* Removed page pinning, fix privately mapped COW pages and other cleanups
* (C) Copyright 2003, 2004 Jamie Lokier
*
+ * Robust futex support started by Ingo Molnar
+ * (C) Copyright 2006 Red Hat Inc, All Rights Reserved
+ * Thanks to Thomas Gleixner for suggestions, analysis and fixes.
+ *
+ * PI-futex support started by Ingo Molnar and Thomas Gleixner
+ * Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
+ * Copyright (C) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com>
+ *
+ * PRIVATE futexes by Eric Dumazet
+ * Copyright (C) 2007 Eric Dumazet <dada1@cosmosbay.com>
+ *
* Thanks to Ben LaHaise for yelling "hashed waitqueues" loudly
* enough at me, Linus for the original (flawed) idea, Matthew
* Kirkwood for proof-of-concept implementation.
#include <linux/pagemap.h>
#include <linux/syscalls.h>
#include <linux/signal.h>
+#include <linux/module.h>
+#include <linux/magic.h>
+#include <linux/pid.h>
+#include <linux/nsproxy.h>
+
#include <asm/futex.h>
+#include "rtmutex_common.h"
+
+int __read_mostly futex_cmpxchg_enabled;
+
#define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)
/*
- * Futexes are matched on equal values of this key.
- * The key type depends on whether it's a shared or private mapping.
- * Don't rearrange members without looking at hash_futex().
- *
- * offset is aligned to a multiple of sizeof(u32) (== 4) by definition.
- * We set bit 0 to indicate if it's an inode-based key.
+ * Priority Inheritance state:
*/
-union futex_key {
- struct {
- unsigned long pgoff;
- struct inode *inode;
- int offset;
- } shared;
- struct {
- unsigned long uaddr;
- struct mm_struct *mm;
- int offset;
- } private;
- struct {
- unsigned long word;
- void *ptr;
- int offset;
- } both;
+struct futex_pi_state {
+ /*
+ * list of 'owned' pi_state instances - these have to be
+ * cleaned up in do_exit() if the task exits prematurely:
+ */
+ struct list_head list;
+
+ /*
+ * The PI object:
+ */
+ struct rt_mutex pi_mutex;
+
+ struct task_struct *owner;
+ atomic_t refcount;
+
+ union futex_key key;
};
/*
* we 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 list_empty(&q->list) || q->lock_ptr == 0.
+ * 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 list_head list;
- wait_queue_head_t waiters;
+ struct plist_node list;
+ /* There can only be a single waiter */
+ wait_queue_head_t waiter;
- /* Which hash list lock to use. */
+ /* Which hash list lock to use: */
spinlock_t *lock_ptr;
- /* Key which the futex is hashed on. */
+ /* 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;
+
+ /* Bitset for the optional bitmasked wakeup */
+ u32 bitset;
};
/*
* Split the global futex_lock into every hash list lock.
*/
struct futex_hash_bucket {
- spinlock_t lock;
- struct list_head chain;
+ spinlock_t lock;
+ struct plist_head chain;
};
static struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS];
-/* Futex-fs vfsmount entry: */
-static struct vfsmount *futex_mnt;
-
/*
* We hash on the keys returned from get_futex_key (see below).
*/
}
/*
- * Get parameters which are the keys for a futex.
+ * Take a reference to the resource addressed by a key.
+ * Can be called while holding spinlocks.
*
- * For shared mappings, it's (page->index, vma->vm_file->f_dentry->d_inode,
- * offset_within_page). For private mappings, it's (uaddr, current->mm).
- * We can usually work out the index without swapping in the page.
+ */
+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
+ * @key: address where result is stored.
*
- * Returns: 0, or negative error code.
+ * Returns a negative error code or 0
* The key words are stored in *key on success.
*
- * Should be called with ¤t->mm->mmap_sem but NOT any spinlocks.
+ * For shared mappings, it's (page->index, vma->vm_file->f_path.dentry->d_inode,
+ * offset_within_page). For private mappings, it's (uaddr, current->mm).
+ * We can usually work out the index without swapping in the page.
+ *
+ * fshared is NULL for PROCESS_PRIVATE futexes
+ * For other futexes, it points to ¤t->mm->mmap_sem and
+ * caller must have taken the reader lock. but NOT any spinlocks.
*/
-static int get_futex_key(unsigned long uaddr, 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 vm_area_struct *vma;
struct page *page;
int err;
/*
* The futex address must be "naturally" aligned.
*/
- key->both.offset = uaddr % PAGE_SIZE;
- if (unlikely((key->both.offset % sizeof(u32)) != 0))
+ key->both.offset = address % PAGE_SIZE;
+ if (unlikely((address % sizeof(u32)) != 0))
return -EINVAL;
- uaddr -= key->both.offset;
+ address -= key->both.offset;
/*
- * The futex is hashed differently depending on whether
- * it's in a shared or private mapping. So check vma first.
+ * PROCESS_PRIVATE futexes are fast.
+ * As the mm cannot disappear under us and the 'key' only needs
+ * virtual address, we dont even have to find the underlying vma.
+ * Note : We do have to check 'uaddr' is a valid user address,
+ * but access_ok() should be faster than find_vma()
*/
- vma = find_extend_vma(mm, uaddr);
- if (unlikely(!vma))
- return -EFAULT;
+ if (!fshared) {
+ if (unlikely(!access_ok(VERIFY_WRITE, uaddr, sizeof(u32))))
+ return -EFAULT;
+ key->private.mm = mm;
+ key->private.address = address;
+ get_futex_key_refs(key);
+ return 0;
+ }
- /*
- * 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, 0, &page);
+ if (err < 0)
+ return err;
+
+ lock_page(page);
+ if (!page->mapping) {
+ unlock_page(page);
+ put_page(page);
+ goto again;
+ }
/*
* Private mappings are handled in a simple way.
*
* NOTE: When userspace waits on a MAP_SHARED mapping, even if
* it's a read-only handle, it's expected that futexes attach to
- * the object not the particular process. 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))) {
+ if (PageAnon(page)) {
+ key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */
key->private.mm = mm;
- key->private.uaddr = uaddr;
- return 0;
+ 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;
}
- /*
- * Linear file mappings are also simple.
- */
- key->shared.inode = vma->vm_file->f_dentry->d_inode;
- key->both.offset++; /* Bit 0 of offset indicates inode-based key. */
- if (likely(!(vma->vm_flags & VM_NONLINEAR))) {
- key->shared.pgoff = (((uaddr - vma->vm_start) >> PAGE_SHIFT)
- + vma->vm_pgoff);
- return 0;
+ get_futex_key_refs(key);
+
+ unlock_page(page);
+ put_page(page);
+ return 0;
+}
+
+static inline
+void put_futex_key(int fshared, union futex_key *key)
+{
+ drop_futex_key_refs(key);
+}
+
+static u32 cmpxchg_futex_value_locked(u32 __user *uaddr, u32 uval, u32 newval)
+{
+ u32 curval;
+
+ pagefault_disable();
+ curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval);
+ pagefault_enable();
+
+ return curval;
+}
+
+static int get_futex_value_locked(u32 *dest, u32 __user *from)
+{
+ int ret;
+
+ pagefault_disable();
+ ret = __copy_from_user_inatomic(dest, from, sizeof(u32));
+ pagefault_enable();
+
+ return ret ? -EFAULT : 0;
+}
+
+/*
+ * Fault handling.
+ */
+static int futex_handle_fault(unsigned long address, int attempt)
+{
+ struct vm_area_struct * vma;
+ struct mm_struct *mm = current->mm;
+ int ret = -EFAULT;
+
+ if (attempt > 2)
+ return ret;
+
+ down_read(&mm->mmap_sem);
+ vma = find_vma(mm, address);
+ if (vma && address >= vma->vm_start &&
+ (vma->vm_flags & VM_WRITE)) {
+ int fault;
+ fault = handle_mm_fault(mm, vma, address, 1);
+ if (unlikely((fault & VM_FAULT_ERROR))) {
+#if 0
+ /* XXX: let's do this when we verify it is OK */
+ if (ret & VM_FAULT_OOM)
+ ret = -ENOMEM;
+#endif
+ } else {
+ ret = 0;
+ if (fault & VM_FAULT_MAJOR)
+ current->maj_flt++;
+ else
+ current->min_flt++;
+ }
}
+ up_read(&mm->mmap_sem);
+ return ret;
+}
- /*
- * 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.
- */
+/*
+ * PI code:
+ */
+static int refill_pi_state_cache(void)
+{
+ struct futex_pi_state *pi_state;
- /*
- * Do a quick atomic lookup first - this is the fastpath.
- */
- page = follow_page(mm, uaddr, FOLL_TOUCH|FOLL_GET);
- if (likely(page != NULL)) {
- key->shared.pgoff =
- page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
- put_page(page);
+ if (likely(current->pi_state_cache))
return 0;
- }
+
+ pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL);
+
+ if (!pi_state)
+ return -ENOMEM;
+
+ INIT_LIST_HEAD(&pi_state->list);
+ /* pi_mutex gets initialized later */
+ pi_state->owner = NULL;
+ atomic_set(&pi_state->refcount, 1);
+ pi_state->key = FUTEX_KEY_INIT;
+
+ current->pi_state_cache = pi_state;
+
+ return 0;
+}
+
+static struct futex_pi_state * alloc_pi_state(void)
+{
+ struct futex_pi_state *pi_state = current->pi_state_cache;
+
+ WARN_ON(!pi_state);
+ current->pi_state_cache = NULL;
+
+ return pi_state;
+}
+
+static void free_pi_state(struct futex_pi_state *pi_state)
+{
+ if (!atomic_dec_and_test(&pi_state->refcount))
+ return;
/*
- * Do it the general way.
+ * If pi_state->owner is NULL, the owner is most probably dying
+ * and has cleaned up the pi_state already
*/
- err = get_user_pages(current, mm, uaddr, 1, 0, 0, &page, NULL);
- if (err >= 0) {
- key->shared.pgoff =
- page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
- put_page(page);
- return 0;
+ if (pi_state->owner) {
+ spin_lock_irq(&pi_state->owner->pi_lock);
+ list_del_init(&pi_state->list);
+ spin_unlock_irq(&pi_state->owner->pi_lock);
+
+ rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner);
+ }
+
+ if (current->pi_state_cache)
+ kfree(pi_state);
+ else {
+ /*
+ * pi_state->list is already empty.
+ * clear pi_state->owner.
+ * refcount is at 0 - put it back to 1.
+ */
+ pi_state->owner = NULL;
+ atomic_set(&pi_state->refcount, 1);
+ current->pi_state_cache = pi_state;
}
- return err;
}
/*
- * Take a reference to the resource addressed by a key.
- * Can be called while holding spinlocks.
- *
- * NOTE: mmap_sem MUST be held between get_futex_key() and calling this
- * function, if it is called at all. mmap_sem keeps key->shared.inode valid.
+ * Look up the task based on what TID userspace gave us.
+ * We dont trust it.
*/
-static inline void get_key_refs(union futex_key *key)
+static struct task_struct * futex_find_get_task(pid_t pid)
{
- if (key->both.ptr != 0) {
- if (key->both.offset & 1)
- atomic_inc(&key->shared.inode->i_count);
+ struct task_struct *p;
+ const struct cred *cred = current_cred(), *pcred;
+
+ rcu_read_lock();
+ p = find_task_by_vpid(pid);
+ if (!p) {
+ p = ERR_PTR(-ESRCH);
+ } else {
+ pcred = __task_cred(p);
+ if (cred->euid != pcred->euid &&
+ cred->euid != pcred->uid)
+ p = ERR_PTR(-ESRCH);
else
- atomic_inc(&key->private.mm->mm_count);
+ get_task_struct(p);
}
+
+ rcu_read_unlock();
+
+ return p;
}
/*
- * Drop a reference to the resource addressed by a key.
- * The hash bucket spinlock must not be held.
+ * This task is holding PI mutexes at exit time => bad.
+ * Kernel cleans up PI-state, but userspace is likely hosed.
+ * (Robust-futex cleanup is separate and might save the day for userspace.)
*/
-static void drop_key_refs(union futex_key *key)
+void exit_pi_state_list(struct task_struct *curr)
{
- if (key->both.ptr != 0) {
- if (key->both.offset & 1)
- iput(key->shared.inode);
- else
- mmdrop(key->private.mm);
+ struct list_head *next, *head = &curr->pi_state_list;
+ struct futex_pi_state *pi_state;
+ struct futex_hash_bucket *hb;
+ union futex_key key = FUTEX_KEY_INIT;
+
+ if (!futex_cmpxchg_enabled)
+ return;
+ /*
+ * We are a ZOMBIE and nobody can enqueue itself on
+ * pi_state_list anymore, but we have to be careful
+ * versus waiters unqueueing themselves:
+ */
+ spin_lock_irq(&curr->pi_lock);
+ while (!list_empty(head)) {
+
+ next = head->next;
+ pi_state = list_entry(next, struct futex_pi_state, list);
+ key = pi_state->key;
+ hb = hash_futex(&key);
+ spin_unlock_irq(&curr->pi_lock);
+
+ spin_lock(&hb->lock);
+
+ spin_lock_irq(&curr->pi_lock);
+ /*
+ * We dropped the pi-lock, so re-check whether this
+ * task still owns the PI-state:
+ */
+ if (head->next != next) {
+ spin_unlock(&hb->lock);
+ continue;
+ }
+
+ WARN_ON(pi_state->owner != curr);
+ WARN_ON(list_empty(&pi_state->list));
+ list_del_init(&pi_state->list);
+ pi_state->owner = NULL;
+ spin_unlock_irq(&curr->pi_lock);
+
+ rt_mutex_unlock(&pi_state->pi_mutex);
+
+ spin_unlock(&hb->lock);
+
+ spin_lock_irq(&curr->pi_lock);
}
+ spin_unlock_irq(&curr->pi_lock);
}
-static inline int get_futex_value_locked(int *dest, int __user *from)
+static int
+lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
+ union futex_key *key, struct futex_pi_state **ps)
{
- int ret;
+ struct futex_pi_state *pi_state = NULL;
+ struct futex_q *this, *next;
+ struct plist_head *head;
+ struct task_struct *p;
+ pid_t pid = uval & FUTEX_TID_MASK;
- inc_preempt_count();
- ret = __copy_from_user_inatomic(dest, from, sizeof(int));
- dec_preempt_count();
+ head = &hb->chain;
- return ret ? -EFAULT : 0;
+ plist_for_each_entry_safe(this, next, head, list) {
+ if (match_futex(&this->key, key)) {
+ /*
+ * Another waiter already exists - bump up
+ * the refcount and return its pi_state:
+ */
+ pi_state = this->pi_state;
+ /*
+ * Userspace might have messed up non PI and PI futexes
+ */
+ if (unlikely(!pi_state))
+ return -EINVAL;
+
+ WARN_ON(!atomic_read(&pi_state->refcount));
+ WARN_ON(pid && pi_state->owner &&
+ pi_state->owner->pid != pid);
+
+ atomic_inc(&pi_state->refcount);
+ *ps = pi_state;
+
+ return 0;
+ }
+ }
+
+ /*
+ * We are the first waiter - try to look up the real owner and attach
+ * the new pi_state to it, but bail out when TID = 0
+ */
+ if (!pid)
+ return -ESRCH;
+ p = futex_find_get_task(pid);
+ if (IS_ERR(p))
+ return PTR_ERR(p);
+
+ /*
+ * We need to look at the task state flags to figure out,
+ * whether the task is exiting. To protect against the do_exit
+ * change of the task flags, we do this protected by
+ * p->pi_lock:
+ */
+ spin_lock_irq(&p->pi_lock);
+ if (unlikely(p->flags & PF_EXITING)) {
+ /*
+ * The task is on the way out. When PF_EXITPIDONE is
+ * set, we know that the task has finished the
+ * cleanup:
+ */
+ int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN;
+
+ spin_unlock_irq(&p->pi_lock);
+ put_task_struct(p);
+ return ret;
+ }
+
+ pi_state = alloc_pi_state();
+
+ /*
+ * Initialize the pi_mutex in locked state and make 'p'
+ * the owner of it:
+ */
+ rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p);
+
+ /* Store the key for possible exit cleanups: */
+ pi_state->key = *key;
+
+ WARN_ON(!list_empty(&pi_state->list));
+ list_add(&pi_state->list, &p->pi_state_list);
+ pi_state->owner = p;
+ spin_unlock_irq(&p->pi_lock);
+
+ put_task_struct(p);
+
+ *ps = pi_state;
+
+ return 0;
}
/*
*/
static void wake_futex(struct futex_q *q)
{
- list_del_init(&q->list);
- if (q->filp)
- send_sigio(&q->filp->f_owner, q->fd, POLL_IN);
+ plist_del(&q->list, &q->list.plist);
/*
* The lock in wake_up_all() is a crucial memory barrier after the
- * list_del_init() and also before assigning to q->lock_ptr.
+ * 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.
*/
+ smp_wmb();
q->lock_ptr = NULL;
}
+static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)
+{
+ struct task_struct *new_owner;
+ struct futex_pi_state *pi_state = this->pi_state;
+ u32 curval, newval;
+
+ if (!pi_state)
+ return -EINVAL;
+
+ spin_lock(&pi_state->pi_mutex.wait_lock);
+ new_owner = rt_mutex_next_owner(&pi_state->pi_mutex);
+
+ /*
+ * This happens when we have stolen the lock and the original
+ * pending owner did not enqueue itself back on the rt_mutex.
+ * Thats not a tragedy. We know that way, that a lock waiter
+ * is on the fly. We make the futex_q waiter the pending owner.
+ */
+ if (!new_owner)
+ new_owner = this->task;
+
+ /*
+ * We pass it to the next owner. (The WAITERS bit is always
+ * kept enabled while there is PI state around. We must also
+ * preserve the owner died bit.)
+ */
+ if (!(uval & FUTEX_OWNER_DIED)) {
+ int ret = 0;
+
+ newval = FUTEX_WAITERS | task_pid_vnr(new_owner);
+
+ curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
+
+ if (curval == -EFAULT)
+ ret = -EFAULT;
+ else if (curval != uval)
+ ret = -EINVAL;
+ if (ret) {
+ spin_unlock(&pi_state->pi_mutex.wait_lock);
+ return ret;
+ }
+ }
+
+ spin_lock_irq(&pi_state->owner->pi_lock);
+ WARN_ON(list_empty(&pi_state->list));
+ list_del_init(&pi_state->list);
+ spin_unlock_irq(&pi_state->owner->pi_lock);
+
+ spin_lock_irq(&new_owner->pi_lock);
+ WARN_ON(!list_empty(&pi_state->list));
+ list_add(&pi_state->list, &new_owner->pi_state_list);
+ pi_state->owner = new_owner;
+ spin_unlock_irq(&new_owner->pi_lock);
+
+ spin_unlock(&pi_state->pi_mutex.wait_lock);
+ rt_mutex_unlock(&pi_state->pi_mutex);
+
+ return 0;
+}
+
+static int unlock_futex_pi(u32 __user *uaddr, u32 uval)
+{
+ u32 oldval;
+
+ /*
+ * There is no waiter, so we unlock the futex. The owner died
+ * bit has not to be preserved here. We are the owner:
+ */
+ oldval = cmpxchg_futex_value_locked(uaddr, uval, 0);
+
+ if (oldval == -EFAULT)
+ return oldval;
+ if (oldval != uval)
+ return -EAGAIN;
+
+ return 0;
+}
+
+/*
+ * Express the locking dependencies for lockdep:
+ */
+static inline void
+double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
+{
+ if (hb1 <= hb2) {
+ spin_lock(&hb1->lock);
+ if (hb1 < hb2)
+ spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING);
+ } else { /* hb1 > hb2 */
+ spin_lock(&hb2->lock);
+ spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING);
+ }
+}
+
/*
* Wake up all waiters hashed on the physical page that is mapped
* to this virtual address:
*/
-static int futex_wake(unsigned long uaddr, int nr_wake)
+static int futex_wake(u32 __user *uaddr, int fshared, int nr_wake, u32 bitset)
{
- union futex_key key;
- struct futex_hash_bucket *bh;
- struct list_head *head;
+ struct futex_hash_bucket *hb;
struct futex_q *this, *next;
+ struct plist_head *head;
+ union futex_key key = FUTEX_KEY_INIT;
int ret;
- down_read(¤t->mm->mmap_sem);
+ if (!bitset)
+ return -EINVAL;
- ret = get_futex_key(uaddr, &key);
+ ret = get_futex_key(uaddr, fshared, &key);
if (unlikely(ret != 0))
goto out;
- bh = hash_futex(&key);
- spin_lock(&bh->lock);
- head = &bh->chain;
+ hb = hash_futex(&key);
+ spin_lock(&hb->lock);
+ head = &hb->chain;
- list_for_each_entry_safe(this, next, head, list) {
+ plist_for_each_entry_safe(this, next, head, list) {
if (match_futex (&this->key, &key)) {
+ if (this->pi_state) {
+ ret = -EINVAL;
+ break;
+ }
+
+ /* Check if one of the bits is set in both bitsets */
+ if (!(this->bitset & bitset))
+ continue;
+
wake_futex(this);
if (++ret >= nr_wake)
break;
}
}
- spin_unlock(&bh->lock);
+ spin_unlock(&hb->lock);
+ put_futex_key(fshared, &key);
out:
- up_read(¤t->mm->mmap_sem);
return ret;
}
* Wake up all waiters hashed on the physical page that is mapped
* to this virtual address:
*/
-static int futex_wake_op(unsigned long uaddr1, unsigned long uaddr2, int nr_wake, int nr_wake2, int op)
+static int
+futex_wake_op(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
+ int nr_wake, int nr_wake2, int op)
{
- union futex_key key1, key2;
- struct futex_hash_bucket *bh1, *bh2;
- struct list_head *head;
+ union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
+ struct futex_hash_bucket *hb1, *hb2;
+ struct plist_head *head;
struct futex_q *this, *next;
int ret, op_ret, attempt = 0;
retryfull:
- down_read(¤t->mm->mmap_sem);
-
- ret = get_futex_key(uaddr1, &key1);
+ ret = get_futex_key(uaddr1, fshared, &key1);
if (unlikely(ret != 0))
goto out;
- ret = get_futex_key(uaddr2, &key2);
+ ret = get_futex_key(uaddr2, fshared, &key2);
if (unlikely(ret != 0))
- goto out;
+ goto out_put_key1;
- bh1 = hash_futex(&key1);
- bh2 = hash_futex(&key2);
+ hb1 = hash_futex(&key1);
+ hb2 = hash_futex(&key2);
retry:
- if (bh1 < bh2)
- spin_lock(&bh1->lock);
- spin_lock(&bh2->lock);
- if (bh1 > bh2)
- spin_lock(&bh1->lock);
+ double_lock_hb(hb1, hb2);
- op_ret = futex_atomic_op_inuser(op, (int __user *)uaddr2);
+ op_ret = futex_atomic_op_inuser(op, uaddr2);
if (unlikely(op_ret < 0)) {
- int dummy;
+ u32 dummy;
- spin_unlock(&bh1->lock);
- if (bh1 != bh2)
- spin_unlock(&bh2->lock);
+ spin_unlock(&hb1->lock);
+ if (hb1 != hb2)
+ spin_unlock(&hb2->lock);
+
+#ifndef CONFIG_MMU
+ /*
+ * we don't get EFAULT from MMU faults if we don't have an MMU,
+ * but we might get them from range checking
+ */
+ ret = op_ret;
+ goto out_put_keys;
+#endif
if (unlikely(op_ret != -EFAULT)) {
ret = op_ret;
- goto out;
+ goto out_put_keys;
}
- /* futex_atomic_op_inuser needs to both read and write
+ /*
+ * 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. */
+ * still holding the mmap_sem.
+ */
if (attempt++) {
- struct vm_area_struct * vma;
- struct mm_struct *mm = current->mm;
-
- ret = -EFAULT;
- if (attempt >= 2 ||
- !(vma = find_vma(mm, uaddr2)) ||
- vma->vm_start > uaddr2 ||
- !(vma->vm_flags & VM_WRITE))
- goto out;
-
- switch (handle_mm_fault(mm, vma, uaddr2, 1)) {
- case VM_FAULT_MINOR:
- current->min_flt++;
- break;
- case VM_FAULT_MAJOR:
- current->maj_flt++;
- break;
- default:
- goto out;
- }
+ ret = futex_handle_fault((unsigned long)uaddr2,
+ attempt);
+ if (ret)
+ goto out_put_keys;
goto retry;
}
- /* If we would have faulted, release mmap_sem,
- * fault it in and start all over again. */
- up_read(¤t->mm->mmap_sem);
-
- ret = get_user(dummy, (int __user *)uaddr2);
+ ret = get_user(dummy, uaddr2);
if (ret)
return ret;
goto retryfull;
}
- head = &bh1->chain;
+ head = &hb1->chain;
- list_for_each_entry_safe(this, next, head, list) {
+ plist_for_each_entry_safe(this, next, head, list) {
if (match_futex (&this->key, &key1)) {
wake_futex(this);
if (++ret >= nr_wake)
}
if (op_ret > 0) {
- head = &bh2->chain;
+ head = &hb2->chain;
op_ret = 0;
- list_for_each_entry_safe(this, next, head, list) {
+ plist_for_each_entry_safe(this, next, head, list) {
if (match_futex (&this->key, &key2)) {
wake_futex(this);
if (++op_ret >= nr_wake2)
ret += op_ret;
}
- spin_unlock(&bh1->lock);
- if (bh1 != bh2)
- spin_unlock(&bh2->lock);
+ spin_unlock(&hb1->lock);
+ if (hb1 != hb2)
+ spin_unlock(&hb2->lock);
+out_put_keys:
+ put_futex_key(fshared, &key2);
+out_put_key1:
+ put_futex_key(fshared, &key1);
out:
- up_read(¤t->mm->mmap_sem);
return ret;
}
* Requeue all waiters hashed on one physical page to another
* physical page.
*/
-static int futex_requeue(unsigned long uaddr1, unsigned long uaddr2,
- int nr_wake, int nr_requeue, int *valp)
+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;
- struct futex_hash_bucket *bh1, *bh2;
- struct list_head *head1;
+ 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:
- down_read(¤t->mm->mmap_sem);
-
- ret = get_futex_key(uaddr1, &key1);
+retry:
+ ret = get_futex_key(uaddr1, fshared, &key1);
if (unlikely(ret != 0))
goto out;
- ret = get_futex_key(uaddr2, &key2);
+ ret = get_futex_key(uaddr2, fshared, &key2);
if (unlikely(ret != 0))
- goto out;
+ goto out_put_key1;
- bh1 = hash_futex(&key1);
- bh2 = hash_futex(&key2);
+ hb1 = hash_futex(&key1);
+ hb2 = hash_futex(&key2);
- if (bh1 < bh2)
- spin_lock(&bh1->lock);
- spin_lock(&bh2->lock);
- if (bh1 > bh2)
- spin_lock(&bh1->lock);
+ double_lock_hb(hb1, hb2);
- if (likely(valp != NULL)) {
- int curval;
+ if (likely(cmpval != NULL)) {
+ u32 curval;
- ret = get_futex_value_locked(&curval, (int __user *)uaddr1);
+ ret = get_futex_value_locked(&curval, uaddr1);
if (unlikely(ret)) {
- spin_unlock(&bh1->lock);
- if (bh1 != bh2)
- spin_unlock(&bh2->lock);
-
- /* If we would have faulted, release mmap_sem, fault
- * it in and start all over again.
- */
- up_read(¤t->mm->mmap_sem);
+ spin_unlock(&hb1->lock);
+ if (hb1 != hb2)
+ spin_unlock(&hb2->lock);
- ret = get_user(curval, (int __user *)uaddr1);
+ ret = get_user(curval, uaddr1);
if (!ret)
goto retry;
- return ret;
+ goto out_put_keys;
}
- if (curval != *valp) {
+ if (curval != *cmpval) {
ret = -EAGAIN;
goto out_unlock;
}
}
- head1 = &bh1->chain;
- list_for_each_entry_safe(this, next, head1, list) {
+ head1 = &hb1->chain;
+ plist_for_each_entry_safe(this, next, head1, list) {
if (!match_futex (&this->key, &key1))
continue;
if (++ret <= nr_wake) {
wake_futex(this);
} else {
- list_move_tail(&this->list, &bh2->chain);
- this->lock_ptr = &bh2->lock;
+ /*
+ * 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_key_refs(&key2);
+ get_futex_key_refs(&key2);
drop_count++;
if (ret - nr_wake >= nr_requeue)
break;
- /* Make sure to stop if key1 == key2 */
- if (head1 == &bh2->chain && head1 != &next->list)
- head1 = &this->list;
}
}
out_unlock:
- spin_unlock(&bh1->lock);
- if (bh1 != bh2)
- spin_unlock(&bh2->lock);
+ spin_unlock(&hb1->lock);
+ if (hb1 != hb2)
+ spin_unlock(&hb2->lock);
- /* drop_key_refs() must be called outside the spinlocks. */
+ /* drop_futex_key_refs() must be called outside the spinlocks. */
while (--drop_count >= 0)
- drop_key_refs(&key1);
+ drop_futex_key_refs(&key1);
+out_put_keys:
+ put_futex_key(fshared, &key2);
+out_put_key1:
+ put_futex_key(fshared, &key1);
out:
- up_read(¤t->mm->mmap_sem);
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 *bh;
+ struct futex_hash_bucket *hb;
- q->fd = fd;
- q->filp = filp;
+ init_waitqueue_head(&q->waiter);
- init_waitqueue_head(&q->waiters);
+ get_futex_key_refs(&q->key);
+ hb = hash_futex(&q->key);
+ q->lock_ptr = &hb->lock;
- get_key_refs(&q->key);
- bh = hash_futex(&q->key);
- q->lock_ptr = &bh->lock;
-
- spin_lock(&bh->lock);
- return bh;
+ spin_lock(&hb->lock);
+ return hb;
}
-static inline void __queue_me(struct futex_q *q, struct futex_hash_bucket *bh)
+static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb)
{
- list_add_tail(&q->list, &bh->chain);
- spin_unlock(&bh->lock);
+ int prio;
+
+ /*
+ * The priority used to register this element is
+ * - either the real thread-priority for the real-time threads
+ * (i.e. threads with a priority lower than MAX_RT_PRIO)
+ * - or MAX_RT_PRIO for non-RT threads.
+ * Thus, all RT-threads are woken first in priority order, and
+ * the others are woken last, in FIFO order.
+ */
+ prio = min(current->normal_prio, MAX_RT_PRIO);
+
+ plist_node_init(&q->list, prio);
+#ifdef CONFIG_DEBUG_PI_LIST
+ q->list.plist.lock = &hb->lock;
+#endif
+ plist_add(&q->list, &hb->chain);
+ q->task = current;
+ spin_unlock(&hb->lock);
}
static inline void
-queue_unlock(struct futex_q *q, struct futex_hash_bucket *bh)
+queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb)
{
- spin_unlock(&bh->lock);
- drop_key_refs(&q->key);
+ spin_unlock(&hb->lock);
+ drop_futex_key_refs(&q->key);
}
/*
* 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 *bh;
- bh = queue_lock(q, fd, filp);
- __queue_me(q, bh);
-}
-
/* Return 1 if we were still queued (ie. 0 means we were woken) */
static int unqueue_me(struct futex_q *q)
{
- int ret = 0;
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;
- if (lock_ptr != 0) {
+ barrier();
+ if (lock_ptr != NULL) {
spin_lock(lock_ptr);
/*
* q->lock_ptr can change between reading it and
spin_unlock(lock_ptr);
goto retry;
}
- WARN_ON(list_empty(&q->list));
- list_del(&q->list);
+ WARN_ON(plist_node_empty(&q->list));
+ plist_del(&q->list, &q->list.plist);
+
+ BUG_ON(q->pi_state);
+
spin_unlock(lock_ptr);
ret = 1;
}
- drop_key_refs(&q->key);
+ drop_futex_key_refs(&q->key);
return ret;
}
-static int futex_wait(unsigned long uaddr, int val, unsigned long time)
+/*
+ * PI futexes can not be requeued and must remove themself from the
+ * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry
+ * and dropped here.
+ */
+static void unqueue_me_pi(struct futex_q *q)
+{
+ WARN_ON(plist_node_empty(&q->list));
+ plist_del(&q->list, &q->list.plist);
+
+ BUG_ON(!q->pi_state);
+ free_pi_state(q->pi_state);
+ q->pi_state = NULL;
+
+ spin_unlock(q->lock_ptr);
+
+ drop_futex_key_refs(&q->key);
+}
+
+/*
+ * Fixup the pi_state owner with the new owner.
+ *
+ * Must be called with hash bucket lock held and mm->sem held for non
+ * private futexes.
+ */
+static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
+ struct task_struct *newowner, int fshared)
+{
+ u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS;
+ struct futex_pi_state *pi_state = q->pi_state;
+ struct task_struct *oldowner = pi_state->owner;
+ u32 uval, curval, newval;
+ int ret, attempt = 0;
+
+ /* Owner died? */
+ if (!pi_state->owner)
+ newtid |= FUTEX_OWNER_DIED;
+
+ /*
+ * We are here either because we stole the rtmutex from the
+ * pending owner or we are the pending owner which failed to
+ * get the rtmutex. We have to replace the pending owner TID
+ * in the user space variable. This must be atomic as we have
+ * to preserve the owner died bit here.
+ *
+ * Note: We write the user space value _before_ changing the
+ * pi_state because we can fault here. Imagine swapped out
+ * pages or a fork, which was running right before we acquired
+ * mmap_sem, that marked all the anonymous memory readonly for
+ * cow.
+ *
+ * Modifying pi_state _before_ the user space value would
+ * leave the pi_state in an inconsistent state when we fault
+ * here, because we need to drop the hash bucket lock to
+ * handle the fault. This might be observed in the PID check
+ * in lookup_pi_state.
+ */
+retry:
+ if (get_futex_value_locked(&uval, uaddr))
+ goto handle_fault;
+
+ while (1) {
+ newval = (uval & FUTEX_OWNER_DIED) | newtid;
+
+ curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
+
+ if (curval == -EFAULT)
+ goto handle_fault;
+ if (curval == uval)
+ break;
+ uval = curval;
+ }
+
+ /*
+ * We fixed up user space. Now we need to fix the pi_state
+ * itself.
+ */
+ if (pi_state->owner != NULL) {
+ spin_lock_irq(&pi_state->owner->pi_lock);
+ WARN_ON(list_empty(&pi_state->list));
+ list_del_init(&pi_state->list);
+ spin_unlock_irq(&pi_state->owner->pi_lock);
+ }
+
+ pi_state->owner = newowner;
+
+ spin_lock_irq(&newowner->pi_lock);
+ WARN_ON(!list_empty(&pi_state->list));
+ list_add(&pi_state->list, &newowner->pi_state_list);
+ spin_unlock_irq(&newowner->pi_lock);
+ return 0;
+
+ /*
+ * To handle the page fault we need to drop the hash bucket
+ * lock here. That gives the other task (either the pending
+ * owner itself or the task which stole the rtmutex) the
+ * chance to try the fixup of the pi_state. So once we are
+ * back from handling the fault we need to check the pi_state
+ * after reacquiring the hash bucket lock and before trying to
+ * do another fixup. When the fixup has been done already we
+ * simply return.
+ */
+handle_fault:
+ spin_unlock(q->lock_ptr);
+
+ ret = futex_handle_fault((unsigned long)uaddr, attempt++);
+
+ spin_lock(q->lock_ptr);
+
+ /*
+ * Check if someone else fixed it for us:
+ */
+ if (pi_state->owner != oldowner)
+ return 0;
+
+ if (ret)
+ return ret;
+
+ goto retry;
+}
+
+/*
+ * In case we must use restart_block to restart a futex_wait,
+ * we encode in the 'flags' shared capability
+ */
+#define FLAGS_SHARED 0x01
+#define FLAGS_CLOCKRT 0x02
+
+static long futex_wait_restart(struct restart_block *restart);
+
+static int futex_wait(u32 __user *uaddr, int fshared,
+ u32 val, ktime_t *abs_time, u32 bitset, int clockrt)
{
- DECLARE_WAITQUEUE(wait, current);
- int ret, curval;
+ struct task_struct *curr = current;
+ struct restart_block *restart;
+ DECLARE_WAITQUEUE(wait, curr);
+ struct futex_hash_bucket *hb;
struct futex_q q;
- struct futex_hash_bucket *bh;
+ u32 uval;
+ int ret;
+ struct hrtimer_sleeper t;
+ int rem = 0;
- retry:
- down_read(¤t->mm->mmap_sem);
+ if (!bitset)
+ return -EINVAL;
- ret = get_futex_key(uaddr, &q.key);
+ 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;
+ goto out;
- bh = queue_lock(&q, -1, NULL);
+ hb = queue_lock(&q);
/*
* Access the page AFTER the futex is queued.
* a wakeup when *uaddr != val on entry to the syscall. This is
* rare, but normal.
*
- * We hold the mmap semaphore, so the mapping cannot have changed
- * since we looked it up in get_futex_key.
+ * 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(&curval, (int __user *)uaddr);
+ ret = get_futex_value_locked(&uval, uaddr);
if (unlikely(ret)) {
- queue_unlock(&q, bh);
+ queue_unlock(&q, hb);
+ put_futex_key(fshared, &q.key);
- /* If we would have faulted, release mmap_sem, fault it in and
- * start all over again.
- */
- up_read(¤t->mm->mmap_sem);
-
- ret = get_user(curval, (int __user *)uaddr);
+ ret = get_user(uval, uaddr);
if (!ret)
goto retry;
- return ret;
+ goto out;
}
- if (curval != val) {
- ret = -EWOULDBLOCK;
- queue_unlock(&q, bh);
- goto out_release_sem;
+ ret = -EWOULDBLOCK;
+ if (unlikely(uval != val)) {
+ queue_unlock(&q, hb);
+ goto out_put_key;
}
/* Only actually queue if *uaddr contained val. */
- __queue_me(&q, bh);
-
- /*
- * Now the futex is queued and we have checked the data, we
- * don't want to hold mmap_sem while we sleep.
- */
- up_read(¤t->mm->mmap_sem);
+ 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);
/*
- * !list_empty() is safe here without any lock.
+ * !plist_node_empty() is safe here without any lock.
* q.lock_ptr != 0 is not safe, because of ordering against wakeup.
*/
- if (likely(!list_empty(&q.list)))
- time = schedule_timeout(time);
+ if (likely(!plist_node_empty(&q.list))) {
+ if (!abs_time)
+ schedule();
+ else {
+ unsigned long slack;
+ slack = current->timer_slack_ns;
+ if (rt_task(current))
+ slack = 0;
+ hrtimer_init_on_stack(&t.timer,
+ clockrt ? CLOCK_REALTIME :
+ CLOCK_MONOTONIC,
+ HRTIMER_MODE_ABS);
+ hrtimer_init_sleeper(&t, current);
+ hrtimer_set_expires_range_ns(&t.timer, *abs_time, slack);
+
+ hrtimer_start_expires(&t.timer, HRTIMER_MODE_ABS);
+ if (!hrtimer_active(&t.timer))
+ t.task = NULL;
+
+ /*
+ * the timer could have already expired, in which
+ * case current would be flagged for rescheduling.
+ * Don't bother calling schedule.
+ */
+ if (likely(t.task))
+ schedule();
+
+ hrtimer_cancel(&t.timer);
+
+ /* Flag if a timeout occured */
+ rem = (t.task == NULL);
+
+ destroy_hrtimer_on_stack(&t.timer);
+ }
+ }
__set_current_state(TASK_RUNNING);
/*
*/
/* If we were woken (and unqueued), we succeeded, whatever. */
+ ret = 0;
if (!unqueue_me(&q))
- return 0;
- if (time == 0)
- return -ETIMEDOUT;
- /* We expect signal_pending(current), but another thread may
- * have handled it for us already. */
- return -EINTR;
-
- out_release_sem:
- up_read(¤t->mm->mmap_sem);
+ goto out_put_key;
+ ret = -ETIMEDOUT;
+ if (rem)
+ goto out_put_key;
+
+ /*
+ * We expect signal_pending(current), but another thread may
+ * have handled it for us already.
+ */
+ ret = -ERESTARTSYS;
+ if (!abs_time)
+ goto out_put_key;
+
+ 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_put_key:
+ put_futex_key(fshared, &q.key);
+out:
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;
+static long futex_wait_restart(struct restart_block *restart)
+{
+ u32 __user *uaddr = (u32 __user *)restart->futex.uaddr;
+ int fshared = 0;
+ ktime_t t;
+
+ t.tv64 = restart->futex.time;
+ restart->fn = do_no_restart_syscall;
+ if (restart->futex.flags & FLAGS_SHARED)
+ fshared = 1;
+ return (long)futex_wait(uaddr, fshared, restart->futex.val, &t,
+ restart->futex.bitset,
+ restart->futex.flags & FLAGS_CLOCKRT);
}
-/* 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)
+
+/*
+ * Userspace tried a 0 -> TID atomic transition of the futex value
+ * and failed. The kernel side here does the whole locking operation:
+ * if there are waiters then it will block, it does PI, etc. (Due to
+ * races the kernel might see a 0 value of the futex too.)
+ */
+static int futex_lock_pi(u32 __user *uaddr, int fshared,
+ int detect, ktime_t *time, int trylock)
{
- struct futex_q *q = filp->private_data;
- int ret = 0;
+ struct hrtimer_sleeper timeout, *to = NULL;
+ struct task_struct *curr = current;
+ struct futex_hash_bucket *hb;
+ u32 uval, newval, curval;
+ struct futex_q q;
+ int ret, lock_taken, ownerdied = 0, attempt = 0;
+
+ if (refill_pi_state_cache())
+ return -ENOMEM;
+
+ if (time) {
+ to = &timeout;
+ hrtimer_init_on_stack(&to->timer, CLOCK_REALTIME,
+ HRTIMER_MODE_ABS);
+ hrtimer_init_sleeper(to, current);
+ hrtimer_set_expires(&to->timer, *time);
+ }
+
+ q.pi_state = NULL;
+retry:
+ q.key = FUTEX_KEY_INIT;
+ ret = get_futex_key(uaddr, fshared, &q.key);
+ if (unlikely(ret != 0))
+ goto out;
+
+retry_unlocked:
+ hb = queue_lock(&q);
+
+retry_locked:
+ ret = lock_taken = 0;
+
+ /*
+ * To avoid races, we attempt to take the lock here again
+ * (by doing a 0 -> TID atomic cmpxchg), while holding all
+ * the locks. It will most likely not succeed.
+ */
+ newval = task_pid_vnr(current);
+
+ curval = cmpxchg_futex_value_locked(uaddr, 0, newval);
+
+ if (unlikely(curval == -EFAULT))
+ goto uaddr_faulted;
+
+ /*
+ * Detect deadlocks. In case of REQUEUE_PI this is a valid
+ * situation and we return success to user space.
+ */
+ if (unlikely((curval & FUTEX_TID_MASK) == task_pid_vnr(current))) {
+ ret = -EDEADLK;
+ goto out_unlock_put_key;
+ }
+
+ /*
+ * Surprise - we got the lock. Just return to userspace:
+ */
+ if (unlikely(!curval))
+ goto out_unlock_put_key;
+
+ uval = curval;
+
+ /*
+ * Set the WAITERS flag, so the owner will know it has someone
+ * to wake at next unlock
+ */
+ newval = curval | FUTEX_WAITERS;
+
+ /*
+ * There are two cases, where a futex might have no owner (the
+ * owner TID is 0): OWNER_DIED. We take over the futex in this
+ * case. We also do an unconditional take over, when the owner
+ * of the futex died.
+ *
+ * This is safe as we are protected by the hash bucket lock !
+ */
+ if (unlikely(ownerdied || !(curval & FUTEX_TID_MASK))) {
+ /* Keep the OWNER_DIED bit */
+ newval = (curval & ~FUTEX_TID_MASK) | task_pid_vnr(current);
+ ownerdied = 0;
+ lock_taken = 1;
+ }
+
+ curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
+
+ if (unlikely(curval == -EFAULT))
+ goto uaddr_faulted;
+ if (unlikely(curval != uval))
+ goto retry_locked;
+
+ /*
+ * We took the lock due to owner died take over.
+ */
+ if (unlikely(lock_taken))
+ goto out_unlock_put_key;
+
+ /*
+ * 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);
+
+ if (unlikely(ret)) {
+ switch (ret) {
+
+ case -EAGAIN:
+ /*
+ * Task is exiting and we just wait for the
+ * exit to complete.
+ */
+ queue_unlock(&q, hb);
+ 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_put_key;
+ }
+ }
+
+ /*
+ * Only actually queue now that the atomic ops are done:
+ */
+ queue_me(&q, hb);
+
+ WARN_ON(!q.pi_state);
+ /*
+ * Block on the PI mutex:
+ */
+ if (!trylock)
+ ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1);
+ else {
+ ret = rt_mutex_trylock(&q.pi_state->pi_mutex);
+ /* Fixup the trylock return value: */
+ ret = ret ? 0 : -EWOULDBLOCK;
+ }
+
+ spin_lock(q.lock_ptr);
+
+ 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);
+ }
+ }
+
+ /* Unqueue and drop the lock */
+ unqueue_me_pi(&q);
+
+ if (to)
+ destroy_hrtimer_on_stack(&to->timer);
+ return ret != -EINTR ? ret : -ERESTARTNOINTR;
- poll_wait(filp, &q->waiters, wait);
+out_unlock_put_key:
+ queue_unlock(&q, hb);
+out_put_key:
+ put_futex_key(fshared, &q.key);
+out:
+ if (to)
+ destroy_hrtimer_on_stack(&to->timer);
+ return ret;
+
+uaddr_faulted:
/*
- * list_empty() is safe here without any lock.
- * q->lock_ptr != 0 is not safe, because of ordering against wakeup.
+ * 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().
*/
- if (list_empty(&q->list))
- ret = POLLIN | POLLRDNORM;
+ queue_unlock(&q, hb);
+ if (attempt++) {
+ ret = futex_handle_fault((unsigned long)uaddr, attempt);
+ if (ret)
+ goto out_put_key;
+ goto retry_unlocked;
+ }
+
+ ret = get_user(uval, uaddr);
+ if (!ret)
+ goto retry;
+
+ if (to)
+ destroy_hrtimer_on_stack(&to->timer);
return ret;
}
-static 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.
+ * 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_fd(unsigned long uaddr, int signal)
+static int futex_unlock_pi(u32 __user *uaddr, int fshared)
{
- struct futex_q *q;
- struct file *filp;
- int ret, err;
+ 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;
- ret = -EINVAL;
- if (!valid_signal(signal))
- goto out;
+retry:
+ if (get_user(uval, uaddr))
+ return -EFAULT;
+ /*
+ * We release only a lock we actually own:
+ */
+ if ((uval & FUTEX_TID_MASK) != task_pid_vnr(current))
+ return -EPERM;
- ret = get_unused_fd();
- if (ret < 0)
- goto out;
- filp = get_empty_filp();
- if (!filp) {
- put_unused_fd(ret);
- ret = -ENFILE;
+ ret = get_futex_key(uaddr, fshared, &key);
+ if (unlikely(ret != 0))
goto out;
+
+ hb = hash_futex(&key);
+retry_unlocked:
+ spin_lock(&hb->lock);
+
+ /*
+ * To avoid races, try to do the TID -> 0 atomic transition
+ * again. If it succeeds then we can return without waking
+ * anyone else up:
+ */
+ if (!(uval & FUTEX_OWNER_DIED))
+ uval = cmpxchg_futex_value_locked(uaddr, task_pid_vnr(current), 0);
+
+
+ if (unlikely(uval == -EFAULT))
+ goto pi_faulted;
+ /*
+ * Rare case: we managed to release the lock atomically,
+ * no need to wake anyone else up:
+ */
+ if (unlikely(uval == task_pid_vnr(current)))
+ goto out_unlock;
+
+ /*
+ * Ok, other tasks may need to be woken up - check waiters
+ * and do the wakeup if necessary:
+ */
+ head = &hb->chain;
+
+ plist_for_each_entry_safe(this, next, head, list) {
+ if (!match_futex (&this->key, &key))
+ continue;
+ ret = wake_futex_pi(uaddr, uval, this);
+ /*
+ * The atomic access to the futex value
+ * generated a pagefault, so retry the
+ * user-access and the wakeup:
+ */
+ if (ret == -EFAULT)
+ goto pi_faulted;
+ goto out_unlock;
+ }
+ /*
+ * No waiters - kernel unlocks the futex:
+ */
+ if (!(uval & FUTEX_OWNER_DIED)) {
+ ret = unlock_futex_pi(uaddr, uval);
+ if (ret == -EFAULT)
+ goto pi_faulted;
}
- filp->f_op = &futex_fops;
- filp->f_vfsmnt = mntget(futex_mnt);
- filp->f_dentry = dget(futex_mnt->mnt_root);
- filp->f_mapping = filp->f_dentry->d_inode->i_mapping;
- if (signal) {
- err = f_setown(filp, current->pid, 1);
- if (err < 0) {
- goto error;
- }
- filp->f_owner.signum = signal;
+out_unlock:
+ spin_unlock(&hb->lock);
+ put_futex_key(fshared, &key);
+
+out:
+ return ret;
+
+pi_faulted:
+ /*
+ * 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, attempt);
+ if (ret)
+ goto out;
+ uval = 0;
+ goto retry_unlocked;
}
- q = kmalloc(sizeof(*q), GFP_KERNEL);
- if (!q) {
- err = -ENOMEM;
- goto error;
+ ret = get_user(uval, uaddr);
+ if (!ret)
+ goto retry;
+
+ return ret;
+}
+
+/*
+ * Support for robust futexes: the kernel cleans up held futexes at
+ * thread exit time.
+ *
+ * Implementation: user-space maintains a per-thread list of locks it
+ * is holding. Upon do_exit(), the kernel carefully walks this list,
+ * and marks all locks that are owned by this thread with the
+ * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is
+ * always manipulated with the lock held, so the list is private and
+ * per-thread. Userspace also maintains a per-thread 'list_op_pending'
+ * field, to allow the kernel to clean up if the thread dies after
+ * acquiring the lock, but just before it could have added itself to
+ * the list. There can only be one such pending lock.
+ */
+
+/**
+ * sys_set_robust_list - set the robust-futex list head of a task
+ * @head: pointer to the list-head
+ * @len: length of the list-head, as userspace expects
+ */
+SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head,
+ size_t, len)
+{
+ if (!futex_cmpxchg_enabled)
+ return -ENOSYS;
+ /*
+ * The kernel knows only one size for now:
+ */
+ if (unlikely(len != sizeof(*head)))
+ return -EINVAL;
+
+ current->robust_list = head;
+
+ return 0;
+}
+
+/**
+ * sys_get_robust_list - get the robust-futex list head of a task
+ * @pid: pid of the process [zero for current task]
+ * @head_ptr: pointer to a list-head pointer, the kernel fills it in
+ * @len_ptr: pointer to a length field, the kernel fills in the header size
+ */
+SYSCALL_DEFINE3(get_robust_list, int, pid,
+ struct robust_list_head __user * __user *, head_ptr,
+ size_t __user *, len_ptr)
+{
+ struct robust_list_head __user *head;
+ unsigned long ret;
+ const struct cred *cred = current_cred(), *pcred;
+
+ if (!futex_cmpxchg_enabled)
+ return -ENOSYS;
+
+ if (!pid)
+ head = current->robust_list;
+ else {
+ struct task_struct *p;
+
+ ret = -ESRCH;
+ rcu_read_lock();
+ p = find_task_by_vpid(pid);
+ if (!p)
+ goto err_unlock;
+ ret = -EPERM;
+ 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();
}
- down_read(¤t->mm->mmap_sem);
- err = get_futex_key(uaddr, &q->key);
+ if (put_user(sizeof(*head), len_ptr))
+ return -EFAULT;
+ return put_user(head, head_ptr);
+
+err_unlock:
+ rcu_read_unlock();
+
+ return ret;
+}
+
+/*
+ * Process a futex-list entry, check whether it's owned by the
+ * dying task, and do notification if so:
+ */
+int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi)
+{
+ u32 uval, nval, mval;
+
+retry:
+ if (get_user(uval, uaddr))
+ return -1;
+
+ if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) {
+ /*
+ * Ok, this dying thread is truly holding a futex
+ * of interest. Set the OWNER_DIED bit atomically
+ * via cmpxchg, and if the value had FUTEX_WAITERS
+ * set, wake up a waiter (if any). (We have to do a
+ * futex_wake() even if OWNER_DIED is already set -
+ * to handle the rare but possible case of recursive
+ * thread-death.) The rest of the cleanup is done in
+ * userspace.
+ */
+ mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED;
+ nval = futex_atomic_cmpxchg_inatomic(uaddr, uval, mval);
+
+ if (nval == -EFAULT)
+ return -1;
- if (unlikely(err != 0)) {
- up_read(¤t->mm->mmap_sem);
- kfree(q);
- goto error;
+ if (nval != uval)
+ goto retry;
+
+ /*
+ * Wake robust non-PI futexes here. The wakeup of
+ * PI futexes happens in exit_pi_state():
+ */
+ if (!pi && (uval & FUTEX_WAITERS))
+ futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY);
}
+ return 0;
+}
+
+/*
+ * Fetch a robust-list pointer. Bit 0 signals PI futexes:
+ */
+static inline int fetch_robust_entry(struct robust_list __user **entry,
+ struct robust_list __user * __user *head,
+ int *pi)
+{
+ unsigned long uentry;
+
+ if (get_user(uentry, (unsigned long __user *)head))
+ return -EFAULT;
+
+ *entry = (void __user *)(uentry & ~1UL);
+ *pi = uentry & 1;
+
+ return 0;
+}
+
+/*
+ * Walk curr->robust_list (very carefully, it's a userspace list!)
+ * and mark any locks found there dead, and notify any waiters.
+ *
+ * We silently return on any sign of list-walking problem.
+ */
+void exit_robust_list(struct task_struct *curr)
+{
+ struct robust_list_head __user *head = curr->robust_list;
+ struct robust_list __user *entry, *next_entry, *pending;
+ unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip;
+ unsigned long futex_offset;
+ int rc;
+
+ if (!futex_cmpxchg_enabled)
+ return;
/*
- * queue_me() must be called before releasing mmap_sem, because
- * key->shared.inode needs to be referenced while holding it.
+ * Fetch the list head (which was registered earlier, via
+ * sys_set_robust_list()):
*/
- filp->private_data = q;
+ if (fetch_robust_entry(&entry, &head->list.next, &pi))
+ return;
+ /*
+ * Fetch the relative futex offset:
+ */
+ if (get_user(futex_offset, &head->futex_offset))
+ return;
+ /*
+ * Fetch any possibly pending lock-add first, and handle it
+ * if it exists:
+ */
+ if (fetch_robust_entry(&pending, &head->list_op_pending, &pip))
+ return;
+
+ next_entry = NULL; /* avoid warning with gcc */
+ while (entry != &head->list) {
+ /*
+ * Fetch the next entry in the list before calling
+ * handle_futex_death:
+ */
+ rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi);
+ /*
+ * A pending lock might already be on the list, so
+ * don't process it twice:
+ */
+ if (entry != pending)
+ if (handle_futex_death((void __user *)entry + futex_offset,
+ curr, pi))
+ return;
+ if (rc)
+ return;
+ entry = next_entry;
+ pi = next_pi;
+ /*
+ * Avoid excessively long or circular lists:
+ */
+ if (!--limit)
+ break;
- queue_me(q, ret, filp);
- up_read(¤t->mm->mmap_sem);
+ cond_resched();
+ }
- /* 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;
+ if (pending)
+ handle_futex_death((void __user *)pending + futex_offset,
+ curr, pip);
}
-long do_futex(unsigned long uaddr, int op, int val, unsigned long timeout,
- unsigned long uaddr2, int val2, int val3)
+long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
+ u32 __user *uaddr2, u32 val2, u32 val3)
{
- int ret;
+ int clockrt, ret = -ENOSYS;
+ int cmd = op & FUTEX_CMD_MASK;
+ int fshared = 0;
+
+ if (!(op & FUTEX_PRIVATE_FLAG))
+ fshared = 1;
+
+ clockrt = op & FUTEX_CLOCK_REALTIME;
+ if (clockrt && cmd != FUTEX_WAIT_BITSET)
+ return -ENOSYS;
- switch (op) {
+ switch (cmd) {
case FUTEX_WAIT:
- ret = futex_wait(uaddr, val, timeout);
+ val3 = FUTEX_BITSET_MATCH_ANY;
+ case FUTEX_WAIT_BITSET:
+ ret = futex_wait(uaddr, fshared, val, timeout, val3, clockrt);
break;
case FUTEX_WAKE:
- ret = futex_wake(uaddr, val);
- break;
- case FUTEX_FD:
- /* non-zero val means F_SETOWN(getpid()) & F_SETSIG(val) */
- ret = futex_fd(uaddr, val);
+ val3 = FUTEX_BITSET_MATCH_ANY;
+ case FUTEX_WAKE_BITSET:
+ ret = futex_wake(uaddr, fshared, val, val3);
break;
case FUTEX_REQUEUE:
- ret = futex_requeue(uaddr, uaddr2, val, val2, NULL);
+ ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, NULL);
break;
case FUTEX_CMP_REQUEUE:
- ret = futex_requeue(uaddr, uaddr2, val, val2, &val3);
+ ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3);
break;
case FUTEX_WAKE_OP:
- ret = futex_wake_op(uaddr, uaddr2, val, val2, val3);
+ ret = futex_wake_op(uaddr, fshared, uaddr2, val, val2, val3);
+ break;
+ case FUTEX_LOCK_PI:
+ if (futex_cmpxchg_enabled)
+ ret = futex_lock_pi(uaddr, fshared, val, timeout, 0);
+ break;
+ case FUTEX_UNLOCK_PI:
+ if (futex_cmpxchg_enabled)
+ ret = futex_unlock_pi(uaddr, fshared);
+ break;
+ case FUTEX_TRYLOCK_PI:
+ if (futex_cmpxchg_enabled)
+ ret = futex_lock_pi(uaddr, fshared, 0, timeout, 1);
break;
default:
ret = -ENOSYS;
}
-asmlinkage long sys_futex(u32 __user *uaddr, int op, int val,
- struct timespec __user *utime, u32 __user *uaddr2,
- int val3)
+SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
+ struct timespec __user *, utime, u32 __user *, uaddr2,
+ u32, val3)
{
- struct timespec t;
- unsigned long timeout = MAX_SCHEDULE_TIMEOUT;
- int val2 = 0;
-
- if ((op == FUTEX_WAIT) && utime) {
- if (copy_from_user(&t, utime, sizeof(t)) != 0)
+ struct timespec ts;
+ ktime_t t, *tp = NULL;
+ u32 val2 = 0;
+ int cmd = op & FUTEX_CMD_MASK;
+
+ if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
+ cmd == FUTEX_WAIT_BITSET)) {
+ if (copy_from_user(&ts, utime, sizeof(ts)) != 0)
return -EFAULT;
- timeout = timespec_to_jiffies(&t) + 1;
+ if (!timespec_valid(&ts))
+ return -EINVAL;
+
+ t = timespec_to_ktime(ts);
+ if (cmd == FUTEX_WAIT)
+ t = ktime_add_safe(ktime_get(), t);
+ tp = &t;
}
/*
- * requeue parameter in 'utime' if op == FUTEX_REQUEUE.
+ * requeue parameter in 'utime' if cmd == FUTEX_REQUEUE.
+ * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP.
*/
- if (op >= FUTEX_REQUEUE)
- val2 = (int) (unsigned long) utime;
+ if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
+ cmd == FUTEX_WAKE_OP)
+ val2 = (u32) (unsigned long) utime;
- return do_futex((unsigned long)uaddr, op, val, timeout,
- (unsigned long)uaddr2, val2, val3);
+ return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
}
-static struct super_block *
-futexfs_get_sb(struct file_system_type *fs_type,
- int flags, const char *dev_name, void *data)
+static int __init futex_init(void)
{
- return get_sb_pseudo(fs_type, "futex", NULL, 0xBAD1DEA);
-}
-
-static struct file_system_type futex_fs_type = {
- .name = "futexfs",
- .get_sb = futexfs_get_sb,
- .kill_sb = kill_anon_super,
-};
-
-static int __init init(void)
-{
- unsigned int i;
+ u32 curval;
+ int i;
- register_filesystem(&futex_fs_type);
- futex_mnt = kern_mount(&futex_fs_type);
+ /*
+ * This will fail and we want it. Some arch implementations do
+ * runtime detection of the futex_atomic_cmpxchg_inatomic()
+ * functionality. We want to know that before we call in any
+ * of the complex code paths. Also we want to prevent
+ * registration of robust lists in that case. NULL is
+ * guaranteed to fault and we get -EFAULT on functional
+ * implementation, the non functional ones will return
+ * -ENOSYS.
+ */
+ curval = cmpxchg_futex_value_locked(NULL, 0, 0);
+ if (curval == -EFAULT)
+ futex_cmpxchg_enabled = 1;
for (i = 0; i < ARRAY_SIZE(futex_queues); i++) {
- INIT_LIST_HEAD(&futex_queues[i].chain);
+ plist_head_init(&futex_queues[i].chain, &futex_queues[i].lock);
spin_lock_init(&futex_queues[i].lock);
}
+
return 0;
}
-__initcall(init);
+__initcall(futex_init);
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff