Re: linux-next: Tree for Apr 18 [ call-trace: drm | x86 | smp | rcu related? ]

[Sedat Dilek <sedat.dilek@gmail.com>]

On Fri, Apr 19, 2013 at 6:43 PM, Sedat Dilek <sedat.dilek@gmail.com> wrote:
> On Fri, Apr 19, 2013 at 12:27 PM, Sedat Dilek <sedat.dilek@gmail.com> wrote:
>> On Fri, Apr 19, 2013 at 12:19 PM, Sedat Dilek <sedat.dilek@gmail.com> wrote:
>>> On Thu, Apr 18, 2013 at 11:59 PM, Sedat Dilek <sedat.dilek@gmail.com> wrote:
>>>> On Thu, Apr 18, 2013 at 9:48 PM, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
>>>>> On Thu, Apr 18, 2013 at 3:05 PM, Sedat Dilek <sedat.dilek@gmail.com> wrote:
>>>>>> On Thu, Apr 18, 2013 at 10:28 AM, Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>>>>>>> Hi all,
>>>>>>>
>>>>>>> Changes since 20130417:
>>>>>>>
>>>>>>> New Trees:      rpmsg (actually added yesterday)
>>>>>>>                 ppc-temp (replacing powerpc for this week)
>>>>>>>
>>>>>>> The ceph tree gained a conflict against Linus' tree.
>>>>>>>
>>>>>>> The net-next tree gained a conflict against the infiniband tree.
>>>>>>>
>>>>>>> The usb tree gained a build failure so I used the version from
>>>>>>> next-20130417.
>>>>>>>
>>>>>>> I added two merge fix patches after the gen-gpio tree.
>>>>>>>
>>>>>>> The ppc-temp tree gained a conflict against the metag tree.
>>>>>>>
>>>>>>> The akpm tree lost a patch that turned up elsewhere.
>>>>>>>
>>>>>>> ----------------------------------------------------------------------------
>>>>>>>
>>>>>>
>>>>>> Not sure what the root-cause for this call-trace is (see screenshot).
>>>>>>
>>>>>> This is reproducible when running my kernel build-script (4 parallel-make-jobs).
>>>>>>
>>>>>> Any hints welcome!
>>>>>
>>>>> The panic handlers in our modeset code are pretty decent fubar - they
>>>>> take mutexes all over the place. So I think the backtrace you see
>>>>> there is actually a secondary effect. I've looked into fixing this up,
>>>>> but the issue is that drivers themselves have tons of state protected
>>>>> with mutexes, which all potentially affects the panic handler. So I've
>>>>> given up on that for now ...
>>>>
>>>> Thanks for taking care.
>>>>
>>>> On suspicion [1] I have reverted [2]... NOPE.
>>>>
>>>> - Sedat -
>>>>
>>>> [1] http://marc.info/?l=linux-kernel&m=136631921208895&w=2
>>>> [2] http://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/commit/?id=5a90d1a95356de7a32acb2e5309ac579a891af8f
>>>>
>>>
>>> Hmmm, the issue seems to be gone with today's Linux-Next (next-20130419).
>>> My kernel-build is still running with no call-trace...
>>>
>>
>> NO, It's no good.
>>
>
> I tried to switch from SLUB to SLAB...
>
> ...and also from VIRT_CPU_ACCOUNTING_GEN to TICK_CPU_ACCOUNTING.
>
> 2x NOPE.
>
> In one kernel-build I saw in my console...
>
>      semop(1): encountered an error: Identifier removed
>
> ...if this says sth. to you.
>

[ CC folks from below thread ]

I have found a thread called "Re: ipc,sem: sysv semaphore scalability"
on LKML with a screenshot that shows the same call-trace.
I followed it a bit.
There is a patch in [3]... unconfirmed.

Comments on the rcu read-lock and "sem_lock()" vs "sem_unlock()" from Linus.

What's the status of this discussion?

- Sedat -

[1] https://lkml.org/lkml/2013/3/30/6
[2] http://i.imgur.com/uk6gmq1.jpg
[3] https://lkml.org/lkml/2013/3/31/12
[4] https://lkml.org/lkml/2013/3/31/77

> - Sedat -
>
> - Sedat -
>
>> - Sedat -
>>
>> [1] http://www.youtube.com/watch?v=LwicaralvS0
>>
>>> - Sedat -
>>>
>>>>> -Daniel
>>>>> --
>>>>> Daniel Vetter
>>>>> Software Engineer, Intel Corporation
>>>>> +41 (0) 79 365 57 48 - http://blog.ffwll.ch