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Date: Wed, 14 Dec 2016 08:36:56 +0100
From: Ingo Molnar <mingo@kernel.org>
To: Alexis Berlemont <alexis.berlemont@gmail.com>
Cc: linux-kernel@vger.kernel.org, peterz@infradead.org, mingo@redhat.com,
        acme@kernel.org, alexander.shishkin@linux.intel.com,
        Jiri Olsa <jolsa@redhat.com>
Subject: Re: [PATCH v5 0/2] perf probe: add sdt probes arguments into the
 uprobe cmd string
Message-ID: <20161214073656.GB1635@gmail.com>
References: <20161207122610.008da636793d38a39accf29b@kernel.org>
 <20161214000732.1710-1-alexis.berlemont@gmail.com>
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* Alexis Berlemont <alexis.berlemont@gmail.com> wrote:

> Hi Masami,
> 
> Many thanks for your mail.
> 
> Here is another patch set which tries to fix the points you mentioned:
> 
> * Skip the arguments containing a constant ($123); 
> * Review the code in charge of the register renaming (search for '%'
>   and parse it);
> * Minor changes (print the argument in case of error, skipping, check
>   the sdt arg type index);
> 
> Many thanks,
> 
> Alexis.
> 
> Alexis Berlemont (2):
>   perf sdt: add scanning of sdt probles arguments
>   perf probe: add sdt probes arguments into the uprobe cmd string

I'd like to hijack this thread to report an SDT oddity - one of my boxen reports 
lots of SDT tracepoints in 'perf list':

  mem:<addr>[/len][:access]                          [Hardware breakpoint]

  sdt_libc:lll_lock_wait_private                     [SDT event]
  sdt_libc:longjmp                                   [SDT event]
  sdt_libc:longjmp_target                            [SDT event]
  sdt_libc:memory_arena_new                          [SDT event]
  sdt_libc:memory_arena_retry                        [SDT event]
  sdt_libc:memory_arena_reuse                        [SDT event]
  sdt_libc:memory_arena_reuse_free_list              [SDT event]
  sdt_libc:memory_arena_reuse_wait                   [SDT event]
  sdt_libc:memory_calloc_retry                       [SDT event]
  sdt_libc:memory_heap_free                          [SDT event]
  ...

But none of them work:

  Error:  No permissions to read /sys/kernel/debug/tracing/events/sdt_libc/longjmp
  Hint:   Try 'sudo mount -o remount,mode=755 /sys/kernel/debug/tracing'

  ...

  Error:  File /sys/kernel/debug/tracing/events/sdt_libc/longjmp not found.
  Hint:   Perhaps this kernel misses some CONFIG_ setting to enable this feature?.

What kind of patches are required for SDT probes to work?

Thanks,

	Ingo