Messages in this thread Patch in this message | | | Subject | Re: 2.6.17-mm5 -- inconsistent {in-softirq-W} -> {softirq-on-W} usage. | From | Arjan van de Ven <> | Date | Mon, 03 Jul 2006 10:42:45 +0200 |
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> stack backtrace:
> [<f9099d31>] rtl8139_start_xmit+0xd9/0xff [8139too] > [<c11ad5ea>] netpoll_send_skb+0x98/0xea
This seems to be a real deadlock...
So netpoll_send_skb takes the _xmit_lock, which is all nitty gritty but then rtl8139_start_xmit comes around while that lock is taken, and does
spin_unlock_irq(&tp->lock);
which.. enables interrupts and softirqs; this is quite bad because the xmit lock is taken in softirq context for the watchdog like this: [<c1200376>] _spin_lock+0x23/0x32 [<c11af282>] dev_watchdog+0x14/0xb1 [<c101dab2>] run_timer_softirq+0xf2/0x14a [<c101a691>] __do_softirq+0x55/0xb0 [<c1004a8d>] do_softirq+0x58/0xbd
Which would deadlock now that the spin_unlock_irq() has enabled irqs/softirqs while the _xmit_lock is still held.
The patch below turns this into a irqsave/irqrestore pair so that interrupts don't get enabled unconditionally.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
--- drivers/net/8139too.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
Index: linux-2.6.17-mm4/drivers/net/8139too.c =================================================================== --- linux-2.6.17-mm4.orig/drivers/net/8139too.c +++ linux-2.6.17-mm4/drivers/net/8139too.c @@ -1710,6 +1710,7 @@ static int rtl8139_start_xmit (struct sk void __iomem *ioaddr = tp->mmio_addr; unsigned int entry; unsigned int len = skb->len; + unsigned long flags; /* Calculate the next Tx descriptor entry. */ entry = tp->cur_tx % NUM_TX_DESC; @@ -1726,7 +1727,7 @@ static int rtl8139_start_xmit (struct sk return 0; } - spin_lock_irq(&tp->lock); + spin_lock_irqsave(&tp->lock, flags); RTL_W32_F (TxStatus0 + (entry * sizeof (u32)), tp->tx_flag | max(len, (unsigned int)ETH_ZLEN)); @@ -1737,7 +1738,7 @@ static int rtl8139_start_xmit (struct sk if ((tp->cur_tx - NUM_TX_DESC) == tp->dirty_tx) netif_stop_queue (dev); - spin_unlock_irq(&tp->lock); + spin_unlock_irqrestore(&tp->lock, flags); if (netif_msg_tx_queued(tp)) printk (KERN_DEBUG "%s: Queued Tx packet size %u to slot %d.\n",
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