Re: [RFC/PATCH 0/22] W1: sysfs, lifetime and other fixes

Evgeniy Polyakov
2005-04-26T07:10:25Z

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On Tue, 2005-04-26 at 00:00 -0700, Greg KH wrote:
> On Tue, Apr 26, 2005 at 10:43:36AM +0400, Evgeniy Polyakov wrote:
> > On Mon, 2005-04-25 at 15:22 -0500, Dmitry Torokhov wrote:
> > > On 4/25/05, Evgeniy Polyakov <johnpol@2ka.mipt.ru> wrote:
> > > > While thinking about locking schema
> > > > with respect to sysfs files I recalled,
> > > > why I implemented such a logic -
> > > > now one can _always_ remove _any_ module
> > > > [corresponding object is removed from accessible
> > > > pathes and waits untill all exsting users are gone],
> > > > which is very good - I really like it in networking model,
> > > > while with whole device driver model
> > > > if we will read device's file very quickly
> > > > in several threads we may end up not unloading it at all.
> > >
> > > I am sorrry, that is complete bull*. sysfs also allows removing
> > > modules at an arbitrary time (and usually without annoying "waiting
> > > for refcount" at that)... You just seem to not understand how driver
> > > code works, thus the need of inventing your own schema.
> >
> > Ok, let's try again - now with explanation,
> > since it looks like you did not even try to understand what I said.
> > If you will remove objects from ->remove() callback
> > you may end up with rmmod being stuck.
>
> Yes, and that is acceptable. networking implemented their own locking
> method to allow unloading of their drivers in such a manner. No other
> subsystem is going to do that kind of implementation, so Dmitry is
> correct here.

w1 does it too :)
It's locking was lurked in network code.
And it _is_ design note to be able to remove objects in any time.
Ok, I can not say, that it is exactly like networking,
since there is waiting in rmmod path, it is very similar to virtual
devices
like vlan.

> thanks,
>
> greg k-h
--
Evgeniy Polyakov

Crash is better than data corruption -- Arthur Grabowski

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