[PATCH 4.9 03/32] net/mlx5e: Disable preemption when doing TC statistics upcall

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Or Gerlitz <ogerlitz@mellanox.com>


[ Upstream commit fed06ee89b78d3af32e235e0e89ad0d946fcb95d ]

When called by HW offloading drivers, the TC action (e.g
net/sched/act_mirred.c) code uses this_cpu logic, e.g

 _bstats_cpu_update(this_cpu_ptr(a->cpu_bstats), bytes, packets)

per the kernel documention, preemption should be disabled, add that.

Before the fix, when running with CONFIG_PREEMPT set, we get a

BUG: using smp_processor_id() in preemptible [00000000] code: tc/3793

asserion from the TC action (mirred) stats_update callback.

Fixes: aad7e08d39bd ('net/mlx5e: Hardware offloaded flower filter statistics support')
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_tc.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
@@ -567,10 +567,14 @@ int mlx5e_stats_flower(struct mlx5e_priv
 
 	mlx5_fc_query_cached(counter, &bytes, &packets, &lastuse);
 
+	preempt_disable();
+
 	tcf_exts_to_list(f->exts, &actions);
 	list_for_each_entry(a, &actions, list)
 		tcf_action_stats_update(a, bytes, packets, lastuse);
 
+	preempt_enable();
+
 	return 0;
 }