Re: locking against myself, mbuf was already freed (was: repeated network-related panics/lock-ups on 8.1)

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Mon, Sep 30, 2019 at 12:56:46PM +0200, Edgar Fuß wrote:
> > It looks that a server of mine will consistently lock up or panic as soon as 
> > I run an Icinga 2 master on it (which will fork /a lot/).
> Good news: I built a DIAGNOSTIC+DEBUG+LOCKDEBUG kernel and now I don't even 
> need Icinga 2 to run any more to make it panic.
> 
> 1. mbuf was already freed at nd6_resolve,2351
> breakpoint
> vpanic
> snprintf
> m_prepend
> ipf_fastroute
> ipf_send_ip
> ipf_check
> pfil_run_hooks
> ip6_input
> ip6intr
> softint_dispatch

Isn't there something missing in the stack trace here ?
I can't see how m_prepend could be called from ipf_fastroute ...
Ot maybe it's not m_prepend but m_freem.

Anyway, I guess the attached patch could fix it.

> 
> 2. LOCKDEBUG: Reader / writer lock error: rw_vector_enter,291: locking against myself
> 
> lock address : 0xffffffff80a89c08 type :         sleep/adaptive
> initialized  : 0xffffffff8040bb31
> shared holds :                  1 exclusive:                  0
> shares wanted:                  1 exclusive:                  0
> current cpo  :                  0 last held:                  0
> current lwp  : 0xfffffe841de11420 last held: 0xfffffe841de11420
> last locked  : 0xffffffff804092d0 unlocked*: 0xffffffff804091dd
> owner/count  : 0x0000000000000010 flags    : 000000000000000000
> 
> breakpoint
> vpanic
> snprintf
> lockdebug_more
> rw_enter
> ipf_check
> pfil_run_hooks
> ip6_output
> nd6_ns_output.part.2
> nd6_resolve
> ether_output
> ipf_if_output
> ipf_fastroute
> ipf_send_ip
> ipf_check
> pfil_run_hooks
> ip6_input
> ip6intr
> softint_dispatch
> 
> 3. Exact same panic again.
> 
> I currently leave the machine in ddb of that panic, in case I should 
> investigate more.
> Is the problem pfil_run_hooks() being callt recursively?

for the lockdebug issue, yes it is. 
Maybe try to
#define FASTROUTE_RECURSION
at the top of fil.c ? It looks like this is needed

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--