File 5e4d4f5b-sched-fix-get_cpu_idle_time-with-core-... of Package xen

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File 5e4d4f5b-sched-fix-get_cpu_idle_time-with-core-sched.patch of Package xen (Revision 7a8cd898a8dbdd04b7bc3f1964776d5c)

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# Commit 132cbe8f35632fb2fea0625ee8fdda53a19a1645
# Date 2020-02-19 16:08:11 +0100
# Author Juergen Gross <jgross@suse.com>
# Committer Jan Beulich <jbeulich@suse.com>
sched: fix get_cpu_idle_time() with core scheduling

get_cpu_idle_time() is calling vcpu_runstate_get() for an idle vcpu.
With core scheduling active this is fragile, as idle vcpus are assigned
to other scheduling units temporarily, and that assignment is changed
in some cases without holding the scheduling lock, and
vcpu_runstate_get() is using v->sched_unit as parameter for
unit_schedule_[un]lock_irq(), resulting in an ASSERT() triggering in
unlock in case v->sched_unit has changed meanwhile.

Fix that by using a local unit variable holding the correct unit.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Dario Faggioli <dfaggioli@suse.com>

--- a/xen/common/schedule.c
+++ b/xen/common/schedule.c
@@ -305,17 +305,26 @@ void vcpu_runstate_get(struct vcpu *v, s
 {
     spinlock_t *lock;
     s_time_t delta;
+    struct sched_unit *unit;
 
     rcu_read_lock(&sched_res_rculock);
 
-    lock = likely(v == current) ? NULL : unit_schedule_lock_irq(v->sched_unit);
+    /*
+     * Be careful in case of an idle vcpu: the assignment to a unit might
+     * change even with the scheduling lock held, so be sure to use the
+     * correct unit for locking in order to avoid triggering an ASSERT() in
+     * the unlock function.
+     */
+    unit = is_idle_vcpu(v) ? get_sched_res(v->processor)->sched_unit_idle
+                           : v->sched_unit;
+    lock = likely(v == current) ? NULL : unit_schedule_lock_irq(unit);
     memcpy(runstate, &v->runstate, sizeof(*runstate));
     delta = NOW() - runstate->state_entry_time;
     if ( delta > 0 )
         runstate->time[runstate->state] += delta;
 
     if ( unlikely(lock != NULL) )
-        unit_schedule_unlock_irq(lock, v->sched_unit);
+        unit_schedule_unlock_irq(lock, unit);
 
     rcu_read_unlock(&sched_res_rculock);
 }

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File 5e4d4f5b-sched-fix-get_cpu_idle_time-with-core-sched.patch of Package xen (Revision 7a8cd898a8dbdd04b7bc3f1964776d5c)

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