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Re: [PATCH v3] page_alloc: assert IRQs are enabled in heap alloc/free
- To: Julien Grall <julien@xxxxxxx>, David Vrabel <dvrabel@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 25 Apr 2022 09:56:21 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, David Vrabel <dvrabel@xxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Mon, 25 Apr 2022 07:56:33 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 24.04.2022 17:52, Julien Grall wrote:
>> Changes in v3:
>> - Use num_online_cpus() in assert.
With this ...
>> --- a/xen/common/page_alloc.c
>> +++ b/xen/common/page_alloc.c
>> @@ -162,6 +162,13 @@
>> static char __initdata opt_badpage[100] = "";
>> string_param("badpage", opt_badpage);
>>
>> +/*
>> + * Heap allocations may need TLB flushes which require IRQs to be
>> + * enabled (except during early boot when only 1 PCPU is online).
>
> Same remark as above. Also, I think there are other cases where
> num_online_cpus() == 1:
> - Xen is only using one core (it will not be a useful system but
> technically supported)
> - During suspend/resume
>
> So I think we should either relax the comment or restrict the assert
> below. I don't have any preference.
... I think it is the comment which wants bringing back in sync.
> + */ > +#define ASSERT_ALLOC_CONTEXT() \
> + ASSERT(!in_irq() && (local_irq_is_enabled() || num_online_cpus() == 1))
While by the time calls here can legitimately occur the online map
should be initialized, I wonder whether it wouldn't be better to use
"<= 1" here nevertheless.
Jan
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