From: Dario Faggioli Date: Fri, 22 Jul 2016 12:04:53 +0000 (+0200) Subject: xen: credit2: don't let b_avgload go negative. X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~709 X-Git-Url: https://dgit.raspbian.org/%22http://www.example.com/cgi/%22/%22http:/www.example.com/cgi/%22?a=commitdiff_plain;h=d933b37eb404f27557e3e8468482c8ddaeaee60e;p=xen.git xen: credit2: don't let b_avgload go negative. The ASSERT() made effective by b5b5876619bd8ec2e ("xen: credit2: fix two s_time_t handling issues in load balancing") triggers for b_avgload (spotted by OSSTest). b_avgload is where we store the prediction of how the load of a runqueue will look like in the medium to long term, because of a vcpu being added to or removed from there. On vcpu removal, saturate down b_avgload to zero, as it makes very few sense to predict that the load of a runqueue will at some point become negative! Signed-off-by: Dario Faggioli Acked-by: George Dunlap --- diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c index b92226c66e..1d79de053d 100644 --- a/xen/common/sched_credit2.c +++ b/xen/common/sched_credit2.c @@ -1323,14 +1323,16 @@ runq_assign(const struct scheduler *ops, struct vcpu *vc) static void __runq_deassign(struct csched2_vcpu *svc) { + struct csched2_runqueue_data *rqd = svc->rqd; + ASSERT(!__vcpu_on_runq(svc)); ASSERT(!(svc->flags & CSFLAG_scheduled)); list_del_init(&svc->rqd_elem); - update_max_weight(svc->rqd, 0, svc->weight); + update_max_weight(rqd, 0, svc->weight); /* Expected new load based on removing this vcpu */ - svc->rqd->b_avgload -= svc->avgload; + rqd->b_avgload = max_t(s_time_t, rqd->b_avgload - svc->avgload, 0); svc->rqd = NULL; } @@ -1590,7 +1592,7 @@ csched2_cpu_pick(const struct scheduler *ops, struct vcpu *vc) if ( rqd == svc->rqd ) { if ( cpumask_intersects(vc->cpu_hard_affinity, &rqd->active) ) - rqd_avgload = rqd->b_avgload - svc->avgload; + rqd_avgload = max_t(s_time_t, rqd->b_avgload - svc->avgload, 0); } else if ( spin_trylock(&rqd->lock) ) {