linux-kernel - [tip:locking/core] sched/deadline/rtmutex: Dont miss the dl_runtime/dl

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Date:   Tue, 4 Apr 2017 02:50:02 -0700
From:   tip-bot for Xunlei Pang <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     peterz@...radead.org, hpa@...or.com, rostedt@...dmis.org,
        tglx@...utronix.de, xlpang@...hat.com,
        linux-kernel@...r.kernel.org, mingo@...nel.org
Subject: [tip:locking/core] sched/deadline/rtmutex: Dont miss the
 dl_runtime/dl_period update

Commit-ID:  85e2d4f992868ad78dc8bb2c077b652fcfb3661a
Gitweb:     http://git.kernel.org/tip/85e2d4f992868ad78dc8bb2c077b652fcfb3661a
Author:     Xunlei Pang <xlpang@...hat.com>
AuthorDate: Thu, 23 Mar 2017 15:56:09 +0100
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Tue, 4 Apr 2017 11:44:05 +0200

sched/deadline/rtmutex: Dont miss the dl_runtime/dl_period update

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.

Signed-off-by: Xunlei Pang <xlpang@...hat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Steven Rostedt <rostedt@...dmis.org>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
Cc: juri.lelli@....com
Cc: bigeasy@...utronix.de
Cc: mathieu.desnoyers@...icios.com
Cc: jdesfossez@...icios.com
Cc: bristot@...hat.com
Link: http://lkml.kernel.org/r/1460633827-345-7-git-send-email-xlpang@redhat.com
Link: http://lkml.kernel.org/r/20170323150216.206577901@infradead.org
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

---
 kernel/locking/rtmutex.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index bc05b10..8faf472 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -605,7 +605,7 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task,
 	 * 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