Re: [Xen-devel] [PATCH V2 2/4] Introduce xen-scsifront module

[Juergen Gross <jgross@xxxxxxxx>]

On 08/01/2014 02:08 PM, Christoph Hellwig wrote:
> On Wed, Jul 30, 2014 at 06:53:59AM +0200, Juergen Gross wrote:
> > Hmm, I looked into scsi_add_device(). It seems as if the caller can't
> > distinguish between a new created and an already existing device. Am I
> > missing something?
> That's right.  If you need that I still think it's better to add a
> variant of scsi_add_device helping you with that.
I'm open to that solution.

Do you have preferences how to do it (IOW: can you give me a hint)?

> > The race is not existing: scsi_add_device() (and scsi_remove_device()
> > as well) for this scsi_host is called in scsifront_do_lun_hotplug()
> > only, and this function is always called in the same thread (xenbus
> > watch). A comment seems to be a good idea.
> Do you disable scanning through procfs and sysfs as well?
No, I don't.

OTOH I don't think I see the problem. What could go wrong? Either
scsi_device_lookup() does find an existing device, then I refuse to add
it again. If I don't find it, it will be added. I can't see how any harm
would be done in either case when the device is added/removed between
the check and the action. What am I missing?

Juergen

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