From mboxrd@z Thu Jan 1 00:00:00 1970 From: Martin Schiller Subject: Re: [PATCH net] net: lapbether: Remove netif_start_queue / netif_stop_queue Date: Tue, 09 Mar 2021 14:48:30 +0100 Message-ID: <6f885ff41da24d41cb5d430d9abe42f7@dev.tdt.de> References: <20210307113309.443631-1-xie.he.0141@gmail.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20210307113309.443631-1-xie.he.0141@gmail.com> List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Xie He Cc: "David S. Miller" , Jakub Kicinski , linux-x25@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org On 2021-03-07 12:33, Xie He wrote: > For the devices in this driver, the default qdisc is "noqueue", > because their "tx_queue_len" is 0. > > In function "__dev_queue_xmit" in "net/core/dev.c", devices with the > "noqueue" qdisc are specially handled. Packets are transmitted without > being queued after a "dev->flags & IFF_UP" check. However, it's > possible > that even if this check succeeds, "ops->ndo_stop" may still have > already > been called. This is because in "__dev_close_many", "ops->ndo_stop" is > called before clearing the "IFF_UP" flag. > > If we call "netif_stop_queue" in "ops->ndo_stop", then it's possible in > "__dev_queue_xmit", it sees the "IFF_UP" flag is present, and then it > checks "netif_xmit_stopped" and finds that the queue is already > stopped. > In this case, it will complain that: > "Virtual device ... asks to queue packet!" > > To prevent "__dev_queue_xmit" from generating this complaint, we should > not call "netif_stop_queue" in "ops->ndo_stop". > > We also don't need to call "netif_start_queue" in "ops->ndo_open", > because after a netdev is allocated and registered, the > "__QUEUE_STATE_DRV_XOFF" flag is initially not set, so there is no need > to call "netif_start_queue" to clear it. > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Signed-off-by: Xie He > --- > drivers/net/wan/lapbether.c | 3 --- > 1 file changed, 3 deletions(-) > > diff --git a/drivers/net/wan/lapbether.c b/drivers/net/wan/lapbether.c > index 605fe555e157..c3372498f4f1 100644 > --- a/drivers/net/wan/lapbether.c > +++ b/drivers/net/wan/lapbether.c > @@ -292,7 +292,6 @@ static int lapbeth_open(struct net_device *dev) > return -ENODEV; > } > > - netif_start_queue(dev); > return 0; > } > > @@ -300,8 +299,6 @@ static int lapbeth_close(struct net_device *dev) > { > int err; > > - netif_stop_queue(dev); > - > if ((err = lapb_unregister(dev)) != LAPB_OK) > pr_err("lapb_unregister error: %d\n", err); Seems reasonable to me. Acked-by: Martin Schiller