wlan-ap/feeds/ipq807x/ipq807x/patches/211-v5.12-net-implement-threaded-able-napi-poll-loop-support.patch

From: Wei Wang <weiwan@google.com>
Date: Mon, 8 Feb 2021 11:34:09 -0800
Subject: [PATCH] net: implement threaded-able napi poll loop support

This patch allows running each napi poll loop inside its own
kernel thread.
The kthread is created during netif_napi_add() if dev->threaded
is set. And threaded mode is enabled in napi_enable(). We will
provide a way to set dev->threaded and enable threaded mode
without a device up/down in the following patch.

Once that threaded mode is enabled and the kthread is
started, napi_schedule() will wake-up such thread instead
of scheduling the softirq.

The threaded poll loop behaves quite likely the net_rx_action,
but it does not have to manipulate local irqs and uses
an explicit scheduling point based on netdev_budget.

Co-developed-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Co-developed-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Co-developed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Wei Wang <weiwan@google.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -319,6 +319,7 @@ struct napi_struct {
 	struct list_head	dev_list;
 	struct hlist_node	napi_hash_node;
 	unsigned int		napi_id;
+	struct task_struct	*thread;
 };
 
 enum {
@@ -326,6 +327,7 @@ enum {
 	NAPI_STATE_DISABLE,	/* Disable pending */
 	NAPI_STATE_NPSVC,	/* Netpoll - don't dequeue from poll_list */
 	NAPI_STATE_HASHED,	/* In NAPI hash */
+	NAPI_STATE_THREADED,	/* The poll is performed inside its own thread*/
 };
 
 enum gro_result {
@@ -501,13 +503,7 @@ void napi_disable(struct napi_struct *n)
  * Resume NAPI from being scheduled on this context.
  * Must be paired with napi_disable.
  */
-static inline void napi_enable(struct napi_struct *n)
-{
-	BUG_ON(!test_bit(NAPI_STATE_SCHED, &n->state));
-	smp_mb__before_atomic();
-	clear_bit(NAPI_STATE_SCHED, &n->state);
-	clear_bit(NAPI_STATE_NPSVC, &n->state);
-}
+void napi_enable(struct napi_struct *n);
 
 /**
  *	napi_synchronize - wait until NAPI is not running
@@ -1573,6 +1569,8 @@ enum netdev_priv_flags_ext {
  *			switch driver and used to set the phys state of the
  *			switch port.
  *
+ *	@threaded:	napi threaded mode is enabled
+ *
  *	FIXME: cleanup struct net_device such that network protocol info
  *	moves out.
  */
@@ -1852,6 +1850,7 @@ struct net_device {
 	struct phy_device *phydev;
 	struct lock_class_key *qdisc_tx_busylock;
 	bool proto_down;
+	unsigned		threaded:1;
 };
 #define to_net_dev(d) container_of(d, struct net_device, dev)
 
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -94,6 +94,7 @@
 #include <linux/ethtool.h>
 #include <linux/notifier.h>
 #include <linux/skbuff.h>
+#include <linux/kthread.h>
 #include <net/net_namespace.h>
 #include <net/sock.h>
 #include <linux/rtnetlink.h>
@@ -1304,6 +1305,27 @@ void netdev_notify_peers(struct net_devi
 }
 EXPORT_SYMBOL(netdev_notify_peers);
 
+static int napi_threaded_poll(void *data);
+
+static int napi_kthread_create(struct napi_struct *n)
+{
+	int err = 0;
+
+	/* Create and wake up the kthread once to put it in
+	 * TASK_INTERRUPTIBLE mode to avoid the blocked task
+	 * warning and work with loadavg.
+	 */
+	n->thread = kthread_run(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_run failed with err %d\n", err);
+		n->thread = NULL;
+	}
+
+	return err;
+}
+
 static int __dev_open(struct net_device *dev)
 {
 	const struct net_device_ops *ops = dev->netdev_ops;
@@ -3248,6 +3270,21 @@ int weight_p __read_mostly = 64;
 static inline void ____napi_schedule(struct softnet_data *sd,
 				     struct napi_struct *napi)
 {
+	struct task_struct *thread;
+
+	if (test_bit(NAPI_STATE_THREADED, &napi->state)) {
+		/* Paired with smp_mb__before_atomic() in
+		 * napi_enable(). Use READ_ONCE() to guarantee
+		 * a complete read on napi->thread. Only call
+		 * wake_up_process() when it's not NULL.
+		 */
+		thread = READ_ONCE(napi->thread);
+		if (thread) {
+			wake_up_process(thread);
+			return;
+		}
+	}
+
 	list_add_tail(&napi->poll_list, &sd->poll_list);
 	__raise_softirq_irqoff(NET_RX_SOFTIRQ);
 }
@@ -4828,9 +4865,33 @@ void netif_napi_add(struct net_device *d
 	napi->poll_owner = -1;
 #endif
 	set_bit(NAPI_STATE_SCHED, &napi->state);
+	/* Create kthread for this napi if dev->threaded is set.
+	 * Clear dev->threaded if kthread creation failed so that
+	 * threaded mode will not be enabled in napi_enable().
+	 */
+	if (dev->threaded && napi_kthread_create(napi))
+		dev->threaded = 0;
 }
 EXPORT_SYMBOL(netif_napi_add);
 
+/**
+ *	napi_enable - enable NAPI scheduling
+ *	@n: NAPI context
+ *
+ * Resume NAPI from being scheduled on this context.
+ * Must be paired with napi_disable.
+ */
+void napi_enable(struct napi_struct *n)
+{
+	BUG_ON(!test_bit(NAPI_STATE_SCHED, &n->state));
+	smp_mb__before_atomic();
+	clear_bit(NAPI_STATE_SCHED, &n->state);
+	clear_bit(NAPI_STATE_NPSVC, &n->state);
+	if (n->dev->threaded && n->thread)
+		set_bit(NAPI_STATE_THREADED, &n->state);
+}
+EXPORT_SYMBOL(napi_enable);
+
 void napi_disable(struct napi_struct *n)
 {
 	might_sleep();
@@ -4844,6 +4905,7 @@ void napi_disable(struct napi_struct *n)
 	hrtimer_cancel(&n->timer);
 
 	clear_bit(NAPI_STATE_DISABLE, &n->state);
+	clear_bit(NAPI_STATE_THREADED, &n->state);
 }
 EXPORT_SYMBOL(napi_disable);
 
@@ -4855,6 +4917,11 @@ void netif_napi_del(struct napi_struct *
 	kfree_skb_list(napi->gro_list);
 	napi->gro_list = NULL;
 	napi->gro_count = 0;
+
+	if (napi->thread) {
+		kthread_stop(napi->thread);
+		napi->thread = NULL;
+	}
 }
 EXPORT_SYMBOL(netif_napi_del);
 
@@ -4940,6 +5007,50 @@ static int napi_poll(struct napi_struct
 	return work;
 }
 
+static int napi_thread_wait(struct napi_struct *napi)
+{
+	set_current_state(TASK_INTERRUPTIBLE);
+
+	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;
+		}
+
+		schedule();
+		set_current_state(TASK_INTERRUPTIBLE);
+	}
+	__set_current_state(TASK_RUNNING);
+	return -1;
+}
+
+static int napi_threaded_poll(void *data)
+{
+	struct napi_struct *napi = data;
+	void *have;
+
+	while (!napi_thread_wait(napi)) {
+		for (;;) {
+			bool repoll = false;
+
+			local_bh_disable();
+
+			have = netpoll_poll_lock(napi);
+			__napi_poll(napi, &repoll);
+			netpoll_poll_unlock(have);
+
+			local_bh_enable();
+
+			if (!repoll)
+				break;
+
+			cond_resched();
+		}
+	}
+	return 0;
+}
+
 static void net_rx_action(struct softirq_action *h)
 {
 	struct softnet_data *sd = this_cpu_ptr(&softnet_data);