Date:	Fri, 24 Sep 2010 06:23:53 -0500
From:	Narendra K <Narendra_K@...l.com>
To:	Jay Vosburgh <fubar@...ibm.com>
Cc:	Jiri Bohac <jbohac@...e.cz>, bonding-devel@...ts.sourceforge.net,
	markine@...gle.com, jarkao2@...il.com, chavey@...gle.com,
	netdev@...r.kernel.org
Subject: Re: [RFC] bonding: fix workqueue re-arming races

On Fri, Sep 17, 2010 at 04:14:33AM +0530, Jay Vosburgh wrote:
> Jay Vosburgh <fubar@...ibm.com> wrote:
> [...]
> 
> 	I had some time to work on this, and I fixed a few nits in the
> most recent patch, and also modified it as I describe above (the
> new_link business).  This seems to do the right thing for the mii/arp
> commit functions.
> 
> 	The alb_promisc alb_promisc function, however, still has a race.
> The curr_active_slave could change between the time the function is
> scheduled and when it executes.  That window is pretty small, but does
> exist.  Losing the race means that some interface stays promisc when it
> shouldn't; I don't believe it will panic.  Fixing that is probably a
> matter of stashing a pointer to the slave to be de-promisc-ified
> somewhere, but that stash would have to be handled if the slave were to
> be removed from the bond.
> 
> 	I've tested this a bit, and it seems ok, but I can't reproduce
> the original problem, so I'm not entirely sure this doesn't break
> something very subtle.
> 
> 	Also, I'll be out of the office for the next two weeks, so I
> won't get back to this until I return.  If any interested parties could
> test this out and provide some feedback before then, it would be
> appreciated.
> 
Thanks.

Original issue was seen when the system was rebooted and while the
network was shutting down. I applied the patch to linux-next (branch-
20100811) and issued service network stop/start in quick succession.

The bond interface had 4 slaves, 3 with link up and 1 with link down
configured in balance-alb mode, miimon=100, bonding driver version:3.7.0

The follwing call trace was seen -

2.6.35.with.upstream.patch-next-20100811-0.7-default+
[14602.945876] ------------[ cut here ]------------
[14602.950474] kernel BUG at kernel/workqueue.c:2844!
[14602.955242] invalid opcode: 0000 [#1] SMP 
[14602.959341] last sysfs file: /sys/class/net/bonding_masters
[14602.964888] CPU 1 
[14602.966714] Modules linked in: af_packet bonding ipv6 cpufreq_conservative cpufreq_userspace cpufreq_powersave acpi_cpufreq mperf microcode fuse loop dm_mod joydev usbhid hid bnx2 tpm_tis tpm tpm_bios rtc_cmos iTCO_wdt iTCO_vendor_support sr_mod power_meter cdrom sg serio_raw mptctl pcspkr rtc_core usb_storage dcdbas rtc_lib button uhci_hcd ehci_hcd usbcore sd_mod crc_t10dif edd ext3 mbcache jbd fan processor ide_pci_generic ide_core ata_generic ata_piix libata mptsas mptscsih mptbase scsi_transport_sas scsi_mod thermal thermal_sys hwmon
[14603.015002] 
[14603.016524] Pid: 4006, comm: ifdown-bonding Not tainted 2.6.35.with.upstream.patch-next-20100811-0.7-default+ #2 0M233H/PowerEdge R710
[14603.028554] RIP: 0010:[<ffffffff81067b50>]  [<ffffffff81067b50>] destroy_workqueue+0x1d0/0x1e0
[14603.037144] RSP: 0018:ffff88022a379d88  EFLAGS: 00010286
[14603.042432] RAX: 000000000000003c RBX: ffff880228674240 RCX: ffff880228f0e800
[14603.049534] RDX: 0000000000001000 RSI: 0000000000000002 RDI: 000000000000001a
[14603.056638] RBP: ffff88022a379da8 R08: ffff88022a379cf8 R09: 0000000000000000
[14603.063741] R10: 00000000ffffffff R11: 0000000000000000 R12: 0000000000000002
[14603.070842] R13: ffffffff817b8560 R14: ffff8802299d1480 R15: ffff8802299d1488
[14603.077944] FS:  00007f8e6a28f700(0000) GS:ffff880001c00000(0000) knlGS:0000000000000000
[14603.085999] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[14603.091719] CR2: 00007f8e6a2c2000 CR3: 0000000127d1c000 CR4: 00000000000006e0
[14603.098822] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[14603.105924] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[14603.113026] Process ifdown-bonding (pid: 4006, threadinfo ffff88022a378000, task ffff8802299b0080)
[14603.121944] Stack:
[14603.123944]  ffff88022a379da8 ffff8802299d1000 ffff8802299d1000 000000010036b6a4
[14603.131182] <0> ffff88022a379dc8 ffffffffa030a91d ffff8802299d1000 000000010036b6a4
[14603.138857] <0> ffff88022a379e28 ffffffff812e0a08 ffff88022a379e38 ffff88022a379de8
[14603.146718] Call Trace:
[14603.149158]  [<ffffffffa030a91d>] bond_destructor+0x1d/0x30 [bonding]
[14603.155572]  [<ffffffff812e0a08>] netdev_run_todo+0x1a8/0x270
[14603.161293]  [<ffffffff812ee859>] rtnl_unlock+0x9/0x10
[14603.166411]  [<ffffffffa0317824>] bonding_store_bonds+0x1c4/0x1f0 [bonding]
[14603.173342]  [<ffffffff810f26be>] ? alloc_pages_current+0x9e/0x110
[14603.179497]  [<ffffffff81285c9e>] class_attr_store+0x1e/0x20
[14603.185132]  [<ffffffff8116e365>] sysfs_write_file+0xc5/0x140
[14603.190853]  [<ffffffff8110a68f>] vfs_write+0xcf/0x190
[14603.195967]  [<ffffffff8110a840>] sys_write+0x50/0x90
[14603.200996]  [<ffffffff81002ec2>] system_call_fastpath+0x16/0x1b
[14603.206974] Code: 00 7f 14 8b 3b eb 91 3d 00 10 00 00 89 c2 77 10 8b 3b e9 07 ff ff ff 3d 00 10 00 00 89 c2 76 f0 8b 3b e9 a9 fe ff ff 0f 0b eb fe <0f> 0b eb fe 66 66 66 2e 0f 1f 84 00 00 00 00 00 55 48 8b 3d 00 
[14603.226419] RIP  [<ffffffff81067b50>] destroy_workqueue+0x1d0/0x1e0
[14603.232669]  RSP <ffff88022a379d88>
[    0.000000] Initializing cgroup subsys cpuset
[    0.000000] Initializing cgroup subsys cpu

With regards,
Narendra K
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