Re: [Xen-devel] [PATCH v6 3/5] IOMMU: Make the pcidevs_lock a recursive one

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 07.03.16 at 12:42, <quan.xu@xxxxxxxxx> wrote:
> On March 07, 2016 7:36pm, <JBeulich@xxxxxxxx> wrote:
>> >>> On 07.03.16 at 12:23, <quan.xu@xxxxxxxxx> wrote:
>> > On March 07, 2016 7:14pm, <JBeulich@xxxxxxxx> wrote:
>> >> >>> On 07.03.16 at 08:05, <quan.xu@xxxxxxxxx> wrote:
>> >
>> >
>> >> > A quick question, is it '-ERESTART', instead of '-EBUSY' ?
>> >>
>> >> No idea what this question is about in this context.
>> >>
>> >
>> > it is in xen/drivers/passthrough/pci.c, assign_device().
>> >
>> > static int assign_device()
>> > {
>> >    ....
>> >     if ( !spin_trylock(&pcidevs_lock) )
>> >         return -ERESTART;
>> >    ....
>> > }
>> 
>> But I still don't understand what you're trying to find out or point out.
> 
> Jan, sorry.
> Now the return error code is '-ERESTART' for ' if ( 
> !spin_trylock(&pcidevs_lock) ', in assign_device(), in 
> xen/drivers/passthrough/pci.c.
> I think it would be '-EBUSY'.

Oh - definitely not. Just follow the call chain back up, and you
should find that this gets taken as an indication to create a
continuation, whereas -EBUSY would bubble back up to the
original (user space) caller (which is _not_ what we want here).

Jan


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