From: David Laight <David.Laight@ACULAB.COM>
To: 'Nikolai Zhubr' <zhubr.2@gmail.com>, 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: Fri, 9 Jul 2021 12:43:32 +0000 [thread overview]
Message-ID: <134a4f75cfe44d898f12038248ff5d56@AcuMS.aculab.com> (raw)
In-Reply-To: <60E75057.60706@gmail.com>
From: Nikolai Zhubr
> Sent: 08 July 2021 20:22
...
> 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.
The timing window (4) happens.
The next receive packet will usually clear it - but that might require a timeout.
I'm sure I got a trip to Sweden out of it.
I also think Linux requires the tx-reap be done in a timely manner.
If that is only done in response to an end of tx interrupt the delay
could be substantial.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2021-07-09 12:43 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
2021-07-09 7:31 ` Arnd Bergmann
2021-07-09 12:43 ` David Laight [this message]
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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