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

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Message-ID: <20200716142537.ecp4icsq7kg6qhdx@linutronix.de>
Date:   Thu, 16 Jul 2020 16:25:37 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Uladzislau Rezki <urezki@...il.com>
Cc:     Joel Fernandes <joel@...lfernandes.org>,
        LKML <linux-kernel@...r.kernel.org>, RCU <rcu@...r.kernel.org>,
        linux-mm <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>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>
Subject: Re: [PATCH 1/1] rcu/tree: Drop the lock before entering to page
 allocator

On 2020-07-16 11:19:13 [+0200], Uladzislau Rezki wrote:
> Sebastian, could you please confirm that if that patch that is in
> question fixes it?
> 
> It would be appreciated!

So that preempt disable should in terms any warnings. However I don't
think that it is strictly needed and from scheduling point of view you
forbid a CPU migration which might be good otherwise.
Also if interrupts and everything is enabled then someone else might
invoke kfree_rcu() from BH context for instance.

Sebastian