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Re: [PATCH] core-parking: fix build with gcc12 and NR_CPUS=1
- To: Julien Grall <julien@xxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Fri, 9 Sep 2022 14:14:04 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Fri, 09 Sep 2022 12:14:15 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 09.09.2022 13:00, Julien Grall wrote:
> On 09/09/2022 11:18, Jan Beulich wrote:
>> Gcc12 takes issue with core_parking_remove()'s
>>
>> for ( ; i < cur_idle_nums; ++i )
>> core_parking_cpunum[i] = core_parking_cpunum[i + 1];
>>
>> complaining that the right hand side array access is past the bounds of
>> 1. Clearly the compiler can't know that cur_idle_nums can only ever be
>> zero in this case (as the sole CPU cannot be parked).
>>
>> Beyond addressing the immediate issue also adjust core_parking_init():
>> There's no point registering any policy when there's no CPU to park.
>> Since this still doesn't result in the compiler spotting that
>> core_parking_policy is never written (and hence is continuously NULL),
>> also amend core_parking_helper() to avoid eventual similar issues there
>> (minimizing generated code at the same time).
>
> Given that CONFIG_NR_CPUS is a build time option. Wouldn't it be better
> to set CONFIG_CORE_PARKING=n and provide dummy helper for any function
> that may be called unconditionally?
That might be an option, yes; not sure whether that's really better. It's
likely a more intrusive change ...
Jan
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