linux-kernel - [PATCH net-next v9 2/6] net: Add control functions for irq suspension

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Message-Id: <20241109050245.191288-3-jdamato@fastly.com>
Date: Sat,  9 Nov 2024 05:02:32 +0000
From: Joe Damato <jdamato@...tly.com>
To: netdev@...r.kernel.org
Cc: corbet@....net,
	hdanton@...a.com,
	bagasdotme@...il.com,
	pabeni@...hat.com,
	namangulati@...gle.com,
	edumazet@...gle.com,
	amritha.nambiar@...el.com,
	sridhar.samudrala@...el.com,
	sdf@...ichev.me,
	peter@...eblog.net,
	m2shafiei@...terloo.ca,
	bjorn@...osinc.com,
	hch@...radead.org,
	willy@...radead.org,
	willemdebruijn.kernel@...il.com,
	skhawaja@...gle.com,
	kuba@...nel.org,
	Martin Karsten <mkarsten@...terloo.ca>,
	Joe Damato <jdamato@...tly.com>,
	"David S. Miller" <davem@...emloft.net>,
	Simon Horman <horms@...nel.org>,
	David Ahern <dsahern@...nel.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Lorenzo Bianconi <lorenzo@...nel.org>,
	Alexander Lobakin <aleksander.lobakin@...el.com>,
	linux-kernel@...r.kernel.org (open list)
Subject: [PATCH net-next v9 2/6] net: Add control functions for irq suspension

From: Martin Karsten <mkarsten@...terloo.ca>

The napi_suspend_irqs routine bootstraps irq suspension by elongating
the defer timeout to irq_suspend_timeout.

The napi_resume_irqs routine effectively cancels irq suspension by
forcing the napi to be scheduled immediately.

Signed-off-by: Martin Karsten <mkarsten@...terloo.ca>
Co-developed-by: Joe Damato <jdamato@...tly.com>
Signed-off-by: Joe Damato <jdamato@...tly.com>
Tested-by: Joe Damato <jdamato@...tly.com>
Tested-by: Martin Karsten <mkarsten@...terloo.ca>
Acked-by: Stanislav Fomichev <sdf@...ichev.me>
Reviewed-by: Sridhar Samudrala <sridhar.samudrala@...el.com>
---
 v8:
  - Drop unneeded exports as pointed out by Jakub.

 v7:
  - This is now patch 2 instead of patch 3; patch 2 from v6 was dropped.

 v1 -> v2:
   - Added a comment to napi_resume_irqs.

 include/net/busy_poll.h |  3 +++
 net/core/dev.c          | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+)

diff --git a/include/net/busy_poll.h b/include/net/busy_poll.h
index f03040baaefd..c858270141bc 100644
--- a/include/net/busy_poll.h
+++ b/include/net/busy_poll.h
@@ -52,6 +52,9 @@ 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);
 
+void napi_suspend_irqs(unsigned int napi_id);
+void napi_resume_irqs(unsigned int napi_id);
+
 #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 4d910872963f..13d00fc10f55 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6507,6 +6507,43 @@ void napi_busy_loop(unsigned int napi_id,
 }
 EXPORT_SYMBOL(napi_busy_loop);
 
+void napi_suspend_irqs(unsigned int napi_id)
+{
+	struct napi_struct *napi;
+
+	rcu_read_lock();
+	napi = napi_by_id(napi_id);
+	if (napi) {
+		unsigned long timeout = napi_get_irq_suspend_timeout(napi);
+
+		if (timeout)
+			hrtimer_start(&napi->timer, ns_to_ktime(timeout),
+				      HRTIMER_MODE_REL_PINNED);
+	}
+	rcu_read_unlock();
+}
+
+void napi_resume_irqs(unsigned int napi_id)
+{
+	struct napi_struct *napi;
+
+	rcu_read_lock();
+	napi = napi_by_id(napi_id);
+	if (napi) {
+		/* If irq_suspend_timeout is set to 0 between the call to
+		 * napi_suspend_irqs and now, the original value still
+		 * determines the safety timeout as intended and napi_watchdog
+		 * will resume irq processing.
+		 */
+		if (napi_get_irq_suspend_timeout(napi)) {
+			local_bh_disable();
+			napi_schedule(napi);
+			local_bh_enable();
+		}
+	}
+	rcu_read_unlock();
+}
+
 #endif /* CONFIG_NET_RX_BUSY_POLL */
 
 static void __napi_hash_add_with_id(struct napi_struct *napi,
-- 
2.25.1