lua-sysctl hang on `vfs.cache.nchstats'

[kaworu]

The following script hang and is killed (hacked version of misc/test-all.lua)

require('sysctl')

function show()
    local sctl, stype = sysctl.get(key)
    if (type(sctl) == 'table') then
        local k,v
        print("{")
        for k,v in pairs(sctl) do
            print("  " .. k .. "=" .. v)
        end
        print("}\t" .. stype)
    else
        print(sctl .. "\t" .. stype)
    end
end

key = 'vfs.cache.nchstats'
print(key)
ok, err = pcall(show);
if (not ok) then
    print("*** FAILED ***")
    print(err);
end
print("------")

[kaworu]

% uname -a
FreeBSD Freesbee 9.1-RELEASE FreeBSD 9.1-RELEASE #0 r243825: Tue Dec  4 09:23:10 UTC 2012     root@farrell.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  amd64
% time lua-5.1 testcase.lua 
vfs.cache.nchstats
zsh: killed     lua-5.1 testcase.lua
lua-5.1 testcase.lua  15.75s user 5.59s system 66% cpu 32.080 total
% dmesg
[...]
swap_pager: out of swap space
swap_pager_getswapspace(16): failed
pid 2218 (lua), uid 1001, was killed: out of swap space

[peikk0]

% time lua-5.1 test.lua
vfs.cache.nchstats
*** FAILED ***
table overflow
------
lua-5.1 test.lua  40.80s user 4.16s system 49% cpu 1:30.17 total

It wasn't killed, but it eated ~3GiB of memory.

[kaworu]

Fixed in d4af558

@peikk0: test welcome ;)

[peikk0]

% lua-5.1 test.lua
vfs.cache.nchstats
*** FAILED ***
test.lua:4: unknown CTLTYPE: fmt=LU ctltype=5
------

[kaworu]

Yes it is expected, for some unknown reason vfs.cache.nchstats is declared as CTLTYPE_OPAQUE although fmt suggest CTLTYPE_ULONG (which seems to work).

Maybe this should be reported to FreeBSD, there are more inconsistencies between formats and types, but changing them may break userland.