linux-kernel - Re: [PATCH RFC] rcu/kfree: Do not request RCU when not needed

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Message-ID: <Y2O3w3d3qmTg6VAP@pc638.lan>
Date:   Thu, 3 Nov 2022 13:44:51 +0100
From:   Uladzislau Rezki <urezki@...il.com>
To:     "Paul E. McKenney" <paulmck@...nel.org>
Cc:     Joel Fernandes <joel@...lfernandes.org>,
        Uladzislau Rezki <urezki@...il.com>, rcu@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC] rcu/kfree: Do not request RCU when not needed

> 
> > Though I am thinking, workqueue context is normally used to invoke
> > code that can block, and would the issue you mentioned affect those as
> > well, or affect RCU when those non-RCU work items block. So for
> > example, when other things in the system that can queue things on the
> > system_wq and block.  (I might be throwing darts in the dark).
> > 
> > To be safe, we can implement your suggestion which is basically a form
> > of my initial patch.
> > 
> > Should we add Tejun to the thread?
> 
> Let's get organized first, but that would be a good thing.  Or I could
> reach out to Tejun internally.
> 
> For but one thing to get organized about, maybe kfree_rcu() should be
> using a workqueue with the WQ_MEM_RECLAIM flag set.
> 
It can be as an option to consider. Because such workqueue has some
special priority for better handling of memory releasing. I can have
a look at it closer to see how kvfree_rcu() works if it goes with WQ_MEM_RECLAIM.

--
Uladzislau Rezki