diff options
author | Elad Kanfi <eladkan@mellanox.com> | 2016-05-09 20:13:19 +0300 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2016-05-10 15:04:49 -0400 |
commit | e5df49d564fe993c68f5cff6d96972a6358b4958 (patch) | |
tree | 899ce25dfc99e15b7454b845a894dabfd4e3d1dd /drivers/net/ethernet/ezchip/nps_enet.h | |
parent | d99079e2fbd5ac38884f498ca99435d525152a88 (diff) | |
download | linux-e5df49d564fe993c68f5cff6d96972a6358b4958.tar.bz2 |
net: nps_enet: Tx handler synchronization
Below is a description of a possible problematic
sequence. CPU-A is sending a frame and CPU-B handles
the interrupt that indicates the frame was sent. CPU-B
reads an invalid value of tx_packet_sent.
CPU-A CPU-B
----- -----
nps_enet_send_frame
.
.
tx_skb = skb
tx_packet_sent = true
order HW to start tx
.
.
HW complete tx
------> get tx complete interrupt
.
.
if(tx_packet_sent == true)
handle tx_skb
end memory transaction
(tx_packet_sent actually
written)
Furthermore there is a dependency between tx_skb and tx_packet_sent.
There is no assurance that tx_skb contains a valid pointer at CPU B
when it sees tx_packet_sent == true.
Solution:
Initialize tx_skb to NULL and use it to indicate that packet was sent,
in this way tx_packet_sent can be removed.
Add a write memory barrier after setting tx_skb in order to make sure
that it is valid before HW is informed and IRQ is fired.
Fixed sequence will be:
CPU-A CPU-B
----- -----
tx_skb = skb
wmb()
.
.
order HW to start tx
.
.
HW complete tx
------> get tx complete interrupt
.
.
if(tx_skb != NULL)
handle tx_skb
tx_skb = NULL
Signed-off-by: Elad Kanfi <eladkan@mellanox.com>
Acked-by: Noam Camus <noamca@mellanox.com>
Acked-by: Gilad Ben-Yossef <giladby@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/ethernet/ezchip/nps_enet.h')
-rw-r--r-- | drivers/net/ethernet/ezchip/nps_enet.h | 2 |
1 files changed, 0 insertions, 2 deletions
diff --git a/drivers/net/ethernet/ezchip/nps_enet.h b/drivers/net/ethernet/ezchip/nps_enet.h index d0cab600bce8..3939ca20cc9f 100644 --- a/drivers/net/ethernet/ezchip/nps_enet.h +++ b/drivers/net/ethernet/ezchip/nps_enet.h @@ -165,14 +165,12 @@ * struct nps_enet_priv - Storage of ENET's private information. * @regs_base: Base address of ENET memory-mapped control registers. * @irq: For RX/TX IRQ number. - * @tx_packet_sent: SW indication if frame is being sent. * @tx_skb: socket buffer of sent frame. * @napi: Structure for NAPI. */ struct nps_enet_priv { void __iomem *regs_base; s32 irq; - bool tx_packet_sent; struct sk_buff *tx_skb; struct napi_struct napi; u32 ge_mac_cfg_2_value; |