netdev - [PATCH net 5/5] net: aquantia: fix out of memory condition on rx side

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Date:   Fri, 30 Aug 2019 12:08:38 +0000
From:   Igor Russkikh <Igor.Russkikh@...antia.com>
To:     "David S . Miller" <davem@...emloft.net>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Igor Russkikh <Igor.Russkikh@...antia.com>,
        Dmitry Bogdanov <Dmitry.Bogdanov@...antia.com>
Subject: [PATCH net 5/5] net: aquantia: fix out of memory condition on rx side

From: Dmitry Bogdanov <dmitry.bogdanov@...antia.com>

On embedded environments with hard memory limits it is a normal although
rare case when skb can't be allocated on rx part under high traffic.

In such OOM cases napi_complete_done() was not called.
So the napi object became in an invalid state like it is "scheduled".
Kernel do not re-schedules the poll of that napi object.

Consequently, kernel can not remove that object the system hangs on
`ifconfig down` waiting for a poll.

We are fixing this by gracefully closing napi poll routine with correct
invocation of napi_complete_done.

This was reproduced with artificially failing the allocation of skb to
simulate an "out of memory" error case and check that traffic does
not get stuck.

Fixes: 970a2e9864b0 ("net: ethernet: aquantia: Vector operations")
Signed-off-by: Igor Russkikh <igor.russkikh@...antia.com>
Signed-off-by: Dmitry Bogdanov <dmitry.bogdanov@...antia.com>
---
 drivers/net/ethernet/aquantia/atlantic/aq_vec.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/aquantia/atlantic/aq_vec.c b/drivers/net/ethernet/aquantia/atlantic/aq_vec.c
index 715685aa48c3..28892b8acd0e 100644
--- a/drivers/net/ethernet/aquantia/atlantic/aq_vec.c
+++ b/drivers/net/ethernet/aquantia/atlantic/aq_vec.c
@@ -86,6 +86,7 @@ static int aq_vec_poll(struct napi_struct *napi, int budget)
 			}
 		}

+err_exit:
 		if (!was_tx_cleaned)
 			work_done = budget;

@@ -95,7 +96,7 @@ static int aq_vec_poll(struct napi_struct *napi, int budget)
 					1U << self->aq_ring_param.vec_idx);
 		}
 	}
-err_exit:
+
 	return work_done;
 }

-- 
2.17.1