* 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.
+ *
* 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/mount.h>
#include <linux/pagemap.h>
#include <linux/syscalls.h>
+#include <linux/signal.h>
+#include <linux/vs_cvirt.h>
+#include <asm/futex.h>
-#define FUTEX_HASHBITS 8
+#define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)
/*
* Futexes are matched on equal values of this key.
*/
struct futex_hash_bucket {
spinlock_t lock;
- unsigned int nqueued;
struct list_head chain;
};
* from swap. But that's a lot of code to duplicate here
* for a rare case, so we simply fetch the page.
*/
-
- /*
- * Do a quick atomic lookup first - this is the fastpath.
- */
- spin_lock(¤t->mm->page_table_lock);
- page = follow_page(mm, uaddr, 0);
- if (likely(page != NULL)) {
- key->shared.pgoff =
- page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
- spin_unlock(¤t->mm->page_table_lock);
- return 0;
- }
- spin_unlock(¤t->mm->page_table_lock);
-
- /*
- * Do it the general way.
- */
err = get_user_pages(current, mm, uaddr, 1, 0, 0, &page, NULL);
if (err >= 0) {
key->shared.pgoff =
inc_preempt_count();
ret = __copy_from_user_inatomic(dest, from, sizeof(int));
dec_preempt_count();
- preempt_check_resched();
return ret ? -EFAULT : 0;
}
/*
* 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.
*/
+ wmb();
q->lock_ptr = NULL;
}
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)
+{
+ union futex_key key1, key2;
+ struct futex_hash_bucket *bh1, *bh2;
+ struct list_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);
+ if (unlikely(ret != 0))
+ goto out;
+ ret = get_futex_key(uaddr2, &key2);
+ if (unlikely(ret != 0))
+ goto out;
+
+ bh1 = hash_futex(&key1);
+ bh2 = hash_futex(&key2);
+
+retry:
+ if (bh1 < bh2)
+ spin_lock(&bh1->lock);
+ spin_lock(&bh2->lock);
+ if (bh1 > bh2)
+ spin_lock(&bh1->lock);
+
+ op_ret = futex_atomic_op_inuser(op, (int __user *)uaddr2);
+ if (unlikely(op_ret < 0)) {
+ int dummy;
+
+ spin_unlock(&bh1->lock);
+ if (bh1 != bh2)
+ spin_unlock(&bh2->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;
+#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++) {
+ 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;
+ }
+ 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);
+ if (ret)
+ return ret;
+
+ goto retryfull;
+ }
+
+ head = &bh1->chain;
+
+ list_for_each_entry_safe(this, next, head, list) {
+ if (match_futex (&this->key, &key1)) {
+ wake_futex(this);
+ if (++ret >= nr_wake)
+ break;
+ }
+ }
+
+ if (op_ret > 0) {
+ head = &bh2->chain;
+
+ op_ret = 0;
+ list_for_each_entry_safe(this, next, head, list) {
+ if (match_futex (&this->key, &key2)) {
+ wake_futex(this);
+ if (++op_ret >= nr_wake2)
+ break;
+ }
+ }
+ ret += op_ret;
+ }
+
+ spin_unlock(&bh1->lock);
+ if (bh1 != bh2)
+ spin_unlock(&bh2->lock);
+out:
+ up_read(¤t->mm->mmap_sem);
+ return ret;
+}
+
/*
* Requeue all waiters hashed on one physical page to another
* physical page.
struct list_head *head1;
struct futex_q *this, *next;
int ret, drop_count = 0;
- unsigned int nqueued;
retry:
down_read(¤t->mm->mmap_sem);
bh1 = hash_futex(&key1);
bh2 = hash_futex(&key2);
- nqueued = bh1->nqueued;
+ if (bh1 < bh2)
+ spin_lock(&bh1->lock);
+ spin_lock(&bh2->lock);
+ if (bh1 > bh2)
+ spin_lock(&bh1->lock);
+
if (likely(valp != NULL)) {
int curval;
- /* In order to avoid doing get_user while
- holding bh1->lock and bh2->lock, nqueued
- (monotonically increasing field) must be first
- read, then *uaddr1 fetched from userland and
- after acquiring lock nqueued field compared with
- the stored value. The smp_mb () below
- makes sure that bh1->nqueued is read from memory
- before *uaddr1. */
- smp_mb();
-
ret = get_futex_value_locked(&curval, (int __user *)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.
*/
}
if (curval != *valp) {
ret = -EAGAIN;
- goto out;
+ goto out_unlock;
}
}
- if (bh1 < bh2)
- spin_lock(&bh1->lock);
- spin_lock(&bh2->lock);
- if (bh1 > bh2)
- spin_lock(&bh1->lock);
-
- if (unlikely(nqueued != bh1->nqueued && valp != NULL)) {
- ret = -EAGAIN;
- goto out_unlock;
- }
-
head1 = &bh1->chain;
list_for_each_entry_safe(this, next, head1, list) {
if (!match_futex (&this->key, &key1))
return ret;
}
-/*
- * queue_me and unqueue_me must be called as a pair, each
- * 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)
+static inline struct futex_hash_bucket *
+queue_lock(struct futex_q *q, int fd, struct file *filp)
{
struct futex_hash_bucket *bh;
q->lock_ptr = &bh->lock;
spin_lock(&bh->lock);
- bh->nqueued++;
+ return bh;
+}
+
+static inline void __queue_me(struct futex_q *q, struct futex_hash_bucket *bh)
+{
list_add_tail(&q->list, &bh->chain);
spin_unlock(&bh->lock);
}
+static inline void
+queue_unlock(struct futex_q *q, struct futex_hash_bucket *bh)
+{
+ spin_unlock(&bh->lock);
+ drop_key_refs(&q->key);
+}
+
+/*
+ * queue_me and unqueue_me must be called as a pair, each
+ * exactly once. They are called with the hashed spinlock held.
+ */
+
+/* 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)
{
DECLARE_WAITQUEUE(wait, current);
int ret, curval;
struct futex_q q;
+ struct futex_hash_bucket *bh;
retry:
down_read(¤t->mm->mmap_sem);
if (unlikely(ret != 0))
goto out_release_sem;
- queue_me(&q, -1, NULL);
+ bh = queue_lock(&q, -1, NULL);
/*
* Access the page AFTER the futex is queued.
ret = get_futex_value_locked(&curval, (int __user *)uaddr);
if (unlikely(ret)) {
+ queue_unlock(&q, bh);
+
/* If we would have faulted, release mmap_sem, fault it in and
* start all over again.
*/
up_read(¤t->mm->mmap_sem);
- if (!unqueue_me(&q)) /* There's a chance we got woken already */
- return 0;
-
ret = get_user(curval, (int __user *)uaddr);
if (!ret)
}
if (curval != val) {
ret = -EWOULDBLOCK;
- goto out_unqueue;
+ queue_unlock(&q, bh);
+ goto out_release_sem;
}
+ /* 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.
* have handled it for us already. */
return -EINTR;
- out_unqueue:
- /* If we were woken (and unqueued), we succeeded, whatever. */
- if (!unqueue_me(&q))
- ret = 0;
out_release_sem:
up_read(¤t->mm->mmap_sem);
return ret;
int ret, err;
ret = -EINVAL;
- if (signal < 0 || signal > _NSIG)
+ if (!valid_signal(signal))
goto out;
ret = get_unused_fd();
filp->f_mapping = filp->f_dentry->d_inode->i_mapping;
if (signal) {
- int err;
err = f_setown(filp, current->pid, 1);
if (err < 0) {
- put_unused_fd(ret);
- put_filp(filp);
- ret = err;
- goto out;
+ goto error;
}
filp->f_owner.signum = signal;
}
q = kmalloc(sizeof(*q), GFP_KERNEL);
if (!q) {
- put_unused_fd(ret);
- put_filp(filp);
- ret = -ENOMEM;
- goto out;
+ err = -ENOMEM;
+ goto error;
}
down_read(¤t->mm->mmap_sem);
if (unlikely(err != 0)) {
up_read(¤t->mm->mmap_sem);
- put_unused_fd(ret);
- put_filp(filp);
kfree(q);
- return err;
+ goto error;
}
/*
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.
+ *
+ * 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_DEAD 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
+ */
+asmlinkage long
+sys_set_robust_list(struct robust_list_head __user *head,
+ size_t len)
+{
+ /*
+ * 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
+ */
+asmlinkage long
+sys_get_robust_list(int pid, struct robust_list_head __user **head_ptr,
+ size_t __user *len_ptr)
+{
+ struct robust_list_head *head;
+ unsigned long ret;
+
+ if (!pid)
+ head = current->robust_list;
+ else {
+ struct task_struct *p;
+
+ ret = -ESRCH;
+ read_lock(&tasklist_lock);
+ p = find_task_by_pid(pid);
+ if (!p)
+ goto err_unlock;
+ ret = -EPERM;
+ if ((current->euid != p->euid) && (current->euid != p->uid) &&
+ !capable(CAP_SYS_PTRACE))
+ goto err_unlock;
+ head = p->robust_list;
+ read_unlock(&tasklist_lock);
+ }
+
+ if (put_user(sizeof(*head), len_ptr))
+ return -EFAULT;
+ return put_user(head, head_ptr);
+
+err_unlock:
+ read_unlock(&tasklist_lock);
+
+ 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)
+{
+ u32 uval;
+
+retry:
+ if (get_user(uval, uaddr))
+ return -1;
+
+ if ((uval & FUTEX_TID_MASK) == curr->pid) {
+ /*
+ * 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.
+ */
+ if (futex_atomic_cmpxchg_inatomic(uaddr, uval,
+ uval | FUTEX_OWNER_DIED) != uval)
+ goto retry;
+
+ if (uval & FUTEX_WAITERS)
+ futex_wake((unsigned long)uaddr, 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, *pending;
+ unsigned int limit = ROBUST_LIST_LIMIT;
+ unsigned long futex_offset;
+
+ /*
+ * Fetch the list head (which was registered earlier, via
+ * sys_set_robust_list()):
+ */
+ if (get_user(entry, &head->list.next))
+ 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 (get_user(pending, &head->list_op_pending))
+ return;
+ if (pending)
+ handle_futex_death((void *)pending + futex_offset, curr);
+
+ while (entry != &head->list) {
+ /*
+ * A pending lock might already be on the list, so
+ * dont process it twice:
+ */
+ if (entry != pending)
+ if (handle_futex_death((void *)entry + futex_offset,
+ curr))
+ return;
+ /*
+ * Fetch the next entry in the list:
+ */
+ if (get_user(entry, &entry->next))
+ return;
+ /*
+ * Avoid excessively long or circular lists:
+ */
+ if (!--limit)
+ break;
+
+ cond_resched();
+ }
}
long do_futex(unsigned long uaddr, int op, int val, unsigned long timeout,
case FUTEX_CMP_REQUEUE:
ret = futex_requeue(uaddr, uaddr2, val, val2, &val3);
break;
+ case FUTEX_WAKE_OP:
+ ret = futex_wake_op(uaddr, uaddr2, val, val2, val3);
+ break;
default:
ret = -ENOSYS;
}
unsigned long timeout = MAX_SCHEDULE_TIMEOUT;
int val2 = 0;
- if ((op == FUTEX_WAIT) && utime) {
+ if (utime && (op == FUTEX_WAIT)) {
if (copy_from_user(&t, utime, sizeof(t)) != 0)
return -EFAULT;
+ if (!timespec_valid(&t))
+ return -EINVAL;
timeout = timespec_to_jiffies(&t) + 1;
}
/*
git://git.onelab.eu / linux-2.6.git / blobdiff