Idle vCPUs should never really be explicitly inserted
in any of the schedulers' runqueue. In fact, they are
just put in execution immediately (either on boot, or
when a pCPU is assigned to a cpupool), and it will be
the first scheduling decision that --by preempting
them-- will 'park' them in the queue.
In fact, avoiding inserting those vCPUs in runqueues
is something that Credit2 and RTDS intercept and
forbid already (when implementing insert_vcpu()).
Credit1 does that implicitly, as the idle vCPU will
always be already running when insert_vcpu() is called,
and hence not put in the runqueue.
Let's make it *always* explicit, as that simplifies
things by quite a bit. For instance, we can now
introduce some BUG_ON() guards, with the twofold
objective of making this assumption clear, and of
catching misuse and bugs.
The check for whether we'd be inserting an idle vCPU
in a queue, now, happens, once and for all schedulers,
in generic code, at vCPU initialization time, while
we can just avoid trying (and always failing!) doing
so when doing cpupools manipulations.
Signed-off-by: Dario Faggioli <dario.faggi...@citrix.com>
---
Cc: George Dunlap <george.dun...@eu.citrix.com>
Cc: Juergen Gross <jgr...@suse.com>
---
xen/common/sched_credit.c | 2 ++
xen/common/sched_credit2.c | 25 ++++++++++---------------
xen/common/sched_rt.c | 4 +---
xen/common/schedule.c | 21 +++++++++++----------
4 files changed, 24 insertions(+), 28 deletions(-)
diff --git a/xen/common/sched_credit.c b/xen/common/sched_credit.c
index fccb368..fc447a7 100644
--- a/xen/common/sched_credit.c
+++ b/xen/common/sched_credit.c
@@ -905,6 +905,8 @@ csched_vcpu_insert(const struct scheduler *ops, struct vcpu
*vc)
struct csched_vcpu *svc = vc->sched_priv;
spinlock_t *lock;
+ BUG_ON( is_idle_vcpu(vc) );
+
lock = vcpu_schedule_lock_irq(vc);
if ( !__vcpu_on_runq(svc) && vcpu_runnable(vc) && !vc->is_running )
diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c
index 912e1a2..234f798 100644
--- a/xen/common/sched_credit2.c
+++ b/xen/common/sched_credit2.c
@@ -870,30 +870,25 @@ csched2_vcpu_insert(const struct scheduler *ops, struct
vcpu *vc)
{
struct csched2_vcpu *svc = vc->sched_priv;
struct csched2_dom * const sdom = svc->sdom;
+ spinlock_t *lock;
printk("%s: Inserting %pv\n", __func__, vc);
- /* NB: On boot, idle vcpus are inserted before alloc_pdata() has
- * been called for that cpu.
- */
- if ( ! is_idle_vcpu(vc) )
- {
- spinlock_t *lock;
+ BUG_ON(is_idle_vcpu(vc));
- /* FIXME: Do we need the private lock here? */
- list_add_tail(&svc->sdom_elem, &svc->sdom->vcpu);
+ /* FIXME: Do we need the private lock here? */
+ list_add_tail(&svc->sdom_elem, &svc->sdom->vcpu);
- /* Add vcpu to runqueue of initial processor */
- lock = vcpu_schedule_lock_irq(vc);
+ /* Add vcpu to runqueue of initial processor */
+ lock = vcpu_schedule_lock_irq(vc);
- runq_assign(ops, vc);
+ runq_assign(ops, vc);
- vcpu_schedule_unlock_irq(lock, vc);
+ vcpu_schedule_unlock_irq(lock, vc);
- sdom->nr_vcpus++;
+ sdom->nr_vcpus++;
- SCHED_STAT_CRANK(vcpu_insert);
- }
+ SCHED_STAT_CRANK(vcpu_insert);
CSCHED2_VCPU_CHECK(vc);
}
diff --git a/xen/common/sched_rt.c b/xen/common/sched_rt.c
index 1086399..37a32a4 100644
--- a/xen/common/sched_rt.c
+++ b/xen/common/sched_rt.c
@@ -624,9 +624,7 @@ rt_vcpu_insert(const struct scheduler *ops, struct vcpu *vc)
s_time_t now = NOW();
spinlock_t *lock;
- /* not addlocate idle vcpu to dom vcpu list */
- if ( is_idle_vcpu(vc) )
- return;
+ BUG_ON( is_idle_vcpu(vc) );
lock = vcpu_schedule_lock_irq(vc);
if ( now >= svc->cur_deadline )
diff --git a/xen/common/schedule.c b/xen/common/schedule.c
index 9aa209d..55daf73 100644
--- a/xen/common/schedule.c
+++ b/xen/common/schedule.c
@@ -240,20 +240,22 @@ int sched_init_vcpu(struct vcpu *v, unsigned int
processor)
init_timer(&v->poll_timer, poll_timer_fn,
v, v->processor);
- /* Idle VCPUs are scheduled immediately. */
+ v->sched_priv = SCHED_OP(DOM2OP(d), alloc_vdata, v, d->sched_priv);
+ if ( v->sched_priv == NULL )
+ return 1;
+
+ TRACE_2D(TRC_SCHED_DOM_ADD, v->domain->domain_id, v->vcpu_id);
+
+ /* Idle VCPUs are scheduled immediately, not inserting them in runqueue. */
if ( is_idle_domain(d) )
{
per_cpu(schedule_data, v->processor).curr = v;
v->is_running = 1;
}
-
- TRACE_2D(TRC_SCHED_DOM_ADD, v->domain->domain_id, v->vcpu_id);
-
- v->sched_priv = SCHED_OP(DOM2OP(d), alloc_vdata, v, d->sched_priv);
- if ( v->sched_priv == NULL )
- return 1;
-
- SCHED_OP(DOM2OP(d), insert_vcpu, v);
+ else
+ {
+ SCHED_OP(DOM2OP(d), insert_vcpu, v);
+ }
return 0;
}
@@ -1514,7 +1516,6 @@ int schedule_cpu_switch(unsigned int cpu, struct cpupool
*c)
ppriv_old = per_cpu(schedule_data, cpu).sched_priv;
per_cpu(schedule_data, cpu).sched_priv = ppriv;
SCHED_OP(new_ops, tick_resume, cpu);
- SCHED_OP(new_ops, insert_vcpu, idle);
SCHED_OP(old_ops, free_vdata, vpriv_old);
SCHED_OP(old_ops, free_pdata, ppriv_old, cpu);
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