netdev - [PATCH v15 2/7] net: add napi_busy_loop

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Message-Id: <20230608163839.2891748-3-shr@devkernel.io>
Date: Thu,  8 Jun 2023 09:38:34 -0700
From: Stefan Roesch <shr@...kernel.io>
To: io-uring@...r.kernel.org,
	kernel-team@...com
Cc: shr@...kernel.io,
	axboe@...nel.dk,
	ammarfaizi2@...weeb.org,
	netdev@...r.kernel.org,
	kuba@...nel.org,
	olivier@...llion01.com
Subject: [PATCH v15 2/7] net: add napi_busy_loop_rcu()

This adds the napi_busy_loop_rcu() function. This function assumes that
the calling function is already holding the rcu read lock and
napi_busy_loop() does not need to take the rcu read lock.

Signed-off-by: Stefan Roesch <shr@...kernel.io>
---
 include/net/busy_poll.h |  4 ++++
 net/core/dev.c          | 11 +++++++++++
 2 files changed, 15 insertions(+)

diff --git a/include/net/busy_poll.h b/include/net/busy_poll.h
index f90f0021f5f2..622623f5740e 100644
--- a/include/net/busy_poll.h
+++ b/include/net/busy_poll.h
@@ -47,6 +47,10 @@ void napi_busy_loop(unsigned int napi_id,
 		    bool (*loop_end)(void *, unsigned long),
 		    void *loop_end_arg, bool prefer_busy_poll, u16 budget);
 
+void napi_busy_loop_rcu(unsigned int napi_id,
+			bool (*loop_end)(void *, unsigned long),
+			void *loop_end_arg, bool prefer_busy_poll, u16 budget);
+
 #else /* CONFIG_NET_RX_BUSY_POLL */
 static inline unsigned long net_busy_loop_on(void)
 {
diff --git a/net/core/dev.c b/net/core/dev.c
index ae90265f4020..60fc54c4aa42 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6260,6 +6260,17 @@ void __napi_busy_loop(unsigned int napi_id,
 		rcu_read_unlock();
 }
 
+/* Warning: can exit without calling need_resched(). */
+void napi_busy_loop_rcu(unsigned int napi_id,
+			bool (*loop_end)(void *, unsigned long),
+			void *loop_end_arg, bool prefer_busy_poll, u16 budget)
+{
+	WARN_ON_ONCE(!rcu_read_lock_held());
+
+	__napi_busy_loop(napi_id, loop_end, loop_end_arg, prefer_busy_poll,
+			 budget, true);
+}
+
 void napi_busy_loop(unsigned int napi_id,
 		    bool (*loop_end)(void *, unsigned long),
 		    void *loop_end_arg, bool prefer_busy_poll, u16 budget)
-- 
2.39.1