There was a pure ->prio comparison left in try_to_wake_rt_mutex(),
convert it to use rt_mutex_waiter_less(), noting that greater-or-equal
is not-less (both in kernel priority view).
This necessitated the introduction of cmp_task() which creates a
pointer to an unnamed stack variable of struct rt_mutex_waiter type to
compare against tasks.
With this, we can now also create and employ rt_mutex_waiter_equal().
Reviewed-and-tested-by: Juri Lelli <juri.le...@arm.com>
Reviewed-by: Thomas Gleixner <t...@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
---
kernel/locking/rtmutex.c | 32 +++++++++++++++++++++++++++++---
1 file changed, 29 insertions(+), 3 deletions(-)
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -158,6 +158,12 @@ static inline bool unlock_rt_mutex_safe(
}
#endif
+/*
+ * Only use with rt_mutex_waiter_{less,equal}()
+ */
+#define cmp_task(p) \
+ &(struct rt_mutex_waiter){ .prio = (p)->prio, .deadline =
(p)->dl.deadline }
+
static inline int
rt_mutex_waiter_less(struct rt_mutex_waiter *left,
struct rt_mutex_waiter *right)
@@ -177,6 +183,25 @@ rt_mutex_waiter_less(struct rt_mutex_wai
return 0;
}
+static inline int
+rt_mutex_waiter_equal(struct rt_mutex_waiter *left,
+ struct rt_mutex_waiter *right)
+{
+ if (left->prio != right->prio)
+ return 0;
+
+ /*
+ * If both waiters have dl_prio(), we check the deadlines of the
+ * associated tasks.
+ * If left waiter has a dl_prio(), and we didn't return 0 above,
+ * then right waiter has a dl_prio() too.
+ */
+ if (dl_prio(left->prio))
+ return left->deadline == right->deadline;
+
+ return 1;
+}
+
static void
rt_mutex_enqueue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter)
{
@@ -487,7 +512,7 @@ static int rt_mutex_adjust_prio_chain(st
* enabled we continue, but stop the requeueing in the chain
* walk.
*/
- if (waiter->prio == task->prio && !dl_task(task)) {
+ if (rt_mutex_waiter_equal(waiter, cmp_task(task))) {
if (!detect_deadlock)
goto out_unlock_pi;
else
@@ -790,7 +815,8 @@ static int try_to_take_rt_mutex(struct r
* the top waiter priority (kernel view),
* @task lost.
*/
- if (task->prio >= rt_mutex_top_waiter(lock)->prio)
+ if (!rt_mutex_waiter_less(cmp_task(task),
+ rt_mutex_top_waiter(lock)))
return 0;
/*
@@ -1055,7 +1081,7 @@ void rt_mutex_adjust_pi(struct task_stru
raw_spin_lock_irqsave(&task->pi_lock, flags);
waiter = task->pi_blocked_on;
- if (!waiter || (waiter->prio == task->prio && !dl_prio(task->prio))) {
+ if (!waiter || rt_mutex_waiter_equal(waiter, cmp_task(task))) {
raw_spin_unlock_irqrestore(&task->pi_lock, flags);
return;
}
