netdev - Re: + gen_estimator-fix-locking-and-timer-related-bugs.patch added to -mm tree

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Date:	Fri, 06 Jul 2007 17:55:32 +0300
From:	Ranko Zivojnovic <ranko@...dernet.net>
To:	Patrick McHardy <kaber@...sh.net>
Cc:	Jarek Poplawski <jarkao2@...pl>, akpm@...ux-foundation.org,
	netdev@...r.kernel.org
Subject: Re: + gen_estimator-fix-locking-and-timer-related-bugs.patch added
	to -mm tree

On Fri, 2007-07-06 at 16:21 +0200, Patrick McHardy wrote:
> Ranko Zivojnovic wrote:
> > BUG: spinlock lockup on CPU#0, swapper/0, c03eff80
> >  [<c01ed1fe>] _raw_spin_lock+0x108/0x13c
> >  [<c02a8468>] __qdisc_run+0x97/0x1b0
> >  [<c02a96f3>] qdisc_watchdog+0x19/0x58
> >  [<c02fe5e7>] __lock_text_start+0x37/0x43
> >  [<c02a9730>] qdisc_watchdog+0x56/0x58
> >  [<c02a96da>] qdisc_watchdog+0x0/0x58
> >  [<c0135d84>] run_hrtimer_softirq+0x58/0xb5
> >  [...]
> 
> > BUG: spinlock lockup on CPU#1, swapper/0, c03eff80
> >  [<c01ed1fe>] _raw_spin_lock+0x108/0x13c
> >  [<c0298b9b>] est_timer+0x53/0x148
> >  [<c01294b3>] run_timer_softirq+0x30/0x184
> >  [<c01295a4>] run_timer_softirq+0x121/0x184
> >  [<c0126252>] __do_softirq+0x66/0xf3
> >  [<c0298b48>] est_timer+0x0/0x148
> >  [...]
> 
> 
> There is at least one ABBA deadlock, est_timer does:
> 
> read_lock(&est_lock)
> spin_lock(e->stats_lock) (which is dev->queue_lock)
> 
> and qdisc_destroy calls htb_destroy under dev->queue_lock, which
> calls htb_destroy_class, then gen_kill_estimator and this
> write_locks est_lock.
> 
> I can't see the problem above though, the qdisc_run path only takes
> dev->queue_lock. Please enable lockdep and post the output if any.

That was with lockdep already enabled:
$ zgrep LOCKDEP /proc/config.gz
CONFIG_LOCKDEP_SUPPORT=y
CONFIG_LOCKDEP=y
# CONFIG_DEBUG_LOCKDEP is not set

also with:
CONFIG_PROVE_LOCKING=y
CONFIG_DEBUG_LOCK_ALLOC=y

that Jarek suggested, and including:
CONFIG_DETECT_SOFTLOCKUP=y
CONFIG_DEBUG_SPINLOCK=y

I will give it another spin as it is, just to see if it will show a
different path - and then I will try 2.6.21.5 with these two patches.

R.

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