0033-xen-sched-fix-race-in-RTDS-scheduler.patch


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From 481465f35da1bcec0b2a4dfd6fc51d86cac28547 Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Mon, 31 Oct 2022 13:22:54 +0100
Subject: [PATCH 33/87] xen/sched: fix race in RTDS scheduler

When a domain gets paused the unit runnable state can change to "not
runnable" without the scheduling lock being involved. This means that
a specific scheduler isn't involved in this change of runnable state.

In the RTDS scheduler this can result in an inconsistency in case a
unit is losing its "runnable" capability while the RTDS scheduler's
scheduling function is active. RTDS will remove the unit from the run
queue, but doesn't do so for the replenish queue, leading to hitting
an ASSERT() in replq_insert() later when the domain is unpaused again.

Fix that by removing the unit from the replenish queue as well in this
case.

Fixes: 7c7b407e7772 ("xen/sched: introduce unit_runnable_state()")
Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Dario Faggioli <dfaggioli@suse.com>
master commit: 73c62927f64ecb48f27d06176befdf76b879f340
master date: 2022-10-21 12:32:23 +0200
---
 xen/common/sched/rt.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/xen/common/sched/rt.c b/xen/common/sched/rt.c
index c24cd2ac3200..ec2ca1bebc26 100644
--- a/xen/common/sched/rt.c
+++ b/xen/common/sched/rt.c
@@ -1087,6 +1087,7 @@ rt_schedule(const struct scheduler *ops, struct sched_unit *currunit,
         else if ( !unit_runnable_state(snext->unit) )
         {
             q_remove(snext);
+            replq_remove(ops, snext);
             snext = rt_unit(sched_idle_unit(sched_cpu));
         }
 
-- 
2.37.4