From mboxrd@z Thu Jan  1 00:00:00 1970
From: Dario Faggioli <dario.faggioli@citrix.com>
Subject: Re: [PATCH 03/16] xen: sched: make implementing
 .alloc_pdata optional
Date: Tue, 5 Apr 2016 18:01:13 +0200
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To: Jan Beulich <JBeulich@suse.com>
Cc: Juergen Gross <JGross@suse.com>, George Dunlap <george.dunlap@eu.citrix.com>, Robert VanVossen <robert.vanvossen@dornerworks.com>, Josh Whitehead <josh.whitehead@dornerworks.com>, Meng Xu <mengxu@cis.upenn.edu>, xen-devel@lists.xenproject.org
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On Mon, 2016-04-04 at 00:13 -0600, Jan Beulich wrote:
> > > > On 01.04.16 at 19:01, <dario.faggioli@citrix.com> wrote:
> > Ok, I'll do:
> >=20
> > =C2=A0=C2=A0=C2=A0=C2=A0sd->sched_priv =3D SCHED_OP(&ops, alloc_pdata, =
cpu);
> > =C2=A0=C2=A0=C2=A0=C2=A0if ( IS_ERR(sd->sched_priv) )
> > =C2=A0=C2=A0=C2=A0=C2=A0{
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0int err =3D PTR_ERR(sd-=
>sched_priv);
> >=20
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0sd->sched_priv =3D NULL=
;
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0return err;
> > =C2=A0=C2=A0=C2=A0=C2=A0}
> >=20
> > Is this ok?
> Depends: Can ->sched_priv be looked at by another CPU between
> the first and second assignments? If yes, you need to use an
> intermediary local variable.
>=20
Mmm... good point. I don't see this happening, but using a local
variable is more "defensive programming oriented", so I'm going for it.

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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