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

Shuo A Liu
2020-09-28T06:29:43Z

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.
2) Add more comments in changelog about the lock. (Now, there is
comment around the acrn_vm_list_lock)

>
>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.

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.

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.

Thanks
shuo