FAILED: patch "[PATCH] sched/fair: Fix enqueue_task_fair() warning some more" failed to apply to 5.6-stable tree

The patch below does not apply to the 5.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From b34cb07dde7c2346dec73d053ce926aeaa087303 Mon Sep 17 00:00:00 2001
From: Phil Auld <[email protected]>
Date: Tue, 12 May 2020 09:52:22 -0400
Subject: [PATCH] sched/fair: Fix enqueue_task_fair() warning some more

sched/fair: Fix enqueue_task_fair warning some more

The recent patch, fe61468b2cb (sched/fair: Fix enqueue_task_fair warning) did not fully resolve the issues with the rq->tmp_alone_branch != &rq->leaf_cfs_rq_list warning in enqueue_task_fair. There is a case where the first for_each_sched_entity loop exits due to on_rq, having incompletely updated the list. In this case the second for_each_sched_entity loop can further modify se. The later code to fix up the list management fails to do what is needed because se does not point to the sched_entity which broke out of the first loop. The list is not fixed up because the throttled parent was already added back to the list by a task enqueue in a parallel child hierarchy.

Address this by calling list_add_leaf_cfs_rq if there are throttled parents while doing the second for_each_sched_entity loop.

Fixes fe61468b2cb ("sched/fair: Fix enqueue_task_fair warning")

Suggested-by Vincent Guittot <[email protected]>

Signed-off-by Phil Auld <[email protected]>

Signed-off-by Peter Zijlstra (Intel) <[email protected]>

Reviewed-by Dietmar Eggemann <[email protected]>

Reviewed-by Vincent Guittot <[email protected]>

Link https://lkml.kernel.org/r/[email protected] open here

kernel/sched/fair.c +7 -0

index 02f323b85b6d..c6d57c334d51 100644
@@ -5479,6 +5479,13 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
                /* end evaluation on encountering a throttled cfs_rq */
                if (cfs_rq_throttled(cfs_rq))
                        goto enqueue_throttle;
+
+               /*
+                * One parent has been throttled and cfs_rq removed from the
+                * list. Add it back to not break the leaf list.
+                */
+               if (throttled_hierarchy(cfs_rq))
+                       list_add_leaf_cfs_rq(cfs_rq);
        }
 
 enqueue_throttle:

Quoted 6 lines · On Mon, 25 May 2020 at 16:42, <[email protected]> wrote:

The patch below does not apply to the 5.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

This patch applies on top of
commit 6d4d22468dae ("sched/fair: Reorder enqueue/dequeue_task_fair path")

commit 5ab297bab984 ("sched/fair: Fix reordering of enqueue/dequeue_task_fair()")

Quoted 10 lines · Vincent Guittot

Quoted 6 lines · On Mon, 25 May 2020 at 16:42, <[email protected]> wrote:

The patch below does not apply to the 5.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

This patch applies on top of
commit 6d4d22468dae ("sched/fair: Reorder enqueue/dequeue_task_fair path")

That applies, but:

Quoted 2 lines

commit 5ab297bab984 ("sched/fair: Fix reordering of enqueue/dequeue_task_fair()")

That one does not.

Can you make a backported patch series of these that I can apply easily?

thanks,

greg k-h

Quoted 18 lines · On Mon, 25 May 2020 at 17:49, [email protected]…

Quoted 10 lines · Vincent Guittot

Quoted 6 lines · On Mon, 25 May 2020 at 16:42, <[email protected]> wrote:

The patch below does not apply to the 5.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

This patch applies on top of
commit 6d4d22468dae ("sched/fair: Reorder enqueue/dequeue_task_fair path")

That applies, but:

Quoted 2 lines

commit 5ab297bab984 ("sched/fair: Fix reordering of enqueue/dequeue_task_fair()")

Quoted 3 lines

That one does not.

Can you make a backported patch series of these that I can apply easily?

I tested the cherry-pick of the 2 commits above on top of v5.6.14 and there were applying without error. Should I use another tag ?