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Cherry-pick upstream fix for transient "ownerless" rtmutex state #10

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Merged
gratian merged 2 commits into from
Dec 11, 2020
Merged

Cherry-pick upstream fix for transient "ownerless" rtmutex state #10

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1542b8f
Revert "futex: Add work-around for inconsistent pi_state"
gratian Dec 8, 2020
739ed34
futex: Handle transient "ownerless" rtmutex state correctly
Nov 4, 2020
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22 changes: 12 additions & 10 deletions kernel/futex.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2445,20 +2445,22 @@ static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
}

/*
* Since we just failed the trylock; there must be an owner.
* The trylock just failed, so either there is an owner or
* there is a higher priority waiter than this one.
*/
newowner = rt_mutex_owner(&pi_state->pi_mutex);
WARN_ON(!newowner);

/*
* pi_state is incorrect, some other task did a lock steal and
* we returned due to timeout or signal without taking the
* rt_mutex. Too late.
* If the higher priority waiter has not yet taken over the
* rtmutex then newowner is NULL. We can't return here with
* that state because it's inconsistent vs. the user space
* state. So drop the locks and try again. It's a valid
* situation and not any different from the other retry
* conditions.
*/
if (!newowner)
newowner = rt_mutex_next_owner(&pi_state->pi_mutex);

BUG_ON(!newowner);
if (unlikely(!newowner)) {
err = -EAGAIN;
goto handle_err;
}
} else {
WARN_ON_ONCE(argowner != current);
if (oldowner == current) {
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