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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: 797047f875 ("net: ks8851: Implement Parallel bus operations")
Signed-off-by: Marek Vasut <marex@denx.de>
Link: https://lore.kernel.org/r/20240405203204.82062-2-marex@denx.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Marek Vasut 2024-04-05 22:30:40 +02:00 committed by Jakub Kicinski
parent f96f700449
commit be0384bf59
1 changed files with 5 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
drivers/net/ethernet/micrel/ks8851_common.c
View File

@ -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;
}