Re: sysctl -a panic on VIMAGE kernels

On Sun, Aug 09, 2015 at 12:28:22PM +0200, Kristof Provost wrote:
K> Hi,
K> 
K> I’ve run into a reproducible panic on a VIMAGE kernel with ‘sysctl -a’.
K> 
K> Relevant backtrace bits:
K> #8  0xffffffff80e7dd28 in trap (frame=0xfffffe01f16b26a0)
K>     at /usr/src/sys/amd64/amd64/trap.c:426
K> #9  0xffffffff80e5e6a2 in calltrap ()
K>     at /usr/src/sys/amd64/amd64/exception.S:235
K> #10 0xffffffff80cea67d in uma_zone_get_cur (zone=0x0)
K>     at /usr/src/sys/vm/uma_core.c:3006
K> #11 0xffffffff80cec029 in sysctl_handle_uma_zone_cur (
K>     oidp=0xffffffff818a7c90, arg1=0xfffffe00010c0438, arg2=0,
K>     req=0xfffffe01f16b2868) at /usr/src/sys/vm/uma_core.c:3580
K> #12 0xffffffff80a28614 in sysctl_root_handler_locked (oid=0xffffffff818a7c90,
K>     arg1=0xfffffe00010c0438, arg2=0, req=0xfffffe01f16b2868)
K>     at /usr/src/sys/kern/kern_sysctl.c:183
K> #13 0xffffffff80a27d70 in sysctl_root (arg1=<value optimized out>,
K>     arg2=<value optimized out>) at /usr/src/sys/kern/kern_sysctl.c:1694
K> #14 0xffffffff80a28372 in userland_sysctl (td=0x0, name=0xfffffe01f16b2930,
K>     namelen=<value optimized out>, old=<value optimized out>,
K>     oldlenp=<value optimized out>, inkernel=<value optimized out>,
K>     new=<value optimized out>, newlen=<value optimized out>,
K>     retval=<value optimized out>, flags=0)
K>     at /usr/src/sys/kern/kern_sysctl.c:1798
K> #15 0xffffffff80a28144 in sys___sysctl (td=0xfffff8000b1e49a0,
K>     uap=0xfffffe01f16b2a40) at /usr/src/sys/kern/kern_sysctl.c:1724
K> 
K> In essence, what happens is that we end up in sysctl_handle_uma_zone_cur() and arg1 is a pointer to NULL, 
K> so we call uma_zone_get_cur(zone); with zone == NULL.
K> 
K> There’s been a bit of churn around tcp_reass_zone, and I think the latest version is wrong.
K> It marks the sysctl as CTLFLAG_VNET, but the exposed variable is not VNET_DEFINE().
K> 
K> The following fixes it for me:
K> 
K> diff --git a/sys/netinet/tcp_reass.c b/sys/netinet/tcp_reass.c
K> index 77d8940..3913ef3 100644
K> --- a/sys/netinet/tcp_reass.c
K> +++ b/sys/netinet/tcp_reass.c
K> _at__at_ -84,7 +84,7 _at__at_ SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN,
K>      "Global maximum number of TCP Segments in Reassembly Queue");
K> 
K>  static uma_zone_t tcp_reass_zone;
K> -SYSCTL_UMA_CUR(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_VNET,
K> +SYSCTL_UMA_CUR(_net_inet_tcp_reass, OID_AUTO, cursegments, 0,
K>      &tcp_reass_zone,
K>      "Global number of TCP Segments currently in Reassembly Queue”);

Right, if a variable isn't virtualized, the CTLFLAG_VNET must be removed.

Patrick, how is your progress wuth improved reassembly?

-- 
Totus tuus, Glebius.