From: Ahmad Fatoum <a.fatoum@pengutronix.de>
To: linux-can@vger.kernel.org, netdev@vger.kernel.org, pabeni@redhat.com
Cc: Sascha Hauer <kernel@pengutronix.de>
Subject: [BUG] pfifo_fast may cause out-of-order CAN frame transmission
Date: Wed, 8 Jan 2020 15:55:34 +0100 [thread overview]
Message-ID: <661cc33a-5f65-2769-cc1a-65791cb4b131@pengutronix.de> (raw)
Hello,
I've run into an issue of CAN frames being sent out-of-order on an i.MX6 Dual
with Linux v5.5-rc5. Bisecting has lead me down to this commit:
ba27b4cdaaa ("net: dev: introduce support for sch BYPASS for lockless qdisc")
With it, using pfifo_fast, every few hundred frames, FlexCAN's .ndo_start_xmit is
passed frames in an order different from how userspace stuffed them into the same
socket.
Reverting it fixes the issue as does booting with maxcpus=1 or using pfifo
instead of pfifo_fast.
According to [1], such reordering shouldn't be happening.
Details on my setup:
Kernel version: v5.5-rc5, (occurs much more often with LOCKDEP turned on)
CAN-Bitrate: 250 kbit/s
CAN frames are generated with:
cangen canX -I2 -L1 -Di -i -g0.12 -p 100
which keeps polling after ENOBUFS until socket is writable, sends out a CAN
frame with one incrementing payload byte and then waits 120 usec before repeating.
Please let me know if any additional info is needed.
Cheers
Ahmad
[1]: http://linux-tc-notes.sourceforge.net/tc/doc/sch_pfifo_fast.txt
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next reply other threads:[~2020-01-08 14:55 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-08 14:55 Ahmad Fatoum [this message]
2020-01-09 12:51 ` [BUG] pfifo_fast may cause out-of-order CAN frame transmission Paolo Abeni
2020-01-09 17:39 ` Ahmad Fatoum
2020-01-10 16:31 ` Paolo Abeni
2020-01-12 21:29 ` Ahmad Fatoum
[not found] ` <57a2352dfc442ea2aa9cd653f8e09db277bf67c7.camel@redhat.com>
2020-01-20 16:06 ` Ahmad Fatoum
2020-02-04 16:25 ` Ahmad Fatoum
2020-02-06 13:21 ` Paolo Abeni
2020-02-06 17:06 ` Oliver Hartkopp
2020-02-14 16:03 ` Ahmad Fatoum
2020-10-07 21:07 ` Vijayendra Suman
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