[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <SJ1PR11MB6083A9F0B30A6009BF00235EFCE6A@SJ1PR11MB6083.namprd11.prod.outlook.com>
Date: Wed, 30 Aug 2023 14:11:14 +0000
From: "Luck, Tony" <tony.luck@...el.com>
To: "Wieczor-Retman, Maciej" <maciej.wieczor-retman@...el.com>
CC: "Yu, Fenghua" <fenghua.yu@...el.com>,
"Chatre, Reinette" <reinette.chatre@...el.com>,
Peter Newman <peternewman@...gle.com>,
"Jonathan Corbet" <corbet@....net>,
Shuah Khan <skhan@...uxfoundation.org>,
"x86@...nel.org" <x86@...nel.org>,
Shaopeng Tan <tan.shaopeng@...itsu.com>,
James Morse <james.morse@....com>,
Jamie Iles <quic_jiles@...cinc.com>,
"Babu Moger" <babu.moger@....com>,
Randy Dunlap <rdunlap@...radead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
"patches@...ts.linux.dev" <patches@...ts.linux.dev>
Subject: RE: [PATCH v5 1/8] x86/resctrl: Prepare for new domain scope
> >+static int get_domain_id_from_scope(int cpu, enum resctrl_scope scope)
> >+{
> >+ switch (scope) {
> >+ case RESCTRL_L3_CACHE:
> >+ return get_cpu_cacheinfo_id(cpu, 3);
> >+ case RESCTRL_L2_CACHE:
> >+ return get_cpu_cacheinfo_id(cpu, 2);
> >+ default:
> >+ WARN_ON_ONCE(1);
> >+ break;
> >+ }
> >+
> >+ return -1;
> >+}
>
> Is there some reason the "return -1" is outside of the default switch
> case?
>
> Other switch statements in this patch do have returns inside the default
> case, is this one different in some way?
I've sometimes had compilers complain about code written:
static int get_domain_id_from_scope(int cpu, enum resctrl_scope scope)
{
switch (scope) {
case RESCTRL_L3_CACHE:
return get_cpu_cacheinfo_id(cpu, 3);
case RESCTRL_L2_CACHE:
return get_cpu_cacheinfo_id(cpu, 2);
default:
WARN_ON_ONCE(1);
return -1;
}
}
because they failed to notice that every path in the switch does a "return and they
issue a warning that the function has no return value because they don't realize
that the end of the function can't be reached.
So it's defensive programming against possible complier issues.
-Tony
Powered by blists - more mailing lists