Kernel panics in tcp_twclose

[Julien Charbon]

 Hi Palle,

On 18/09/15 11:12, Palle Girgensohn wrote:
> We see daily panics on our production systems (web server, apache
> running MPM event, openjdk8. Kernel with VIMAGE. Jails using netgraph
> interfaces [not epair]).
> 
> The problem started after the summer. Normal port upgrades seems to
> be the only difference. The problem occurs with 10.2-p2 kernel as
> well as 10.1-p4 and 10.1-p15.
> 
> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=203175
> 
> Any ideas?

 Thanks for you detailed report.  I am not aware of any tcp_twclose()
related issues (without VIMAGE) since FreeBSD 10.0 (does not mean there
are none).  Few interesting facts (at least for me):

 - Your crash happens when unlocking a inp exclusive lock with INP_WUNLOCK()

 - Something is already wrong before calling turnstile_broadcast() as it
is called with ts = NULL:

turnstile_broadcast (ts=0x0, queue=1) at
/usr/src/sys/kern/subr_turnstile.c:838
__rw_wunlock_hard () at /usr/src/sys/kern/kern_rwlock.c:988
tcp_twclose () at /usr/src/sys/netinet/tcp_timewait.c:540
tcp_tw_2msl_scan () at /usr/src/sys/netinet/tcp_timewait.c:748
tcp_slowtimo () at /usr/src/sys/netinet/tcp_timer.c:198

 I won't go to far here as I am not expert enough in VIMAGE, but one
question anyway:

 - Can you correlate this kernel panic to a particular event?  Like for
example a VIMAGE/VNET jail destruction.

 I will test that on my side on a 10.2 machine.

--
Julien

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