Messages in this thread | | | Subject | Re: [PATCH v1 1/1] mm: buddy page accessed before initialized | From | Pavel Tatashin <> | Date | Thu, 2 Nov 2017 10:00:59 -0400 |
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On 11/02/2017 09:54 AM, Michal Hocko wrote: > On Thu 02-11-17 09:39:58, Pavel Tatashin wrote: > [...] >> Hi Michal, >> >> Previously as before my project? That is because memory for all struct pages >> was always zeroed in memblock, and in __free_one_page() page_is_buddy() was >> always returning false, thus we never tried to incorrectly remove it from >> the list: >> >> 837 list_del(&buddy->lru); >> >> Now, that memory is not zeroed, page_is_buddy() can return true after kexec >> when memory is dirty (unfortunately memset(1) with CONFIG_VM_DEBUG does not >> catch this case). And proceed further to incorrectly remove buddy from the >> list. > > OK, I thought this was a regression from one of the recent patches. So > the problem is not new. Why don't we see the same problem during the > standard boot?
Because, I believe, BIOS is zeroing all the memory for us.
> >> This is why we must initialize the computed buddy page beforehand. > > Ble, this is really ugly. I will think about it more. >
Another approach that I considered is to split loop inside deferred_init_range() into two loops: one where we initialize pages by calling __init_single_page(), another where we free them to buddy allocator by calling deferred_free_range().
Pasha
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