Re: [PATCH, RESEND] Avoid that SCSI device removal through sysfs triggers a deadlock

["tj@kernel.org" <tj@kernel.org>]

Hello,

On Mon, Jul 30, 2018 at 05:50:02PM +0000, Bart Van Assche wrote:
> On Mon, 2018-07-30 at 10:31 -0700, tj@kernel.org wrote:
> > On Mon, Jul 30, 2018 at 05:28:11PM +0000, Bart Van Assche wrote:
> > > It's not clear to me how the sysfs_break_active_protection() should obtain
> > > the struct kernfs_node pointer to the attribute. Calling that function before
> > > device_remove_file_self() causes a double call to kernfs_break_active_protection(),
> > > which is wrong. Calling kernfs_find_and_get(kobj->sd, attr->name) after the
> > 
> > So, if you braek active protection explicitly, there's no need to call
> > remove_self().  It can just use regular remove.
> 
> But how to avoid that scsi_remove_device(to_scsi_device(dev)) gets called
> multiple times when using device_remove_self() and in case of concurrent
> writes into the SCSI device "delete" sysfs attribute?

So, scsi_remove_device() internally protects using scan_mutex and if
the whole thing is wrapped with break_active_prot, I don't think you
need to call remove_file_self at all, right?

Thanks.

-- 
tejun