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Date: Mon, 02 Feb 2015 17:41:52 +0900
From: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, namhyung@...nel.org,
Ingo Molnar <mingo@...nel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH perf/core 1/2] [BUGFIX] perf-probe: Fix to handle optimized
not-inlined but has no instance
(2015/01/30 23:32), Arnaldo Carvalho de Melo wrote:
> Em Fri, Jan 30, 2015 at 11:21:35AM -0300, Arnaldo Carvalho de Melo escreveu:
>> Em Fri, Jan 30, 2015 at 06:37:44PM +0900, Masami Hiramatsu escreveu:
>>> Fix to handle optimized no-inline functions which have
>>> only function definition but no actual instance at
>>> that point. To fix this problem, we need to find actual
>>> instance of the function.
>>>
>>> Without this patch:
>>> ----
>>> # perf probe -a __up
>>> Failed to get entry address of __up.
>>> Error: Failed to add events.
>>> # perf probe -L __up
>>> Specified source line is not found.
>>> Error: Failed to show lines.
>>> ----
>>>
>>> With this patch:
>>> ----
>>> # perf probe -a __up
>>> Added new event:
>>> probe:__up (on __up)
>>>
>>> You can now use it in all perf tools, such as:
>>>
>>> perf record -e probe:__up -aR sleep 1
>>>
>>> # perf probe -L __up
>>> <__up@...me/fedora/ksrc/linux-3/kernel/locking/semaphore.c:0>
>>> 0 static noinline void __sched __up(struct semaphore *sem)
>>> {
>>> struct semaphore_waiter *waiter = list_first_entry(&sem->wait_
>>> struct semaphore_waite
>>> 4 list_del(&waiter->list);
>>> 5 waiter->up = true;
>>> 6 wake_up_process(waiter->task);
>>> 7 }
>>> ----
>>
>> Since __up here was built in some other way, I looked for another
>
> Nah, I saw you trying to add "perf probe -a __up" and stopped there,
> hadn't seen that it fails _as well_ for just listing the source code...
>
> Yes, I managed to reproduce the problem and test your fix, it works:
Thanks for testing!
>
> [root@zoo ~]# perf probe --del __up
> Removed event: probe:__up
> [root@zoo ~]# perf probe -L __up
> Specified source line is not found.
> Error: Failed to show lines.
>
> ---->>>>>> APPLY THE PATCH, rebuild and try again:
>
> [root@zoo ~]#
> [root@zoo ~]# perf probe -L __up
> <__up@...me/git/linux/kernel/locking/semaphore.c:0>
> 0 static noinline void __sched __up(struct semaphore *sem)
> {
> struct semaphore_waiter *waiter = list_first_entry(&sem->wait_list,
> struct semaphore_waiter, list);
> 4 list_del(&waiter->list);
> 5 waiter->up = true;
> 6 wake_up_process(waiter->task);
> 7 }
> [root@zoo ~]#
>
> --------------------------------------------------------------
>
> So its just this other case that fails, vmalloc_fault, can you check
> this one? Does it happen in your machine as well?
OK, I'll try reproducing this and dig deeper.
>
> Applying your patch, thanks,
Thank you!
>
> - Arnaldo
>
>> 'noinline' function to try, and it failed here:
>>
>> [root@zoo ~]# perf probe -L vmalloc_fault | head -5
>> <vmalloc_fault@...me/git/linux/arch/x86/mm/fault.c:0>
>> 0 static noinline int vmalloc_fault(unsigned long address)
>> 1 {
>> pgd_t *pgd, *pgd_ref;
>> pud_t *pud, *pud_ref;
>> [root@zoo ~]# perf probe vmalloc_fault
>> Added new event:
>> Failed to write event: Invalid argument
>> Error: Failed to add events.
>>
>> ---->>>>>> APPLY THE PATCH, rebuild and try again:
>>
>> [root@zoo ~]# perf probe vmalloc_fault
>> Added new event:
>> Failed to write event: Invalid argument
>> Error: Failed to add events.
>> [root@zoo ~]# perf probe -v vmalloc_fault
>> probe-definition(0): vmalloc_fault
>> symbol:vmalloc_fault file:(null) line:0 offset:0 return:0 lazy:(null)
>> 0 arguments
>> Looking at the vmlinux_path (7 entries long)
>> Using /lib/modules/3.19.0-rc6+/build/vmlinux for symbols
>> Open Debuginfo file: /lib/modules/3.19.0-rc6+/build/vmlinux
>> Try to find probe point from debuginfo.
>> Probe point found: vmalloc_fault+0
>> Found 1 probe_trace_events.
>> Opening /sys/kernel/debug/tracing/kprobe_events write=1
>> Added new event:
>> Writing event: p:probe/vmalloc_fault _text+289600
>> Failed to write event: Invalid argument
>> Error: Failed to add events. Reason: Invalid argument (Code: -22)
>> [root@zoo ~]# grep -w vmalloc_fault /proc/kallsyms
>> ffffffff81046b40 t vmalloc_fault
>> [root@zoo ~]# grep -w _text /proc/kallsyms
>> ffffffff81000000 T _text
>> [root@zoo ~]# python
>> Python 2.7.5 (default, Nov 3 2014, 14:26:24)
>> [GCC 4.8.3 20140911 (Red Hat 4.8.3-7)] on linux2
>> Type "help", "copyright", "credits" or "license" for more information.
>> >>> 0xffffffff81046b40 - 0xffffffff81000000
>> 289600L
>> >>>
>> [root@zoo ~]# readelf -s /lib/modules/3.19.0-rc6+/build/vmlinux | egrep -w _text\|vmalloc_fault
>> 3499: ffffffff81046b40 410 FUNC LOCAL DEFAULT 1 vmalloc_fault
>> 48873: ffffffff81000000 0 NOTYPE GLOBAL DEFAULT 1 _text
>> [root@zoo ~]#
>>
>> ---------------------------------------------------------------------------
>>
>> So perhaps I need a 'noinline' _and_ '__sched', so that I have a "optimized
>> no-inline functions which have only function definition but no actual instance
>> at that point"?
>>
>> Looking for one, will post here after objdump -dS finishes...
>>
>> - Arnaldo
>
--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com
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