Re: [Xen-devel] [PATCH 4/5] xen: use masking operation instead of test_bit for VPF bits

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.10.15 at 15:24, <george.dunlap@xxxxxxxxxx> wrote:
> On 02/10/15 05:40, Juergen Gross wrote:
>> Use a bit mask for testing of a set bit instead of test_bit in case no
>> atomic operation is needed, as this will lead to smaller and more
>> effective code.
>> 
>> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> 
> On a side note, a handful of functions seem to access the vcpu structure
> with the *domain* lock held, rather than the *scheduler* lock; for example:
> 
> xen/arch/x86/hvm/vlapic.c:vlapic_accept_irq()
> xen/common/domain.c:vcpu_reset()

Why would the scheduler lock be needed there? In both cases it would
- at a first glance - seem as if the domain lock isn't needed there.

> Is this a bug (perhaps left over from when we used the domain lock for
> vcpus rather than the scheduler lock)?

Not completely impossible there is too little locking now, but generally
I don't think all vcpu structure accesses need to happen under one
single lock.

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel