Re: [Xen-devel] [PATCH] schedule: mask out XEN_RUNSTATE_UPDATE from state entry time

[Andrii Anisov <andrii.anisov@xxxxxxxxx>]

Hello Jan,

On 18.07.19 14:10, Jan Beulich wrote:
> Considering the value of XEN_RUNSTATE_UPDATE it must be a rather rare race
> anyway, I would guess.
I'm not sure about the exact rate of the race, but with following prints:

diff --git a/xen/common/schedule.c b/xen/common/schedule.c
index 25f6ab3..6ba82b8 100644
--- a/xen/common/schedule.c
+++ b/xen/common/schedule.c
@@ -188,6 +188,13 @@ static inline void vcpu_runstate_change(
         v->runstate.time[v->runstate.state] += delta;
         v->runstate.state_entry_time = new_entry_time;
     }
+    else
+    {
+        printk("delta %"PRIx64", v->runstate.state_entry_time is %"PRIx64", new_entry_time 
%"PRIx64"\n",
+            (long unsigned int)delta,
+            (long unsigned int)v->runstate.state_entry_time,
+            (long unsigned int)new_entry_time);
+    }
 
     v->runstate.state = new_state;
 }

I've got my console completely flooded with something like following:

(XEN) delta 80000000000008e8, v->runstate.state_entry_time is 80000018d58e3cb3, 
new_entry_time 18d58e459b
(XEN) delta 8000000000001c98, v->runstate.state_entry_time is 80000018d8224fa5, 
new_entry_time 18d8226c3d
(XEN) delta 80000000000012c0, v->runstate.state_entry_time is 80000018d94fea14, 
new_entry_time 18d94ffcd4
(XEN) delta 8000000000000ca8, v->runstate.state_entry_time is 80000018da874e8c, 
new_entry_time 18da875b34
(XEN) delta 8000000000001338, v->runstate.state_entry_time is 80000018db2602bc, 
new_entry_time 18db2615f4
(XEN) delta 8000000000000780, v->runstate.state_entry_time is 80000018ddd9ed1a, 
new_entry_time 18ddd9f49a
(XEN) delta 80000000000016f8, v->runstate.state_entry_time is 80000018e19def39, 
new_entry_time 18e19e0631
(XEN) delta 800000000001669c, v->runstate.state_entry_time is 80000018e22b1553, 
new_entry_time 18e22c7bef
(XEN) delta 80000000000010e0, v->runstate.state_entry_time is 80000018e2d28e72, 
new_entry_time 18e2d29f52

--
Sincerely,
Andrii Anisov.

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