linux-kernel - Re: [PATCH RFC fs/namespace] Make kern_unmount() use synchronize_rcu

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Message-ID: <20220426231100.GL4285@paulmck-ThinkPad-P17-Gen-1>
Date:   Tue, 26 Apr 2022 16:11:00 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Christoph Bartoschek <bartoschek@...gle.com>
Cc:     Chris Mason <clm@...com>, Giuseppe Scrivano <gscrivan@...hat.com>,
        linux-kernel@...r.kernel.org,
        "riel@...riel.com" <riel@...riel.com>,
        "viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>
Subject: Re: [PATCH RFC fs/namespace] Make kern_unmount() use
 synchronize_rcu_expedited()

On Wed, Apr 27, 2022 at 12:58:34AM +0200, Christoph Bartoschek wrote:
> > 3. https://lore.kernel.org/lkml/20220218183114.2867528-1-riel@surriel.com/
> >         Refined queue_rcu_work() approach.
> >
> > #1 should work, but the resulting IPIs are not going to make the real-time
> > guys happy.  #2 and #3 have been subject to reasonably heavy testing
> > and did fix a very similar issue to the one that you are reporting,
> > but last I knew there were doubts about the concurrency consequences.
> >
> > Could you please give at least #3 a shot and see if it helps you?
> 
> I have tried #3 and it works well with my testcases as far as I can see it.

Thank you for giving it a try!

Al, are further adjustments needed to make this patch cover all the
corner cases?

							Thanx, Paul