Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fixes from Ingo Molnar: "Misc fixes: pvqspinlocks: - an instrumentation fix futexes: - preempt-count vs pagefault_disable decouple corner case fix - futex requeue plist race window fix - futex UNLOCK_PI transaction fix for a corner case" * 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: asm-generic/futex: Re-enable preemption in futex_atomic_cmpxchg_inatomic() futex: Acknowledge a new waiter in counter before plist futex: Handle unlock_pi race gracefully locking/pvqspinlock: Fix division by zero in qstat_read()
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0e11d25651
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@ -108,11 +108,15 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
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u32 val;
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preempt_disable();
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if (unlikely(get_user(val, uaddr) != 0))
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if (unlikely(get_user(val, uaddr) != 0)) {
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preempt_enable();
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return -EFAULT;
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}
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if (val == oldval && unlikely(put_user(newval, uaddr) != 0))
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if (val == oldval && unlikely(put_user(newval, uaddr) != 0)) {
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preempt_enable();
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return -EFAULT;
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}
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*uval = val;
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preempt_enable();
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@ -1295,10 +1295,20 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this,
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if (unlikely(should_fail_futex(true)))
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ret = -EFAULT;
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if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval))
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if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)) {
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ret = -EFAULT;
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else if (curval != uval)
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} else if (curval != uval) {
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/*
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* If a unconditional UNLOCK_PI operation (user space did not
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* try the TID->0 transition) raced with a waiter setting the
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* FUTEX_WAITERS flag between get_user() and locking the hash
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* bucket lock, retry the operation.
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*/
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if ((FUTEX_TID_MASK & curval) == uval)
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ret = -EAGAIN;
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else
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ret = -EINVAL;
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}
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if (ret) {
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raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
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return ret;
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@ -1525,8 +1535,8 @@ void requeue_futex(struct futex_q *q, struct futex_hash_bucket *hb1,
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if (likely(&hb1->chain != &hb2->chain)) {
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plist_del(&q->list, &hb1->chain);
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hb_waiters_dec(hb1);
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plist_add(&q->list, &hb2->chain);
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hb_waiters_inc(hb2);
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plist_add(&q->list, &hb2->chain);
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q->lock_ptr = &hb2->lock;
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}
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get_futex_key_refs(key2);
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@ -2622,6 +2632,15 @@ retry:
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*/
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if (ret == -EFAULT)
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goto pi_faulted;
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/*
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* A unconditional UNLOCK_PI op raced against a waiter
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* setting the FUTEX_WAITERS bit. Try again.
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*/
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if (ret == -EAGAIN) {
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spin_unlock(&hb->lock);
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put_futex_key(&key);
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goto retry;
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}
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/*
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* wake_futex_pi has detected invalid state. Tell user
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* space.
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@ -136,10 +136,12 @@ static ssize_t qstat_read(struct file *file, char __user *user_buf,
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}
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if (counter == qstat_pv_hash_hops) {
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u64 frac;
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u64 frac = 0;
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if (kicks) {
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frac = 100ULL * do_div(stat, kicks);
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frac = DIV_ROUND_CLOSEST_ULL(frac, kicks);
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}
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/*
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* Return a X.XX decimal number
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