Iyappan Subramanian ecf6ba83d7 drivers: net: xgene: fix: Out of order descriptor bytes read ... This patch fixes the following kernel crash, WARNING: CPU: 2 PID: 0 at net/ipv4/tcp_input.c:3079 tcp_clean_rtx_queue+0x658/0x80c() Call trace: [<fffffe0000096b7c>] dump_backtrace+0x0/0x184 [<fffffe0000096d10>] show_stack+0x10/0x1c [<fffffe0000685ea0>] dump_stack+0x74/0x98 [<fffffe00000b44e0>] warn_slowpath_common+0x88/0xb0 [<fffffe00000b461c>] warn_slowpath_null+0x14/0x20 [<fffffe00005b5c1c>] tcp_clean_rtx_queue+0x654/0x80c [<fffffe00005b6228>] tcp_ack+0x454/0x688 [<fffffe00005b6ca8>] tcp_rcv_established+0x4a4/0x62c [<fffffe00005bf4b4>] tcp_v4_do_rcv+0x16c/0x350 [<fffffe00005c225c>] tcp_v4_rcv+0x8e8/0x904 [<fffffe000059d470>] ip_local_deliver_finish+0x100/0x26c [<fffffe000059dad8>] ip_local_deliver+0xac/0xc4 [<fffffe000059d6c4>] ip_rcv_finish+0xe8/0x328 [<fffffe000059dd3c>] ip_rcv+0x24c/0x38c [<fffffe0000563950>] __netif_receive_skb_core+0x29c/0x7c8 [<fffffe0000563ea4>] __netif_receive_skb+0x28/0x7c [<fffffe0000563f54>] netif_receive_skb_internal+0x5c/0xe0 [<fffffe0000564810>] napi_gro_receive+0xb4/0x110 [<fffffe0000482a2c>] xgene_enet_process_ring+0x144/0x338 [<fffffe0000482d18>] xgene_enet_napi+0x1c/0x50 [<fffffe0000565454>] net_rx_action+0x154/0x228 [<fffffe00000b804c>] __do_softirq+0x110/0x28c [<fffffe00000b8424>] irq_exit+0x8c/0xc0 [<fffffe0000093898>] handle_IRQ+0x44/0xa8 [<fffffe000009032c>] gic_handle_irq+0x38/0x7c [...] Software writes poison data into the descriptor bytes[15:8] and upon receiving the interrupt, if those bytes are overwritten by the hardware with the valid data, software also reads bytes[7:0] and executes receive/tx completion logic. If the CPU executes the above two reads in out of order fashion, then the bytes[7:0] will have older data and causing the kernel panic. We have to force the order of the reads and thus this patch introduces read memory barrier between these reads. Signed-off-by: Iyappan Subramanian <isubramanian@apm.com> Signed-off-by: Keyur Chudgar <kchudgar@apm.com> Signed-off-by: David S. Miller <davem@davemloft.net>		2015-01-30 18:17:31 -08:00
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xgene	drivers: net: xgene: fix: Out of order descriptor bytes read	2015-01-30 18:17:31 -08:00
Kconfig
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