* (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>
+ *
* 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/signal.h>
#include <asm/futex.h>
+#include "rtmutex_common.h"
+
#define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)
/*
} both;
};
+/*
+ * Priority Inheritance state:
+ */
+struct futex_pi_state {
+ /*
+ * list of 'owned' pi_state instances - these have to be
+ * cleaned up in do_exit() if the task exits prematurely:
+ */
+ struct list_head list;
+
+ /*
+ * The PI object:
+ */
+ struct rt_mutex pi_mutex;
+
+ struct task_struct *owner;
+ atomic_t refcount;
+
+ union futex_key key;
+};
+
/*
* We use this hashed waitqueue instead of a normal wait_queue_t, so
* we can wake only the relevant ones (hashed queues may be shared).
/* 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;
};
/*
return ret ? -EFAULT : 0;
}
+/*
+ * Fault handling. Called with current->mm->mmap_sem held.
+ */
+static int futex_handle_fault(unsigned long address, int attempt)
+{
+ struct vm_area_struct * vma;
+ struct mm_struct *mm = current->mm;
+
+ if (attempt > 2 || !(vma = find_vma(mm, address)) ||
+ vma->vm_start > address || !(vma->vm_flags & VM_WRITE))
+ return -EFAULT;
+
+ switch (handle_mm_fault(mm, vma, address, 1)) {
+ case VM_FAULT_MINOR:
+ current->min_flt++;
+ break;
+ case VM_FAULT_MAJOR:
+ current->maj_flt++;
+ break;
+ default:
+ return -EFAULT;
+ }
+ return 0;
+}
+
+/*
+ * PI code:
+ */
+static int refill_pi_state_cache(void)
+{
+ struct futex_pi_state *pi_state;
+
+ if (likely(current->pi_state_cache))
+ return 0;
+
+ pi_state = kmalloc(sizeof(*pi_state), GFP_KERNEL);
+
+ if (!pi_state)
+ return -ENOMEM;
+
+ memset(pi_state, 0, sizeof(*pi_state));
+ INIT_LIST_HEAD(&pi_state->list);
+ /* pi_mutex gets initialized later */
+ pi_state->owner = NULL;
+ atomic_set(&pi_state->refcount, 1);
+
+ 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;
+
+ /*
+ * If pi_state->owner is NULL, the owner is most probably dying
+ * and has cleaned up the pi_state already
+ */
+ 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;
+ }
+}
+
+/*
+ * Look up the task based on what TID userspace gave us.
+ * We dont trust it.
+ */
+static struct task_struct * futex_find_get_task(pid_t pid)
+{
+ struct task_struct *p;
+
+ rcu_read_lock();
+ p = find_task_by_pid(pid);
+ if (!p)
+ goto out_unlock;
+ if ((current->euid != p->euid) && (current->euid != p->uid)) {
+ p = NULL;
+ goto out_unlock;
+ }
+ if (p->exit_state != 0) {
+ p = NULL;
+ goto out_unlock;
+ }
+ get_task_struct(p);
+out_unlock:
+ rcu_read_unlock();
+
+ return p;
+}
+
+/*
+ * This task is holding PI mutexes at exit time => bad.
+ * Kernel cleans up PI-state, but userspace is likely hosed.
+ * (Robust-futex cleanup is separate and might save the day for userspace.)
+ */
+void exit_pi_state_list(struct task_struct *curr)
+{
+ struct list_head *next, *head = &curr->pi_state_list;
+ struct futex_pi_state *pi_state;
+ struct futex_hash_bucket *hb;
+ union futex_key key;
+
+ /*
+ * 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 int
+lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, struct futex_q *me)
+{
+ struct futex_pi_state *pi_state = NULL;
+ struct futex_q *this, *next;
+ struct list_head *head;
+ struct task_struct *p;
+ pid_t pid;
+
+ head = &hb->chain;
+
+ list_for_each_entry_safe(this, next, head, list) {
+ if (match_futex(&this->key, &me->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));
+
+ atomic_inc(&pi_state->refcount);
+ me->pi_state = 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 the owner died bit is set
+ * and TID = 0:
+ */
+ pid = uval & FUTEX_TID_MASK;
+ if (!pid && (uval & FUTEX_OWNER_DIED))
+ return -ESRCH;
+ p = futex_find_get_task(pid);
+ if (!p)
+ return -ESRCH;
+
+ 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 = me->key;
+
+ spin_lock_irq(&p->pi_lock);
+ 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);
+
+ me->pi_state = pi_state;
+
+ return 0;
+}
+
/*
* The hash bucket lock must be held when this is called.
* Afterwards, the futex_q must not be accessed.
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;
+
+ 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)) {
+ newval = FUTEX_WAITERS | new_owner->pid;
+
+ inc_preempt_count();
+ curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval);
+ dec_preempt_count();
+ if (curval == -EFAULT)
+ return -EFAULT;
+ if (curval != uval)
+ return -EINVAL;
+ }
+
+ 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);
+
+ 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:
+ */
+ inc_preempt_count();
+ oldval = futex_atomic_cmpxchg_inatomic(uaddr, uval, 0);
+ dec_preempt_count();
+
+ 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:
list_for_each_entry_safe(this, next, head, list) {
if (match_futex (&this->key, &key)) {
+ if (this->pi_state) {
+ ret = -EINVAL;
+ break;
+ }
wake_futex(this);
if (++ret >= nr_wake)
break;
hb2 = hash_futex(&key2);
retry:
- if (hb1 < hb2)
- spin_lock(&hb1->lock);
- spin_lock(&hb2->lock);
- if (hb1 > hb2)
- spin_lock(&hb1->lock);
+ double_lock_hb(hb1, hb2);
op_ret = futex_atomic_op_inuser(op, uaddr2);
if (unlikely(op_ret < 0)) {
* still holding the mmap_sem.
*/
if (attempt++) {
- struct vm_area_struct * vma;
- struct mm_struct *mm = current->mm;
- unsigned long address = (unsigned long)uaddr2;
-
- ret = -EFAULT;
- if (attempt >= 2 ||
- !(vma = find_vma(mm, address)) ||
- vma->vm_start > address ||
- !(vma->vm_flags & VM_WRITE))
- goto out;
-
- switch (handle_mm_fault(mm, vma, address, 1)) {
- case VM_FAULT_MINOR:
- current->min_flt++;
- break;
- case VM_FAULT_MAJOR:
- current->maj_flt++;
- break;
- default:
+ if (futex_handle_fault((unsigned long)uaddr2,
+ attempt)) {
+ ret = -EFAULT;
goto out;
}
goto retry;
hb1 = hash_futex(&key1);
hb2 = hash_futex(&key2);
- if (hb1 < hb2)
- spin_lock(&hb1->lock);
- spin_lock(&hb2->lock);
- if (hb1 > hb2)
- spin_lock(&hb1->lock);
+ double_lock_hb(hb1, hb2);
if (likely(cmpval != NULL)) {
u32 curval;
if (++ret <= nr_wake) {
wake_futex(this);
} else {
- list_move_tail(&this->list, &hb2->chain);
- this->lock_ptr = &hb2->lock;
+ /*
+ * If key1 and key2 hash to the same bucket, no need to
+ * requeue.
+ */
+ if (likely(head1 != &hb2->chain)) {
+ list_move_tail(&this->list, &hb2->chain);
+ this->lock_ptr = &hb2->lock;
+ }
this->key = key2;
get_key_refs(&key2);
drop_count++;
if (ret - nr_wake >= nr_requeue)
break;
- /* Make sure to stop if key1 == key2: */
- if (head1 == &hb2->chain && head1 != &next->list)
- head1 = &this->list;
}
}
static inline void __queue_me(struct futex_q *q, struct futex_hash_bucket *hb)
{
list_add_tail(&q->list, &hb->chain);
+ q->task = current;
spin_unlock(&hb->lock);
}
/* In the common case we don't take the spinlock, which is nice. */
retry:
lock_ptr = q->lock_ptr;
+ barrier();
if (lock_ptr != 0) {
spin_lock(lock_ptr);
/*
}
WARN_ON(list_empty(&q->list));
list_del(&q->list);
+
+ BUG_ON(q->pi_state);
+
spin_unlock(lock_ptr);
ret = 1;
}
return ret;
}
+/*
+ * PI futexes can not be requeued and must remove themself from the
+ * hash bucket. The hash bucket lock is held on entry and dropped here.
+ */
+static void unqueue_me_pi(struct futex_q *q, struct futex_hash_bucket *hb)
+{
+ WARN_ON(list_empty(&q->list));
+ list_del(&q->list);
+
+ BUG_ON(!q->pi_state);
+ free_pi_state(q->pi_state);
+ q->pi_state = NULL;
+
+ spin_unlock(&hb->lock);
+
+ drop_key_refs(&q->key);
+}
+
static int futex_wait(u32 __user *uaddr, u32 val, unsigned long time)
{
- DECLARE_WAITQUEUE(wait, current);
+ struct task_struct *curr = current;
+ DECLARE_WAITQUEUE(wait, curr);
struct futex_hash_bucket *hb;
struct futex_q q;
u32 uval;
int ret;
+ q.pi_state = NULL;
retry:
- down_read(¤t->mm->mmap_sem);
+ down_read(&curr->mm->mmap_sem);
ret = get_futex_key(uaddr, &q.key);
if (unlikely(ret != 0))
* If we would have faulted, release mmap_sem, fault it in and
* start all over again.
*/
- up_read(¤t->mm->mmap_sem);
+ up_read(&curr->mm->mmap_sem);
ret = get_user(uval, uaddr);
goto retry;
return ret;
}
- if (uval != val) {
- ret = -EWOULDBLOCK;
- queue_unlock(&q, hb);
- goto out_release_sem;
- }
+ ret = -EWOULDBLOCK;
+ if (uval != val)
+ goto out_unlock_release_sem;
/* 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.
- */
- up_read(¤t->mm->mmap_sem);
+ */
+ up_read(&curr->mm->mmap_sem);
/*
* There might have been scheduling since the queue_me(), as we
*/
return -EINTR;
+ out_unlock_release_sem:
+ queue_unlock(&q, hb);
+
+ out_release_sem:
+ up_read(&curr->mm->mmap_sem);
+ return ret;
+}
+
+/*
+ * 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 detect, unsigned long sec,
+ long nsec, int trylock)
+{
+ struct hrtimer_sleeper timeout, *to = NULL;
+ struct task_struct *curr = current;
+ struct futex_hash_bucket *hb;
+ u32 uval, newval, curval;
+ struct futex_q q;
+ int ret, attempt = 0;
+
+ if (refill_pi_state_cache())
+ return -ENOMEM;
+
+ if (sec != MAX_SCHEDULE_TIMEOUT) {
+ to = &timeout;
+ hrtimer_init(&to->timer, CLOCK_REALTIME, HRTIMER_ABS);
+ hrtimer_init_sleeper(to, current);
+ to->timer.expires = ktime_set(sec, nsec);
+ }
+
+ q.pi_state = NULL;
+ retry:
+ down_read(&curr->mm->mmap_sem);
+
+ ret = get_futex_key(uaddr, &q.key);
+ if (unlikely(ret != 0))
+ goto out_release_sem;
+
+ hb = queue_lock(&q, -1, NULL);
+
+ retry_locked:
+ /*
+ * 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 = current->pid;
+
+ inc_preempt_count();
+ curval = futex_atomic_cmpxchg_inatomic(uaddr, 0, newval);
+ dec_preempt_count();
+
+ if (unlikely(curval == -EFAULT))
+ goto uaddr_faulted;
+
+ /* We own the lock already */
+ if (unlikely((curval & FUTEX_TID_MASK) == current->pid)) {
+ if (!detect && 0)
+ force_sig(SIGKILL, current);
+ ret = -EDEADLK;
+ goto out_unlock_release_sem;
+ }
+
+ /*
+ * Surprise - we got the lock. Just return
+ * to userspace:
+ */
+ if (unlikely(!curval))
+ goto out_unlock_release_sem;
+
+ uval = curval;
+ newval = uval | FUTEX_WAITERS;
+
+ inc_preempt_count();
+ curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval);
+ dec_preempt_count();
+
+ if (unlikely(curval == -EFAULT))
+ goto uaddr_faulted;
+ if (unlikely(curval != uval))
+ goto retry_locked;
+
+ /*
+ * 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);
+
+ if (unlikely(ret)) {
+ /*
+ * There were no waiters and the owner task lookup
+ * failed. When the OWNER_DIED bit is set, then we
+ * know that this is a robust futex and we actually
+ * take the lock. This is safe as we are protected by
+ * the hash bucket lock. We also set the waiters bit
+ * unconditionally here, to simplify glibc handling of
+ * multiple tasks racing to acquire the lock and
+ * cleanup the problems which were left by the dead
+ * owner.
+ */
+ if (curval & FUTEX_OWNER_DIED) {
+ uval = newval;
+ newval = current->pid |
+ FUTEX_OWNER_DIED | FUTEX_WAITERS;
+
+ inc_preempt_count();
+ curval = futex_atomic_cmpxchg_inatomic(uaddr,
+ uval, newval);
+ dec_preempt_count();
+
+ if (unlikely(curval == -EFAULT))
+ goto uaddr_faulted;
+ if (unlikely(curval != uval))
+ goto retry_locked;
+ ret = 0;
+ }
+ goto out_unlock_release_sem;
+ }
+
+ /*
+ * 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.
+ */
+ up_read(&curr->mm->mmap_sem);
+
+ 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;
+ }
+
+ down_read(&curr->mm->mmap_sem);
+ spin_lock(q.lock_ptr);
+
+ /*
+ * 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 (!ret && q.pi_state->owner != curr) {
+ u32 newtid = current->pid | FUTEX_WAITERS;
+
+ /* Owner died? */
+ if (q.pi_state->owner != NULL) {
+ spin_lock_irq(&q.pi_state->owner->pi_lock);
+ WARN_ON(list_empty(&q.pi_state->list));
+ list_del_init(&q.pi_state->list);
+ spin_unlock_irq(&q.pi_state->owner->pi_lock);
+ } else
+ newtid |= FUTEX_OWNER_DIED;
+
+ q.pi_state->owner = current;
+
+ spin_lock_irq(¤t->pi_lock);
+ WARN_ON(!list_empty(&q.pi_state->list));
+ list_add(&q.pi_state->list, ¤t->pi_state_list);
+ spin_unlock_irq(¤t->pi_lock);
+
+ /* Unqueue and drop the lock */
+ unqueue_me_pi(&q, hb);
+ up_read(&curr->mm->mmap_sem);
+ /*
+ * 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.
+ */
+ ret = get_user(uval, uaddr);
+ while (!ret) {
+ newval = (uval & FUTEX_OWNER_DIED) | newtid;
+ curval = futex_atomic_cmpxchg_inatomic(uaddr,
+ uval, newval);
+ if (curval == -EFAULT)
+ ret = -EFAULT;
+ if (curval == uval)
+ break;
+ uval = curval;
+ }
+ } else {
+ /*
+ * Catch the rare case, where the lock was released
+ * when we were on the way back before we locked
+ * the hash bucket.
+ */
+ if (ret && q.pi_state->owner == curr) {
+ if (rt_mutex_trylock(&q.pi_state->pi_mutex))
+ ret = 0;
+ }
+ /* Unqueue and drop the lock */
+ unqueue_me_pi(&q, hb);
+ up_read(&curr->mm->mmap_sem);
+ }
+
+ if (!detect && ret == -EDEADLK && 0)
+ force_sig(SIGKILL, current);
+
+ return ret != -EINTR ? ret : -ERESTARTNOINTR;
+
+ out_unlock_release_sem:
+ queue_unlock(&q, hb);
+
out_release_sem:
+ up_read(&curr->mm->mmap_sem);
+ return ret;
+
+ 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.
+ */
+ if (attempt++) {
+ if (futex_handle_fault((unsigned long)uaddr, attempt)) {
+ ret = -EFAULT;
+ goto out_unlock_release_sem;
+ }
+ goto retry_locked;
+ }
+
+ queue_unlock(&q, hb);
+ up_read(&curr->mm->mmap_sem);
+
+ ret = get_user(uval, uaddr);
+ if (!ret && (uval != -EFAULT))
+ goto retry;
+
+ return ret;
+}
+
+/*
+ * 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 futex_hash_bucket *hb;
+ struct futex_q *this, *next;
+ u32 uval;
+ struct list_head *head;
+ union futex_key key;
+ int ret, attempt = 0;
+
+retry:
+ if (get_user(uval, uaddr))
+ return -EFAULT;
+ /*
+ * We release only a lock we actually own:
+ */
+ if ((uval & FUTEX_TID_MASK) != current->pid)
+ return -EPERM;
+ /*
+ * First take all the futex related locks:
+ */
+ down_read(¤t->mm->mmap_sem);
+
+ ret = get_futex_key(uaddr, &key);
+ if (unlikely(ret != 0))
+ goto out;
+
+ hb = hash_futex(&key);
+ spin_lock(&hb->lock);
+
+retry_locked:
+ /*
+ * 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)) {
+ inc_preempt_count();
+ uval = futex_atomic_cmpxchg_inatomic(uaddr, current->pid, 0);
+ dec_preempt_count();
+ }
+
+ 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 == current->pid))
+ goto out_unlock;
+
+ /*
+ * Ok, other tasks may need to be woken up - check waiters
+ * and do the wakeup if necessary:
+ */
+ head = &hb->chain;
+
+ list_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;
+ }
+
+out_unlock:
+ spin_unlock(&hb->lock);
+out:
+ up_read(¤t->mm->mmap_sem);
+
+ 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.
+ */
+ if (attempt++) {
+ if (futex_handle_fault((unsigned long)uaddr, attempt)) {
+ ret = -EFAULT;
+ goto out_unlock;
+ }
+ goto retry_locked;
+ }
+
+ spin_unlock(&hb->lock);
up_read(¤t->mm->mmap_sem);
+
+ ret = get_user(uval, uaddr);
+ if (!ret && (uval != -EFAULT))
+ goto retry;
+
return ret;
}
filp->f_mapping = filp->f_dentry->d_inode->i_mapping;
if (signal) {
- err = f_setown(filp, current->pid, 1);
+ err = __f_setown(filp, task_pid(current), PIDTYPE_PID, 1);
if (err < 0) {
goto error;
}
err = -ENOMEM;
goto error;
}
+ q->pi_state = NULL;
down_read(¤t->mm->mmap_sem);
err = get_futex_key(uaddr, &q->key);
* 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
+ * 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
* @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,
+sys_get_robust_list(int pid, struct robust_list_head __user * __user *head_ptr,
size_t __user *len_ptr)
{
- struct robust_list_head *head;
+ struct robust_list_head __user *head;
unsigned long ret;
if (!pid)
struct task_struct *p;
ret = -ESRCH;
- read_lock(&tasklist_lock);
+ rcu_read_lock();
p = find_task_by_pid(pid);
if (!p)
goto err_unlock;
!capable(CAP_SYS_PTRACE))
goto err_unlock;
head = p->robust_list;
- read_unlock(&tasklist_lock);
+ rcu_read_unlock();
}
if (put_user(sizeof(*head), len_ptr))
return put_user(head, head_ptr);
err_unlock:
- read_unlock(&tasklist_lock);
+ 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 handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi)
{
- u32 uval;
+ u32 uval, nval, mval;
retry:
if (get_user(uval, uaddr))
* thread-death.) The rest of the cleanup is done in
* userspace.
*/
- if (futex_atomic_cmpxchg_inatomic(uaddr, uval,
- uval | FUTEX_OWNER_DIED) != uval)
+ mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED;
+ nval = futex_atomic_cmpxchg_inatomic(uaddr, uval, mval);
+
+ if (nval == -EFAULT)
+ return -1;
+
+ if (nval != uval)
goto retry;
- if (uval & FUTEX_WAITERS)
- futex_wake(uaddr, 1);
+ /*
+ * Wake robust non-PI futexes here. The wakeup of
+ * PI futexes happens in exit_pi_state():
+ */
+ if (!pi) {
+ if (uval & FUTEX_WAITERS)
+ futex_wake(uaddr, 1);
+ }
}
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.
{
struct robust_list_head __user *head = curr->robust_list;
struct robust_list __user *entry, *pending;
- unsigned int limit = ROBUST_LIST_LIMIT;
+ unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
unsigned long futex_offset;
/*
* Fetch the list head (which was registered earlier, via
* sys_set_robust_list()):
*/
- if (get_user(entry, &head->list.next))
+ if (fetch_robust_entry(&entry, &head->list.next, &pi))
return;
/*
* Fetch the relative futex offset:
* Fetch any possibly pending lock-add first, and handle it
* if it exists:
*/
- if (get_user(pending, &head->list_op_pending))
+ if (fetch_robust_entry(&pending, &head->list_op_pending, &pip))
return;
+
if (pending)
- handle_futex_death((void *)pending + futex_offset, curr);
+ handle_futex_death((void __user *)pending + futex_offset, curr, pip);
while (entry != &head->list) {
/*
* A pending lock might already be on the list, so
- * dont process it twice:
+ * don't process it twice:
*/
if (entry != pending)
- if (handle_futex_death((void *)entry + futex_offset,
- curr))
+ if (handle_futex_death((void __user *)entry + futex_offset,
+ curr, pi))
return;
/*
* Fetch the next entry in the list:
*/
- if (get_user(entry, &entry->next))
+ if (fetch_robust_entry(&entry, &entry->next, &pi))
return;
/*
* Avoid excessively long or circular lists:
case FUTEX_WAKE_OP:
ret = futex_wake_op(uaddr, uaddr2, val, val2, val3);
break;
+ case FUTEX_LOCK_PI:
+ ret = futex_lock_pi(uaddr, val, timeout, val2, 0);
+ break;
+ case FUTEX_UNLOCK_PI:
+ ret = futex_unlock_pi(uaddr);
+ break;
+ case FUTEX_TRYLOCK_PI:
+ ret = futex_lock_pi(uaddr, 0, timeout, val2, 1);
+ break;
default:
ret = -ENOSYS;
}
unsigned long timeout = MAX_SCHEDULE_TIMEOUT;
u32 val2 = 0;
- if (utime && (op == FUTEX_WAIT)) {
+ if (utime && (op == FUTEX_WAIT || op == FUTEX_LOCK_PI)) {
if (copy_from_user(&t, utime, sizeof(t)) != 0)
return -EFAULT;
if (!timespec_valid(&t))
return -EINVAL;
- timeout = timespec_to_jiffies(&t) + 1;
+ if (op == FUTEX_WAIT)
+ timeout = timespec_to_jiffies(&t) + 1;
+ else {
+ timeout = t.tv_sec;
+ val2 = t.tv_nsec;
+ }
}
/*
* requeue parameter in 'utime' if op == FUTEX_REQUEUE.
*/
- if (op >= FUTEX_REQUEUE)
+ if (op == FUTEX_REQUEUE || op == FUTEX_CMP_REQUEUE)
val2 = (u32) (unsigned long) utime;
return do_futex(uaddr, op, val, timeout, uaddr2, val2, val3);
projects / linux-2.6 / blobdiff