Re: [Xen-devel] [PATCH v2 2/2] kexec: remove spinlock now that all KEXEC hypercall ops are protected at the top-level

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 19/04/17 12:20, Jan Beulich wrote:
>>>> On 19.04.17 at 12:56, <daniel.kiper@xxxxxxxxxx> wrote:
>> On Tue, Apr 18, 2017 at 04:49:48AM -0600, Jan Beulich wrote:
>>>>>> On 17.04.17 at 21:09, <eric.devolder@xxxxxxxxxx> wrote:
>>>> The spinlock in kexec_swap_images() was removed as
>>>> this function is only reachable on the kexec hypercall, which is
>>>> now protected at the top-level in do_kexec_op_internal(),
>>>> thus the local spinlock is no longer necessary.
>>> But perhaps leave an ASSERT() there, making sure the in-hypercall
>>> flag is set?
>> I am not sure why but if at all I think that we should also consider
>> other key kexec functions then. Or put ASSERT() into do_kexec_op_internal()
>> just before "switch ( op )".
> The point of my placement suggestion was that the ASSERT()
> effectively replaces the lock acquire - the places you name
> didn't previously require any synchronization.

I'd recommend adding the ASSERT(), just to be on the safe side.

~Andrew

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