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authorPeter Zijlstra <peterz@infradead.org>2017-03-22 11:35:51 +0100
committerThomas Gleixner <tglx@linutronix.de>2017-03-23 19:10:07 +0100
commit5293c2efda37775346885c7e924d4ef7018ea60b (patch)
tree77868b67d43f614989c465d06415d6e1a90f5c4b /kernel/futex.c
parentfffa954fb528963c2fb7b0c0084eb77e2be7ab52 (diff)
downloadlinux-5293c2efda37775346885c7e924d4ef7018ea60b.tar.bz2
futex,rt_mutex: Provide futex specific rt_mutex API
Part of what makes futex_unlock_pi() intricate is that rt_mutex_futex_unlock() -> rt_mutex_slowunlock() can drop rt_mutex::wait_lock. This means it cannot rely on the atomicy of wait_lock, which would be preferred in order to not rely on hb->lock so much. The reason rt_mutex_slowunlock() needs to drop wait_lock is because it can race with the rt_mutex fastpath, however futexes have their own fast path. Since futexes already have a bunch of separate rt_mutex accessors, complete that set and implement a rt_mutex variant without fastpath for them. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: juri.lelli@arm.com Cc: bigeasy@linutronix.de Cc: xlpang@redhat.com Cc: rostedt@goodmis.org Cc: mathieu.desnoyers@efficios.com Cc: jdesfossez@efficios.com Cc: dvhart@infradead.org Cc: bristot@redhat.com Link: http://lkml.kernel.org/r/20170322104151.702962446@infradead.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/futex.c')
-rw-r--r--kernel/futex.c30
1 files changed, 14 insertions, 16 deletions
diff --git a/kernel/futex.c b/kernel/futex.c
index cc1034038285..af022919933a 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -916,7 +916,7 @@ void exit_pi_state_list(struct task_struct *curr)
pi_state->owner = NULL;
raw_spin_unlock_irq(&curr->pi_lock);
- rt_mutex_unlock(&pi_state->pi_mutex);
+ rt_mutex_futex_unlock(&pi_state->pi_mutex);
spin_unlock(&hb->lock);
@@ -1364,20 +1364,18 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *top_waiter
pi_state->owner = new_owner;
raw_spin_unlock(&new_owner->pi_lock);
- raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
-
- deboost = rt_mutex_futex_unlock(&pi_state->pi_mutex, &wake_q);
-
/*
- * First unlock HB so the waiter does not spin on it once he got woken
- * up. Second wake up the waiter before the priority is adjusted. If we
- * deboost first (and lose our higher priority), then the task might get
- * scheduled away before the wake up can take place.
+ * We've updated the uservalue, this unlock cannot fail.
*/
+ deboost = __rt_mutex_futex_unlock(&pi_state->pi_mutex, &wake_q);
+
+ raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
spin_unlock(&hb->lock);
- wake_up_q(&wake_q);
- if (deboost)
+
+ if (deboost) {
+ wake_up_q(&wake_q);
rt_mutex_adjust_prio(current);
+ }
return 0;
}
@@ -2253,7 +2251,7 @@ static int fixup_owner(u32 __user *uaddr, struct futex_q *q, int locked)
* task acquired the rt_mutex after we removed ourself from the
* rt_mutex waiters list.
*/
- if (rt_mutex_trylock(&q->pi_state->pi_mutex)) {
+ if (rt_mutex_futex_trylock(&q->pi_state->pi_mutex)) {
locked = 1;
goto out;
}
@@ -2568,7 +2566,7 @@ retry_private:
if (!trylock) {
ret = rt_mutex_timed_futex_lock(&q.pi_state->pi_mutex, to);
} else {
- ret = rt_mutex_trylock(&q.pi_state->pi_mutex);
+ ret = rt_mutex_futex_trylock(&q.pi_state->pi_mutex);
/* Fixup the trylock return value: */
ret = ret ? 0 : -EWOULDBLOCK;
}
@@ -2591,7 +2589,7 @@ retry_private:
* it and return the fault to userspace.
*/
if (ret && (rt_mutex_owner(&q.pi_state->pi_mutex) == current))
- rt_mutex_unlock(&q.pi_state->pi_mutex);
+ rt_mutex_futex_unlock(&q.pi_state->pi_mutex);
/* Unqueue and drop the lock */
unqueue_me_pi(&q);
@@ -2898,7 +2896,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
spin_lock(q.lock_ptr);
ret = fixup_pi_state_owner(uaddr2, &q, current);
if (ret && rt_mutex_owner(&q.pi_state->pi_mutex) == current)
- rt_mutex_unlock(&q.pi_state->pi_mutex);
+ rt_mutex_futex_unlock(&q.pi_state->pi_mutex);
/*
* Drop the reference to the pi state which
* the requeue_pi() code acquired for us.
@@ -2938,7 +2936,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
* userspace.
*/
if (ret && rt_mutex_owner(pi_mutex) == current)
- rt_mutex_unlock(pi_mutex);
+ rt_mutex_futex_unlock(pi_mutex);
/* Unqueue and drop the lock. */
unqueue_me_pi(&q);