On Sat, Dec 13, 2014 at 12:50:37AM -0500, Steven Rostedt wrote:
>
> Add the kernel command line tracepoint_printk option that will
> have tracepoints that are active sent to printk().
>
> Passing "tracepoint_printk" will activate this. To turn it off
> the sysctl /proc/sys/kernel/tracepoint_printk can have '0' echoed
> into it. Note, this only works if the cmdline option is used.
> Echoing 1 into the sysctl file without the cmdline option will
> have no affect.
>
> Note, this is a dangerous option. Having high frequency
> tracepoints send their data to printk() can possibly cause
> a live lock.
>
> Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1412121539300.16494@nanos
>
> Suggested-by: Thomas Gleixner <t...@linutronix.de>
> Signed-off-by: Steven Rostedt <rost...@goodmis.org>
> ---
> Documentation/kernel-parameters.txt | 18 ++++++++++++++++++
> include/linux/ftrace.h | 1 +
> kernel/sysctl.c | 7 +++++++
> kernel/trace/trace.c | 17 +++++++++++++++++
> kernel/trace/trace.h | 1 +
> kernel/trace/trace_events.c | 32 ++++++++++++++++++++++++++++++++
> 6 files changed, 76 insertions(+)
>
> diff --git a/Documentation/kernel-parameters.txt
> b/Documentation/kernel-parameters.txt
> index 1d09eb37c562..d81f464a7358 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -3500,6 +3500,24 @@ bytes respectively. Such letter suffixes can also be
> entirely omitted.
> See also Documentation/trace/ftrace.txt "trace options"
> section.
>
> + tracepoint_printk[FTRACE]
Damn, this is long and most likely nasty to type on some dingy box when
you're trying to debug stuff. Can we shorten it?
trace_printk
tp_printk
tp_print
tp_pr
...
Last one is my favourite - we should call it ToiletPaper_Print :-)
> + Have the tracepoints sent to printk as well as the
> + tracing ring buffer. This is useful for early boot up
> + where the system hangs or reboots and does not give the
> + option for reading the tracing buffer or performing a
> + ftrace_dump_on_oops.
--
Regards/Gruss,
Boris.
Sent from a fat crate under my desk. Formatting is fine.
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