From: Esben Haabendal <esben@geanix.com>
To: netdev@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, "Andrew Lunn" <andrew@lunn.ch>,
"David S . Miller" <davem@davemloft.net>,
"Michal Simek" <michal.simek@xilinx.com>,
"Petr Štetiar" <ynezz@true.cz>,
stable@vger.kernel.org
Subject: [PATCH 1/8] net: ll_temac: Fix race condition causing TX hang
Date: Tue, 18 Feb 2020 09:26:19 +0100 [thread overview]
Message-ID: <20200218082619.7119-1-esben@geanix.com> (raw)
It is possible that the interrupt handler fires and frees up space in
the TX ring in between checking for sufficient TX ring space and
stopping the TX queue in temac_start_xmit. If this happens, the
queue wake from the interrupt handler will occur before the queue is
stopped, causing a lost wakeup and the adapter's transmit hanging.
To avoid this, after stopping the queue, check again whether there is
sufficient space in the TX ring. If so, wake up the queue again.
This is a port of the similar fix in axienet driver,
commit 7de44285c1f6 ("net: axienet: Fix race condition causing TX hang").
Signed-off-by: Esben Haabendal <esben@geanix.com>
Cc: stable@vger.kernel.org
---
drivers/net/ethernet/xilinx/ll_temac_main.c | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)
diff --git a/drivers/net/ethernet/xilinx/ll_temac_main.c b/drivers/net/ethernet/xilinx/ll_temac_main.c
index 6f11f52c9a9e..996004ef8bd4 100644
--- a/drivers/net/ethernet/xilinx/ll_temac_main.c
+++ b/drivers/net/ethernet/xilinx/ll_temac_main.c
@@ -788,6 +788,9 @@ static void temac_start_xmit_done(struct net_device *ndev)
stat = be32_to_cpu(cur_p->app0);
}
+ /* Matches barrier in temac_start_xmit */
+ smp_mb();
+
netif_wake_queue(ndev);
}
@@ -830,9 +833,19 @@ temac_start_xmit(struct sk_buff *skb, struct net_device *ndev)
cur_p = &lp->tx_bd_v[lp->tx_bd_tail];
if (temac_check_tx_bd_space(lp, num_frag + 1)) {
- if (!netif_queue_stopped(ndev))
- netif_stop_queue(ndev);
- return NETDEV_TX_BUSY;
+ if (netif_queue_stopped(ndev))
+ return NETDEV_TX_BUSY;
+
+ netif_stop_queue(ndev);
+
+ /* Matches barrier in temac_start_xmit_done */
+ smp_mb();
+
+ /* Space might have just been freed - check again */
+ if (temac_check_tx_bd_space(lp, num_frag))
+ return NETDEV_TX_BUSY;
+
+ netif_wake_queue(ndev);
}
cur_p->app0 = 0;
--
2.25.0
reply other threads:[~2020-02-18 8:26 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200218082619.7119-1-esben@geanix.com \
--to=esben@geanix.com \
--cc=andrew@lunn.ch \
--cc=davem@davemloft.net \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=michal.simek@xilinx.com \
--cc=netdev@vger.kernel.org \
--cc=stable@vger.kernel.org \
--cc=ynezz@true.cz \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).