diff options
Diffstat (limited to 'kernel/futex.c')
| -rw-r--r-- | kernel/futex.c | 58 |
1 files changed, 32 insertions, 26 deletions
diff --git a/kernel/futex.c b/kernel/futex.c index b2d51a7..037287b 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -716,7 +716,7 @@ static int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb, struct futex_pi_state **ps, struct task_struct *task, int set_waiters) { - int lock_taken, ret, ownerdied = 0; + int lock_taken, ret, force_take = 0; u32 uval, newval, curval, vpid = task_pid_vnr(task); retry: @@ -755,17 +755,15 @@ retry: 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 ! + * Should we force take the futex? See below. */ - if (unlikely(ownerdied || !(curval & FUTEX_TID_MASK))) { - /* Keep the OWNER_DIED bit */ + if (unlikely(force_take)) { + /* + * Keep the OWNER_DIED and the WAITERS bit and set the + * new TID value. + */ newval = (curval & ~FUTEX_TID_MASK) | vpid; - ownerdied = 0; + force_take = 0; lock_taken = 1; } @@ -775,7 +773,7 @@ retry: goto retry; /* - * We took the lock due to owner died take over. + * We took the lock due to forced take over. */ if (unlikely(lock_taken)) return 1; @@ -790,20 +788,25 @@ retry: switch (ret) { 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. + * We failed to find an owner for this + * futex. So we have no pi_state to block + * on. This can happen in two cases: + * + * 1) The owner died + * 2) A stale FUTEX_WAITERS bit + * + * Re-read the futex value. */ if (get_futex_value_locked(&curval, uaddr)) return -EFAULT; /* - * We simply start over in case of a robust - * futex. The code above will take the futex - * and return happy. + * If the owner died or we have a stale + * WAITERS bit the owner TID in the user space + * futex is 0. */ - if (curval & FUTEX_OWNER_DIED) { - ownerdied = 1; + if (!(curval & FUTEX_TID_MASK)) { + force_take = 1; goto retry; } default: @@ -2231,11 +2234,11 @@ int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb, * @uaddr2: the pi futex we will take prior to returning to user-space * * The caller will wait on uaddr and will be requeued by futex_requeue() to - * uaddr2 which must be PI aware. Normal wakeup will wake on uaddr2 and - * complete the acquisition of the rt_mutex prior to returning to userspace. - * This ensures the rt_mutex maintains an owner when it has waiters; without - * one, the pi logic wouldn't know which task to boost/deboost, if there was a - * need to. + * uaddr2 which must be PI aware and unique from uaddr. Normal wakeup will wake + * on uaddr2 and complete the acquisition of the rt_mutex prior to returning to + * userspace. This ensures the rt_mutex maintains an owner when it has waiters; + * without one, the pi logic would not know which task to boost/deboost, if + * there was a need to. * * We call schedule in futex_wait_queue_me() when we enqueue and return there * via the following: @@ -2272,6 +2275,9 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags, struct futex_q q = futex_q_init; int res, ret; + if (uaddr == uaddr2) + return -EINVAL; + if (!bitset) return -EINVAL; @@ -2343,7 +2349,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags, * signal. futex_unlock_pi() will not destroy the lock_ptr nor * the pi_state. */ - WARN_ON(!&q.pi_state); + WARN_ON(!q.pi_state); pi_mutex = &q.pi_state->pi_mutex; ret = rt_mutex_finish_proxy_lock(pi_mutex, to, &rt_waiter, 1); debug_rt_mutex_free_waiter(&rt_waiter); @@ -2370,7 +2376,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags, * fault, unlock the rt_mutex and return the fault to userspace. */ if (ret == -EFAULT) { - if (rt_mutex_owner(pi_mutex) == current) + if (pi_mutex && rt_mutex_owner(pi_mutex) == current) rt_mutex_unlock(pi_mutex); } else if (ret == -EINTR) { /* |