Re: [PATCH 2/4] build: Alloc space for sched list in the link file

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 18/12/15 17:11, Jonathan Creekmore wrote:
>> On Dec 18, 2015, at 11:07 AM, Jan Beulich <JBeulich@suse.com> wrote:
>>
>>>>> On 18.12.15 at 17:48, <andrew.cooper3@citrix.com> wrote:
>>> On 18/12/15 16:40, Jonathan Creekmore wrote:
>>>>> On Dec 18, 2015, at 3:01 AM, Andrew Cooper <andrew.cooper3@citrix.com> wrote:
>>>>>
>>>>> On 17/12/2015 20:59, Jonathan Creekmore wrote:
>>>>>> Creates a section to contain scheduler entry pointers that are gathered
>>>>>> together into an array. This will allow, in a follow-on patch, scheduler
>>>>>> entries to be automatically gathered together into the array for
>>>>>> automatic parsing.
>>>>>>
>>>>>> CC: Ian Campbell <ian.campbell@citrix.com>
>>>>>> CC: Stefano Stabellini <stefano.stabellini@citrix.com>
>>>>>> CC: Keir Fraser <keir@xen.org>
>>>>>> CC: Jan Beulich <jbeulich@suse.com>
>>>>>> CC: Andrew Cooper <andrew.cooper3@citrix.com>
>>>>>> Signed-off-by: Jonathan Creekmore <jonathan.creekmore@gmail.com>
>>>>>> ---
>>>>>> xen/arch/arm/xen.lds.S | 4 ++++
>>>>>> xen/arch/x86/xen.lds.S | 4 ++++
>>>>>> 2 files changed, 8 insertions(+)
>>>>>>
>>>>>> diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S
>>>>>> index 0488f37..39a4c86 100644
>>>>>> --- a/xen/arch/arm/xen.lds.S
>>>>>> +++ b/xen/arch/arm/xen.lds.S
>>>>>> @@ -57,6 +57,10 @@ SECTIONS
>>>>>>       . = ALIGN(PAGE_SIZE);
>>>>>>       *(.data.page_aligned)
>>>>>>       *(.data)
>>>>>> +       . = ALIGN(8);
>>>>>> +       __schedulers_start = .;
>>>>>> +       *(.data.schedulers)
>>>>>> +       __schedulers_end = .;
>>>>> These arrays are only ever used in __init scheduler_init().  They should
>>>>> be in .init.data rather than .data, which allows their memory to be
>>>>> reclaimed after boot.
>>>>>
>>>>> With that, Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
>>>> So, they are used in scheduler_init() which is marked __init, but 
>>> scheduler_alloc
>>>> also uses that array (and did before my patch) and it is not marked __init.
>>> Ah yes - so they are.  Apologies for the noise.  This should be in .data
>>> and my R-b stands.
>> In .rodata perhaps?
> I initially put it in .rodata, but the current algorithm for choosing the scheduler NULLs out
> the pointers in the array if the global_init() function fails. To emulate that behavior, I had to 
> move the section to .data instead of .rodata.

Hmm.  That is unfortunate.

Best to leave it in .data, and leave fixing the scheduler initialisation
to the other scheduler clean-up work; there is plenty of other cleanup
work to do, and conflating the two issues is best avoided.

~Andrew