From: Ingo Molnar While using netconsole on forcedeth, lockdep noticed the following locking bug: ================================= [ INFO: inconsistent lock state ] 2.6.24-rc6 #6 Signed-off-by: Ingo Molnar --------------------------------- inconsistent {softirq-on-W} -> {in-softirq-W} usage. udevd/719 [HC0[0]:SC1[1]:HE1:SE0] takes: (_xmit_ETHER){-+..}, at: [] dev_watchdog+0x1c/0xb9 {softirq-on-W} state was registered at: [] mark_held_locks+0x4e/0x66 [] trace_hardirqs_on+0xfe/0x136 [] _spin_unlock_irq+0x22/0x42 [] nv_start_xmit_optimized+0x347/0x37a [] netpoll_send_skb+0xa4/0x147 [] netpoll_send_udp+0x238/0x242 [] write_msg+0x6d/0x9b [] __call_console_drivers+0x4e/0x5a [] _call_console_drivers+0x57/0x5b [] release_console_sem+0x11c/0x1b9 [] register_console+0x1eb/0x1f3 [] init_netconsole+0x119/0x15f [] kernel_init+0x147/0x294 [] kernel_thread_helper+0x7/0x10 [] 0xffffffff irq event stamp: 950 hardirqs last enabled at (950): [] _spin_unlock_irq+0x22/0x42 hardirqs last disabled at (949): [] _spin_lock_irq+0xc/0x38 softirqs last enabled at (0): [] copy_process+0x375/0x126d softirqs last disabled at (947): [] do_softirq+0x61/0xc6 other info that might help us debug this: no locks held by udevd/719. stack backtrace: Pid: 719, comm: udevd Not tainted 2.6.24-rc6 #6 [] show_trace_log_lvl+0x12/0x25 [] show_trace+0xd/0x10 [] dump_stack+0x57/0x5f [] print_usage_bug+0x10a/0x117 [] mark_lock+0x121/0x402 [] __lock_acquire+0x3d1/0xb64 [] lock_acquire+0x4e/0x6a [] _spin_lock+0x23/0x32 [] dev_watchdog+0x1c/0xb9 [] run_timer_softirq+0x133/0x193 [] __do_softirq+0x78/0xed [] do_softirq+0x61/0xc6 ======================= eth1: link down The fix is to disable/restore irqs instead of disable/enable. Signed-off-by: Ingo Molnar Cc: Ayaz Abdulla Cc: Jeff Garzik Signed-off-by: Andrew Morton --- drivers/net/forcedeth.c | 18 ++++++++++-------- net/core/netpoll.c | 3 +++ 2 files changed, 13 insertions(+), 8 deletions(-) diff -puN drivers/net/forcedeth.c~forcedeth-fix-locking-bug-with-netconsole drivers/net/forcedeth.c --- a/drivers/net/forcedeth.c~forcedeth-fix-locking-bug-with-netconsole +++ a/drivers/net/forcedeth.c @@ -1854,6 +1854,7 @@ static int nv_start_xmit(struct sk_buff struct ring_desc* start_tx; struct ring_desc* prev_tx; struct nv_skb_map* prev_tx_ctx; + unsigned long flags; /* add fragments to entries count */ for (i = 0; i < fragments; i++) { @@ -1863,10 +1864,10 @@ static int nv_start_xmit(struct sk_buff empty_slots = nv_get_empty_tx_slots(np); if (unlikely(empty_slots <= entries)) { - spin_lock_irq(&np->lock); + spin_lock_irqsave(&np->lock, flags); netif_stop_queue(dev); np->tx_stop = 1; - spin_unlock_irq(&np->lock); + spin_unlock_irqrestore(&np->lock, flags); return NETDEV_TX_BUSY; } @@ -1929,13 +1930,13 @@ static int nv_start_xmit(struct sk_buff tx_flags_extra = skb->ip_summed == CHECKSUM_PARTIAL ? NV_TX2_CHECKSUM_L3 | NV_TX2_CHECKSUM_L4 : 0; - spin_lock_irq(&np->lock); + spin_lock_irqsave(&np->lock, flags); /* set tx flags */ start_tx->flaglen |= cpu_to_le32(tx_flags | tx_flags_extra); np->put_tx.orig = put_tx; - spin_unlock_irq(&np->lock); + spin_unlock_irqrestore(&np->lock, flags); dprintk(KERN_DEBUG "%s: nv_start_xmit: entries %d queued for transmission. tx_flags_extra: %x\n", dev->name, entries, tx_flags_extra); @@ -1971,6 +1972,7 @@ static int nv_start_xmit_optimized(struc struct ring_desc_ex* prev_tx; struct nv_skb_map* prev_tx_ctx; struct nv_skb_map* start_tx_ctx; + unsigned long flags; /* add fragments to entries count */ for (i = 0; i < fragments; i++) { @@ -1980,10 +1982,10 @@ static int nv_start_xmit_optimized(struc empty_slots = nv_get_empty_tx_slots(np); if (unlikely(empty_slots <= entries)) { - spin_lock_irq(&np->lock); + spin_lock_irqsave(&np->lock, flags); netif_stop_queue(dev); np->tx_stop = 1; - spin_unlock_irq(&np->lock); + spin_unlock_irqrestore(&np->lock, flags); return NETDEV_TX_BUSY; } @@ -2059,7 +2061,7 @@ static int nv_start_xmit_optimized(struc start_tx->txvlan = 0; } - spin_lock_irq(&np->lock); + spin_lock_irqsave(&np->lock, flags); if (np->tx_limit) { /* Limit the number of outstanding tx. Setup all fragments, but @@ -2085,7 +2087,7 @@ static int nv_start_xmit_optimized(struc start_tx->flaglen |= cpu_to_le32(tx_flags | tx_flags_extra); np->put_tx.ex = put_tx; - spin_unlock_irq(&np->lock); + spin_unlock_irqrestore(&np->lock, flags); dprintk(KERN_DEBUG "%s: nv_start_xmit_optimized: entries %d queued for transmission. tx_flags_extra: %x\n", dev->name, entries, tx_flags_extra); diff -puN net/core/netpoll.c~forcedeth-fix-locking-bug-with-netconsole net/core/netpoll.c