| Message ID | 20210307113309.443631-1-xie.he.0141@gmail.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | f7d9d4854519fdf4d45c70a4d953438cd88e7e58 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net] net: lapbether: Remove netif_start_queue / netif_stop_queue | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Clearly marked for net |
| netdev/subject_prefix | success | Link |
| netdev/cc_maintainers | success | CCed 5 of 5 maintainers |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 0 this patch: 0 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 15 lines checked |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 0 this patch: 0 |
| netdev/header_inline | success | Link |
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 <xie.he.0141@gmail.com> > --- > 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 <ms@dev.tdt.de>
Hello: This patch was applied to netdev/net.git (refs/heads/master): On Sun, 7 Mar 2021 03:33:07 -0800 you 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. > > [...] Here is the summary with links: - [net] net: lapbether: Remove netif_start_queue / netif_stop_queue https://git.kernel.org/netdev/net/c/f7d9d4854519 You are awesome, thank you! -- Deet-doot-dot, I am a bot. https://korg.docs.kernel.org/patchwork/pwbot.html
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);
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 <xie.he.0141@gmail.com> --- drivers/net/wan/lapbether.c | 3 --- 1 file changed, 3 deletions(-)