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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()
This commit is contained in:
Linus Torvalds 2016-04-23 11:39:48 -07:00
parent 16ecb41410 fba7cd681b
commit 0e11d25651
3 changed files with 34 additions and 9 deletions
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8
include/asm-generic/futex.h
View File

@ -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();

27
kernel/futex.c
View File

@ -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)
ret = -EINVAL;
} 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 @@ retry:
*/
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.

8
kernel/locking/qspinlock_stat.h
View File

@ -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;
frac = 100ULL * do_div(stat, kicks);
frac = DIV_ROUND_CLOSEST_ULL(frac, kicks);
if (kicks) {
frac = 100ULL * do_div(stat, kicks);
frac = DIV_ROUND_CLOSEST_ULL(frac, kicks);
}
/*
* Return a X.XX decimal number