generic: 6.6: replace (broken) downstream patch with upstream solution

Our downstream patch "net/core: add optional threading for backlog processing"
has been broken with the switch to Linux 6.6.
Replace it by backporting the now available upstream solution.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Link: openwrt#15592
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>

target/linux/generic/backport-6.6/600-v6.10-net-Remove-conditional-threaded-NAPI-wakeup-based-on.patch

@@ -0,0 +1,75 @@
+From 56364c910691f6d10ba88c964c9041b9ab777bd6 Mon Sep 17 00:00:00 2001
+From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+Date: Mon, 25 Mar 2024 08:40:28 +0100
+Subject: [PATCH 1/4] net: Remove conditional threaded-NAPI wakeup based on
+ task state.
+
+A NAPI thread is scheduled by first setting NAPI_STATE_SCHED bit. If
+successful (the bit was not yet set) then the NAPI_STATE_SCHED_THREADED
+is set but only if thread's state is not TASK_INTERRUPTIBLE (is
+TASK_RUNNING) followed by task wakeup.
+
+If the task is idle (TASK_INTERRUPTIBLE) then the
+NAPI_STATE_SCHED_THREADED bit is not set. The thread is no relying on
+the bit but always leaving the wait-loop after returning from schedule()
+because there must have been a wakeup.
+
+The smpboot-threads implementation for per-CPU threads requires an
+explicit condition and does not support "if we get out of schedule()
+then there must be something to do".
+
+Removing this optimisation simplifies the following integration.
+
+Set NAPI_STATE_SCHED_THREADED unconditionally on wakeup and rely on it
+in the wait path by removing the `woken' condition.
+
+Acked-by: Jakub Kicinski <kuba@kernel.org>
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+Signed-off-by: Paolo Abeni <pabeni@redhat.com>
+---
+ net/core/dev.c | 14 ++------------
+ 1 file changed, 2 insertions(+), 12 deletions(-)
+
+--- a/net/core/dev.c
++++ b/net/core/dev.c
+@@ -4473,13 +4473,7 @@ static inline void ____napi_schedule(str
+ 		 */
+ 		thread = READ_ONCE(napi->thread);
+ 		if (thread) {
+-			/* Avoid doing set_bit() if the thread is in
+-			 * INTERRUPTIBLE state, cause napi_thread_wait()
+-			 * makes sure to proceed with napi polling
+-			 * if the thread is explicitly woken from here.
+-			 */
+-			if (READ_ONCE(thread->__state) != TASK_INTERRUPTIBLE)
+-				set_bit(NAPI_STATE_SCHED_THREADED, &napi->state);
++			set_bit(NAPI_STATE_SCHED_THREADED, &napi->state);
+ 			wake_up_process(thread);
+ 			return;
+ 		}
+@@ -6635,8 +6629,6 @@ static int napi_poll(struct napi_struct
+
+ static int napi_thread_wait(struct napi_struct *napi)
+ {
+-	bool woken = false;
+-
+ 	set_current_state(TASK_INTERRUPTIBLE);
+
+ 	while (!kthread_should_stop()) {
+@@ -6645,15 +6637,13 @@ static int napi_thread_wait(struct napi_
+ 		 * Testing SCHED bit is not enough because SCHED bit might be
+ 		 * set by some other busy poll thread or by napi_disable().
+ 		 */
+-		if (test_bit(NAPI_STATE_SCHED_THREADED, &napi->state) || woken) {
++		if (test_bit(NAPI_STATE_SCHED_THREADED, &napi->state)) {
+ 			WARN_ON(!list_empty(&napi->poll_list));
+ 			__set_current_state(TASK_RUNNING);
+ 			return 0;
+ 		}
+
+ 		schedule();
+-		/* woken being true indicates this thread owns this napi. */
+-		woken = true;
+ 		set_current_state(TASK_INTERRUPTIBLE);
+ 	}
+ 	__set_current_state(TASK_RUNNING);