Re: [Xen-devel] Xen 4.4 Testing: Platform Op XENPF_microcode_update Leaves VCPU Lock Set?

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 24/04/14 14:35, John McDermott wrote:
> Xen Developers,
>
> In arch/x86/platform_hypercall.c, in function do_platform_op, the case 
> XENPF_microcode_update appears to leave the vcpu_alloc_lock set when creating 
> a hypercall continuation, but I don't understand the hypercall continuation 
> code as releasing that lock. The lock is not released at target label of the 
> following goto, in case XENPF_microcode_update.
>
> I don't have the facilities to exercise this case on my development platform, 
> but it looks like a possible problem or does the hypercall continuation 
> somehow take care of this lock?
>
> Sincerely,
>
> John

spin_trylock() will try to take the spinlock, but return failure rather
than spinning.

The body of the while loop is therefore strictly when the
vcpu_alloc_lock is not held, so the goto out is safe in context.

>
> ps. I tried subscribing to the Xen dev list 3 times but it never worked.

That is curious.  Any indication of an error?  You certainly havn't
successfully signed up as I had to approve this email through moderation.

~Andrew

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