Messages in this thread | | | Subject | Re: [PATCH v2] kernel/resource: Fix locking in request_free_mem_region | From | David Hildenbrand <> | Date | Fri, 26 Mar 2021 09:57:51 +0100 |
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On 26.03.21 02:20, Alistair Popple wrote: > request_free_mem_region() is used to find an empty range of physical > addresses for hotplugging ZONE_DEVICE memory. It does this by iterating > over the range of possible addresses using region_intersects() to see if > the range is free.
Just a high-level question: how does this iteract with memory hot(un)plug? IOW, how defines and manages the "range of possible addresses" ?
> > region_intersects() obtains a read lock before walking the resource tree > to protect against concurrent changes. However it drops the lock prior > to returning. This means by the time request_mem_region() is called in > request_free_mem_region() another thread may have already reserved the > requested region resulting in unexpected failures and a message in the > kernel log from hitting this condition:
I am confused. Why can't we return an error to the caller and let the caller continue searching? This feels much simpler than what you propose here. What am I missing?
-- Thanks,
David / dhildenb
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