From 5e6a76be8acf4d08c2c96598f5d0700b35d2a2a1 Mon Sep 17 00:00:00 2001
From: Hans Petter Selasky <hselasky@FreeBSD.org>
Date: Fri, 27 Jan 2017 08:32:50 +0000
Subject: [PATCH] Enforce reading the consumer and producer counters once to
 ensure consistent return values from the mlx5e_sq_has_room_for() function.
 The two counters are incremented by different threads under different locks.

MFC after:		1 week
Sponsored by:		Mellanox Technologies
---
 sys/dev/mlx5/mlx5_en/en.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/sys/dev/mlx5/mlx5_en/en.h b/sys/dev/mlx5/mlx5_en/en.h
index b05d13baff7c..2415f3b6a97f 100644
--- a/sys/dev/mlx5/mlx5_en/en.h
+++ b/sys/dev/mlx5/mlx5_en/en.h
@@ -546,8 +546,10 @@ struct mlx5e_sq {
 static inline bool
 mlx5e_sq_has_room_for(struct mlx5e_sq *sq, u16 n)
 {
-	return ((sq->wq.sz_m1 & (sq->cc - sq->pc)) >= n ||
-	    sq->cc == sq->pc);
+	u16 cc = sq->cc;
+	u16 pc = sq->pc;
+
+	return ((sq->wq.sz_m1 & (cc - pc)) >= n || cc == pc);
 }
 
 struct mlx5e_channel {