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Commit 0e11d256 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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()
parents 16ecb414 fba7cd68

include/asm-generic/futex.h

+6 −2
Original line number Diff line number Diff line
@@ -108,11 +108,15 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, 
	u32 val;



	preempt_disable();

	if (unlikely(get_user(val, uaddr) != 0))

	if (unlikely(get_user(val, uaddr) != 0)) {

		preempt_enable();

		return -EFAULT;

	}



	if (val == oldval && unlikely(put_user(newval, uaddr) != 0))

	if (val == oldval && unlikely(put_user(newval, uaddr) != 0)) {

		preempt_enable();

		return -EFAULT;

	}



	*uval = val;

	preempt_enable();

kernel/futex.c

+23 −4
Original line number Diff line number Diff line
@@ -1295,10 +1295,20 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this, 
	if (unlikely(should_fail_futex(true)))

		ret = -EFAULT;



	if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval))

	if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)) {

		ret = -EFAULT;

	else if (curval != uval)

	} else if (curval != uval) {

		/*

		 * If a unconditional UNLOCK_PI operation (user space did not

		 * try the TID->0 transition) raced with a waiter setting the

		 * FUTEX_WAITERS flag between get_user() and locking the hash

		 * bucket lock, retry the operation.

		 */

		if ((FUTEX_TID_MASK & curval) == uval)

			ret = -EAGAIN;

		else

			ret = -EINVAL;

	}

	if (ret) {

		raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);

		return ret;
@@ -1525,8 +1535,8 @@ void requeue_futex(struct futex_q *q, struct futex_hash_bucket *hb1, 
	if (likely(&hb1->chain != &hb2->chain)) {

		plist_del(&q->list, &hb1->chain);

		hb_waiters_dec(hb1);

		plist_add(&q->list, &hb2->chain);

		hb_waiters_inc(hb2);

		plist_add(&q->list, &hb2->chain);

		q->lock_ptr = &hb2->lock;

	}

	get_futex_key_refs(key2);
@@ -2622,6 +2632,15 @@ static int futex_unlock_pi(u32 __user *uaddr, unsigned int flags) 
		 */

		if (ret == -EFAULT)

			goto pi_faulted;

		/*

		 * A unconditional UNLOCK_PI op raced against a waiter

		 * setting the FUTEX_WAITERS bit. Try again.

		 */

		if (ret == -EAGAIN) {

			spin_unlock(&hb->lock);

			put_futex_key(&key);

			goto retry;

		}

		/*

		 * wake_futex_pi has detected invalid state. Tell user

		 * space.

kernel/locking/qspinlock_stat.h

+5 −3
Original line number Diff line number Diff line
@@ -136,10 +136,12 @@ static ssize_t qstat_read(struct file *file, char __user *user_buf, 
	}



	if (counter == qstat_pv_hash_hops) {

		u64 frac;

		u64 frac = 0;



		if (kicks) {

			frac = 100ULL * do_div(stat, kicks);

			frac = DIV_ROUND_CLOSEST_ULL(frac, kicks);

		}



		/*

		 * Return a X.XX decimal number