From 07b0eb5d0ef0be154606aa46b5b4c5c59b158505 Mon Sep 17 00:00:00 2001 From: Dario Faggioli Date: Fri, 28 May 2021 17:12:48 +0200 Subject: [PATCH] credit2: make sure we pick a runnable unit from the runq if there is one MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit A !runnable unit (temporarily) present in the runq may cause us to stop scanning the runq itself too early. Of course, we don't run any non-runnable vCPUs, but we end the scan and we fallback to picking the idle unit. In other word, this prevent us to find there and pick the actual unit that we're meant to start running (which might be further ahead in the runq). Depending on the vCPU pinning configuration, this may lead to such unit to be stuck in the runq for long time, causing malfunctioning inside the guest. Fix this by checking runnable/non-runnable status up-front, in the runq scanning function. Reported-by: Michał Leszczyński Reported-by: Dion Kant Signed-off-by: Dario Faggioli Reviewed-by: George Dunlap --- xen/common/sched/credit2.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/xen/common/sched/credit2.c b/xen/common/sched/credit2.c index eb5e5a78c5..f5c1e5b944 100644 --- a/xen/common/sched/credit2.c +++ b/xen/common/sched/credit2.c @@ -3463,6 +3463,10 @@ runq_candidate(struct csched2_runqueue_data *rqd, (unsigned char *)&d); } + /* Skip non runnable units that we (temporarily) have in the runq */ + if ( unlikely(!unit_runnable_state(svc->unit)) ) + continue; + /* Only consider vcpus that are allowed to run on this processor. */ if ( !cpumask_test_cpu(cpu, svc->unit->cpu_hard_affinity) ) continue; @@ -3496,8 +3500,7 @@ runq_candidate(struct csched2_runqueue_data *rqd, * some budget, then choose it. */ if ( (yield || svc->credit > snext->credit) && - (!has_cap(svc) || unit_grab_budget(svc)) && - unit_runnable_state(svc->unit) ) + (!has_cap(svc) || unit_grab_budget(svc)) ) snext = svc; /* In any case, if we got this far, break. */ -- 2.30.2