diff mbox series

[net,1/2] net: xilinx: axienet: Enqueue Tx packets in dql before dmaengine starts

Message ID 20241030062533.2527042-2-suraj.gupta2@amd.com (mailing list archive)
State Accepted
Commit 5ccdcdf186aec6b9111845fd37e1757e9b413e2f
Delegated to: Netdev Maintainers
Headers show
Series net: xilinx: axienet: Fix kernel crash in dmaengine transmit path | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag present in non-next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 5 this patch: 5
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers success CCed 8 of 8 maintainers
netdev/build_clang success Errors and warnings before: 3 this patch: 3
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 6 this patch: 6
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 15 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 3 this patch: 3
netdev/source_inline success Was 0 now: 0
netdev/contest success net-next-2024-11-03--21-00 (tests: 781)

Commit Message

Gupta, Suraj Oct. 30, 2024, 6:25 a.m. UTC 
Enqueue packets in dql after dma engine starts causes race condition.
Tx transfer starts once dma engine is started and may execute dql dequeue
in completion before it gets queued. It results in following kernel crash
while running iperf stress test:

kernel BUG at lib/dynamic_queue_limits.c:99!
<snip>
Internal error: Oops - BUG: 00000000f2000800 [#1] SMP
pc : dql_completed+0x238/0x248
lr : dql_completed+0x3c/0x248

Call trace:
  dql_completed+0x238/0x248
  axienet_dma_tx_cb+0xa0/0x170
  xilinx_dma_do_tasklet+0xdc/0x290
  tasklet_action_common+0xf8/0x11c
  tasklet_action+0x30/0x3c
  handle_softirqs+0xf8/0x230
<snip>

Start dmaengine after enqueue in dql fixes the crash.

Fixes: 6a91b846af85 ("net: axienet: Introduce dmaengine support")
Signed-off-by: Suraj Gupta <suraj.gupta2@amd.com>
---
 drivers/net/ethernet/xilinx/xilinx_axienet_main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
index 273ec5f70005..0f4b02fe6f85 100644
--- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
+++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
@@ -924,13 +924,13 @@  axienet_start_xmit_dmaengine(struct sk_buff *skb, struct net_device *ndev)
 	skbuf_dma->sg_len = sg_len;
 	dma_tx_desc->callback_param = lp;
 	dma_tx_desc->callback_result = axienet_dma_tx_cb;
-	dmaengine_submit(dma_tx_desc);
-	dma_async_issue_pending(lp->tx_chan);
 	txq = skb_get_tx_queue(lp->ndev, skb);
 	netdev_tx_sent_queue(txq, skb->len);
 	netif_txq_maybe_stop(txq, CIRC_SPACE(lp->tx_ring_head, lp->tx_ring_tail, TX_BD_NUM_MAX),
 			     MAX_SKB_FRAGS + 1, 2 * MAX_SKB_FRAGS);
 
+	dmaengine_submit(dma_tx_desc);
+	dma_async_issue_pending(lp->tx_chan);
 	return NETDEV_TX_OK;
 
 xmit_error_unmap_sg: