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From: "Ahmed S. Darwish" <darwish.07@gmail.com>
To: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: Olivier Sobrie <olivier@sobrie.be>,
	Oliver Hartkopp <socketcan@hartkopp.net>,
	Wolfgang Grandegger <wg@grandegger.com>,
	Andri Yngvason <andri.yngvason@marel.com>,
	Linux-CAN <linux-can@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	netdev@vger.kernel.org
Subject: Re: [PATCH v4 1/3] can: kvaser_usb: Fix tx queue start/stop race conditions
Date: Sat, 14 Mar 2015 17:19:45 +0200
Message-ID: <20150314151945.GA18736@vivalin-002> (raw)
In-Reply-To: <55044C9F.2070105@pengutronix.de>

On Sat, Mar 14, 2015 at 03:58:39PM +0100, Marc Kleine-Budde wrote:
> On 03/14/2015 03:38 PM, Ahmed S. Darwish wrote:
> >> Applied to can. This will go into David's net tree and finally into
> >> net-next. Then I'll apply patches 2+3. Nag me, if I forget about them ;)
> >>
> > 
> > Thanks! :-)
> > 
> > So if I've understood correctly, this patch will go to -rc5 and
> > the rest will go into net-next?
> > 
> > If so, IMHO patch #2 should also go to -rc5. I know it's usually
> > frowned up on to add further patches at this late -rc stage, but
> > here's my logic:
> > 
> > The original driver code just _arbitrarily_ assumed a MAX_TX_URB
> > value of 16 parallel transmissions. This value was chosen, it seems,
> > because the driver was heavily based on esd_usb2.c and the esd code
> > just did so :-(
> > 
> > Meanwhile, in the Kvaser hardware at hand, if I've increased the
> > driver's max parallel transmissions little above the recommended
> > limit reported by firmware, the firmware breaks up badly, reports a
> > massive list of internal errors, and the candump traces becomes
> > sort of an internal mess hardly related to the actual frames sent
> > and received.
> 
> In this particular hardware, what's the limit as reported by the firmware?
> 

48 max oustanding tx, which is quite big in itself it seems.

Other drivers in the tree range between 10 (Peak) and 20 tx (8dev).

> > In my case, I was lucky that the brand we own here (*) had a higher
> > max outstanding transmissions value than 16. But if there is hardware
> 
> Okay - higher.
> 
> > out there with a max oustanding tx support < 16 (#), such hardware
> > will break badly under a heavy transmission load :-(
> 
> I see.
> 
> If you add this motivation to the patch description and let the subject
> reflect that this is a "fix" or safety measure rather than a possible
> performance improvement, no-one will say anything against this patch :D
> 

True; I admit the "fix" part should've been clearer :-)

Will send a better worded commit message then.

Thanks a lot,
Darwish

  reply index

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-02-26 15:20 [PATCH 1/5] can: kvaser_usb: Avoid double free on URB submission failures Ahmed S. Darwish
2015-02-26 15:22 ` [PATCH 2/5] can: kvaser_usb: Read all messages in a bulk-in URB buffer Ahmed S. Darwish
2015-02-26 15:24   ` [PATCH 3/5] can: kvaser_usb: Utilize all possible tx URBs Ahmed S. Darwish
2015-02-26 15:25     ` [PATCH 4/5] can: kvaser_usb: Use can-dev unregistration mechanism Ahmed S. Darwish
2015-02-26 15:29       ` [PATCH 5/5] can: kvaser_usb: Fix tx queue start/stop race conditions Ahmed S. Darwish
2015-03-14 14:26   ` [PATCH 2/5] can: kvaser_usb: Read all messages in a bulk-in URB buffer Marc Kleine-Budde
2015-03-04  9:15 ` [PATCH 1/5] can: kvaser_usb: Avoid double free on URB submission failures Marc Kleine-Budde
2015-03-09 12:32   ` Ahmed S. Darwish
2015-03-09 12:56     ` Marc Kleine-Budde
2015-03-11 15:23 ` [PATCH v2 1/3] can: kvaser_usb: Fix tx queue start/stop race conditions Ahmed S. Darwish
2015-03-11 15:28   ` [PATCH v2 2/3] can: kvaser_usb: Utilize all possible tx URBs Ahmed S. Darwish
2015-03-11 15:30     ` [PATCH v2 3/3] can: kvaser_usb: Use can-dev unregistration mechanism Ahmed S. Darwish
2015-03-11 15:36   ` [PATCH v2 1/3] can: kvaser_usb: Fix tx queue start/stop race conditions Marc Kleine-Budde
2015-03-11 15:57     ` Ahmed S. Darwish
2015-03-11 17:37 ` [PATCH v3 " Ahmed S. Darwish
2015-03-11 17:39   ` [PATCH v3 2/3] can: kvaser_usb: Utilize all possible tx URBs Ahmed S. Darwish
2015-03-11 17:39     ` [PATCH v3 3/3] can: kvaser_usb: Use can-dev unregistration mechanism Ahmed S. Darwish
2015-03-11 21:53     ` [PATCH v3 2/3] can: kvaser_usb: Utilize all possible tx URBs Marc Kleine-Budde
2015-03-12 10:52       ` Ahmed S. Darwish
2015-03-12 11:29         ` Marc Kleine-Budde
2015-03-11 21:43   ` [PATCH v3 1/3] can: kvaser_usb: Fix tx queue start/stop race conditions Marc Kleine-Budde
2015-03-12 19:30     ` Ahmed S. Darwish
2015-03-14 13:02 ` [PATCH v4 " Ahmed S. Darwish
2015-03-14 13:09   ` [PATCH v4 2/3] can: kvaser_usb: Utilize all possible tx URBs Ahmed S. Darwish
2015-03-14 13:11     ` [PATCH v4 3/3] can: kvaser_usb: Use can-dev unregistration mechanism Ahmed S. Darwish
2015-03-14 15:26       ` Marc Kleine-Budde
2015-03-14 15:41         ` Ahmed S. Darwish
2015-03-14 15:55           ` Marc Kleine-Budde
2015-03-14 16:06             ` Ahmed S. Darwish
2015-03-14 13:41   ` [PATCH v4 1/3] can: kvaser_usb: Fix tx queue start/stop race conditions Marc Kleine-Budde
2015-03-14 14:38     ` Ahmed S. Darwish
2015-03-14 14:58       ` Marc Kleine-Budde
2015-03-14 15:19         ` Ahmed S. Darwish [this message]
2015-03-15 15:03 ` [PATCH v5 1/2] can: kvaser_usb: Comply with firmware max tx URBs value Ahmed S. Darwish
2015-03-15 15:10   ` [PATCH v5 2/2] can: kvaser_usb: Fix sparse warning __le16 degrades to integer Ahmed S. Darwish
2015-03-15 18:08   ` [PATCH v5 1/2] can: kvaser_usb: Comply with firmware max tx URBs value Marc Kleine-Budde
2015-03-16 12:16     ` Ahmed S. Darwish
2015-03-16 12:56       ` Marc Kleine-Budde

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