From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Jakub Kicinski <kuba@kernel.org>,
Julia Lawall <Julia.Lawall@inria.fr>,
linux-block@vger.kernel.org, kernel-janitors@vger.kernel.org,
bridge@lists.linux.dev, linux-trace-kernel@vger.kernel.org,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
kvm@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
"Naveen N. Rao" <naveen.n.rao@linux.ibm.com>,
Christophe Leroy <christophe.leroy@csgroup.eu>,
Nicholas Piggin <npiggin@gmail.com>,
netdev@vger.kernel.org, wireguard@lists.zx2c4.com,
linux-kernel@vger.kernel.org, ecryptfs@vger.kernel.org,
Neil Brown <neilb@suse.de>, Olga Kornievskaia <kolga@netapp.com>,
Dai Ngo <Dai.Ngo@oracle.com>, Tom Talpey <tom@talpey.com>,
linux-nfs@vger.kernel.org, linux-can@vger.kernel.org,
Lai Jiangshan <jiangshanlai@gmail.com>,
netfilter-devel@vger.kernel.org, coreteam@netfilter.org,
Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [PATCH 00/14] replace call_rcu by kfree_rcu for simple kmem_cache_free callback
Date: Thu, 13 Jun 2024 16:11:52 +0200 [thread overview]
Message-ID: <Zmr-KPG9F6w-uzys@zx2c4.com> (raw)
In-Reply-To: <e06440e2-9121-4c92-8bf2-945977987052@paulmck-laptop>
On Thu, Jun 13, 2024 at 05:46:11AM -0700, Paul E. McKenney wrote:
> How about a kmem_cache_destroy_rcu() that marks that specified cache
> for destruction, and then a kmem_cache_destroy_barrier() that waits?
>
> I took the liberty of adding your name to the Google document [1] and
> adding this section:
Cool, though no need to make me yellow!
> > But then, if that mechanism generally works, we don't really need a new
> > function and we can just go with the first option of making
> > kmem_cache_destroy() asynchronously wait. It'll wait, as you described,
> > but then we adjust the tail of every kfree_rcu batch freeing cycle to
> > check if there are _still_ any old outstanding kmem_cache_destroy()
> > requests. If so, then we can splat and keep the old debugging info we
> > currently have for finding memleaks.
>
> The mechanism can always be sabotaged by memory-leak bugs on the part
> of the user of the kmem_cache structure in play, right?
>
> OK, but I see your point. I added this to the existing
> "kmem_cache_destroy() Lingers for kfree_rcu()" section:
>
> One way of preserving this debugging information is to splat if
> all of the slab’s memory has not been freed within a reasonable
> timeframe, perhaps the same 21 seconds that causes an RCU CPU
> stall warning.
>
> Does that capture it?
Not quite what I was thinking. Your 21 seconds as a time-based thing I
guess could be fine. But I was mostly thinking:
1) kmem_cache_destroy() is called, but there are outstanding objects, so
it defers.
2) Sometime later, a kfree_rcu_work batch freeing operation runs.
3) At the end of this batch freeing, the kernel notices that the
kmem_cache whose destruction was previously deferred still has
outstanding objects and has not been destroyed. It can conclude that
there's thus been a memory leak.
In other words, instead of having to do this based on timers, you can
just have the batch freeing code ask, "did those pending kmem_cache
destructions get completed as a result of this last operation?"
next prev parent reply other threads:[~2024-06-13 14:12 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-06-09 8:27 Julia Lawall
2024-06-09 8:27 ` [PATCH 01/14] wireguard: allowedips: " Julia Lawall
2024-06-09 14:32 ` Jason A. Donenfeld
2024-06-09 14:36 ` Julia Lawall
2024-06-10 20:38 ` Vlastimil Babka
2024-06-10 20:59 ` Jason A. Donenfeld
2024-06-12 21:33 ` [PATCH 00/14] " Jakub Kicinski
2024-06-12 22:37 ` Paul E. McKenney
2024-06-12 22:46 ` Jakub Kicinski
2024-06-12 22:52 ` Jens Axboe
2024-06-12 23:04 ` Paul E. McKenney
2024-06-12 23:31 ` Jason A. Donenfeld
2024-06-13 0:31 ` Jason A. Donenfeld
2024-06-13 3:38 ` Paul E. McKenney
2024-06-13 12:22 ` Jason A. Donenfeld
2024-06-13 12:46 ` Paul E. McKenney
2024-06-13 14:11 ` Jason A. Donenfeld [this message]
2024-06-13 15:12 ` Paul E. McKenney
2024-06-17 15:10 ` Vlastimil Babka
2024-06-17 16:12 ` Paul E. McKenney
2024-06-17 17:23 ` Vlastimil Babka
2024-06-17 18:42 ` Uladzislau Rezki
2024-06-17 21:08 ` Vlastimil Babka
2024-06-18 9:31 ` Uladzislau Rezki
2024-06-18 16:48 ` Paul E. McKenney
2024-06-18 17:21 ` Vlastimil Babka
2024-06-18 17:53 ` Paul E. McKenney
2024-06-19 9:28 ` Vlastimil Babka
2024-06-19 16:46 ` Paul E. McKenney
2024-06-21 9:32 ` Uladzislau Rezki
2024-07-15 20:39 ` Vlastimil Babka
2024-07-24 13:53 ` Paul E. McKenney
2024-07-24 14:40 ` Vlastimil Babka
2024-10-08 16:41 ` Vlastimil Babka
2024-10-08 20:02 ` Paul E. McKenney
2024-10-09 17:08 ` Julia Lawall
2024-10-09 21:02 ` Paul E. McKenney
2024-06-19 9:51 ` Uladzislau Rezki
2024-06-19 9:56 ` Vlastimil Babka
2024-06-19 11:22 ` Uladzislau Rezki
2024-06-17 18:54 ` Paul E. McKenney
2024-06-17 21:34 ` Vlastimil Babka
2024-06-13 14:17 ` Jakub Kicinski
2024-06-13 14:53 ` Paul E. McKenney
2024-06-13 11:58 ` Jason A. Donenfeld
2024-06-13 12:47 ` Paul E. McKenney
2024-06-13 13:06 ` Uladzislau Rezki
2024-06-13 15:06 ` Paul E. McKenney
2024-06-13 17:38 ` Uladzislau Rezki
2024-06-13 17:45 ` Paul E. McKenney
2024-06-13 17:58 ` Uladzislau Rezki
2024-06-13 18:13 ` Paul E. McKenney
2024-06-14 12:35 ` Uladzislau Rezki
2024-06-14 14:17 ` Paul E. McKenney
2024-06-14 14:50 ` Uladzislau Rezki
2024-06-14 19:33 ` Jason A. Donenfeld
2024-06-17 13:50 ` Uladzislau Rezki
2024-06-17 14:56 ` Jason A. Donenfeld
2024-06-17 16:30 ` Uladzislau Rezki
2024-06-17 16:33 ` Jason A. Donenfeld
2024-06-17 16:38 ` Vlastimil Babka
2024-06-17 17:04 ` Jason A. Donenfeld
2024-06-17 21:19 ` Vlastimil Babka
2024-06-17 16:42 ` Uladzislau Rezki
2024-06-17 16:57 ` Jason A. Donenfeld
2024-06-17 17:19 ` Uladzislau Rezki
2024-06-17 14:37 ` Vlastimil Babka
2024-10-08 16:36 ` Vlastimil Babka
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=Zmr-KPG9F6w-uzys@zx2c4.com \
--to=jason@zx2c4.com \
--cc=Dai.Ngo@oracle.com \
--cc=Julia.Lawall@inria.fr \
--cc=bridge@lists.linux.dev \
--cc=christophe.leroy@csgroup.eu \
--cc=coreteam@netfilter.org \
--cc=ecryptfs@vger.kernel.org \
--cc=jiangshanlai@gmail.com \
--cc=kernel-janitors@vger.kernel.org \
--cc=kolga@netapp.com \
--cc=kuba@kernel.org \
--cc=kvm@vger.kernel.org \
--cc=linux-block@vger.kernel.org \
--cc=linux-can@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-nfs@vger.kernel.org \
--cc=linux-trace-kernel@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=mathieu.desnoyers@efficios.com \
--cc=naveen.n.rao@linux.ibm.com \
--cc=neilb@suse.de \
--cc=netdev@vger.kernel.org \
--cc=netfilter-devel@vger.kernel.org \
--cc=npiggin@gmail.com \
--cc=paulmck@kernel.org \
--cc=tom@talpey.com \
--cc=vbabka@suse.cz \
--cc=wireguard@lists.zx2c4.com \
/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).