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Date: Fri, 28 Mar 2008 22:09:47 -0400
From: Jeff Garzik <jeff@...zik.org>
To: akpm@...ux-foundation.org
CC: netdev@...r.kernel.org, mingo@...e.hu, aabdulla@...dia.com
Subject: Re: [patch 20/21] forcedeth: fix locking bug with netconsole
akpm@...ux-foundation.org wrote:
> From: Ingo Molnar <mingo@...e.hu>
>
> 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 <mingo@...e.hu>
> ---------------------------------
> inconsistent {softirq-on-W} -> {in-softirq-W} usage.
> udevd/719 [HC0[0]:SC1[1]:HE1:SE0] takes:
> (_xmit_ETHER){-+..}, at: [<c043062e>] dev_watchdog+0x1c/0xb9
> {softirq-on-W} state was registered at:
> [<c0147f67>] mark_held_locks+0x4e/0x66
> [<c014810e>] trace_hardirqs_on+0xfe/0x136
> [<c048ae63>] _spin_unlock_irq+0x22/0x42
> [<c02ec617>] nv_start_xmit_optimized+0x347/0x37a
> [<c042c80d>] netpoll_send_skb+0xa4/0x147
> [<c042d4a6>] netpoll_send_udp+0x238/0x242
> [<c02f44f6>] write_msg+0x6d/0x9b
> [<c012c129>] __call_console_drivers+0x4e/0x5a
> [<c012c18c>] _call_console_drivers+0x57/0x5b
> [<c012c2dd>] release_console_sem+0x11c/0x1b9
> [<c012caeb>] register_console+0x1eb/0x1f3
> [<c06ae673>] init_netconsole+0x119/0x15f
> [<c069149b>] kernel_init+0x147/0x294
> [<c01058cb>] kernel_thread_helper+0x7/0x10
> [<ffffffff>] 0xffffffff
> irq event stamp: 950
> hardirqs last enabled at (950): [<c048ae63>] _spin_unlock_irq+0x22/0x42
> hardirqs last disabled at (949): [<c048aaf7>] _spin_lock_irq+0xc/0x38
> softirqs last enabled at (0): [<c012a29c>] copy_process+0x375/0x126d
> softirqs last disabled at (947): [<c0106d43>] 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
> [<c0105c46>] show_trace_log_lvl+0x12/0x25
> [<c01063ec>] show_trace+0xd/0x10
> [<c010670c>] dump_stack+0x57/0x5f
> [<c0147505>] print_usage_bug+0x10a/0x117
> [<c0147c38>] mark_lock+0x121/0x402
> [<c01488b6>] __lock_acquire+0x3d1/0xb64
> [<c0149405>] lock_acquire+0x4e/0x6a
> [<c048a99b>] _spin_lock+0x23/0x32
> [<c043062e>] dev_watchdog+0x1c/0xb9
> [<c0133e4a>] run_timer_softirq+0x133/0x193
> [<c0130907>] __do_softirq+0x78/0xed
> [<c0106d43>] do_softirq+0x61/0xc6
> =======================
> eth1: link down
>
> The fix is to disable/restore irqs instead of disable/enable.
>
> Signed-off-by: Ingo Molnar <mingo@...e.hu>
> Cc: Ayaz Abdulla <aabdulla@...dia.com>
> Cc: Jeff Garzik <jeff@...zik.org>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> ---
>
> 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);
applied (this forcedeth.c portion only)
--
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