Re: Crash on removal of 400 interfaces (3.7.6+)

[Ben Greear <greearb@candelatech.com>]

On 02/19/2013 03:24 PM, Ben Greear wrote:
> On 02/19/2013 02:52 PM, Ben Greear wrote:
>> On 02/18/2013 02:16 PM, Johannes Berg wrote:
>>> On Mon, 2013-02-18 at 14:14 -0800, Ben Greear wrote:
>>>> We often see crashes in work-queue processing when deleting
>>>> lots of wifi station interfaces.  I'm guessing that there is probably
>>>> a work item that was not properly un-registered before deleting
>>>> memory.  I have backported some wifi fixes from upstream, so
>>>> maybe they are to blame, but in case anyone has any suggestions
>>>> for places to look, please let me know.
>>>
>>> Enable CONFIG_DEBUG_OBJECTS and CONFIG_DEBUG_OBJECTS_WORK :)
>>
>> That did not catch anything.

So, maybe the problem is in the sta_quiesce logic.

It cancels the work items before it stops the timers, so
I think it could re-add the work before the timers are
stopped??



void ieee80211_sta_quiesce(struct ieee80211_sub_if_data *sdata)
{
	struct ieee80211_if_managed *ifmgd = &sdata->u.mgd;

	/*
	 * we need to use atomic bitops for the running bits
	 * only because both timers might fire at the same
	 * time -- the code here is properly synchronised.
	 */

	cancel_work_sync(&ifmgd->request_smps_work);

	sdata_err(sdata, "Canceling monitor_work in sta_quiesce.\n");
	cancel_work_sync(&ifmgd->monitor_work);
	cancel_work_sync(&ifmgd->beacon_connection_loss_work);
	cancel_work_sync(&ifmgd->csa_connection_drop_work);
	if (del_timer_sync(&ifmgd->timer))
		set_bit(TMR_RUNNING_TIMER, &ifmgd->timers_running);

	cancel_work_sync(&ifmgd->chswitch_work);
	if (del_timer_sync(&ifmgd->chswitch_timer))
		set_bit(TMR_RUNNING_CHANSW, &ifmgd->timers_running);

	/* these will just be re-established on connection */
	del_timer_sync(&ifmgd->conn_mon_timer);
	del_timer_sync(&ifmgd->bcn_mon_timer);
}

>
> Ahh, enabled a bunch more debugging options, and got this:
>
> sta40: deauthenticating from 00:88:aa:88:aa:88 by local choice (reason=3)
> ------------[ cut here ]------------
> WARNING: at /home/greearb/git/linux-3.7.dev.y/lib/debugobjects.c:261 debug_print_object+0x7c/0x8d()
> Hardware name: To be filled by O.E.M.
> ODEBUG: free active (active state 0) object type: work_struct hint: ieee80211_sta_monitor_work+0x0/0x14 [mac80211]
> Modules linked in: nf_nat_ipv4 nf_nat 8021q garp stp llc macvlan pktgen lockd sunrpc f71882fg iTCO_wdt iTCO_vendor_support coretemp gpio_ich hwmon mperf kvm
> cdc_acm snd_hda_codec_realtek snd_hda_intel snd_hda_codec snd_hwdep microcode snd_seq snd_seq_device serio_raw pcspkr snd_pcm ath9k ath9k_common ath9k_hw ath
> i2c_i801 ppdev mac80211 lpc_ich cfg80211 snd_page_alloc e1000e snd_timer snd soundcore parport_pc parport uinput ipv6 i915 video i2c_algo_bit drm_kms_helper drm
> i2c_core [last unloaded: iptable_nat]
> Pid: 14743, comm: iw Tainted: G         C O 3.7.9+ #11
> Call Trace:
>   [<ffffffff81087ef8>] warn_slowpath_common+0x80/0x98
>   [<ffffffff81087fa4>] warn_slowpath_fmt+0x41/0x43
>   [<ffffffff812a2608>] debug_print_object+0x7c/0x8d
>   [<ffffffffa025f5ad>] ? ieee80211_beacon_connection_loss_work+0x88/0x88 [mac80211]
>   [<ffffffff812a2b9a>] ? debug_check_no_obj_freed+0x65/0x1c3
>   [<ffffffff812a2bca>] debug_check_no_obj_freed+0x95/0x1c3
>   [<ffffffff8149f465>] ? netdev_release+0x39/0x3e
>   [<ffffffff8114cc69>] slab_free_hook+0x70/0x79
>   [<ffffffff8114ea3e>] kfree+0x62/0xb7
>   [<ffffffff8149f465>] netdev_release+0x39/0x3e
>   [<ffffffff8136ad67>] device_release+0x52/0x8a
>   [<ffffffff812937db>] kobject_release+0x121/0x158
>   [<ffffffff81293612>] kobject_put+0x4c/0x50
>   [<ffffffff8148f0d7>] netdev_run_todo+0x25c/0x27e
>   [<ffffffff8149b2a0>] rtnl_unlock+0x9/0xb
>   [<ffffffffa01d31a7>] nl80211_post_doit+0x49/0x4e [cfg80211]
>   [<ffffffff814b0928>] genl_rcv_msg+0x25b/0x288
>   [<ffffffff814b06a3>] ? genl_lock+0x12/0x14
>   [<ffffffff814b06cd>] ? genl_rcv+0x28/0x28
>   [<ffffffff814aef13>] netlink_rcv_skb+0x3e/0x8f
>   [<ffffffff814b06c6>] genl_rcv+0x21/0x28
>   [<ffffffff814aecd1>] netlink_unicast+0xe9/0x16f
>   [<ffffffff814af4b3>] netlink_sendmsg+0x264/0x282
>   [<ffffffff8147d785>] ? rcu_read_unlock+0x5b/0x5d
>   [<ffffffff814784ab>] __sock_sendmsg_nosec+0x58/0x61
>   [<ffffffff814798e6>] __sock_sendmsg+0x3d/0x48
>   [<ffffffff8147995a>] sock_sendmsg+0x69/0x82
>   [<ffffffff8112c835>] ? might_fault+0x84/0x8b
>   [<ffffffff814849ce>] ? copy_from_user+0x2a/0x2c
>   [<ffffffff81484da0>] ? verify_iovec+0x4f/0xa3
>   [<ffffffff8147b8e7>] __sys_sendmsg+0x1fe/0x280
>   [<ffffffff810a8058>] ? up_read+0x1e/0x36
>   [<ffffffff8116ea14>] ? fcheck_files+0xac/0xea
>   [<ffffffff8116efd3>] ? fget_light+0x35/0xae
>   [<ffffffff8147badb>] sys_sendmsg+0x3d/0x5b
>   [<ffffffff815595e9>] system_call_fastpath+0x16/0x1b
> ---[ end trace 791ff0751a368327 ]---
>
>
> Will go poke around in the code to see what I can see....
>
>
> Thanks,
> Ben
>
>


-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com