linux-kernel - Re: ipc-msg broken again on 3.11-rc7? (was Re: linux-next: Tree for Jun 21 [ BROKEN ipc/ipc-msg ])

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Date:	Thu, 29 Aug 2013 07:21:49 +0000
From:	Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:	"sedat.dilek@...il.com" <sedat.dilek@...il.com>
CC:	Davidlohr Bueso <davidlohr.bueso@...com>,
	linux-next <linux-next@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"Stephen Rothwell" <sfr@...b.auug.org.au>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-mm <linux-mm@...ck.org>, Andi Kleen <andi@...stfloor.org>,
	Rik van Riel <riel@...hat.com>,
	Manfred Spraul <manfred@...orfullife.com>,
	"Jonathan Gonzalez" <jgonzalez@...ets.cl>
Subject: Re: ipc-msg broken again on 3.11-rc7? (was Re: linux-next: Tree for
 Jun 21 [ BROKEN ipc/ipc-msg ])

On 08/29/2013 08:34 AM, Sedat Dilek wrote:
> On Wed, Aug 28, 2013 at 1:58 PM, Vineet Gupta
> <Vineet.Gupta1@...opsys.com> wrote:
>> Hi David,
>>
>> On 06/26/2013 04:59 AM, Davidlohr Bueso wrote:
>>> On Tue, 2013-06-25 at 23:41 +0200, Sedat Dilek wrote:
>>>> On Tue, Jun 25, 2013 at 10:33 PM, Davidlohr Bueso
>>>> <davidlohr.bueso@...com> wrote:
>>>>> On Tue, 2013-06-25 at 18:10 +0200, Sedat Dilek wrote:
>>>>> [...]
>>>>>
>>>>>> I did some more testing with Linux-Testing-Project (release:
>>>>>> ltp-full-20130503) and next-20130624 (Monday) which has still the
>>>>>> issue, here.
>>>>>>
>>>>>> If I revert the mentioned two commits from my local
>>>>>> revert-ipc-next20130624-5089fd1c6a6a-ab9efc2d0db5 GIT repo, everything
>>>>>> is fine.
>>>>>>
>>>>>> I have tested the LTP ***IPC*** and ***SYSCALLS*** testcases.
>>>>>>
>>>>>>    root# ./runltp -f ipc
>>>>>>
>>>>>>    root# ./runltp -f syscalls
>>>>> These are nice test cases!
>>>>>
>>>>> So I was able to reproduce the issue with LTP and manually running
>>>>> msgctl08. We seemed to be racing at find_msg(), so take to q_perm lock
>>>>> before calling it. The following changes fixes the issue and passes all
>>>>> 'runltp -f syscall' tests, could you give it a try?
>>>>>
>>>> Cool, that fixes the issues here.
>>>>
>>>> Building with fakeroot & make deb-pkg is now OK, again.
>>>>
>>>> The syscalls/msgctl08 test-case ran successfully!
>>> Andrew, could you pick this one up? I've made the patch on top of
>>> 3.10.0-rc7-next-20130625
>> LTP msgctl08 hangs on 3.11-rc7 (ARC port) with some of my local changes. I
>> bisected it, sigh... didn't look at this thread earlier :-( and landed into this.
>>
>> ------------->8------------------------------------
>> 3dd1f784ed6603d7ab1043e51e6371235edf2313 is the first bad commit
>> commit 3dd1f784ed6603d7ab1043e51e6371235edf2313
>> Author: Davidlohr Bueso <davidlohr.bueso@...com>
>> Date:   Mon Jul 8 16:01:17 2013 -0700
>>
>>     ipc,msg: shorten critical region in msgsnd
>>
>>     do_msgsnd() is another function that does too many things with the ipc
>>     object lock acquired.  Take it only when needed when actually updating
>>     msq.
>> ------------->8------------------------------------
>>
>> If I revert 3dd1f784ed66 and 9ad66ae "ipc: remove unused functions" - the test
>> passes. I can confirm that linux-next also has the issue (didn't try the revert
>> there though).
>>
>> 1. arc 3.11-rc7 config attached (UP + PREEMPT)
>> 2. dmesg prints "msgmni has been set to 479"
>> 3. LTP output (this is slightly dated source, so prints might vary)
>>
>> ------------->8------------------------------------
>> <<<test_start>>>
>> tag=msgctl08 stime=1377689180
>> cmdline="msgctl08"
>> contacts=""
>> analysis=exit
>> initiation_status="ok"
>> <<<test_output>>>
>> ------------->8-------- hung here ------------------
>>
>>
>> Let me know if you need more data/test help.
>>
> Cannot say much to your constellation as I had the issue on x86-64 and
> Linux-next.
> But I have just seen a post-v3.11-rc7 IPC-fix in [1].
>
> I have here a v3.11-rc7 kernel with drm-intel-nightly on top... did not run LTP.

Not sure what you mean - I'd posted that Im seeing the issue on ARC Linux (an FPGA
board) 3.11-rc7 as well as linux-next of yesterday.

> Which LTP release do you use?

The LTP build I generally use is from a 2007 based sources (lazy me). However I
knew this would come up so before posting, I'd built the latest from buildroot and
ran the msgctl08 from there standalone and it did the same thing.

> Might be good to attach your kernel-config for followers?

It was already there in my orig msg - you probably missed it.

> [1] http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=368ae537e056acd3f751fa276f48423f06803922

I tried linux-next of today, same deal - msgctl08 still hangs.

-Vineet
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