"Daniel P. Berrange" <berrange@xxxxxxxxxx> wrote:
> On Sat, Jan 19, 2008 at 09:21:07PM +0100, Jim Meyering wrote:
>> "Daniel P. Berrange" <berrange@xxxxxxxxxx> wrote:
>>
>> > Xen 3.2.0 removed the sockets_per_node field from the nodeinfo data returned
>> > by XenD. I previously add compat for this, but got it in the wrong place
>> > so it would most likely end up in a divide-by-zero error. This patch
>> > re-arranges it to be correct.
>> >
>> > diff -rup libvirt-0.4.0.orig/src/xend_internal.c libvirt-0.4.0.new/src/xend_internal.c
>> > --- libvirt-0.4.0.orig/src/xend_internal.c 2007-12-17 18:05:27.000000000 -0500
>> > +++ libvirt-0.4.0.new/src/xend_internal.c 2008-01-18 21:13:30.000000000 -0500
>> > @@ -1907,6 +1907,9 @@ sexpr_to_xend_node_info(struct sexpr *ro
>> > info->mhz = sexpr_int(root, "node/cpu_mhz");
>> > info->nodes = sexpr_int(root, "node/nr_nodes");
>> > info->sockets = sexpr_int(root, "node/sockets_per_node");
>> > + info->cores = sexpr_int(root, "node/cores_per_socket");
>> > + info->threads = sexpr_int(root, "node/threads_per_core");
>> > +
>> > /* Xen 3.2.0 replaces sockets_per_node with 'nr_cpus'.
>> > * Old Xen calculated sockets_per_node using its internal
>> > * nr_cpus / (nodes*cores*threads), so fake it ourselves
>> > @@ -1921,8 +1924,6 @@ sexpr_to_xend_node_info(struct sexpr *ro
>> > if (info->sockets == 0)
>> > info->sockets = 1;
>> > }
>> > - info->cores = sexpr_int(root, "node/cores_per_socket");
>> > - info->threads = sexpr_int(root, "node/threads_per_core");
>> > return (0);
>> > }
>>
>> ACK.
>>
>> Now that you mention divide-by-zero,
>> is there something that guarantees none of the
>> terms in the denominator there is zero?
>>
>> info->sockets = nr_cpus / (info->nodes * info->cores * info->threads);
>
> You always have at least 1 numa node, at least 1 core, and at least 1
> hyperthread, so you'd only get a zero in those if there was a bug in the
> Xen hypervisor
Yes, I understood that any of those being zero would not make
sense. I mean, what if a caller of sexpr_to_xend_node_info
were to provide a bogus root sexpr?
Is it worth the added comparison to protect against that?
int p = info->nodes * info->cores * info->threads;
if (p == 0)
return -1;
info->sockets = nr_cpus / p;
--
Libvir-list mailing list
Libvir-list@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/libvir-list