linux-kernel - Re: [PATCH 1/1] rcu/tree: Drop the lock before entering to page allocator

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Message-ID: <20200715193250.axntj7jdt6bw52dr@linutronix.de>
Date:   Wed, 15 Jul 2020 21:32:50 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Uladzislau Rezki <urezki@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, RCU <rcu@...r.kernel.org>,
        linux-mm@...ck.org, "Paul E . McKenney" <paulmck@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Theodore Y . Ts'o" <tytso@....edu>,
        Matthew Wilcox <willy@...radead.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>
Subject: Re: [PATCH 1/1] rcu/tree: Drop the lock before entering to page
 allocator

On 2020-07-15 21:02:43 [+0200], Uladzislau Rezki wrote:
> 
> <snip>
>     spin_lock();
>     __get_free_page(GFP_NOWAIT | __GFP_NOWARN);
>     spin_unlock();
> <snip>
> 
> Also, please note we do it for regular kernel.

ach right okay then.

> >
> > What happened to the part where I asked for a spinlock_t?
> > 
> What do you mean?

Please drop that raw_spinlock_t for the kfree_rcu() based locking and
use just a plain spinlock_t for the locking. Then you can keep the same
code flow for RT and !RT without any special cases and everything.

> --
> Vlad Rezki

Sebastian