From be0384bf599cf1eb8d337517feeb732d71f75a6f Mon Sep 17 00:00:00 2001 From: Marek Vasut Date: Fri, 5 Apr 2024 22:30:40 +0200 Subject: [PATCH] net: ks8851: Handle softirqs at the end of IRQ thread to fix hang The ks8851_irq() thread may call ks8851_rx_pkts() in case there are any packets in the MAC FIFO, which calls netif_rx(). This netif_rx() implementation is guarded by local_bh_disable() and local_bh_enable(). The local_bh_enable() may call do_softirq() to run softirqs in case any are pending. One of the softirqs is net_rx_action, which ultimately reaches the driver .start_xmit callback. If that happens, the system hangs. The entire call chain is below: ks8851_start_xmit_par from netdev_start_xmit netdev_start_xmit from dev_hard_start_xmit dev_hard_start_xmit from sch_direct_xmit sch_direct_xmit from __dev_queue_xmit __dev_queue_xmit from __neigh_update __neigh_update from neigh_update neigh_update from arp_process.constprop.0 arp_process.constprop.0 from __netif_receive_skb_one_core __netif_receive_skb_one_core from process_backlog process_backlog from __napi_poll.constprop.0 __napi_poll.constprop.0 from net_rx_action net_rx_action from __do_softirq __do_softirq from call_with_stack call_with_stack from do_softirq do_softirq from __local_bh_enable_ip __local_bh_enable_ip from netif_rx netif_rx from ks8851_irq ks8851_irq from irq_thread_fn irq_thread_fn from irq_thread irq_thread from kthread kthread from ret_from_fork The hang happens because ks8851_irq() first locks a spinlock in ks8851_par.c ks8851_lock_par() spin_lock_irqsave(&ksp->lock, ...) and with that spinlock locked, calls netif_rx(). Once the execution reaches ks8851_start_xmit_par(), it calls ks8851_lock_par() again which attempts to claim the already locked spinlock again, and the hang happens. Move the do_softirq() call outside of the spinlock protected section of ks8851_irq() by disabling BHs around the entire spinlock protected section of ks8851_irq() handler. Place local_bh_enable() outside of the spinlock protected section, so that it can trigger do_softirq() without the ks8851_par.c ks8851_lock_par() spinlock being held, and safely call ks8851_start_xmit_par() without attempting to lock the already locked spinlock. Since ks8851_irq() is protected by local_bh_disable()/local_bh_enable() now, replace netif_rx() with __netif_rx() which is not duplicating the local_bh_disable()/local_bh_enable() calls. Fixes: 797047f875b5 ("net: ks8851: Implement Parallel bus operations") Signed-off-by: Marek Vasut Link: https://lore.kernel.org/r/20240405203204.82062-2-marex@denx.de Signed-off-by: Jakub Kicinski --- drivers/net/ethernet/micrel/ks8851_common.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/net/ethernet/micrel/ks8851_common.c b/drivers/net/ethernet/micrel/ks8851_common.c index 896d43bb8883..d4cdf3d4f552 100644 --- a/drivers/net/ethernet/micrel/ks8851_common.c +++ b/drivers/net/ethernet/micrel/ks8851_common.c @@ -299,7 +299,7 @@ static void ks8851_rx_pkts(struct ks8851_net *ks) ks8851_dbg_dumpkkt(ks, rxpkt); skb->protocol = eth_type_trans(skb, ks->netdev); - netif_rx(skb); + __netif_rx(skb); ks->netdev->stats.rx_packets++; ks->netdev->stats.rx_bytes += rxlen; @@ -330,6 +330,8 @@ static irqreturn_t ks8851_irq(int irq, void *_ks) unsigned long flags; unsigned int status; + local_bh_disable(); + ks8851_lock(ks, &flags); status = ks8851_rdreg16(ks, KS_ISR); @@ -406,6 +408,8 @@ static irqreturn_t ks8851_irq(int irq, void *_ks) if (status & IRQ_LCI) mii_check_link(&ks->mii); + local_bh_enable(); + return IRQ_HANDLED; } -- 2.39.5