netdev - RE: [PATCH net-next] igb: fix stats handling

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Date:	Sat, 9 Oct 2010 17:57:19 -0600
From:	"Tantilov, Emil S" <emil.s.tantilov@...el.com>
To:	Eric Dumazet <eric.dumazet@...il.com>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>
CC:	Jesper Dangaard Brouer <hawk@...u.dk>,
	"Duyck, Alexander H" <alexander.h.duyck@...el.com>,
	Jesper Dangaard Brouer <hawk@...x.dk>,
	"David S. Miller" <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	"Wyborny, Carolyn" <carolyn.wyborny@...el.com>
Subject: RE: [PATCH net-next] igb: fix stats handling

Eric Dumazet wrote:
> Le mercredi 06 octobre 2010 à 05:28 +0200, Eric Dumazet a écrit :
> 
>> I'll let Intel guys doing the backporting work, but for old kernels,
>> you'll probably need to use "unsigned long" instead of "u64"
>> 
>> My plan is :
>> 
>> - Provide 64bit counters even on 32bit arch
>> - with proper synchro (include/linux/u64_stats_sync.h)
>> - Add a spinlock so we can apply Jesper patch.
> 
> Here is the net-next-2.6 patch, I am currently enable to test it, the
> dev machine with IGB NIC cannot be restarted until tomorrow, my son
> Nicolas is currently using it ;)
> 
> Could you and/or Jesper test it, possibly on 32 and 64 bit kernels ?
> 
> Thanks !
> 
> [PATCH net-next] igb: fix stats handling
> 
> There are currently some problems with igb.
> 
> - On 32bit arches, maintaining 64bit counters without proper
> synchronization between writers and readers.
> 
> - Stats updated every two seconds, as reported by Jesper.
>    (Jesper provided a patch for this)
> 
> - Potential problem between worker thread and ethtool -S
> 
> This patch uses u64_stats_sync, and convert everything to be 64bit
> safe, 
> SMP safe, even on 32bit arches.
> 
> Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
> ---
>  drivers/net/igb/igb.h         |    7 +-
>  drivers/net/igb/igb_ethtool.c |   10 +-
>  drivers/net/igb/igb_main.c    |  111 +++++++++++++++++++++++---------
>  3 files changed, 94 insertions(+), 34 deletions(-)

This patch is causing a hang when testing with 2 sessions in a while loop reading /proc/net/dev/ and ethtool -S. I think even just reading /proc/net/dev/ is sufficient, but have not confirmed it yet. I have seen the hang somewhere between 15 min to an hour. Without the patch same test ran 24+ hours without issues.

There was no trace on the screen, I got this with magic sysrq:

[15388.393579] SysRq : Show Regs 
[15388.397341] Modules linked in: igb [last unloaded: scsi_wait_scan] [15388.404846]  
[15388.406889] Pid: 16218, comm: kworker/4:1 Not tainted 2.6.36-rc3-net-next-igb-100810+ #2 S5520HC/S5520HC 
[15388.418393] EIP: 0060:[<c13fead2>] EFLAGS: 00000297 CPU: 4 
[15388.424908] EIP is at _raw_spin_lock+0x13/0x19 
[15388.430257] EAX: f6eab55c EBX: f6eab380 ECX: 00000001 EDX: 00004e4a [15388.437629] ESI: f6eab000 EDI: f6eab41c EBP: f3d9bf4c ESP: f3d9bf4c [15388.445011]  DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 
[15388.451422] Process kworker/4:1 (pid: 16218, ti=f3d9a000 task=f5ce0ed0 task.ti=f3d9a000) 
[15388.461173] Stack: 
[15388.463796]  f3d9bf64 f8586c57 f3d9bf5c f6eab41c f6901e00 c8703cc0 f3d9bf90 c1041379 
[15388.473116] <0> 00000004 00000000 f8586b16 00000000 c8707b05 c8707b00 f6901e00 c8703cc4 
[15388.483379] <0> c8703cc0 f3d9bfb8 c1042879 c16bb640 c8703cc4 00000c54 c16bb640 f6901e10 
[15388.494219] Call Trace: 
[15388.497336]  [<f8586c57>] ? igb_watchdog_task+0x141/0x21a [igb] 
[15388.504336]  [<c1041379>] ? process_one_work+0x18e/0x265 
[15388.510643]  [<f8586b16>] ? igb_watchdog_task+0x0/0x21a [igb] 
[15388.517455]  [<c1042879>] ? worker_thread+0xf3/0x1ef 
[15388.523384]  [<c1042786>] ? worker_thread+0x0/0x1ef 
[15388.529222]  [<c104506b>] ? kthread+0x62/0x67 
[15388.534475]  [<c1045009>] ? kthread+0x0/0x67 
[15388.539623]  [<c1002d36>] ? kernel_thread_helper+0x6/0x10 
[15388.546034] Code: 00 75 05 f0 66 0f b1 0a 0f 94 c1 0f b6 c1 85 c0 0f 95 c0 0f b6 c0 5d c3 55 ba 00 01 00 00 89 e5 f0 66 0f c1 10 38 f2 74 06 f3 90 <8a> 10 eb f6 5d c3 55 89 e5 9c 59 fa ba 00 01 00 00 f0 66 0f c1

Thanks,
Emil