From mboxrd@z Thu Jan  1 00:00:00 1970
From: Dario Faggioli <dario.faggioli@citrix.com>
Subject: Re: [PATCH for-4.5 v3] Xen and tools: Fix listing of
 vcpus when domains lacking any vcpus exist
Date: Wed, 22 Oct 2014 18:18:43 +0200
Message-ID: <1413994723.17454.10.camel@Abyss>
References: <1413910014-4249-1-git-send-email-andrew.cooper3@citrix.com>
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To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Keir Fraser <keir@xen.org>, Ian Campbell <Ian.Campbell@citrix.com>, Ian Jackson <Ian.Jackson@eu.citrix.com>, Xen-devel <xen-devel@lists.xen.org>, Euan Harris <euan.harris@citrix.com>, Jan Beulich <jbeulich@suse.com>, Wei Liu <wei.liu2@citrix.com>
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On Tue, 2014-10-21 at 17:46 +0100, Andrew Cooper wrote:

> As part of this change, remove the pointless call to libxl_get_max_cpus()=
,
> whose returned value is unconditionally clobbered in the for() loop.
>=20
Is it? You mind pointing me at where?

> diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
> index f27b581..ee127d8 100644
> --- a/tools/libxl/libxl.c
> +++ b/tools/libxl/libxl.c
> @@ -5246,7 +5246,12 @@ libxl_vcpuinfo *libxl_list_vcpu(libxl_ctx *ctx, ui=
nt32_t domid,
>          GC_FREE;
>          return NULL;
>      }
> -    *nr_cpus_out =3D libxl_get_max_cpus(ctx);
>
I may be wrong, but the only other occurrence of nr_cpus_out, which is
where the result from libxl_get_max_cpus() is stored, seems to be in the
parameter list of the function.

About the for, here's how it looks like here:

    for (*nr_vcpus_out =3D 0;
         *nr_vcpus_out <=3D domaininfo.max_vcpu_id;
         ++*nr_vcpus_out, ++ptr) {

I.e., it uses nr_vcpus_out. Note: _v_cpus, different from _p_cpus.

Without such call, callers that expect to see the parameter filled with
the maximum possible number of _P_CPUs, will break!

Regards,
Dario

--=20
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)


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