netdev - [PATCH bpf-next 04/11] net: add napi_if_scheduled_mark

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Date:   Tue, 28 Aug 2018 14:44:28 +0200
From:   Björn Töpel <bjorn.topel@...il.com>
To:     bjorn.topel@...il.com, magnus.karlsson@...el.com,
        magnus.karlsson@...il.com, alexander.h.duyck@...el.com,
        alexander.duyck@...il.com, ast@...nel.org, brouer@...hat.com,
        daniel@...earbox.net, netdev@...r.kernel.org,
        jesse.brandeburg@...el.com, anjali.singhai@...el.com,
        peter.waskiewicz.jr@...el.com
Cc:     michael.lundkvist@...csson.com, willemdebruijn.kernel@...il.com,
        john.fastabend@...il.com, jakub.kicinski@...ronome.com,
        neerav.parikh@...el.com, mykyta.iziumtsev@...aro.org,
        francois.ozog@...aro.org, ilias.apalodimas@...aro.org,
        brian.brooks@...aro.org, u9012063@...il.com, pavel@...tnetmon.com,
        qi.z.zhang@...el.com
Subject: [PATCH bpf-next 04/11] net: add napi_if_scheduled_mark_missed

From: Magnus Karlsson <magnus.karlsson@...el.com>

The function napi_if_scheduled_mark_missed is used to check if the
NAPI context is scheduled, if so set NAPIF_STATE_MISSED and return
true. Used by the AF_XDP zero-copy i40e Tx code implementation in
order to make sure that irq affinity is honored by the napi context.

Signed-off-by: Magnus Karlsson <magnus.karlsson@...el.com>
---
 include/linux/netdevice.h | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index ca5ab98053c8..4271f6b4e419 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -535,6 +535,32 @@ static inline void napi_synchronize(const struct napi_struct *n)
 		barrier();
 }
 
+/**
+ *	napi_if_scheduled_mark_missed - if napi is running, set the
+ *	NAPIF_STATE_MISSED
+ *	@n: NAPI context
+ *
+ * If napi is running, set the NAPIF_STATE_MISSED, and return true if
+ * NAPI is scheduled.
+ **/
+static inline bool napi_if_scheduled_mark_missed(struct napi_struct *n)
+{
+	unsigned long val, new;
+
+	do {
+		val = READ_ONCE(n->state);
+		if (val & NAPIF_STATE_DISABLE)
+			return true;
+
+		if (!(val & NAPIF_STATE_SCHED))
+			return false;
+
+		new = val | NAPIF_STATE_MISSED;
+	} while (cmpxchg(&n->state, val, new) != val);
+
+	return true;
+}
+
 enum netdev_queue_state_t {
 	__QUEUE_STATE_DRV_XOFF,
 	__QUEUE_STATE_STACK_XOFF,
-- 
2.17.1