linux-kernel - RE: [PATCH 1/1] rcu/rcuscale: Stop kfree_scale_thread thread(s) after unloading rcuscale

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Date:   Thu, 16 Mar 2023 13:53:43 +0000
From:   "Zhuo, Qiuxu" <qiuxu.zhuo@...el.com>
To:     Joel Fernandes <joel@...lfernandes.org>,
        "paulmck@...nel.org" <paulmck@...nel.org>
CC:     Frederic Weisbecker <frederic@...nel.org>,
        Josh Triplett <josh@...htriplett.org>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        "rcu@...r.kernel.org" <rcu@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/1] rcu/rcuscale: Stop kfree_scale_thread thread(s) after
 unloading rcuscale

> From: Joel Fernandes <joel@...lfernandes.org>
> Sent: Thursday, March 16, 2023 9:29 PM
> To: Zhuo, Qiuxu <qiuxu.zhuo@...el.com>
> Cc: paulmck@...nel.org; Frederic Weisbecker <frederic@...nel.org>; Josh
> Triplett <josh@...htriplett.org>; Neeraj Upadhyay
> <quic_neeraju@...cinc.com>; Davidlohr Bueso <dave@...olabs.net>; Steven
> Rostedt <rostedt@...dmis.org>; Mathieu Desnoyers
> <mathieu.desnoyers@...icios.com>; Lai Jiangshan
> <jiangshanlai@...il.com>; rcu@...r.kernel.org; linux-
> kernel@...r.kernel.org
> Subject: Re: [PATCH 1/1] rcu/rcuscale: Stop kfree_scale_thread thread(s)
> after unloading rcuscale
> 
> 
> > On Mar 16, 2023, at 9:17 AM, Zhuo, Qiuxu <qiuxu.zhuo@...el.com> wrote:
> >
> > 
> >>
> >> From: Paul E. McKenney <paulmck@...nel.org> [...]
> >>>>
> >>>> How about to pull the rcu_scale_cleanup() function after
> >> kfree_scale_cleanup().
> >>>> This groups kfree_* functions and groups rcu_scale_* functions.
> >>>> Then the code would look cleaner.
> >>>> So, do you think the changes below are better?
> >>>
> >>> IMHO, I don't think doing such a code move is better. Just add a new
> >>> header file and declare the function there. But see what Paul says
> >>> first.
> >>
> >> This situation is likely to be an early hint that the kvfree_rcu()
> >> testing should be split out from kernel/rcu/rcuscale.c.
> >
> > Another is that it's a bit expensive to create a new header file just
> > for eliminating a function declaration. ;-)
> 
> What is so expensive about new files? It is a natural organization structure.
>
> > So, if no objections, I'd like to send out the v2 patch with the updates below:
> >
> >   - Move rcu_scale_cleanup() after kfree_scale_cleanup() to eliminate the
> >     declaration of kfree_scale_cleanup(). Though this makes the patch bigger,
> >     get the file rcuscale.c much cleaner.
> >
> >   - Remove the unnecessary step "modprobe torture" from the commit
> message.
> >
> >   - Add the description for why move rcu_scale_cleanup() after
> >     kfree_scale_cleanup() to the commit message.
> 
> Honestly if you are moving so many lines around, you may as well split it out
> into a new module.
> The kfree stuff being clubbed in the same file has also been a major
> annoyance.

I'm OK with creating a new kernel module for these kfree stuffs, 
but do we really need to do that?

@paulmck, what's your suggestion for the next step? 

>  - Joel
> 
> 
> > Thanks!
> > -Qiuxu
> >
> >> [...]