net: xilinx: axienet: Fix race in axienet_stop

axienet_dma_err_handler can race with axienet_stop in the following
manner:

CPU 1                       CPU 2
======================      ==================
axienet_stop()
    napi_disable()
    axienet_dma_stop()
                            axienet_dma_err_handler()
                                napi_disable()
                                axienet_dma_stop()
                                axienet_dma_start()
                                napi_enable()
    cancel_work_sync()
    free_irq()

Fix this by setting a flag in axienet_stop telling
axienet_dma_err_handler not to bother doing anything. I chose not to use
disable_work_sync to allow for easier backporting.

Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
Fixes: 8a3b7a252dca ("drivers/net/ethernet/xilinx: added Xilinx AXI Ethernet driver")
Link: https://patch.msgid.link/20240903175141.4132898-1-sean.anderson@linux.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet.h b/drivers/net/ethernet/xilinx/xilinx_axienet.h
index 09c9f9787180bf1dd9faedcdb337322c0211927b..1223fcc1a8daee16e1399bb293298ba326d663d8 100644 (file)
--- a/drivers/net/ethernet/xilinx/xilinx_axienet.h
+++ b/drivers/net/ethernet/xilinx/xilinx_axienet.h
@@ -436,6 +436,8 @@ struct skbuf_dma_descriptor {
  * @tx_bytes:  TX byte count for statistics
  * @tx_stat_sync: Synchronization object for TX stats
  * @dma_err_task: Work structure to process Axi DMA errors
+ * @stopping:   Set when @dma_err_task shouldn't do anything because we are
+ *              about to stop the device.
  * @tx_irq:    Axidma TX IRQ number
  * @rx_irq:    Axidma RX IRQ number
  * @eth_irq:   Ethernet core IRQ number
@@ -507,6 +509,7 @@ struct axienet_local {
        struct u64_stats_sync tx_stat_sync;
 
        struct work_struct dma_err_task;
+       bool stopping;
 
        int tx_irq;
        int rx_irq;

diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
index 9aeb7b9f3ae408e2b843fc6d24c47fb04648b708..9eb300fc359096f9fe48993bd5694189c1c95373 100644 (file)
--- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
+++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
@@ -1460,6 +1460,7 @@ static int axienet_init_legacy_dma(struct net_device *ndev)
        struct axienet_local *lp = netdev_priv(ndev);
 
        /* Enable worker thread for Axi DMA error handling */
+       lp->stopping = false;
        INIT_WORK(&lp->dma_err_task, axienet_dma_err_handler);
 
        napi_enable(&lp->napi_rx);
@@ -1580,6 +1581,9 @@ static int axienet_stop(struct net_device *ndev)
        dev_dbg(&ndev->dev, "axienet_close()\n");
 
        if (!lp->use_dmaengine) {
+               WRITE_ONCE(lp->stopping, true);
+               flush_work(&lp->dma_err_task);
+
                napi_disable(&lp->napi_tx);
                napi_disable(&lp->napi_rx);
        }
@@ -2154,6 +2158,10 @@ static void axienet_dma_err_handler(struct work_struct *work)
                                                dma_err_task);
        struct net_device *ndev = lp->ndev;
 
+       /* Don't bother if we are going to stop anyway */
+       if (READ_ONCE(lp->stopping))
+               return;
+
        napi_disable(&lp->napi_tx);
        napi_disable(&lp->napi_rx);