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futex: Restructure futex_requeue() 

No point in taking two more 'requeue_pi' conditionals just to get to the
requeue. Same for the requeue_pi case just the other way round.

No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211305.468835790@linutronix.de
This commit is contained in:
Thomas Gleixner 2021-08-15 23:29:12 +02:00 committed by Ingo Molnar
parent 59c7ecf154
commit 64b7b715f7
1 changed files with 41 additions and 49 deletions
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90
kernel/futex.c
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@ -2104,20 +2104,17 @@ retry_private:
break;
}
/*
* Wake nr_wake waiters. For requeue_pi, if we acquired the
* lock, we already woke the top_waiter. If not, it will be
* woken by futex_unlock_pi().
*/
if (++task_count <= nr_wake && !requeue_pi) {
mark_wake_futex(&wake_q, this);
/* Plain futexes just wake or requeue and are done */
if (!requeue_pi) {
if (++task_count <= nr_wake)
mark_wake_futex(&wake_q, this);
else
requeue_futex(this, hb1, hb2, &key2);
continue;
}
/* Ensure we requeue to the expected futex for requeue_pi. */
if (requeue_pi && !match_futex(this->requeue_pi_key, &key2)) {
/* Don't account for it */
task_count--;
if (!match_futex(this->requeue_pi_key, &key2)) {
ret = -EINVAL;
break;
}
@ -2125,50 +2122,45 @@ retry_private:
/*
* Requeue nr_requeue waiters and possibly one more in the case
* of requeue_pi if we couldn't acquire the lock atomically.
*
* Prepare the waiter to take the rt_mutex. Take a refcount
* on the pi_state and store the pointer in the futex_q
* object of the waiter.
*/
if (requeue_pi) {
get_pi_state(pi_state);
this->pi_state = pi_state;
ret = rt_mutex_start_proxy_lock(&pi_state->pi_mutex,
this->rt_waiter, this->task);
if (ret == 1) {
/*
* Prepare the waiter to take the rt_mutex. Take a
* refcount on the pi_state and store the pointer in
* the futex_q object of the waiter.
* We got the lock. We do neither drop the refcount
* on pi_state nor clear this->pi_state because the
* waiter needs the pi_state for cleaning up the
* user space value. It will drop the refcount
* after doing so.
*/
get_pi_state(pi_state);
this->pi_state = pi_state;
ret = rt_mutex_start_proxy_lock(&pi_state->pi_mutex,
this->rt_waiter,
this->task);
if (ret == 1) {
/*
* We got the lock. We do neither drop the
* refcount on pi_state nor clear
* this->pi_state because the waiter needs the
* pi_state for cleaning up the user space
* value. It will drop the refcount after
* doing so.
*/
requeue_pi_wake_futex(this, &key2, hb2);
continue;
} else if (ret) {
/*
* rt_mutex_start_proxy_lock() detected a
* potential deadlock when we tried to queue
* that waiter. Drop the pi_state reference
* which we took above and remove the pointer
* to the state from the waiters futex_q
* object.
*/
this->pi_state = NULL;
put_pi_state(pi_state);
/* Don't account for it */
task_count--;
/*
* We stop queueing more waiters and let user
* space deal with the mess.
*/
break;
}
requeue_pi_wake_futex(this, &key2, hb2);
task_count++;
continue;
} else if (ret) {
/*
* rt_mutex_start_proxy_lock() detected a potential
* deadlock when we tried to queue that waiter.
* Drop the pi_state reference which we took above
* and remove the pointer to the state from the
* waiters futex_q object.
*/
this->pi_state = NULL;
put_pi_state(pi_state);
/*
* We stop queueing more waiters and let user space
* deal with the mess.
*/
break;
}
/* Waiter is queued, move it to hb2 */
requeue_futex(this, hb1, hb2, &key2);
task_count++;
}
/*