[LTP] [PATCH] lsmod01: parse a copy of /proc/modules

[Stanislav Kholmanskikh <stanislav.kholmanskikh@oracle.com>]

On 08/29/2016 05:00 PM, Stanislav Kholmanskikh wrote:
> 
> 
> On 08/29/2016 04:34 PM, Jan Stancek wrote:
>>
>>
>>
>>
>> ----- Original Message -----
>>> From: "Stanislav Kholmanskikh" <stanislav.kholmanskikh@oracle.com>
>>> To: "Cyril Hrubis" <chrubis@suse.cz>
>>> Cc: "vasily isaenko" <vasily.isaenko@oracle.com>, ltp@lists.linux.it
>>> Sent: Monday, 29 August, 2016 3:05:11 PM
>>> Subject: Re: [LTP] [PATCH] lsmod01: parse a copy of /proc/modules
>>>
>>>
>>>
>>> On 08/29/2016 03:50 PM, Cyril Hrubis wrote:
>>>> Hi!
>>>>> In my environment, if TMPDIR is on NFSv4, this test case fails with:
>>>>>
>>>>> lsmod01 1 TFAIL : lsmod output different from /proc/modules.
>>>>>   21c21
>>>>>   < sunrpc 207591 28
>>>>>   ---
>>>>>   > sunrpc 207591 29
>>>>>
>>>>> To avoid such problems I separate the process of getting data from
>>>>> /proc/modules and the process of parsing it in the pipe structure.
>>>>
>>>> So the sunrpc module gets its ref counter incremented from somewhere of
>>>> the nfs kernel code once we open file on NFS?
>>>
>>> Looks so. I hava a share mounted from localhost:
>>>
>>> [root@skholman-m7 mnt]# mount|grep mnt
>>> 127.0.0.1:/opt on /mnt type nfs
>>> (rw,vers=4,addr=127.0.0.1,clientaddr=127.0.0.1)
>>> [root@skholman-m7 mnt]# awk '{print $1, $2, $3}' /proc/modules|sort >
>>> /tmp/not_nfs
>>> [root@skholman-m7 mnt]# awk '{print $1, $2, $3}' /proc/modules|sort > nfs
>>> [root@skholman-m7 mnt]# grep sunrpc nfs
>>> sunrpc 207591 29
>>> [root@skholman-m7 mnt]# grep sunrpc /tmp/not_nfs
>>> sunrpc 207591 28
>>> [root@skholman-m7 mnt]#
>>
>> And if you do that with just "cat /proc/modules", then there's no difference?
>> Could it be that it's actually first write that takes extra ref?
>> cat is reading in 65536 byte chunks for me, awk only 1024.
> 
> Yes, there is no difference if I use "cat /proc/modules":
> 
> [root@skholman-m7 mnt]# awk '{print $1, $2, $3}' /proc/modules|sort > nfs
> [root@skholman-m7 mnt]# grep sunrpc nfs
> sunrpc 207591 29
> [root@skholman-m7 mnt]# cat /proc/modules > temp
> [root@skholman-m7 mnt]# awk '{print $1, $2, $3}' temp|sort > nfs
> [root@skholman-m7 mnt]# grep sunrpc temp
> sunrpc 207591 28 nfs,nfsd,lockd,nfs_acl,auth_rpcgss, Live 0x00000000101ec000
> [root@skholman-m7 mnt]#
> 
> As for 1024. lsmod also reads /proc/modules in 1024 bytes chunks.

I suppose it's something related to using the pipe construction, since
this change also "fixes" the issue:

[root@skholman-m7 lsmod]# git diff
diff --git a/testcases/commands/lsmod/lsmod01.sh
b/testcases/commands/lsmod/lsmod01.sh
index 5cf2fee..0970d2f 100755
--- a/testcases/commands/lsmod/lsmod01.sh
+++ b/testcases/commands/lsmod/lsmod01.sh
@@ -45,7 +45,8 @@ lsmod_test()

        awk '!/Module/{print $1, $2, $3}' temp |sort >temp1

-       awk '{print $1, $2, $3}' /proc/modules |sort >temp2
+       awk '{print $1, $2, $3}' /proc/modules > temp
+       sort temp >temp2

        diff temp1 temp2 >temp3
        if [ $? -ne 0 ]; then
[root@skholman-m7 lsmod]#



> 
>>
>> Regards,
>> Jan
>>
>>>
>>>
>>>
>>>>
>>>> But shouldn't the shell open the temp file the output is redirected to
>>>> before it executes the command line anyway?
>>>>
>>>
>>> --
>>> Mailing list info: https://lists.linux.it/listinfo/ltp
>>>
>