * Drop a reference to the resource addressed by a key.
- * The hash bucket spinlock must not be held.
- */
-static void drop_futex_key_refs(union futex_key *key)
-{
- if (!key->both.ptr)
- 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;
- }
+ drop_futex_key_refs(key);
}
static u32 cmpxchg_futex_value_locked(u32 __user *uaddr, u32 uval, u32 newval)
return ret ? -EFAULT : 0;
}
-/*
- * Fault handling.
- * if fshared is non NULL, current->mm->mmap_sem is already held
- */
-static int futex_handle_fault(unsigned long address,
- struct rw_semaphore *fshared, int attempt)
-{
- struct vm_area_struct * vma;
- struct mm_struct *mm = current->mm;
- int ret = -EFAULT;
-
- if (attempt > 2)
- return ret;
-
- if (!fshared)
- 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++;
- }
- }
- if (!fshared)
- up_read(&mm->mmap_sem);
- return ret;
-}
/*
* PI code:
/* 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;
static struct task_struct * futex_find_get_task(pid_t pid)
{
struct task_struct *p;
+ const struct cred *cred = current_cred(), *pcred;
rcu_read_lock();
p = find_task_by_vpid(pid);
- if (!p || ((current->euid != p->euid) && (current->euid != p->uid)))
+ if (!p) {
p = ERR_PTR(-ESRCH);
- else
- get_task_struct(p);
+ } else {
+ pcred = __task_cred(p);
+ if (cred->euid != pcred->euid &&
+ cred->euid != pcred->uid)
+ p = ERR_PTR(-ESRCH);
+ else
+ get_task_struct(p);
+ }
rcu_read_unlock();
struct list_head *next, *head = &curr->pi_state_list;
struct futex_pi_state *pi_state;
struct futex_hash_bucket *hb;
- union futex_key key;
+ union futex_key key = FUTEX_KEY_INIT;
if (!futex_cmpxchg_enabled)
return;
static void wake_futex(struct futex_q *q)
{
plist_del(&q->list, &q->list.plist);
- if (q->filp)
- send_sigio(&q->filp->f_owner, q->fd, POLL_IN);
/*
* The lock in wake_up_all() is a crucial memory barrier after the
* plist_del() and also before assigning to q->lock_ptr.
*/
- wake_up_all(&q->waiters);
+ wake_up(&q->waiter);
/*
* The waiting task can free the futex_q as soon as this is written,
* without taking any locks. This must come last.
*
- * A memory barrier is required here to prevent the following store
- * to lock_ptr from getting ahead of the wakeup. Clearing the lock
- * at the end of wake_up_all() does not prevent this store from
- * moving.
+ * 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() does not prevent this store from moving.
*/
smp_wmb();
q->lock_ptr = NULL;
}
}
+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, struct rw_semaphore *fshared,
- int nr_wake, u32 bitset)
+static int futex_wake(u32 __user *uaddr, int fshared, int nr_wake, u32 bitset)
{
struct futex_hash_bucket *hb;
struct futex_q *this, *next;
struct plist_head *head;
- union futex_key key;
+ union futex_key key = FUTEX_KEY_INIT;
int ret;
if (!bitset)
return -EINVAL;
- futex_lock_mm(fshared);
-
- ret = get_futex_key(uaddr, fshared, &key);
+ ret = get_futex_key(uaddr, fshared, &key, VERIFY_READ);
if (unlikely(ret != 0))
goto out;
}
spin_unlock(&hb->lock);
+ put_futex_key(fshared, &key);
out:
- futex_unlock_mm(fshared);
return ret;
}
* to this virtual address:
*/
static int
-futex_wake_op(u32 __user *uaddr1, struct rw_semaphore *fshared,
- u32 __user *uaddr2,
+futex_wake_op(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
int nr_wake, int nr_wake2, int op)
{
- union futex_key key1, key2;
+ 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:
- futex_lock_mm(fshared);
-
- ret = get_futex_key(uaddr1, fshared, &key1);
+retry:
+ ret = get_futex_key(uaddr1, fshared, &key1, VERIFY_READ);
if (unlikely(ret != 0))
goto out;
- ret = get_futex_key(uaddr2, fshared, &key2);
+ ret = get_futex_key(uaddr2, fshared, &key2, VERIFY_WRITE);
if (unlikely(ret != 0))
- goto out;
+ goto out_put_key1;
hb1 = hash_futex(&key1);
hb2 = hash_futex(&key2);
-retry:
double_lock_hb(hb1, hb2);
-
+retry_private:
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,
- fshared, attempt);
- if (ret)
- goto out;
- goto retry;
+ goto out_put_keys;
}
- /*
- * If we would have faulted, release mmap_sem,
- * fault it in and start all over again.
- */
- futex_unlock_mm(fshared);
-
ret = get_user(dummy, uaddr2);
if (ret)
- return ret;
+ goto out_put_keys;
+
+ if (!fshared)
+ goto retry_private;
- goto retryfull;
+ put_futex_key(fshared, &key2);
+ put_futex_key(fshared, &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(fshared, &key2);
+out_put_key1:
+ put_futex_key(fshared, &key1);
out:
- futex_unlock_mm(fshared);
-
return ret;
}
* Requeue all waiters hashed on one physical page to another
* physical page.
*/
-static int futex_requeue(u32 __user *uaddr1, struct rw_semaphore *fshared,
- u32 __user *uaddr2,
+static int futex_requeue(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
int nr_wake, int nr_requeue, u32 *cmpval)
{
- union futex_key key1, 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:
- futex_lock_mm(fshared);
-
- ret = get_futex_key(uaddr1, fshared, &key1);
+retry:
+ ret = get_futex_key(uaddr1, fshared, &key1, VERIFY_READ);
if (unlikely(ret != 0))
goto out;
- ret = get_futex_key(uaddr2, fshared, &key2);
+ ret = get_futex_key(uaddr2, fshared, &key2, VERIFY_READ);
if (unlikely(ret != 0))
- goto out;
+ goto out_put_key1;
hb1 = hash_futex(&key1);
hb2 = hash_futex(&key2);
+retry_private:
double_lock_hb(hb1, hb2);
if (likely(cmpval != NULL)) {
ret = get_futex_value_locked(&curval, uaddr1);
if (unlikely(ret)) {
- spin_unlock(&hb1->lock);
- if (hb1 != hb2)
- spin_unlock(&hb2->lock);
-
- /*
- * If we would have faulted, release mmap_sem, fault
- * it in and start all over again.
- */
- futex_unlock_mm(fshared);
+ double_unlock_hb(hb1, hb2);
ret = get_user(curval, uaddr1);
+ if (ret)
+ goto out_put_keys;
- if (!ret)
- goto retry;
+ if (!fshared)
+ goto retry_private;
- return ret;
+ put_futex_key(fshared, &key2);
+ put_futex_key(fshared, &key1);
+ goto retry;
}
if (curval != *cmpval) {
ret = -EAGAIN;
}
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(fshared, &key2);
+out_put_key1:
+ put_futex_key(fshared, &key1);
out:
- futex_unlock_mm(fshared);
return ret;
}
/* The key must be already stored in q->key. */
-static inline struct futex_hash_bucket *
-queue_lock(struct futex_q *q, int fd, struct file *filp)
+static inline struct futex_hash_bucket *queue_lock(struct futex_q *q)
{
struct futex_hash_bucket *hb;
- q->fd = fd;
- q->filp = filp;
-
- init_waitqueue_head(&q->waiters);
+ init_waitqueue_head(&q->waiter);
get_futex_key_refs(&q->key);
hb = hash_futex(&q->key);
return hb;
}
-static inline void __queue_me(struct futex_q *q, struct futex_hash_bucket *hb)
+static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb)
{
int prio;
* exactly once. They are called with the hashed spinlock held.
*/
-/* The key must be already stored in q->key. */
-static void queue_me(struct futex_q *q, int fd, struct file *filp)
-{
- struct futex_hash_bucket *hb;
-
- hb = queue_lock(q, fd, filp);
- __queue_me(q, hb);
-}
-
/* Return 1 if we were still queued (ie. 0 means we were woken) */
static int unqueue_me(struct futex_q *q)
{
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) {
* private futexes.
*/
static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
- struct task_struct *newowner)
+ struct task_struct *newowner, int fshared)
{
u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS;
struct futex_pi_state *pi_state = q->pi_state;
+ struct task_struct *oldowner = pi_state->owner;
u32 uval, curval, newval;
int ret;
/* Owner died? */
+ if (!pi_state->owner)
+ newtid |= FUTEX_OWNER_DIED;
+
+ /*
+ * We are here either because we stole the rtmutex from the
+ * pending owner or we are the pending owner which failed to
+ * get the rtmutex. We have to replace the pending owner TID
+ * in the user space variable. This must be atomic as we have
+ * to preserve the owner died bit here.
+ *
+ * Note: We write the user space value _before_ changing the pi_state
+ * because we can fault here. Imagine swapped out pages or a fork
+ * that marked all the anonymous memory readonly for cow.
+ *
+ * Modifying pi_state _before_ the user space value would
+ * leave the pi_state in an inconsistent state when we fault
+ * here, because we need to drop the hash bucket lock to
+ * handle the fault. This might be observed in the PID check
+ * in lookup_pi_state.
+ */
+retry:
+ if (get_futex_value_locked(&uval, uaddr))
+ goto handle_fault;
+
+ while (1) {
+ newval = (uval & FUTEX_OWNER_DIED) | newtid;
+
+ curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
+
+ if (curval == -EFAULT)
+ goto handle_fault;
+ if (curval == uval)
+ break;
+ uval = curval;
+ }
+
+ /*
+ * We fixed up user space. Now we need to fix the pi_state
+ * itself.
+ */
if (pi_state->owner != NULL) {
spin_lock_irq(&pi_state->owner->pi_lock);
WARN_ON(list_empty(&pi_state->list));
list_del_init(&pi_state->list);
spin_unlock_irq(&pi_state->owner->pi_lock);
- } else
- newtid |= FUTEX_OWNER_DIED;
+ }
pi_state->owner = newowner;
WARN_ON(!list_empty(&pi_state->list));
list_add(&pi_state->list, &newowner->pi_state_list);
spin_unlock_irq(&newowner->pi_lock);
+ return 0;
/*
- * We own it, so we have to replace the pending owner
- * TID. This must be atomic as we have preserve the
- * owner died bit here.
+ * To handle the page fault we need to drop the hash bucket
+ * lock here. That gives the other task (either the pending
+ * owner itself or the task which stole the rtmutex) the
+ * chance to try the fixup of the pi_state. So once we are
+ * back from handling the fault we need to check the pi_state
+ * after reacquiring the hash bucket lock and before trying to
+ * do another fixup. When the fixup has been done already we
+ * simply return.
*/
- ret = get_futex_value_locked(&uval, uaddr);
+handle_fault:
+ spin_unlock(q->lock_ptr);
- while (!ret) {
- newval = (uval & FUTEX_OWNER_DIED) | newtid;
+ ret = get_user(uval, uaddr);
- curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
+ spin_lock(q->lock_ptr);
- if (curval == -EFAULT)
- ret = -EFAULT;
- if (curval == uval)
- break;
- uval = curval;
- }
- return ret;
+ /*
+ * Check if someone else fixed it for us:
+ */
+ if (pi_state->owner != oldowner)
+ return 0;
+
+ if (ret)
+ return ret;
+
+ goto retry;
}
/*
* In case we must use restart_block to restart a futex_wait,
* we encode in the 'flags' shared capability
*/
-#define FLAGS_SHARED 1
+#define FLAGS_SHARED 0x01
+#define FLAGS_CLOCKRT 0x02
static long futex_wait_restart(struct restart_block *restart);
-static int futex_wait(u32 __user *uaddr, struct rw_semaphore *fshared,
- u32 val, ktime_t *abs_time, u32 bitset)
+static int futex_wait(u32 __user *uaddr, int fshared,
+ u32 val, ktime_t *abs_time, u32 bitset, int clockrt)
{
struct task_struct *curr = current;
+ struct restart_block *restart;
DECLARE_WAITQUEUE(wait, curr);
struct futex_hash_bucket *hb;
struct futex_q q;
q.pi_state = NULL;
q.bitset = bitset;
- retry:
- futex_lock_mm(fshared);
-
- ret = get_futex_key(uaddr, fshared, &q.key);
+retry:
+ q.key = FUTEX_KEY_INIT;
+ ret = get_futex_key(uaddr, fshared, &q.key, VERIFY_READ);
if (unlikely(ret != 0))
- goto out_release_sem;
+ goto out;
- hb = queue_lock(&q, -1, NULL);
+retry_private:
+ hb = queue_lock(&q);
/*
- * Access the page AFTER the futex is queued.
+ * Access the page AFTER the hash-bucket is locked.
* Order is important:
*
* Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val);
* 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
+ * For shared futexes, we hold the mmap semaphore, so the mapping
* cannot have changed since we looked it up in get_futex_key.
*/
ret = get_futex_value_locked(&uval, uaddr);
if (unlikely(ret)) {
queue_unlock(&q, hb);
- /*
- * If we would have faulted, release mmap_sem, fault it in and
- * start all over again.
- */
- futex_unlock_mm(fshared);
-
ret = get_user(uval, uaddr);
+ if (ret)
+ goto out_put_key;
- if (!ret)
- goto retry;
- return ret;
+ if (!fshared)
+ goto retry_private;
+
+ put_futex_key(fshared, &q.key);
+ goto retry;
}
ret = -EWOULDBLOCK;
- if (uval != val)
- goto out_unlock_release_sem;
+ if (unlikely(uval != val)) {
+ queue_unlock(&q, hb);
+ goto out_put_key;
+ }
/* Only actually queue if *uaddr contained val. */
- __queue_me(&q, hb);
-
- /*
- * Now the futex is queued and we have checked the data, we
- * don't want to hold mmap_sem while we sleep.
- */
- futex_unlock_mm(fshared);
+ queue_me(&q, hb);
/*
* There might have been scheduling since the queue_me(), as we
/* add_wait_queue is the barrier after __set_current_state. */
__set_current_state(TASK_INTERRUPTIBLE);
- add_wait_queue(&q.waiters, &wait);
+ 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 (!abs_time)
schedule();
else {
- hrtimer_init(&t.timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+ hrtimer_init_on_stack(&t.timer,
+ clockrt ? CLOCK_REALTIME :
+ CLOCK_MONOTONIC,
+ HRTIMER_MODE_ABS);
hrtimer_init_sleeper(&t, current);
- t.timer.expires = *abs_time;
+ hrtimer_set_expires_range_ns(&t.timer, *abs_time,
+ current->timer_slack_ns);
- hrtimer_start(&t.timer, t.timer.expires, HRTIMER_MODE_ABS);
+ hrtimer_start_expires(&t.timer, HRTIMER_MODE_ABS);
if (!hrtimer_active(&t.timer))
t.task = NULL;
/* Flag if a timeout occured */
rem = (t.task == NULL);
+
+ destroy_hrtimer_on_stack(&t.timer);
}
}
__set_current_state(TASK_RUNNING);
*/
/* If we were woken (and unqueued), we succeeded, whatever. */
+ ret = 0;
if (!unqueue_me(&q))
- return 0;
+ goto out_put_key;
+ ret = -ETIMEDOUT;
if (rem)
- return -ETIMEDOUT;
+ goto out_put_key;
/*
* We expect signal_pending(current), but another thread may
* have handled it for us already.
*/
+ 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;
- return -ERESTART_RESTARTBLOCK;
- }
+ goto out_put_key;
- out_unlock_release_sem:
- queue_unlock(&q, hb);
+ 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;
+
+ ret = -ERESTART_RESTARTBLOCK;
- out_release_sem:
- futex_unlock_mm(fshared);
+out_put_key:
+ put_futex_key(fshared, &q.key);
+out:
return ret;
}
static long futex_wait_restart(struct restart_block *restart)
{
u32 __user *uaddr = (u32 __user *)restart->futex.uaddr;
- struct rw_semaphore *fshared = NULL;
+ int fshared = 0;
ktime_t t;
t.tv64 = restart->futex.time;
restart->fn = do_no_restart_syscall;
if (restart->futex.flags & FLAGS_SHARED)
- fshared = ¤t->mm->mmap_sem;
+ fshared = 1;
return (long)futex_wait(uaddr, fshared, restart->futex.val, &t,
- restart->futex.bitset);
+ restart->futex.bitset,
+ restart->futex.flags & FLAGS_CLOCKRT);
}
* 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, struct rw_semaphore *fshared,
+static int futex_lock_pi(u32 __user *uaddr, int fshared,
int detect, ktime_t *time, int trylock)
{
struct hrtimer_sleeper timeout, *to = NULL;
struct futex_hash_bucket *hb;
u32 uval, newval, curval;
struct futex_q q;
- int ret, lock_taken, ownerdied = 0, attempt = 0;
+ int ret, lock_taken, ownerdied = 0;
if (refill_pi_state_cache())
return -ENOMEM;
if (time) {
to = &timeout;
- hrtimer_init(&to->timer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
+ hrtimer_init_on_stack(&to->timer, CLOCK_REALTIME,
+ HRTIMER_MODE_ABS);
hrtimer_init_sleeper(to, current);
- to->timer.expires = *time;
+ hrtimer_set_expires(&to->timer, *time);
}
q.pi_state = NULL;
- retry:
- futex_lock_mm(fshared);
-
- ret = get_futex_key(uaddr, fshared, &q.key);
+retry:
+ q.key = FUTEX_KEY_INIT;
+ ret = get_futex_key(uaddr, fshared, &q.key, VERIFY_WRITE);
if (unlikely(ret != 0))
- goto out_release_sem;
+ goto out;
- retry_unlocked:
- hb = queue_lock(&q, -1, NULL);
+retry_private:
+ hb = queue_lock(&q);
- retry_locked:
+retry_locked:
ret = lock_taken = 0;
/*
*/
if (unlikely((curval & FUTEX_TID_MASK) == task_pid_vnr(current))) {
ret = -EDEADLK;
- goto out_unlock_release_sem;
+ goto out_unlock_put_key;
}
/*
* Surprise - we got the lock. Just return to userspace:
*/
if (unlikely(!curval))
- goto out_unlock_release_sem;
+ goto out_unlock_put_key;
uval = curval;
* We took the lock due to owner died take over.
*/
if (unlikely(lock_taken))
- goto out_unlock_release_sem;
+ goto out_unlock_put_key;
/*
* We dont have the lock. Look up the PI state (or create it if
* exit to complete.
*/
queue_unlock(&q, hb);
- futex_unlock_mm(fshared);
+ put_futex_key(fshared, &q.key);
cond_resched();
goto retry;
goto retry_locked;
}
default:
- goto out_unlock_release_sem;
+ goto out_unlock_put_key;
}
}
/*
* Only actually queue now that the atomic ops are done:
*/
- __queue_me(&q, hb);
-
- /*
- * Now the futex is queued and we have checked the data, we
- * don't want to hold mmap_sem while we sleep.
- */
- futex_unlock_mm(fshared);
+ queue_me(&q, hb);
WARN_ON(!q.pi_state);
/*
ret = ret ? 0 : -EWOULDBLOCK;
}
- futex_lock_mm(fshared);
spin_lock(q.lock_ptr);
if (!ret) {
* that case:
*/
if (q.pi_state->owner != curr)
- ret = fixup_pi_state_owner(uaddr, &q, curr);
+ ret = fixup_pi_state_owner(uaddr, &q, curr, fshared);
} else {
/*
* Catch the rare case, where the lock was released
int res;
owner = rt_mutex_owner(&q.pi_state->pi_mutex);
- res = fixup_pi_state_owner(uaddr, &q, owner);
+ res = fixup_pi_state_owner(uaddr, &q, owner,
+ fshared);
/* propagate -EFAULT, if the fixup failed */
if (res)
}
}
+ /*
+ * If fixup_pi_state_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);
- futex_unlock_mm(fshared);
+ if (to)
+ destroy_hrtimer_on_stack(&to->timer);
return ret != -EINTR ? ret : -ERESTARTNOINTR;
- out_unlock_release_sem:
+out_unlock_put_key:
queue_unlock(&q, hb);
- out_release_sem:
- futex_unlock_mm(fshared);
+out_put_key:
+ put_futex_key(fshared, &q.key);
+out:
+ if (to)
+ destroy_hrtimer_on_stack(&to->timer);
return ret;
- uaddr_faulted:
+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
+ * We have to r/w *(int __user *)uaddr, and we have to modify it
+ * atomically. Therefore, if we continue to fault after get_user()
+ * below, we need to handle the fault ourselves, while still holding
+ * the mmap_sem. This can occur if the uaddr is under contention as
+ * we have to drop the mmap_sem in order to call get_user().
*/
queue_unlock(&q, hb);
- if (attempt++) {
- ret = futex_handle_fault((unsigned long)uaddr, fshared,
- attempt);
- if (ret)
- goto out_release_sem;
- goto retry_unlocked;
- }
-
- futex_unlock_mm(fshared);
-
ret = get_user(uval, uaddr);
- if (!ret && (uval != -EFAULT))
- goto retry;
+ if (ret)
+ goto out_put_key;
- return ret;
+ if (!fshared)
+ goto retry_private;
+
+ put_futex_key(fshared, &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, struct rw_semaphore *fshared)
+static int futex_unlock_pi(u32 __user *uaddr, int fshared)
{
struct futex_hash_bucket *hb;
struct futex_q *this, *next;
u32 uval;
struct plist_head *head;
- union futex_key key;
- int ret, attempt = 0;
+ union futex_key key = FUTEX_KEY_INIT;
+ int ret;
retry:
if (get_user(uval, uaddr))
*/
if ((uval & FUTEX_TID_MASK) != task_pid_vnr(current))
return -EPERM;
- /*
- * First take all the futex related locks:
- */
- futex_lock_mm(fshared);
- ret = get_futex_key(uaddr, fshared, &key);
+ ret = get_futex_key(uaddr, fshared, &key, VERIFY_WRITE);
if (unlikely(ret != 0))
goto out;
hb = hash_futex(&key);
-retry_unlocked:
spin_lock(&hb->lock);
/*
out_unlock:
spin_unlock(&hb->lock);
-out:
- futex_unlock_mm(fshared);
+ put_futex_key(fshared, &key);
+out:
return ret;
pi_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
+ * We have to r/w *(int __user *)uaddr, and we have to modify it
+ * atomically. Therefore, if we continue to fault after get_user()
+ * below, we need to handle the fault ourselves, while still holding
+ * the mmap_sem. This can occur if the uaddr is under contention as
+ * we have to drop the mmap_sem in order to call get_user().
*/
spin_unlock(&hb->lock);
-
- if (attempt++) {
- ret = futex_handle_fault((unsigned long)uaddr, fshared,
- attempt);
- if (ret)
- goto out;
- uval = 0;
- goto retry_unlocked;
- }
-
- futex_unlock_mm(fshared);
+ put_futex_key(fshared, &key);
ret = get_user(uval, uaddr);
- if (!ret && (uval != -EFAULT))
+ if (!ret)
goto retry;
return ret;
}
-static int futex_close(struct inode *inode, struct file *filp)
-{
- struct futex_q *q = filp->private_data;
-
- unqueue_me(q);
- kfree(q);
-
- return 0;
-}
-
-/* This is one-shot: once it's gone off you need a new fd */
-static unsigned int futex_poll(struct file *filp,
- struct poll_table_struct *wait)
-{
- struct futex_q *q = filp->private_data;
- int ret = 0;
-
- poll_wait(filp, &q->waiters, wait);
-
- /*
- * plist_node_empty() is safe here without any lock.
- * q->lock_ptr != 0 is not safe, because of ordering against wakeup.
- */
- if (plist_node_empty(&q->list))
- ret = POLLIN | POLLRDNORM;
-
- return ret;
-}
-
-static const struct file_operations futex_fops = {
- .release = futex_close,
- .poll = futex_poll,
-};
-
-/*
- * Signal allows caller to avoid the race which would occur if they
- * set the sigio stuff up afterwards.
- */
-static int futex_fd(u32 __user *uaddr, int signal)
-{
- struct futex_q *q;
- struct file *filp;
- int ret, err;
- struct rw_semaphore *fshared;
- static unsigned long printk_interval;
-
- if (printk_timed_ratelimit(&printk_interval, 60 * 60 * 1000)) {
- printk(KERN_WARNING "Process `%s' used FUTEX_FD, which "
- "will be removed from the kernel in June 2007\n",
- current->comm);
- }
-
- ret = -EINVAL;
- if (!valid_signal(signal))
- goto out;
-
- ret = get_unused_fd();
- if (ret < 0)
- goto out;
- filp = get_empty_filp();
- if (!filp) {
- put_unused_fd(ret);
- ret = -ENFILE;
- goto out;
- }
- filp->f_op = &futex_fops;
- filp->f_path.mnt = mntget(futex_mnt);
- filp->f_path.dentry = dget(futex_mnt->mnt_root);
- filp->f_mapping = filp->f_path.dentry->d_inode->i_mapping;
-
- if (signal) {
- err = __f_setown(filp, task_pid(current), PIDTYPE_PID, 1);
- if (err < 0) {
- goto error;
- }
- filp->f_owner.signum = signal;
- }
-
- q = kmalloc(sizeof(*q), GFP_KERNEL);
- if (!q) {
- err = -ENOMEM;
- goto error;
- }
- q->pi_state = NULL;
-
- fshared = ¤t->mm->mmap_sem;
- down_read(fshared);
- err = get_futex_key(uaddr, fshared, &q->key);
-
- if (unlikely(err != 0)) {
- up_read(fshared);
- kfree(q);
- goto error;
- }
-
- /*
- * queue_me() must be called before releasing mmap_sem, because
- * key->shared.inode needs to be referenced while holding it.
- */
- filp->private_data = q;
-
- queue_me(q, ret, filp);
- up_read(fshared);
-
- /* Now we map fd to filp, so userspace can access it */
- fd_install(ret, filp);
-out:
- return ret;
-error:
- put_unused_fd(ret);
- put_filp(filp);
- ret = err;
- goto out;
-}
-
/*
* Support for robust futexes: the kernel cleans up held futexes at
* thread exit time.
* @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;
* @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();
* PI futexes happens in exit_pi_state():
*/
if (!pi && (uval & FUTEX_WAITERS))
- futex_wake(uaddr, &curr->mm->mmap_sem, 1,
- FUTEX_BITSET_MATCH_ANY);
+ futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY);
}
return 0;
}
long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
u32 __user *uaddr2, u32 val2, u32 val3)
{
- int ret = -ENOSYS;
+ int clockrt, ret = -ENOSYS;
int cmd = op & FUTEX_CMD_MASK;
- struct rw_semaphore *fshared = NULL;
+ int fshared = 0;
if (!(op & FUTEX_PRIVATE_FLAG))
- fshared = ¤t->mm->mmap_sem;
+ fshared = 1;
+
+ clockrt = op & FUTEX_CLOCK_REALTIME;
+ if (clockrt && cmd != FUTEX_WAIT_BITSET)
+ return -ENOSYS;
switch (cmd) {
case FUTEX_WAIT:
val3 = FUTEX_BITSET_MATCH_ANY;
case FUTEX_WAIT_BITSET:
- ret = futex_wait(uaddr, fshared, val, timeout, val3);
+ ret = futex_wait(uaddr, fshared, val, timeout, val3, clockrt);
break;
case FUTEX_WAKE:
val3 = FUTEX_BITSET_MATCH_ANY;
case FUTEX_WAKE_BITSET:
ret = futex_wake(uaddr, fshared, val, val3);
break;
- case FUTEX_FD:
- /* non-zero val means F_SETOWN(getpid()) & F_SETSIG(val) */
- ret = futex_fd(uaddr, val);
- break;
case FUTEX_REQUEUE:
ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, NULL);
break;
}
-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;
return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
}
-static int futexfs_get_sb(struct file_system_type *fs_type,
- int flags, const char *dev_name, void *data,
- struct vfsmount *mnt)
-{
- return get_sb_pseudo(fs_type, "futex", NULL, FUTEXFS_SUPER_MAGIC, mnt);
-}
-
-static struct file_system_type futex_fs_type = {
- .name = "futexfs",
- .get_sb = futexfs_get_sb,
- .kill_sb = kill_anon_super,
-};
-
static int __init futex_init(void)
{
u32 curval;
spin_lock_init(&futex_queues[i].lock);
}
- i = register_filesystem(&futex_fs_type);
- if (i)
- return i;
-
- futex_mnt = kern_mount(&futex_fs_type);
- if (IS_ERR(futex_mnt)) {
- unregister_filesystem(&futex_fs_type);
- return PTR_ERR(futex_mnt);
- }
-
return 0;
}
__initcall(futex_init);
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff