From: Petr Machata <petrm@mellanox.com>
Date: Mon, 3 Aug 2020 19:11:36 +0300
Subject: mlxsw: spectrum_span: On policer_id_base_ref_count, use dec_and_test
Patch-mainline: v5.9-rc1
Git-commit: 928345c08b72dd175d4eefa24900f09706a9a3b5
References: bsc#1176774

When unsetting policer base, the SPAN code currently uses refcount_dec().
However that function splats when the counter reaches zero, because
reaching zero without actually testing is in general indicative of a
missing cleanup. There is no cleanup to be done here, but nonetheless, use
refcount_dec_and_test() as required.

Signed-off-by: Petr Machata <petrm@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/ethernet/mellanox/mlxsw/spectrum_span.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_span.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_span.c
@@ -837,7 +837,8 @@ static int mlxsw_sp_span_policer_id_base
 
 static void mlxsw_sp_span_policer_id_base_unset(struct mlxsw_sp_span *span)
 {
-	refcount_dec(&span->policer_id_base_ref_count);
+	if (refcount_dec_and_test(&span->policer_id_base_ref_count))
+		span->policer_id_base = 0;
 }
 
 static struct mlxsw_sp_span_entry *