From: Pavel Machek <pavel@ucw.cz>
To: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Cc: bh74.an@samsung.com, ks.giri@samsung.com,
vipul.pandya@samsung.com, peppe.cavallaro@st.com,
alexandre.torgue@st.com, davem@davemloft.net,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: [PATCH 2/2] net: ethernet: stmmac: remove private tx queue lock
Date: Thu, 8 Dec 2016 00:21:41 +0100 [thread overview]
Message-ID: <20161207232141.GD2250@amd> (raw)
In-Reply-To: <afcae723-5804-305f-2756-c4dbf9045943@gmx.de>
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On Wed 2016-12-07 23:34:19, Lino Sanfilippo wrote:
> On 07.12.2016 22:43, Lino Sanfilippo wrote:
> > Hi Pavel,
> >
> > On 07.12.2016 22:37, Pavel Machek wrote:
> >> On Wed 2016-12-07 21:05:38, Lino Sanfilippo wrote:
> >>> The driver uses a private lock for synchronization between the xmit
> >>> function and the xmit completion handler, but since the NETIF_F_LLTX flag
> >>> is not set, the xmit function is also called with the xmit_lock held.
> >>>
> >>> On the other hand the xmit completion handler first takes the private lock
> >>> and (in case that the tx queue has been stopped) the xmit_lock, leading to
> >>> a reverse locking order and the potential danger of a deadlock.
> >>>
> >>> Fix this by removing the private lock completely and synchronizing the xmit
> >>> function and completion handler solely by means of the xmit_lock. By doing
> >>> this remove also the now unnecessary double check for a stopped tx queue.
> >>>
> >>
> >> FYI, here's modified version. I believe _bh versions are needed, and
> >> I'm testing that version now. (Oh and I also ported it to net-next).
> >>
> >> It survived 30 minutes of testing so far...
> >>
> >
> > First off, thanks for testing.
> > Hmm. I dont understand why _bh would be needed. We call that function from
> > BH context only (napi poll and timer).
> > Any idea?
> >
>
> Could this once again be caused by irq coalescing? When the tx queue has been stopped
> the cleanup handler has to wakeup the queue within a certain time span, otherwise the
> watchdog will complain (as it happened in your test). Could you retest this with
> irq coalescing disabled?
I actually had TX coalescing disabled, with
-#define STMMAC_TX_FRAMES 64
+#define STMMAC_TX_FRAMES 0
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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next prev parent reply other threads:[~2016-12-07 23:21 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-07 20:05 Remove private locks to avoid possible deadlock Lino Sanfilippo
2016-12-07 20:05 ` [PATCH 1/2] net: ethernet: sxgbe: remove private tx queue lock Lino Sanfilippo
2016-12-07 23:15 ` Francois Romieu
2016-12-08 20:32 ` Lino Sanfilippo
2016-12-08 21:54 ` Pavel Machek
2016-12-08 22:12 ` Lino Sanfilippo
2016-12-08 22:18 ` Pavel Machek
2016-12-08 22:45 ` Lino Sanfilippo
2016-12-08 23:19 ` Francois Romieu
2016-12-09 11:21 ` Pavel Machek
2016-12-10 2:25 ` Lino Sanfilippo
2016-12-11 20:11 ` Pavel Machek
2016-12-15 19:27 ` Lino Sanfilippo
2016-12-15 21:03 ` Pavel Machek
2016-12-15 21:32 ` Lino Sanfilippo
2016-12-15 22:33 ` Lino Sanfilippo
2016-12-17 17:31 ` Pavel Machek
2016-12-18 0:15 ` Francois Romieu
2016-12-18 16:15 ` Lino Sanfilippo
2016-12-18 17:23 ` Pavel Machek
2016-12-18 18:30 ` Pavel Machek
2016-12-19 22:49 ` Lino Sanfilippo
2016-12-18 20:16 ` Pavel Machek
2016-12-19 10:02 ` Pavel Machek
2016-12-20 0:05 ` Francois Romieu
2016-12-07 20:05 ` [PATCH 2/2] net: ethernet: stmmac: " Lino Sanfilippo
2016-12-07 20:55 ` Pavel Machek
2016-12-07 20:59 ` Pavel Machek
2016-12-07 21:37 ` Pavel Machek
2016-12-07 21:43 ` Lino Sanfilippo
2016-12-07 22:34 ` Lino Sanfilippo
2016-12-07 23:21 ` Pavel Machek [this message]
2016-12-07 23:41 ` David Miller
2016-12-08 14:08 ` Pavel Machek
2016-12-08 15:26 ` David Miller
2016-12-08 15:46 ` Pavel Machek
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