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

[Jonathan Creekmore <jonathan.creekmore@xxxxxxxxx>]

> On Dec 18, 2015, at 11:07 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
> 
>>>> On 18.12.15 at 17:48, <andrew.cooper3@xxxxxxxxxx> wrote:
>> On 18/12/15 16:40, Jonathan Creekmore wrote:
>>>> On Dec 18, 2015, at 3:01 AM, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> 
>>>> 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@xxxxxxxxxx>
>>>>> CC: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
>>>>> CC: Keir Fraser <keir@xxxxxxx>
>>>>> CC: Jan Beulich <jbeulich@xxxxxxxx>
>>>>> CC: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>>>>> Signed-off-by: Jonathan Creekmore <jonathan.creekmore@xxxxxxxxx>
>>>>> ---
>>>>> 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@xxxxxxxxxx>
>>> 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.



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