linux-kernel - Re: [PATCH -mm -V7] mm, swap: fix race between swapoff and some swap operations

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Message-ID: <20190212101316.GA6905@andrea>
Date:   Tue, 12 Feb 2019 11:13:16 +0100
From:   Andrea Parri <andrea.parri@...rulasolutions.com>
To:     "Huang, Ying" <ying.huang@...el.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Hugh Dickins <hughd@...gle.com>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        Minchan Kim <minchan@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Jérôme Glisse <jglisse@...hat.com>,
        Michal Hocko <mhocko@...e.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Rientjes <rientjes@...gle.com>,
        Rik van Riel <riel@...hat.com>, Jan Kara <jack@...e.cz>,
        Dave Jiang <dave.jiang@...el.com>,
        Daniel Jordan <daniel.m.jordan@...cle.com>
Subject: Re: [PATCH -mm -V7] mm, swap: fix race between swapoff and some swap
 operations

> Alternative implementation could be replacing disable preemption with
> rcu_read_lock_sched and stop_machine() with synchronize_sched().

JFYI, starting with v4.20-rc1, synchronize_rcu{,expedited}() also wait
for preempt-disable sections (the intent seems to retire the RCU-sched
update-side API), so that here you could instead use preempt-disable +
synchronize_rcu{,expedited}().  This LWN article gives an overview of
the latest RCU API/semantics changes: https://lwn.net/Articles/777036/.

  Andrea