Date:	Fri, 14 Dec 2007 15:36:33 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Miles Lane" <miles.lane@...il.com>
Cc:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: 2.6.24-rc5-mm1 -- inconsistent {in-softirq-W} -> {softirq-on-R}
 usage.

On Fri, 14 Dec 2007 17:13:21 -0500
"Miles Lane" <miles.lane@...il.com> wrote:

> Sorry Andrew, I don't know who to forward this problem to.
> 
> I tried running:  find /proc | xargs cat
> and got this:
> 
> =================================
> [ INFO: inconsistent lock state ]
> 2.6.24-rc5-mm1 #26
> ---------------------------------
> inconsistent {in-softirq-W} -> {softirq-on-R} usage.
> cat/6944 [HC0[0]:SC0[0]:HE1:SE1] takes:
> BUG: unable to handle kernel paging request at virtual address 0f1eff0b
> printing ip: c01fe64d *pde = 00000000
> Oops: 0000 [#1] PREEMPT SMP
> last sysfs file: /sys/block/sda/sda3/stat
> Modules linked in: aes_generic i915 drm rfcomm l2cap bluetooth
> cpufreq_stats cpufreq_conservative cpufreq_performance sbs sbshc
> dm_crypt sbp2 parport_pc lp parport pcmcia arc4 ecb crypto_blkcipher
> cryptomgr crypto_algapi tifm_7xx1 tifm_core yenta_socket
> rsrc_nonstatic pcmcia_core iwl3945 iTCO_wdt iTCO_vendor_support
> watchdog_core watchdog_dev snd_hda_intel mac80211 snd_pcm_oss
> snd_mixer_oss cfg80211 snd_pcm sky2 snd_seq_dummy snd_seq_oss
> snd_seq_midi snd_rawmidi snd_seq_midi_event snd_seq snd_timer
> snd_seq_device snd soundcore snd_page_alloc shpchp pci_hotplug
> firewire_ohci firewire_core crc_itu_t ata_generic piix ide_core
> 
> Pid: 6944, comm: cat Not tainted (2.6.24-rc5-mm1 #26)
> EIP: 0060:[<c01fe64d>] EFLAGS: 00210097 CPU: 0
> EIP is at strnlen+0x9/0x1c
> EAX: 0f1eff0b EBX: 0f1eff0b ECX: 0f1eff0b EDX: fffffffe
> ESI: c05b74f6 EDI: d6267d94 EBP: d6267cc8 ESP: d6267cc8
>  DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
> Process cat (pid: 6944, ti=d6267000 task=d5a09000 task.ti=d6267000)
> Stack: d6267cfc c01fdd22 00000400 c05b74f4 00000001 c05b78f4 00000000 ffffffff
>        ffffffff c048f503 00000400 d5a09000 00000002 d6267d0c c01fdf41 d6267d94
>        db68c04a d6267d74 c012ae81 d6267d94 00000028 c05b89f7 00200046 00000000
> Call Trace:
>  [<c0108eb2>] show_trace_log_lvl+0x12/0x25
>  [<c0108f4f>] show_stack_log_lvl+0x8a/0x95
>  [<c0108fe4>] show_registers+0x8a/0x1bd
>  [<c010922f>] die+0x118/0x1dc
>  [<c03cf706>] do_page_fault+0x5a4/0x681
>  [<c03cdd72>] error_code+0x72/0x78
>  [<c01fdd22>] vsnprintf+0x277/0x40e
>  [<c01fdf41>] vscnprintf+0xe/0x1d
>  [<c012ae81>] vprintk+0xcb/0x2f3
>  [<c012b0be>] printk+0x15/0x17
>  [<c0145e55>] print_lock_name+0x4e/0xa2
>  [<c0146099>] print_lock+0xe/0x3a
>  [<c01464cf>] print_usage_bug+0xbc/0x117
>  [<c0146fb6>] mark_lock+0x2e7/0x3fe
>  [<c0147b9a>] __lock_acquire+0x498/0xbf4
>  [<c014836c>] lock_acquire+0x76/0x9d
>  [<c03cd6d2>] _read_lock+0x23/0x32
>  [<c03491ae>] sock_i_ino+0x14/0x30
>  [<c03c88ed>] packet_seq_show+0x22/0x75
>  [<c019b41a>] seq_read+0x19d/0x26f
>  [<c01b0ded>] proc_reg_read+0x60/0x74
>  [<c01854aa>] vfs_read+0x8a/0x106
>  [<c01858a8>] sys_read+0x3b/0x60
>  [<c0107cea>] sysenter_past_esp+0x6b/0xc1
>  =======================
> Code: 01 00 00 00 4f 89 fa 5f 89 d0 5d c3 55 85 c9 89 e5 57 89 c7 89
> d0 74 05 f2 ae 75 01 4f 89 f8 5f 5d c3 55 89 c1 89 e5 89 c8 eb 06 <80>
> 38 00 74 07 40 4a 83 fa ff 75 f4 29 c8 5d c3 90 90 90 55 83
> EIP: [<c01fe64d>] strnlen+0x9/0x1c SS:ESP 0068:d6267cc8
> note: cat[6944] exited with preempt_count 4

I'd say you hit a networking locking bug and then when trying to report
that bug, lockdep crashed.

The networking bug looks to be around sock_i_ino()'s taking of
sk_callback_lock with softirq's enabled.  Perhaps this will fix it.

diff -puN net/core/sock.c~a net/core/sock.c
--- a/net/core/sock.c~a
+++ a/net/core/sock.c
@@ -1115,9 +1115,9 @@ int sock_i_uid(struct sock *sk)
 {
 	int uid;
 
-	read_lock(&sk->sk_callback_lock);
+	read_lock_bh(&sk->sk_callback_lock);
 	uid = sk->sk_socket ? SOCK_INODE(sk->sk_socket)->i_uid : 0;
-	read_unlock(&sk->sk_callback_lock);
+	read_unlock_bh(&sk->sk_callback_lock);
 	return uid;
 }
 
@@ -1125,9 +1125,9 @@ unsigned long sock_i_ino(struct sock *sk
 {
 	unsigned long ino;
 
-	read_lock(&sk->sk_callback_lock);
+	read_lock_bh(&sk->sk_callback_lock);
 	ino = sk->sk_socket ? SOCK_INODE(sk->sk_socket)->i_ino : 0;
-	read_unlock(&sk->sk_callback_lock);
+	read_unlock_bh(&sk->sk_callback_lock);
 	return ino;
 }
 
_

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