Messages in this thread Patch in this message | | | Date | Fri, 21 Mar 2008 16:52:13 +0100 | From | Ingo Molnar <> | Subject | [patch] forcedeth: fix locking bug with netconsole |
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Subject: forcedeth: fix locking bug with netconsole From: Ingo Molnar <mingo@elte.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@elte.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@elte.hu> --- drivers/net/forcedeth.c | 18 ++++++++++-------- net/core/netpoll.c | 3 +++ 2 files changed, 13 insertions(+), 8 deletions(-)
Index: linux/drivers/net/forcedeth.c =================================================================== --- linux.orig/drivers/net/forcedeth.c +++ linux/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); Index: linux/net/core/netpoll.c =================================================================== --- linux.orig/net/core/netpoll.c +++ linux/net/core/netpoll.c @@ -284,6 +284,7 @@ static void netpoll_send_skb(struct netp /* try until next clock tick */ for (tries = jiffies_to_usecs(1)/USEC_PER_POLL; tries > 0; --tries) { + WARN_ON_ONCE(!irqs_disabled()); if (netif_tx_trylock(dev)) { if (!netif_queue_stopped(dev) && !netif_subqueue_stopped(dev, skb)) @@ -297,8 +298,10 @@ static void netpoll_send_skb(struct netp /* tickle device maybe there is some cleanup */ netpoll_poll(np); + WARN_ON_ONCE(!irqs_disabled()); udelay(USEC_PER_POLL); + WARN_ON_ONCE(!irqs_disabled()); } local_irq_restore(flags); }
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