From: Uladzislau Rezki <urezki@gmail.com>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com>,
LKML <linux-kernel@vger.kernel.org>, RCU <rcu@vger.kernel.org>,
linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Michal Hocko <mhocko@suse.com>, Vlastimil Babka <vbabka@suse.cz>,
Thomas Gleixner <tglx@linutronix.de>,
"Theodore Y . Ts'o" <tytso@mit.edu>,
Joel Fernandes <joel@joelfernandes.org>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Subject: Re: [PATCH 4/4] rcu/tree: Use schedule_delayed_work() instead of WQ_HIGHPRI queue
Date: Mon, 21 Sep 2020 15:27:41 +0200 [thread overview]
Message-ID: <20200921132741.GA20907@pc636> (raw)
In-Reply-To: <20200920150638.GA5453@paulmck-ThinkPad-P72>
On Sun, Sep 20, 2020 at 08:06:38AM -0700, Paul E. McKenney wrote:
> On Fri, Sep 18, 2020 at 09:48:17PM +0200, Uladzislau Rezki (Sony) wrote:
> > Recently the separate worker thread has been introduced to
> > maintain the local page cache from the regular kernel context,
> > instead of kvfree_rcu() contexts. That was done because a caller
> > of the k[v]free_rcu() can be any context type what is a problem
> > from the allocation point of view.
> >
> > >From the other hand, the lock-less way of obtaining a page has
> > been introduced and directly injected to the k[v]free_rcu() path.
> >
> > Therefore it is not important anymore to use a high priority "wq"
> > for the external job that used to fill a page cache ASAP when it
> > was empty.
> >
> > Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
>
> And I needed to apply the patch below to make this one pass rcutorture
> scenarios SRCU-P and TREE05. Repeat by:
>
> tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 3 --configs "SRCU-P TREE05" --trust-make
>
> Without the patch below, the system hangs very early in boot.
>
> Please let me know if some other fix would be better.
>
> Thanx, Paul
>
> ------------------------------------------------------------------------
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 8ce1ea4..2424e2a 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -3481,7 +3481,8 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
> success = kvfree_call_rcu_add_ptr_to_bulk(krcp, ptr);
> if (!success) {
> // Use delayed work, so we do not deadlock with rq->lock.
> - if (!atomic_xchg(&krcp->work_in_progress, 1))
> + if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING &&
> + !atomic_xchg(&krcp->work_in_progress, 1))
> schedule_delayed_work(&krcp->page_cache_work, 1);
>
> if (head == NULL)
I will double check!
--
Vlad Rezki
next prev parent reply other threads:[~2020-09-21 13:27 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-18 19:48 [PATCH 0/4] kvfree_rcu() and _LOCK_NESTING/_PREEMPT_RT Uladzislau Rezki (Sony)
2020-09-18 19:48 ` [PATCH 1/4] rcu/tree: Add a work to allocate pages from regular context Uladzislau Rezki (Sony)
2020-09-18 19:48 ` [RFC-PATCH 2/4] mm: Add __rcu_alloc_page_lockless() func Uladzislau Rezki (Sony)
2020-09-21 7:47 ` Michal Hocko
2020-09-21 15:45 ` Paul E. McKenney
2020-09-21 16:03 ` Michal Hocko
2020-09-21 19:48 ` Uladzislau Rezki
2020-09-22 7:50 ` Michal Hocko
2020-09-22 13:12 ` Uladzislau Rezki
2020-09-22 15:35 ` Michal Hocko
2020-09-23 10:37 ` Mel Gorman
2020-09-23 15:41 ` Paul E. McKenney
2020-09-23 23:22 ` Mel Gorman
2020-09-24 8:16 ` Uladzislau Rezki
2020-09-24 11:16 ` Peter Zijlstra
2020-09-24 15:16 ` Uladzislau Rezki
2020-09-24 11:19 ` Peter Zijlstra
2020-09-24 15:21 ` Uladzislau Rezki
2020-09-25 8:15 ` Peter Zijlstra
2020-09-25 10:25 ` Uladzislau Rezki
2020-09-24 15:38 ` Paul E. McKenney
2020-09-25 8:26 ` Peter Zijlstra
2020-09-26 14:37 ` Paul E. McKenney
2020-09-25 8:05 ` Michal Hocko
2020-09-25 15:31 ` Uladzislau Rezki
2020-09-25 15:47 ` Michal Hocko
2020-09-29 16:25 ` Uladzislau Rezki
2020-09-30 9:27 ` Michal Hocko
2020-09-30 12:35 ` Uladzislau Rezki
2020-09-30 12:44 ` Michal Hocko
2020-09-30 13:39 ` Uladzislau Rezki
2020-09-30 16:46 ` Michal Hocko
2020-09-30 20:36 ` Uladzislau Rezki
2020-09-30 15:25 ` Joel Fernandes
2020-09-30 16:48 ` Michal Hocko
2020-09-30 17:03 ` Joel Fernandes
2020-09-30 17:22 ` Michal Hocko
2020-09-30 17:48 ` Joel Fernandes
2020-09-25 16:17 ` Mel Gorman
2020-09-25 17:57 ` Uladzislau Rezki
2020-09-22 15:49 ` Paul E. McKenney
2020-09-22 3:35 ` Paul E. McKenney
2020-09-22 8:03 ` Michal Hocko
2020-09-22 15:46 ` Paul E. McKenney
2020-09-23 11:27 ` Uladzislau Rezki
2020-09-29 10:15 ` Vlastimil Babka
2020-09-29 22:07 ` Uladzislau Rezki
2020-09-30 10:35 ` Michal Hocko
2020-10-01 19:32 ` Uladzislau Rezki
2020-09-30 14:39 ` Vlastimil Babka
2020-09-30 15:37 ` Joel Fernandes
2020-10-01 19:26 ` Uladzislau Rezki
2020-10-02 7:11 ` Michal Hocko
2020-10-02 8:50 ` Mel Gorman
2020-10-02 9:05 ` Michal Hocko
2020-10-05 15:08 ` Uladzislau Rezki
2020-10-05 15:41 ` Michal Hocko
2020-10-06 22:25 ` Uladzislau Rezki
2020-10-07 10:02 ` Michal Hocko
2020-10-07 11:02 ` Uladzislau Rezki
2020-10-02 9:07 ` Peter Zijlstra
2020-10-02 9:45 ` Mel Gorman
2020-10-02 9:58 ` Peter Zijlstra
2020-10-02 10:19 ` Mel Gorman
2020-10-02 14:41 ` Paul E. McKenney
2020-10-06 10:03 ` Mel Gorman
2020-10-06 15:41 ` Paul E. McKenney
2020-10-05 13:58 ` Uladzislau Rezki
2020-10-02 8:06 ` Mel Gorman
2020-10-05 14:12 ` Uladzislau Rezki
2020-09-18 19:48 ` [PATCH 3/4] rcu/tree: use " Uladzislau Rezki (Sony)
2020-09-18 19:48 ` [PATCH 4/4] rcu/tree: Use schedule_delayed_work() instead of WQ_HIGHPRI queue Uladzislau Rezki (Sony)
2020-09-20 15:06 ` Paul E. McKenney
2020-09-21 13:27 ` Uladzislau Rezki [this message]
2020-09-18 22:15 ` [PATCH 0/4] kvfree_rcu() and _LOCK_NESTING/_PREEMPT_RT Paul E. McKenney
2020-09-30 15:52 ` Joel Fernandes
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