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>
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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 |
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next prev parent 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
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