Re: [PATCH v4 06/17] virt: acrn: Introduce VM management interfaces

[Shuo A Liu]

On Mon 28.Sep'20 at 14:26:02 +0200, Greg Kroah-Hartman wrote:
> On Mon, Sep 28, 2020 at 02:29:34PM +0800, Shuo A Liu wrote:
> > On Mon 28.Sep'20 at  7:25:16 +0200, Greg Kroah-Hartman wrote:
> > > On Mon, Sep 28, 2020 at 11:50:30AM +0800, Shuo A Liu wrote:
> > > > > > +	write_lock_bh(&acrn_vm_list_lock);
> > > > > > +	list_add(&vm->list, &acrn_vm_list);
> > > > > > +	write_unlock_bh(&acrn_vm_list_lock);
> > > > >
> > > > > Why are the _bh() variants being used here?
> > > > >
> > > > > You are only accessing this list from userspace context in this patch.
> > > > >
> > > > > Heck, you aren't even reading from the list, only writing to it...
> > > >
> > > > acrn_vm_list is read in a tasklet which dispatch I/O requests and is wrote
> > > > in VM creation ioctl. Use the rwlock mechanism to protect it.
> > > > The reading operation is introduced in the following patches of this
> > > > series. So i keep the lock type at the moment of introduction.
> > >
> > > Ok, but think about someone trying to review this code.  Does this lock
> > > actually make sense here?  No, it does not.  How am I supposed to know
> > > to look at future patches to determine that it changes location and
> > > usage to require this?
> >
> > OK. May i know how to handle such kind of code submission? Or which way
> > following do you prefer?
> >  1) Use a mutex lock here, then change it to rwlock in a later patch
> >     of this series.
>
> Wouldn't this make more sense if you had to read these one after
> another?

OK. I will change to mutex firstly for more readable. 

> >  2) Add more comments in changelog about the lock. (Now, there is
> >     comment around the acrn_vm_list_lock)
>
> It's hard to verify a comment's statement without digging through other
> patches in the series, right?  You want the reviewer to just trust you?
> :)
>
> Again, what would _YOU_ want to see if you had to review this?
>
> > > That's just not fair, would you want to review something like this?
> > >
> > > And a HUGE meta-comment, again, why am I the only one reviewing this
> > > stuff?  Why do you have a ton of Intel people on the Cc: yet it is, once
> > > again, my job to do this?
> >
> > The patchset has been reviewed in Intel's internal mailist several
> > rounds and got Reviewed-by: before send out. That's why i Cced many
> > Intel people as well.
>
> Then why didn't any of those intel people on the cc: actually review it
> after you have sent it out?  Why is it only me?  Do I need to wait
> longer for them to get to this?  I'll gladly do so next time...
>
> > This patchset is all about a common driver for the ACRN hypervisor
> > support. I put the code in drivers/virt/ and found you are one of the
> > maintainer of vboxguest driver which is in the same subdirectory. I
> > thought you should be the right person to be Cced when i submitted this
> > series.
>
> I am, I'm not complaining about that.  I'm complaining that it seems to
> be _only_ me reviewing this here, and not any of the people you are cc:ing
> from intel.  Most of those people should be giving you this same type of
> review comments and not forcing an external person to do so, right?
>
> > Certainly, any comments are welcome. And really appreciate your review
> > and help. I have little experience to submit a new driver to the
> > community, my apologies if thing goes wrong.
>
> You didn't do anything wrong, I'm arguing about the larger meta-issue I
> have right now with Intel and the lack of reviews that seems to happen
> from other Intel people on their co-workers patches.
>
> Anyway, you are doing fine, it's an iterative process, hopefully you can
> also review other people's patches in this area that are being posted as
> well.

Sorry, i have no answer about some of your question above. :(
However, i will try my best to help review other people's patches in
this area.

Thanks
shuo