[Xen-devel] dump runq with debug key 'r' may cause dead loop

["Wei, Gang" <gang.wei@xxxxxxxxx>]

Recently I found dump runq with debug key 'r' may cause dead loop like below:

(XEN) active vcpus:
(XEN)     1: [1.0] pri=0 flags=0 cpu=0 credit=263 [w=256]
(XEN)     2: [0.2] pri=0 flags=0 cpu=5 credit=284 [w=256]
(XEN)     3: [0.2] pri=0 flags=0 cpu=5 credit=282 [w=256]
...
(XEN)  xxxxx: [0.2] pri=0 flags=0 cpu=2 credit=54 [w=256]
...
(XEN)  xxxxx: [0.2] pri=0 flags=0 cpu=3 credit=-48 [w=256]
...

This means the active vcpu 0.2 became non-active just after it was access in 
the loop '2:', and that list element became empty state (head->next==next).

Should we always hold a lock before access any schedule related list, even in 
the debug purpose dump code? If it is not acceptable, then we'd better add a 
list_empty() check in the dump functions which access schedule related list at 
least to avoid such a dead loop.

Jimmy

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel