netdev.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Marc Kleine-Budde <mkl@pengutronix.de>
To: Oliver Hartkopp <socketcan@hartkopp.net>
Cc: "Ziyang Xuan (William)" <william.xuanziyang@huawei.com>,
	davem@davemloft.net, kuba@kernel.org, linux-can@vger.kernel.org,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH net] can: isotp: isotp_rcv_cf(): fix so->rx race problem
Date: Mon, 7 Feb 2022 09:11:23 +0100	[thread overview]
Message-ID: <20220207081123.sdmczptqffwr64al@pengutronix.de> (raw)
In-Reply-To: <07c69ccd-dbc0-5c74-c68e-8636ec9179ef@hartkopp.net>

[-- Attachment #1: Type: text/plain, Size: 2578 bytes --]

On 28.01.2022 15:48:05, Oliver Hartkopp wrote:
> Hello Marc, hello William,
> 
> On 28.01.22 09:46, Marc Kleine-Budde wrote:
> > On 28.01.2022 09:32:40, Oliver Hartkopp wrote:
> > > 
> > > 
> > > On 28.01.22 09:07, Marc Kleine-Budde wrote:
> > > > On 28.01.2022 08:56:19, Oliver Hartkopp wrote:
> > > > > I've seen the frame processing sometimes freezes for one second when
> > > > > stressing the isotp_rcv() from multiple sources. This finally freezes
> > > > > the entire softirq which is either not good and not needed as we only
> > > > > need to fix this race for stress tests - and not for real world usage
> > > > > that does not create this case.
> > > > 
> > > > Hmmm, this doesn't sound good. Can you test with LOCKDEP enabled?
> 
> 
> > > #
> > > # Lock Debugging (spinlocks, mutexes, etc...)
> > > #
> > > CONFIG_LOCK_DEBUGGING_SUPPORT=y
> > > # CONFIG_PROVE_LOCKING is not set
> > CONFIG_PROVE_LOCKING=y
> 
> Now enabled even more locking (seen relevant kernel config at the end).
> 
> It turns out that there is no visible difference when using spin_lock() or
> spin_trylock().
> 
> I only got some of these kernel log entries
> 
> Jan 28 11:13:14 silver kernel: [ 2396.323211] perf: interrupt took too long
> (2549 > 2500), lowering kernel.perf_event_max_sample_rate to 78250
> Jan 28 11:25:49 silver kernel: [ 3151.172773] perf: interrupt took too long
> (3188 > 3186), lowering kernel.perf_event_max_sample_rate to 62500
> Jan 28 11:45:24 silver kernel: [ 4325.583328] perf: interrupt took too long
> (4009 > 3985), lowering kernel.perf_event_max_sample_rate to 49750
> Jan 28 12:15:46 silver kernel: [ 6148.238246] perf: interrupt took too long
> (5021 > 5011), lowering kernel.perf_event_max_sample_rate to 39750
> Jan 28 13:01:45 silver kernel: [ 8907.303715] perf: interrupt took too long
> (6285 > 6276), lowering kernel.perf_event_max_sample_rate to 31750
> 
> But I get these sporadically anyway. No other LOCKDEP splat.
> 
> At least the issue reported by William should be fixed now - but I'm still
> unclear whether spin_lock() or spin_trylock() is the best approach here in
> the NET_RX softirq?!?

With the !spin_trylock() -> return you are saying if something
concurrent happens, drop it. This doesn't sound correct.

Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

  reply	other threads:[~2022-02-07  9:19 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-17 12:01 [PATCH net] can: isotp: isotp_rcv_cf(): fix so->rx race problem Ziyang Xuan
2022-01-18  7:58 ` Oliver Hartkopp
2022-01-18 12:46   ` Ziyang Xuan (William)
2022-01-18 14:44     ` Oliver Hartkopp
2022-01-20  6:24       ` Ziyang Xuan (William)
2022-01-20  8:23         ` Oliver Hartkopp
2022-01-20 11:28           ` Ziyang Xuan (William)
2022-01-20 14:46             ` Oliver Hartkopp
2022-01-21  1:50               ` Ziyang Xuan (William)
2022-01-27 19:44                 ` Oliver Hartkopp
2022-01-28  7:56                   ` Oliver Hartkopp
2022-01-28  8:07                     ` Marc Kleine-Budde
2022-01-28  8:32                       ` Oliver Hartkopp
2022-01-28  8:46                         ` Marc Kleine-Budde
2022-01-28 14:48                           ` Oliver Hartkopp
2022-02-07  8:11                             ` Marc Kleine-Budde [this message]
2022-02-09  7:54                               ` Oliver Hartkopp

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=20220207081123.sdmczptqffwr64al@pengutronix.de \
    --to=mkl@pengutronix.de \
    --cc=davem@davemloft.net \
    --cc=kuba@kernel.org \
    --cc=linux-can@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=netdev@vger.kernel.org \
    --cc=socketcan@hartkopp.net \
    --cc=william.xuanziyang@huawei.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).