netdev - Re: [BUG] RTNL and flush_scheduled

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Date:	Fri, 16 Feb 2007 08:29:28 +0100
From:	Jarek Poplawski <jarkao2@...pl>
To:	Stephen Hemminger <shemminger@...ux-foundation.org>
Cc:	Francois Romieu <romieu@...zoreil.com>, netdev@...r.kernel.org,
	Ben Greear <greearb@...delatech.com>,
	Kyle Lucke <klucke@...ibm.com>,
	Raghavendra Koushik <raghavendra.koushik@...erion.com>,
	Al Viro <viro@....linux.org.uk>
Subject: Re: [BUG] RTNL and flush_scheduled_work deadlocks

On 14-02-2007 22:27, Stephen Hemminger wrote:
> Ben found this but the problem seems pretty widespread.
> 
> The following places are subject to deadlock between flush_scheduled_work
> and the RTNL mutex. What can happen is that a work queue routine (like
> bridge port_carrier_check) is waiting forever for RTNL, and the driver
> routine has called flush_scheduled_work with RTNL held and is waiting
> for the work queue to clear.
> 
> Several other places have comments like: "can't call flush_scheduled_work
> here or it will deadlock". Most of the problem places are in device close
> routine. My recommendation would be to add a check for device netif_running in
> what ever work routine is used, and move the flush_scheduled_work to the
> remove routine.
> 
> 8139too.c: rtl8139_close --> rtl8139_stop_thread
> r8169.c:   rtl8169_down
> cassini.c: cas_change_mtu
> iseries_veth.c: veth_stop_connection
> s2io.c: s2io_close
> sis190.c: sis190_down
> 

There is probably more than this...

I think the same problem is with
cancel_rearming_delayed_work. Plus indirect calling
these functions: eg. by ieee8021softmac_stop.

I found these dangerous places (probably not all):

cxgb3/cxgb3_main.c (cxgb_close -> cxgb_down),

macb.c (macb_close),

skge.c (skge_down),

wireless/bcm43xx/bcm43xx_main.c (bcm_net_stop both
	ieee80211...  and flush_...),
wireless/zd1211rw/zd_mac.c (zd_mac_stop ->
	housekeeping_disable),

chelsio/my3126.c (t1_interrupts_disable ->
	my3126_interrupt_disable), /* not sure */

drivers/usb/net/kaweth.c (kaweth_close ->
	kaweth_kill_urbs)

Regards,
Jarek P.
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