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Groups > linux.kernel > #1416585

[RFC][PATCH 3/8] sched/deadline/rtmutex: Dont miss the dl_runtime/dl_period update

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From: Xunlei Pang <xlpang@redhat.com>

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 <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Xunlei Pang <xlpang@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1460633827-345-7-git-send-email-xlpang@redhat.com
---
 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

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Thread

[RFC][PATCH 0/8] PI and assorted failings Peter Zijlstra <peterz@infradead.org> - 2016-06-07 22:20 +0200
  [RFC][PATCH 1/8] rtmutex: Deboost before waking up the top waiter Peter Zijlstra <peterz@infradead.org> - 2016-06-07 22:20 +0200
  [RFC][PATCH 3/8] sched/deadline/rtmutex: Dont miss the dl_runtime/dl_period update Peter Zijlstra <peterz@infradead.org> - 2016-06-07 22:30 +0200
  [RFC][PATCH 8/8] rtmutex: Fix PI chain order integrity Peter Zijlstra <peterz@infradead.org> - 2016-06-07 22:30 +0200
  [RFC][PATCH 4/8] rtmutex: Remove rt_mutex_fastunlock() Peter Zijlstra <peterz@infradead.org> - 2016-06-07 22:30 +0200
  [RFC][PATCH 6/8] sched/rtmutex: Refactor rt_mutex_setprio() Peter Zijlstra <peterz@infradead.org> - 2016-06-07 22:30 +0200
  [RFC][PATCH 5/8] rtmutex: Clean up Peter Zijlstra <peterz@infradead.org> - 2016-06-07 22:30 +0200
  [RFC][PATCH 2/8] sched/rtmutex/deadline: Fix a PI crash for deadline tasks Peter Zijlstra <peterz@infradead.org> - 2016-06-07 22:30 +0200
  [RFC][PATCH 7/8] sched,tracing: Update trace_sched_pi_setprio() Peter Zijlstra <peterz@infradead.org> - 2016-06-07 22:30 +0200

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