printk instrumentation with LTTng

[Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>]

* Alan Cox (alan@lxorguk.ukuu.org.uk) wrote:
> In addition ideally we want a mechanism that is also sufficient that
> printk can be mangled into so that you can pull all the printk text
> strings _out_ of the kernel and into the debug traces for embedded work.
> 

Further on, in LTTng 0.5.113, I added the possibility to trace the location
where the printk happened. Within a huge amount of information, this kind of
data identification can be very useful.

Example of a printk as shown from the text dump of a trace :

kernel.printk_locate: 181.713815470 (/tmp/trace2/cpu_0),
  4357, 0, insmod, UNBRANDED, 4234, 0x0, SYSCALL,
  { file = "/home/compudj/repository/tests/kernel/test-printk.c",
    function = "init_module", line = 14, address = 0xf88eb000 }

kernel.printk: 181.713817590 (/tmp/trace2/cpu_0),
  4357, 0, insmod, UNBRANDED, 4234, 0x0, SYSCALL,
  { loglevel = 0, text = { printk message } }

Regards,


Mathieu



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