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-rw-r--r--kernel/futex.c121
1 files changed, 85 insertions, 36 deletions
diff --git a/kernel/futex.c b/kernel/futex.c
index cf0c8e21d1aba..dda2049692a23 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -415,15 +415,15 @@ out_unlock:
*/
void exit_pi_state_list(struct task_struct *curr)
{
- struct futex_hash_bucket *hb;
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 themselfs
+ * versus waiters unqueueing themselves:
*/
spin_lock_irq(&curr->pi_lock);
while (!list_empty(head)) {
@@ -431,21 +431,24 @@ void exit_pi_state_list(struct task_struct *curr)
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);
- hb = hash_futex(&key);
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;
}
- list_del_init(&pi_state->list);
-
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);
@@ -470,7 +473,7 @@ lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, struct futex_q *me)
head = &hb->chain;
list_for_each_entry_safe(this, next, head, list) {
- if (match_futex (&this->key, &me->key)) {
+ if (match_futex(&this->key, &me->key)) {
/*
* Another waiter already exists - bump up
* the refcount and return its pi_state:
@@ -482,6 +485,8 @@ lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, struct futex_q *me)
if (unlikely(!pi_state))
return -EINVAL;
+ WARN_ON(!atomic_read(&pi_state->refcount));
+
atomic_inc(&pi_state->refcount);
me->pi_state = pi_state;
@@ -490,10 +495,13 @@ lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, struct futex_q *me)
}
/*
- * We are the first waiter - try to look up the real owner and
- * attach the new pi_state to it:
+ * 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;
@@ -510,6 +518,7 @@ lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, struct futex_q *me)
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);
@@ -573,20 +582,29 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)
* kept enabled while there is PI state around. We must also
* preserve the owner died bit.)
*/
- newval = (uval & FUTEX_OWNER_DIED) | FUTEX_WAITERS | new_owner->pid;
+ 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();
+ inc_preempt_count();
+ curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval);
+ dec_preempt_count();
+ if (curval == -EFAULT)
+ return -EFAULT;
+ if (curval != uval)
+ return -EINVAL;
+ }
- 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);
- list_del_init(&pi_state->owner->pi_state_list);
+ 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;
@@ -1236,6 +1254,7 @@ static int do_futex_lock_pi(u32 __user *uaddr, int detect, int trylock,
/* 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
@@ -1244,6 +1263,7 @@ static int do_futex_lock_pi(u32 __user *uaddr, int detect, int trylock,
q.pi_state->owner = current;
spin_lock_irq(&current->pi_lock);
+ WARN_ON(!list_empty(&q.pi_state->list));
list_add(&q.pi_state->list, &current->pi_state_list);
spin_unlock_irq(&current->pi_lock);
@@ -1427,9 +1447,11 @@ retry_locked:
* again. If it succeeds then we can return without waking
* anyone else up:
*/
- inc_preempt_count();
- uval = futex_atomic_cmpxchg_inatomic(uaddr, current->pid, 0);
- dec_preempt_count();
+ 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;
@@ -1462,9 +1484,11 @@ retry_locked:
/*
* No waiters - kernel unlocks the futex:
*/
- ret = unlock_futex_pi(uaddr, uval);
- if (ret == -EFAULT)
- goto pi_faulted;
+ if (!(uval & FUTEX_OWNER_DIED)) {
+ ret = unlock_futex_pi(uaddr, uval);
+ if (ret == -EFAULT)
+ goto pi_faulted;
+ }
out_unlock:
spin_unlock(&hb->lock);
@@ -1683,9 +1707,9 @@ err_unlock:
* 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, nval;
+ u32 uval, nval, mval;
retry:
if (get_user(uval, uaddr))
@@ -1702,21 +1726,45 @@ retry:
* thread-death.) The rest of the cleanup is done in
* userspace.
*/
- nval = futex_atomic_cmpxchg_inatomic(uaddr, uval,
- uval | FUTEX_OWNER_DIED);
+ 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 **head, int *pi)
+{
+ unsigned long uentry;
+
+ if (get_user(uentry, (unsigned long *)head))
+ return -EFAULT;
+
+ *entry = (void *)(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.
*
@@ -1726,14 +1774,14 @@ 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 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:
@@ -1744,10 +1792,11 @@ void exit_robust_list(struct task_struct *curr)
* 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 *)pending + futex_offset, curr, pip);
while (entry != &head->list) {
/*
@@ -1756,12 +1805,12 @@ void exit_robust_list(struct task_struct *curr)
*/
if (entry != pending)
if (handle_futex_death((void *)entry + futex_offset,
- curr))
+ 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:
generated by cgit 1.2.3-korg (git 2.39.0) at 2024-05-20 01:52:35 +0000