From: Nikolai Zhubr <zhubr.2@gmail.com>
To: Arnd Bergmann <arnd@kernel.org>
Cc: "Maciej W. Rozycki" <macro@orcam.me.uk>,
Thomas Gleixner <tglx@linutronix.de>,
Heiner Kallweit <hkallweit1@gmail.com>,
netdev <netdev@vger.kernel.org>,
the arch/x86 maintainers <x86@kernel.org>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: Realtek 8139 problem on 486.
Date: Thu, 08 Jul 2021 22:21:59 +0300 [thread overview]
Message-ID: <60E75057.60706@gmail.com> (raw)
In-Reply-To: <CAK8P3a2=d0wT9UWgkKDJS5Bd8dPYswah79O5tAg5tHpr4vMH4Q@mail.gmail.com>
Hello Arnd,
03.07.2021 12:10, Arnd Bergmann:
> The simplest workaround would be to just move the
> "spin_lock_irqsave(&tp->lock, flags);" a few lines down, below the rx
> processing. This keeps the locking rules exactly how they were before
Indeed, moving spin_lock_irqsave below rtl8139_rx eliminated the warn_on
message apparently, here is a new log:
https://pastebin.com/dVFNVEu4
and here is my resulting diff:
https://pastebin.com/CzNzsUPu
My usual tests run fine. However I still see 2 issues:
1. I do not understand all this locking thing enough to do a good
cleanup myself, and it looks like it needs one;
2. It looks like in case of incorrect (edge) triggering mode, the "poll
approach" with no loop added in the poll function would still allow a
race window, as explained in following outline (from some previous mails):
22.06.2021 14:12, David Laight:
> Typically you need to:
> 1) stop the chip driving IRQ low.
> 2) process all the completed RX and TX entries.
> 3) clear the chip's interrupt pending bits (often write to clear).
> 4) check for completed RX/TX entries, back to 2 if found.
> 5) enable driving IRQ.
>
> The loop (4) is needed because of the timing window between
> (2) and (3).
> You can swap (2) and (3) over - but then you get an additional
> interrupt if packets arrive during processing - which is common.
So in terms of such outline, the "poll approach" now implements 1, 2, 3,
5 but still misses 4, and my understanding is that it is therefore still
not a complete solution for the broken triggering case (Although
practically, the time window might be too small for the race effect to
be ever observable) From my previous testing I know that such a loop
does not affect the perfomance too much anyway, so it seems quite safe
to add it. Maybe I've missunderstood something though.
Thank you,
Regards,
Nikolai
> your patch, and anything beyond that could be done as a follow-up
> cleanup, if someone wants to think this through more.
>
> Arnd
>
next prev parent reply other threads:[~2021-07-08 19:10 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-29 14:08 Realtek 8139 problem on 486 Nikolai Zhubr
2021-05-29 18:42 ` Heiner Kallweit
2021-05-29 21:44 ` tedheadster
2021-05-30 0:49 ` Nikolai Zhubr
2021-05-30 10:36 ` Nikolai Zhubr
2021-05-30 17:27 ` Nikolai Zhubr
2021-05-30 20:54 ` Arnd Bergmann
2021-05-30 23:17 ` Nikolai Zhubr
2021-05-31 16:53 ` Nikolai Zhubr
2021-05-31 18:39 ` Arnd Bergmann
2021-05-31 22:18 ` Nikolai Zhubr
2021-05-31 22:30 ` Heiner Kallweit
2021-06-01 7:20 ` Arnd Bergmann
2021-06-01 10:53 ` Nikolai Zhubr
2021-06-01 11:42 ` Heiner Kallweit
2021-06-01 16:09 ` Nikolai Zhubr
2021-06-01 21:48 ` Heiner Kallweit
2021-06-01 23:37 ` Nikolai Zhubr
2021-06-02 9:12 ` Arnd Bergmann
2021-06-07 23:07 ` Nikolai Zhubr
2021-06-08 7:44 ` Arnd Bergmann
2021-06-08 20:32 ` Nikolai Zhubr
2021-06-08 20:45 ` Arnd Bergmann
2021-06-08 22:07 ` Nikolai Zhubr
2021-06-09 7:09 ` Arnd Bergmann
2021-06-12 17:40 ` Nikolai Zhubr
2021-06-12 22:41 ` Arnd Bergmann
2021-06-13 14:10 ` Nikolai Zhubr
2021-06-13 21:52 ` Arnd Bergmann
2021-06-03 18:32 ` Maciej W. Rozycki
2021-06-04 7:36 ` Arnd Bergmann
2021-06-20 0:34 ` Thomas Gleixner
2021-06-20 10:19 ` Arnd Bergmann
2021-06-21 4:10 ` Maciej W. Rozycki
2021-06-21 11:22 ` Arnd Bergmann
2021-06-21 14:42 ` Maciej W. Rozycki
2021-06-21 15:20 ` Arnd Bergmann
2021-06-22 11:12 ` David Laight
2021-06-22 12:42 ` Nikolai Zhubr
2021-06-22 13:22 ` Arnd Bergmann
2021-06-22 18:42 ` Nikolai Zhubr
2021-06-22 19:26 ` Arnd Bergmann
2021-06-23 1:04 ` Maciej W. Rozycki
2021-06-24 17:56 ` Nikolai Zhubr
2021-06-24 18:25 ` Maciej W. Rozycki
2021-07-14 23:32 ` Maciej W. Rozycki
2021-07-15 7:32 ` Nikolai Zhubr
2021-07-16 23:48 ` Maciej W. Rozycki
2021-06-23 16:31 ` Nikolai Zhubr
2021-06-23 23:39 ` Maciej W. Rozycki
2021-06-24 8:28 ` Arnd Bergmann
2021-07-02 19:02 ` Nikolai Zhubr
2021-07-03 9:10 ` Arnd Bergmann
2021-07-08 19:21 ` Nikolai Zhubr [this message]
2021-07-09 7:31 ` Arnd Bergmann
2021-07-09 12:43 ` David Laight
2021-06-01 17:44 ` Maciej W. Rozycki
2021-06-02 15:14 ` Nikolai Zhubr
2021-06-02 15:28 ` Arnd Bergmann
2021-05-31 19:05 ` Heiner Kallweit
2021-05-31 18:29 ` Denis Kirjanov
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