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Date: Fri, 30 Jan 2015 11:32:20 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
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
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:
[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?
Applying your patch, thanks,
- 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
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