kernel: backport fix for hang on napi_disable with threaded NAPI

Signed-off-by: Felix Fietkau <nbd@nbd.name>

2 files changed, 57 insertions, 4 deletions

diff --git a/target/linux/generic/backport-5.10/604-v5.12-net-fix-hangup-on-napi_disable-for-threaded-napi.patch b/target/linux/generic/backport-5.10/604-v5.12-net-fix-hangup-on-napi_disable-for-threaded-napi.patch
new file mode 100644
index 0000000000..4b83641291
--- /dev/null
+++ b/target/linux/generic/backport-5.10/604-v5.12-net-fix-hangup-on-napi_disable-for-threaded-napi.patch
@@ -0,0 +1,53 @@
+From: Paolo Abeni <pabeni@redhat.com>
+Date: Fri, 9 Apr 2021 17:24:17 +0200
+Subject: [PATCH] net: fix hangup on napi_disable for threaded napi
+
+napi_disable() is subject to an hangup, when the threaded
+mode is enabled and the napi is under heavy traffic.
+
+If the relevant napi has been scheduled and the napi_disable()
+kicks in before the next napi_threaded_wait() completes - so
+that the latter quits due to the napi_disable_pending() condition,
+the existing code leaves the NAPI_STATE_SCHED bit set and the
+napi_disable() loop waiting for such bit will hang.
+
+This patch addresses the issue by dropping the NAPI_STATE_DISABLE
+bit test in napi_thread_wait(). The later napi_threaded_poll()
+iteration will take care of clearing the NAPI_STATE_SCHED.
+
+This also addresses a related problem reported by Jakub:
+before this patch a napi_disable()/napi_enable() pair killed
+the napi thread, effectively disabling the threaded mode.
+On the patched kernel napi_disable() simply stops scheduling
+the relevant thread.
+
+v1 -> v2:
+  - let the main napi_thread_poll() loop clear the SCHED bit
+
+Reported-by: Jakub Kicinski <kuba@kernel.org>
+Fixes: 29863d41bb6e ("net: implement threaded-able napi poll loop support")
+Signed-off-by: Paolo Abeni <pabeni@redhat.com>
+Reviewed-by: Eric Dumazet <edumazet@google.com>
+Link: https://lore.kernel.org/r/883923fa22745a9589e8610962b7dc59df09fb1f.1617981844.git.pabeni@redhat.com
+Signed-off-by: Jakub Kicinski <kuba@kernel.org>
+---
+
+--- a/net/core/dev.c
++++ b/net/core/dev.c
+@@ -6951,7 +6951,7 @@ static int napi_thread_wait(struct napi_
+ 
+ 	set_current_state(TASK_INTERRUPTIBLE);
+ 
+-	while (!kthread_should_stop() && !napi_disable_pending(napi)) {
++	while (!kthread_should_stop()) {
+ 		/* Testing SCHED_THREADED bit here to make sure the current
+ 		 * kthread owns this napi and could poll on this napi.
+ 		 * Testing SCHED bit is not enough because SCHED bit might be
+@@ -6969,6 +6969,7 @@ static int napi_thread_wait(struct napi_
+ 		set_current_state(TASK_INTERRUPTIBLE);
+ 	}
+ 	__set_current_state(TASK_RUNNING);
++
+ 	return -1;
+ }
+ 
diff --git a/target/linux/generic/pending-5.10/680-NET-skip-GRO-for-foreign-MAC-addresses.patch b/target/linux/generic/pending-5.10/680-NET-skip-GRO-for-foreign-MAC-addresses.patch
index 8b5ec9c305..3b485e3cc9 100644
--- a/target/linux/generic/pending-5.10/680-NET-skip-GRO-for-foreign-MAC-addresses.patch
+++ b/target/linux/generic/pending-5.10/680-NET-skip-GRO-for-foreign-MAC-addresses.patch
@@ -42,7 +42,7 @@ Signed-off-by: Felix Fietkau <nbd@nbd.name>
  	if (netif_elide_gro(skb->dev))
  		goto normal;
  
-@@ -7986,6 +7989,48 @@ static void __netdev_adjacent_dev_unlink
+@@ -7987,6 +7990,48 @@ static void __netdev_adjacent_dev_unlink
  					   &upper_dev->adj_list.lower);
  }
  
@@ -91,7 +91,7 @@ Signed-off-by: Felix Fietkau <nbd@nbd.name>
  static int __netdev_upper_dev_link(struct net_device *dev,
  				   struct net_device *upper_dev, bool master,
  				   void *upper_priv, void *upper_info,
-@@ -8037,6 +8082,7 @@ static int __netdev_upper_dev_link(struc
+@@ -8038,6 +8083,7 @@ static int __netdev_upper_dev_link(struc
  	if (ret)
  		return ret;
  
@@ -99,7 +99,7 @@ Signed-off-by: Felix Fietkau <nbd@nbd.name>
  	ret = call_netdevice_notifiers_info(NETDEV_CHANGEUPPER,
  					    &changeupper_info.info);
  	ret = notifier_to_errno(ret);
-@@ -8133,6 +8179,7 @@ static void __netdev_upper_dev_unlink(st
+@@ -8134,6 +8180,7 @@ static void __netdev_upper_dev_unlink(st
  
  	__netdev_adjacent_dev_unlink_neighbour(dev, upper_dev);
  
@@ -107,7 +107,7 @@ Signed-off-by: Felix Fietkau <nbd@nbd.name>
  	call_netdevice_notifiers_info(NETDEV_CHANGEUPPER,
  				      &changeupper_info.info);
  
-@@ -8919,6 +8966,7 @@ int dev_set_mac_address(struct net_devic
+@@ -8920,6 +8967,7 @@ int dev_set_mac_address(struct net_devic
  	if (err)
  		return err;
  	dev->addr_assign_type = NET_ADDR_SET;