95 lines
3.1 KiB
Diff
95 lines
3.1 KiB
Diff
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References: bsc#991934
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# Commit 9f358ddd69463fa8fb65cf67beb5f6f0d3350e32
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# Date 2016-07-26 10:42:49 +0100
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# Author George Dunlap <george.dunlap@citrix.com>
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# Committer George Dunlap <george.dunlap@citrix.com>
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xen: Have schedulers revise initial placement
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The generic domain creation logic in
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xen/common/domctl.c:default_vcpu0_location() attempts to try to do
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initial placement load-balancing by placing vcpu 0 on the least-busy
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non-primary hyperthread available. Unfortunately, the logic can end
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up picking a pcpu that's not in the online mask. When this is passed
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to a scheduler such which assumes that the initial assignment is
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valid, it causes a null pointer dereference looking up the runqueue.
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Furthermore, this initial placement doesn't take into account hard or
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soft affinity, or any scheduler-specific knowledge (such as historic
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runqueue load, as in credit2).
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To solve this, when inserting a vcpu, always call the per-scheduler
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"pick" function to revise the initial placement. This will
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automatically take all knowledge the scheduler has into account.
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csched2_cpu_pick ASSERTs that the vcpu's pcpu scheduler lock has been
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taken. Grab and release the lock to minimize time spend with irqs
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disabled.
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Signed-off-by: George Dunlap <george.dunlap@citrix.com>
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Reviewed-by: Meng Xu <mengxu@cis.upenn.edu>
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Reviwed-by: Dario Faggioli <dario.faggioli@citrix.com>
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--- a/xen/common/sched_credit.c
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+++ b/xen/common/sched_credit.c
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@@ -994,6 +994,9 @@ csched_vcpu_insert(const struct schedule
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BUG_ON( is_idle_vcpu(vc) );
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+ /* This is safe because vc isn't yet being scheduled */
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+ vc->processor = csched_cpu_pick(ops, vc);
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+
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lock = vcpu_schedule_lock_irq(vc);
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if ( !__vcpu_on_runq(svc) && vcpu_runnable(vc) && !vc->is_running )
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--- a/xen/common/sched_credit2.c
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+++ b/xen/common/sched_credit2.c
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@@ -318,6 +318,8 @@ struct csched2_dom {
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uint16_t nr_vcpus;
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};
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+static int csched2_cpu_pick(const struct scheduler *ops, struct vcpu *vc);
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+
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/*
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* When a hard affinity change occurs, we may not be able to check some
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* (any!) of the other runqueues, when looking for the best new processor
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@@ -956,9 +958,16 @@ csched2_vcpu_insert(const struct schedul
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BUG_ON(is_idle_vcpu(vc));
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- /* Add vcpu to runqueue of initial processor */
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+ /* csched2_cpu_pick() expects the pcpu lock to be held */
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lock = vcpu_schedule_lock_irq(vc);
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+ vc->processor = csched2_cpu_pick(ops, vc);
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+
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+ spin_unlock_irq(lock);
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+
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+ lock = vcpu_schedule_lock_irq(vc);
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+
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+ /* Add vcpu to runqueue of initial processor */
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runq_assign(ops, vc);
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vcpu_schedule_unlock_irq(lock, vc);
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--- a/xen/common/sched_rt.c
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+++ b/xen/common/sched_rt.c
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@@ -203,6 +203,8 @@ struct rt_dom {
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struct domain *dom; /* pointer to upper domain */
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};
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+static int rt_cpu_pick(const struct scheduler *ops, struct vcpu *vc);
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+
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/*
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* Useful inline functions
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*/
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@@ -845,6 +847,9 @@ rt_vcpu_insert(const struct scheduler *o
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BUG_ON( is_idle_vcpu(vc) );
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+ /* This is safe because vc isn't yet being scheduled */
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+ vc->processor = rt_cpu_pick(ops, vc);
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+
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lock = vcpu_schedule_lock_irq(vc);
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now = NOW();
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