Re: [Xen-devel] [PATCH v2 2/2] x86/mem_sharing: replace using page_lock with our own lock

[Tamas K Lengyel <tamas@xxxxxxxxxxxxx>]

On Fri, Apr 12, 2019 at 1:50 PM Tamas K Lengyel <tamas@xxxxxxxxxxxxx> wrote:
>
> The page_lock system was not intended to be used outside the PV pagetable
> code. Replace its use in mem_sharing with an internal rwlock.
>

After further testing I'm actually running into a lot of strange
problems with this when domains with shared memory get destroyed,
oddly enough after mem_sharing finishes cleaning up: (XEN)
[<ffff82d0802729b9>] domain.c#relinquish_memory+0x62/0x4f8. I tried
moving the lock into page_info instead (in a new struct with
sharing_info) but this approach seems to require a lot more effort and
a lot more thought put into it as page_lock seems to have some other
side-effect that makes this all work. Unfortunately at this time I
can't afford chasing this path further so I'll just go with the
band-aid solution of making page_lock/page_unlock mem_sharing
friendly.

Tamas

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