linux-kernel - Re: [ltt-dev] LTTng 0.193 fixes RT kernel support

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Date:	Tue, 23 Feb 2010 16:59:03 +0530
From:	naresh kamboju <naresh.kernel@...il.com>
To:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	ltt-dev@...ts.casi.polymtl.ca, linux-kernel@...r.kernel.org,
	Steven Rostedt <rostedt@...dmis.org>,
	linux-rt-users@...r.kernel.org
Subject: Re: [ltt-dev] LTTng 0.193 fixes RT kernel support

On Mon, Feb 22, 2010 at 9:07 PM, naresh kamboju <naresh.kernel@...il.com> wrote:
> On Thu, Feb 18, 2010 at 4:38 AM, Mathieu Desnoyers
> <mathieu.desnoyers@...icios.com> wrote:
>> * naresh kamboju (naresh.kernel@...il.com) wrote:
>>> Hi,
>>>
>>> On Tue, Feb 16, 2010 at 10:35 PM, Mathieu Desnoyers <compudj@...stal.dyndns.org> wrote:
>> [...]
>>> > Oh, right. Thanks for the explanation. I'll look into moving LTTng to a
>>> > saner del_timer_sync() scheme to delete the timers.
>>>
>>> Could you give more info regarding, what kind of changes we can work on.
>>> let me also work around on it.
>>>
>>
>> I just released LTTng 0.193 for kernel 2.6.32.4 which includes patches
>> fixing these odd per-cpu timer teardowns.
>
> I have downloaded LTTng 0.193 patches and viewed i can see below patches
>
> 1. lttng-transport-lockless-add-timer-on-works-with-del-timer-sync.patch
> 2. omap-trace-clock-use-del-timer-sync.patch
> 3. x86-trace-clock-use-mod-timer.patch
> 4. trace-clock-32-to-64-use-del-timer-sync.patch

FYI.

I have ported  LTTng 0.193 these four patches and able to resolve the
issues on Uni-processor (UP) on ARM arch Thank you.

A different bug is reported on SMP.

BUG: using smp_processor_id() in preemptible [00000000] code: lttctl/754
caller is put_synthetic_tsc+0x7c/0xf8

Backtrace:
[<c002d438>] (dump_backtrace+0x0/0x10c) from [<c03a7150>] (dump_stack+0x18/0x1c)
 r7:c04c4994 r6:c008e24c r5:00000003 r4:ce0b6000
[<c03a7138>] (dump_stack+0x0/0x1c) from [<c02423b4>]
(debug_smp_processor_id+0xc0/0xec)
[<c02422f4>] (debug_smp_processor_id+0x0/0xec) from [<c008e24c>]
(put_synthetic_tsc+0x7c/0xf8)
 r6:c04f82cc r5:c0023600 r4:00000003
[<c008e1d0>] (put_synthetic_tsc+0x0/0xf8) from [<c008e610>]
(put_trace_clock+0x68/0x7c)
 r8:bece6eb9 r7:0000000b r6:ce0b7d2a r5:cc037600 r4:00000000
[<c008e5a8>] (put_trace_clock+0x0/0x7c) from [<c022a96c>]
(ltt_trace_destroy+0x40/0x94)
[<c022a92c>] (ltt_trace_destroy+0x0/0x94) from [<c0232f6c>]
(destroy_trace_write+0xbc/0x140)
 r5:00000000 r4:0000000b
[<c0232eb0>] (destroy_trace_write+0x0/0x140) from [<c00be240>]
(vfs_write+0xb4/0x144)
 r7:0000000b r6:ce0b7f70 r5:bece6eb9 r4:ceae7860
[<c00be18c>] (vfs_write+0x0/0x144) from [<c00be424>] (sys_write+0x48/0xf4)
 r7:0000000b r6:ceae7860 r5:00000000 r4:00000000
[<c00be3dc>] (sys_write+0x0/0xf4) from [<c0028e3c>]
(__sys_trace_return+0x0/0x24)


patch trace-clock-32-to-64-use-del-timer-sync.patch is causing above
problem on SMP.

with out this patch on SMP reported the previous bug as BUG: sleeping
function called from invalid context at kernel/rtmutex.c:685

However, i'll investigate.

Best regards,
Naresh Kamboju
>> Thanks,
>>
>> Mathieu
>>
>> --
>> Mathieu Desnoyers
>> OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
>>
>
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