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futex: Provide and use pi_state_update_owner()

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Updating pi_state::owner is done at several places with the same
code. Provide a function for it and use that at the obvious places.

This is also a preparation for a bug fix to avoid yet another copy of the
same code or alternatively introducing a completely unpenetratable mess of
gotos.

Originally-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
This commit is contained in:
Thomas Gleixner 2021-01-19 15:21:35 +01:00
parent 04b79c5520
commit c5cade200a
1 changed files with 33 additions and 33 deletions
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66
kernel/futex.c
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@ -763,6 +763,29 @@ static struct futex_pi_state *alloc_pi_state(void)
return pi_state;
}
static void pi_state_update_owner(struct futex_pi_state *pi_state,
struct task_struct *new_owner)
{
struct task_struct *old_owner = pi_state->owner;
lockdep_assert_held(&pi_state->pi_mutex.wait_lock);
if (old_owner) {
raw_spin_lock(&old_owner->pi_lock);
WARN_ON(list_empty(&pi_state->list));
list_del_init(&pi_state->list);
raw_spin_unlock(&old_owner->pi_lock);
}
if (new_owner) {
raw_spin_lock(&new_owner->pi_lock);
WARN_ON(!list_empty(&pi_state->list));
list_add(&pi_state->list, &new_owner->pi_state_list);
pi_state->owner = new_owner;
raw_spin_unlock(&new_owner->pi_lock);
}
}
static void get_pi_state(struct futex_pi_state *pi_state)
{
WARN_ON_ONCE(!refcount_inc_not_zero(&pi_state->refcount));
@ -1521,26 +1544,15 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_pi_state *pi_
ret = -EINVAL;
}
if (ret)
goto out_unlock;
/*
* This is a point of no return; once we modify the uval there is no
* going back and subsequent operations must not fail.
*/
raw_spin_lock(&pi_state->owner->pi_lock);
WARN_ON(list_empty(&pi_state->list));
list_del_init(&pi_state->list);
raw_spin_unlock(&pi_state->owner->pi_lock);
raw_spin_lock(&new_owner->pi_lock);
WARN_ON(!list_empty(&pi_state->list));
list_add(&pi_state->list, &new_owner->pi_state_list);
pi_state->owner = new_owner;
raw_spin_unlock(&new_owner->pi_lock);
postunlock = __rt_mutex_futex_unlock(&pi_state->pi_mutex, &wake_q);
if (!ret) {
/*
* This is a point of no return; once we modified the uval
* there is no going back and subsequent operations must
* not fail.
*/
pi_state_update_owner(pi_state, new_owner);
postunlock = __rt_mutex_futex_unlock(&pi_state->pi_mutex, &wake_q);
}
out_unlock:
raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
@ -2433,19 +2445,7 @@ retry:
* We fixed up user space. Now we need to fix the pi_state
* itself.
*/
if (pi_state->owner != NULL) {
raw_spin_lock(&pi_state->owner->pi_lock);
WARN_ON(list_empty(&pi_state->list));
list_del_init(&pi_state->list);
raw_spin_unlock(&pi_state->owner->pi_lock);
}
pi_state->owner = newowner;
raw_spin_lock(&newowner->pi_lock);
WARN_ON(!list_empty(&pi_state->list));
list_add(&pi_state->list, &newowner->pi_state_list);
raw_spin_unlock(&newowner->pi_lock);
pi_state_update_owner(pi_state, newowner);
raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
return argowner == current;