From: Xunlei Pang <[email protected]>
Currently dl tasks will actually return at the very beginning
of rt_mutex_adjust_prio_chain() in !detect_deadlock cases:
if (waiter->prio == task->prio) {
if (!detect_deadlock)
goto out_unlock_pi; // out here
else
requeue = false;
}
As the deadline value of blocked deadline tasks(waiters) without
changing their sched_class(thus prio doesn't change) never changes,
this seems reasonable, but it actually misses the chance of updating
rt_mutex_waiter's "dl_runtime(period)_copy" if a waiter updates its
deadline parameters(dl_runtime, dl_period) or boosted waiter changes
to !deadline class.
Thus, force deadline task not out by adding the !dl_prio() condition.
[peterz: I should introduce more task state comparators like
rt_mutex_waiter_less, all PI prio comparisons already have this DL
exception, except this one]
Cc: Steven Rostedt <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Juri Lelli <[email protected]>
Signed-off-by: Xunlei Pang <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
---
kernel/locking/rtmutex.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -488,7 +488,7 @@ static int rt_mutex_adjust_prio_chain(st
* enabled we continue, but stop the requeueing in the chain
* walk.
*/
- if (waiter->prio == task->prio) {
+ if (waiter->prio == task->prio && !dl_task(task)) {
if (!detect_deadlock)
goto out_unlock_pi;
else
