linux-mm.kvack.org archive mirror
 help / color / mirror / Atom feed
From: "Paul E. McKenney" <paulmck@kernel.org>
To: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Cc: 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: Sun, 20 Sep 2020 08:06:38 -0700	[thread overview]
Message-ID: <20200920150638.GA5453@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <20200918194817.48921-5-urezki@gmail.com>

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)


  reply	other threads:[~2020-09-20 15:06 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 [this message]
2020-09-21 13:27     ` Uladzislau Rezki
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200920150638.GA5453@paulmck-ThinkPad-P72 \
    --to=paulmck@kernel.org \
    --cc=akpm@linux-foundation.org \
    --cc=bigeasy@linutronix.de \
    --cc=joel@joelfernandes.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mhocko@suse.com \
    --cc=oleksiy.avramchenko@sonymobile.com \
    --cc=peterz@infradead.org \
    --cc=rcu@vger.kernel.org \
    --cc=tglx@linutronix.de \
    --cc=tytso@mit.edu \
    --cc=urezki@gmail.com \
    --cc=vbabka@suse.cz \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).