Thread (27 messages) 27 messages, 6 authors, 2020-10-03
STALE2072d
Revisions (3)
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  2. v2 [diff vs current]
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[PATCH net-next 5/5] net: improve napi threaded config

From: Wei Wang <hidden>
Date: 2020-09-30 19:22:41
Subsystem: networking [general], the rest · Maintainers: "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds

This commit mainly addresses the threaded config to make the switch
between softirq based and kthread based NAPI processing not require
a device down/up.
It also moves the kthread_create() call to the sysfs handler when user
tries to enable "threaded" on napi, and properly handles the
kthread_create() failure. This is because certain drivers do not have
the napi created and linked to the dev when dev_open() is called. So
the previous implementation does not work properly there.

Signed-off-by: Wei Wang <redacted>
---
Changes since RFC:
changed the thread name to napi/<dev>-<napi-id>

 net/core/dev.c       | 49 +++++++++++++++++++++++++-------------------
 net/core/net-sysfs.c |  9 +++-----
 2 files changed, 31 insertions(+), 27 deletions(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index b4f33e442b5e..bf878d3a9d89 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1490,17 +1490,24 @@ EXPORT_SYMBOL(netdev_notify_peers);
 
 static int napi_threaded_poll(void *data);
 
-static void napi_thread_start(struct napi_struct *n)
+static int napi_kthread_create(struct napi_struct *n)
 {
-	if (test_bit(NAPI_STATE_THREADED, &n->state) && !n->thread)
-		n->thread = kthread_create(napi_threaded_poll, n, "%s-%d",
-					   n->dev->name, n->napi_id);
+	int err = 0;
+
+	n->thread = kthread_create(napi_threaded_poll, n, "napi/%s-%d",
+				   n->dev->name, n->napi_id);
+	if (IS_ERR(n->thread)) {
+		err = PTR_ERR(n->thread);
+		pr_err("kthread_create failed with err %d\n", err);
+		n->thread = NULL;
+	}
+
+	return err;
 }
 
 static int __dev_open(struct net_device *dev, struct netlink_ext_ack *extack)
 {
 	const struct net_device_ops *ops = dev->netdev_ops;
-	struct napi_struct *n;
 	int ret;
 
 	ASSERT_RTNL();
@@ -1532,9 +1539,6 @@ static int __dev_open(struct net_device *dev, struct netlink_ext_ack *extack)
 	if (!ret && ops->ndo_open)
 		ret = ops->ndo_open(dev);
 
-	list_for_each_entry(n, &dev->napi_list, dev_list)
-		napi_thread_start(n);
-
 	netpoll_poll_enable(dev);
 
 	if (ret)
@@ -1585,6 +1589,7 @@ static void napi_thread_stop(struct napi_struct *n)
 	if (!n->thread)
 		return;
 	kthread_stop(n->thread);
+	clear_bit(NAPI_STATE_THREADED, &n->state);
 	n->thread = NULL;
 }
 
@@ -4267,7 +4272,7 @@ int gro_normal_batch __read_mostly = 8;
 static inline void ____napi_schedule(struct softnet_data *sd,
 				     struct napi_struct *napi)
 {
-	if (napi->thread) {
+	if (test_bit(NAPI_STATE_THREADED, &napi->state)) {
 		wake_up_process(napi->thread);
 		return;
 	}
@@ -6687,25 +6692,25 @@ static void init_gro_hash(struct napi_struct *napi)
 
 int napi_set_threaded(struct napi_struct *n, bool threaded)
 {
-	ASSERT_RTNL();
+	int err = 0;
 
-	if (n->dev->flags & IFF_UP)
-		return -EBUSY;
+	ASSERT_RTNL();
 
 	if (threaded == !!test_bit(NAPI_STATE_THREADED, &n->state))
 		return 0;
-	if (threaded)
+	if (threaded) {
+		if (!n->thread) {
+			err = napi_kthread_create(n);
+			if (err)
+				goto out;
+		}
 		set_bit(NAPI_STATE_THREADED, &n->state);
-	else
+	} else {
 		clear_bit(NAPI_STATE_THREADED, &n->state);
+	}
 
-	/* if the device is initializing, nothing todo */
-	if (test_bit(__LINK_STATE_START, &n->dev->state))
-		return 0;
-
-	napi_thread_stop(n);
-	napi_thread_start(n);
-	return 0;
+out:
+	return err;
 }
 EXPORT_SYMBOL(napi_set_threaded);
 
@@ -6750,6 +6755,7 @@ void napi_disable(struct napi_struct *n)
 		msleep(1);
 
 	hrtimer_cancel(&n->timer);
+	napi_thread_stop(n);
 
 	clear_bit(NAPI_STATE_DISABLE, &n->state);
 }
@@ -6870,6 +6876,7 @@ static int napi_thread_wait(struct napi_struct *napi)
 
 	while (!kthread_should_stop() && !napi_disable_pending(napi)) {
 		if (test_bit(NAPI_STATE_SCHED, &napi->state)) {
+			WARN_ON(!list_empty(&napi->poll_list));
 			__set_current_state(TASK_RUNNING);
 			return 0;
 		}
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index fe81b344447d..b54dbccf00be 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -609,11 +609,6 @@ static ssize_t threaded_store(struct device *dev,
 		goto unlock;
 	}
 
-	if (netdev->flags & IFF_UP) {
-		ret = -EBUSY;
-		goto unlock;
-	}
-
 	bmap = __alloc_thread_bitmap(netdev, &bits);
 	if (!bmap) {
 		ret = -ENOMEM;
@@ -626,7 +621,9 @@ static ssize_t threaded_store(struct device *dev,
 
 	i = 0;
 	list_for_each_entry(n, &netdev->napi_list, dev_list) {
-		napi_set_threaded(n, test_bit(i, bmap));
+		ret = napi_set_threaded(n, test_bit(i, bmap));
+		if (ret)
+			goto free_unlock;
 		i++;
 	}
 	ret = len;
-- 
2.28.0.709.gb0816b6eb0-goog
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