Re: fcntl always fails to delete lock file, and PID is always -6464

From: Garrett Cooper <gcooper_at_FreeBSD.org>
Date: Tue, 5 Oct 2010 10:09:18 -0700
On Tue, Oct 5, 2010 at 8:58 AM, Garrett Cooper <gcooper_at_freebsd.org> wrote:
> On Tue, Oct 5, 2010 at 7:52 AM, Garrett Cooper <gcooper_at_freebsd.org> wrote:
>> On Tue, Oct 5, 2010 at 1:55 AM, Daichi GOTO <daichi_at_ongs.co.jp> wrote:
>>> On Tue, 5 Oct 2010 01:23:02 -0700
>>> Garrett Cooper <gcooper_at_FreeBSD.org> wrote:
>>>> 2010/10/4 Daichi GOTO <daichi_at_ongs.co.jp>:
>>>> > Thanks nice test tool :)  And at last I got it excepting one mystery!
>>>> >
>>>> > On Mon, 4 Oct 2010 20:17:08 -0700
>>>> > Garrett Cooper <gcooper_at_FreeBSD.org> wrote:
>>>> >> Following through the same process on FreeBSD...
>>>> >>
>>>> >> Window 1:
>>>> >> $ ls -l /tmp/lockfile
>>>> >> ls: /tmp/lockfile: No such file or directory
>>>> >> $ ./test_fcntl
>>>> >>
>>>> >> Window 2:
>>>> >>
>>>> >> $ ls -l /tmp/lockfile
>>>> >> -rwsr-x---  1 garrcoop  wheel  0 Oct  4 20:14 /tmp/lockfile
>>>> >> $ ./test_fcntl
>>>> >> test_fcntl: fcntl: Resource temporarily unavailable
>>>> >
>>>> > Just my mystery is as follow:
>>>> >
>>>> > Windows 1:
>>>> > % ./test_fcntl
>>>> > My pid: 43490
>>>> >
>>>> > Windows 2:
>>>> > % ls -l /tmp/lockfile
>>>> > -r-sr-x---  1 daichi  wheel  0 10月  5 15:02 /tmp/lockfile    <--- is it weird, isn't it?
>>>> > % ./test_fcntl
>>>> > test_fcntl: open: Permission denied
>>>> > %
>>>> >
>>>> > Oops... What's wrong... /tmp is as follow:
>>>> >
>>>> > % mount | grep tmp
>>>> > /dev/ada0s1f on /tmp (ufs, local, noatime, soft-updates)
>>>> > % dumpfs /tmp | grep journal
>>>> > flags   soft-updates+journal
>>>> > %
>>>> >
>>>> > And working scene:
>>>> >
>>>> > Windows 2:
>>>> > % chmod u+w /tmp/lockfile
>>>> > % ls -l /tmp/lockfile
>>>> > -rwsr-x---  1 daichi  wheel  0 10月  5 15:22 /tmp/lockfile
>>>> > % ./test_fcntl
>>>> > My pid: 43646
>>>> > test_fcntl: fcntl[1]: Resource temporarily unavailable
>>>> > PID=43490 has the lock
>>>> > %
>>>>
>>>> What's your umask and what are the permissions on /tmp?
>>>
>>> % ll / | grep tmp
>>> drwxrwxrwt  14 root  wheel      1024 10月  5 17:19 tmp
>>> % umask
>>> 022
>>> % rm -f test
>>> % touch test
>>> % ll | grep test
>>> -rw-r--r--   1 daichi  wheel     0 10月  5 17:52 test
>>> %
>>
>>    The permissions look ok from my perspective, but the umask is
>> different, so you might want to try my umask to make sure that your
>> results match mine (and we need to check the requirements to determine
>> whether or not the behavior for FreeBSD's umask syscall is correct):
>>
>> $ ls -la /tmp/ | head -n 2
>> total 462686
>> drwxrwxrwt  51 root     wheel         11776 Oct  5 03:11 .
>> $ umask
>> 0022
>>
>>    Where and how is /tmp mounted (is it a real partition, what
>> filesystem, etc)?
>>    BTW, when I change my umask to match your's I don't get the same
>> results you do on my home machine:
>>
>> Window 1:
>>
>> $ umask 022
>> $ ./test_fcntl
>> My pid: 17353
>>
>> Window 2:
>>
>> $ ./test_fcntl
>> My pid: 17356
>> test_fcntl: fcntl[1]: Resource temporarily unavailable
>> PID=17353 has the lock
>> $ ls -l /tmp/lockfile
>> -rwSr-----  1 gcooper  wheel  0 Oct  5 07:49 /tmp/lockfile
>>
>>    Just to note, the tests before were run on the RHEL 4.8 box with
>> the following info, and the FreeBSD box with the following info:
>>
>> Red Hat Enterprise Linux AS release 4 (Nahant Update 8)
>> Linux sjc-lds-102 2.6.9-89.0.11.ELsmp #1 SMP Mon Aug 31 11:00:34 EDT
>> 2009 x86_64 x86_64 x86_64 GNU/Linux
>>
>> FreeBSD bioshock.cisco.com 9.0-CURRENT FreeBSD 9.0-CURRENT #1
>> r211767M: Sat Aug 28 00:28:45 PDT 2010
>> garrcoop_at_bioshock.cisco.com:/usr/obj/usr/src/sys/BIOSHOCK  amd64
>>
>>    The tests above were run on a FreeBSD box with the following info:
>>
>> FreeBSD bayonetta.local 9.0-CURRENT FreeBSD 9.0-CURRENT #9 r211309M:
>> Thu Aug 19 22:50:36 PDT 2010
>> root_at_bayonetta.local:/usr/obj/usr/src/sys/BAYONETTA  amd64
>>
>>    On bayonetta /tmp is SUJ backed (probably should change that
>> though), and on bioshock it's not SUJ backed.
>
> And while this might be a good mental exercise, I think we're missing
> the original point of your bug:
>
> You were getting ECONNREFUSED because a socket was in `use', even
> though all instances of mozc_server were dead (at least that's the
> case with me). So the question I guess that's worth asking is:

Statement incorrect: socket wasn't in use. The logic needs to be
rewritten to account for this case and setup the socket again if this
occurs. It would be a good idea to do this if the file wasn't locked.

> 1. What process/application does it need to establish a Unix style socket with?
> 2. Why isn't that socket being cleaned up by the OS at exit?

Thanks!
-Garrett
Received on Tue Oct 05 2010 - 15:09:19 UTC

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