linux-kernel - Re: [PATCH] printk: add console output tracing

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Message-ID: <1321491688.4181.42.camel@frodo>
Date:	Wed, 16 Nov 2011 20:01:28 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Johannes Berg <johannes@...solutions.net>
Cc:	Christoph Hellwig <hch@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH] printk: add console output tracing

Thomas, Peter, Frederic, Christoph,

Would you ack this patch please.

Thanks,

-- Steve


On Wed, 2011-11-16 at 22:25 +0100, Johannes Berg wrote:
> From: Johannes Berg <johannes.berg@...el.com>
> 
> Add a printk.console trace point to record any printk
> messages into the trace, regardless of the current
> console loglevel. This can help correlate (existing)
> printk debugging with other tracing.
> 
> Signed-off-by: Johannes Berg <johannes.berg@...el.com>
> ---
>  include/trace/events/printk.h |   44 ++++++++++++++++++++++++++++++++++++++++++
>  kernel/printk.c               |    3 ++
>  kernel/trace/Makefile         |    1 
>  kernel/trace/printk-trace.c   |   14 +++++++++++++
>  4 files changed, 62 insertions(+)
> 
> --- /dev/null	1970-01-01 00:00:00.000000000 +0000
> +++ b/include/trace/events/printk.h	2011-11-16 22:06:43.000000000 +0100
> @@ -0,0 +1,44 @@
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM printk
> +
> +#if !defined(_TRACE_PRINTK_H) || defined(TRACE_HEADER_MULTI_READ)
> +#define _TRACE_PRINTK_H
> +
> +#include <linux/tracepoint.h>
> +
> +TRACE_EVENT_CONDITION(console,
> +	TP_PROTO(const char *log_buf, unsigned start, unsigned end,
> +		 unsigned log_buf_len),
> +
> +	TP_ARGS(log_buf, start, end, log_buf_len),
> +
> +	TP_CONDITION(start != end),
> +
> +	TP_STRUCT__entry(
> +		__dynamic_array(char, msg,
> +				((end - start + log_buf_len) &
> +				 (log_buf_len - 1)) + 1)
> +	),
> +
> +	TP_fast_assign(
> +		if ((start & (log_buf_len - 1)) > (end & (log_buf_len - 1))) {
> +			memcpy(__get_dynamic_array(msg),
> +			       log_buf + (start & (log_buf_len - 1)),
> +			       log_buf_len - (start & (log_buf_len - 1)));
> +			memcpy((char *)__get_dynamic_array(msg) +
> +			       log_buf_len - (start & (log_buf_len - 1)),
> +			       log_buf, end & (log_buf_len - 1));
> +		} else
> +			memcpy(__get_dynamic_array(msg),
> +			       log_buf + (start & (log_buf_len - 1)),
> +			       (end - start + log_buf_len) & (log_buf_len - 1));
> +		((char *)__get_dynamic_array(msg))[(end - start + log_buf_len) &
> +						   (log_buf_len - 1)] = 0;
> +	),
> +
> +	TP_printk("%s", __get_str(msg))
> +);
> +#endif /* _TRACE_PRINTK_H */
> +
> +/* This part must be outside protection */
> +#include <trace/define_trace.h>
> --- a/kernel/printk.c	2011-11-16 16:37:20.000000000 +0100
> +++ b/kernel/printk.c	2011-11-16 21:47:20.000000000 +0100
> @@ -41,6 +41,7 @@
>  #include <linux/cpu.h>
>  #include <linux/notifier.h>
>  #include <linux/rculist.h>
> +#include <trace/events/printk.h>
>  
>  #include <asm/uaccess.h>
>  
> @@ -542,6 +543,8 @@ MODULE_PARM_DESC(ignore_loglevel, "ignor
>  static void _call_console_drivers(unsigned start,
>  				unsigned end, int msg_log_level)
>  {
> +	trace_console(&LOG_BUF(0), start, end, log_buf_len);
> +
>  	if ((msg_log_level < console_loglevel || ignore_loglevel) &&
>  			console_drivers && start != end) {
>  		if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
> --- /dev/null	1970-01-01 00:00:00.000000000 +0000
> +++ b/kernel/trace/printk-trace.c	2011-11-16 21:22:20.000000000 +0100
> @@ -0,0 +1,14 @@
> +/*
> + * printk trace points
> + *
> + * Copyright (C) 2011 Johannes Berg <johannes.berg@...el.com>
> + */
> +
> +#include <linux/string.h>
> +#include <linux/types.h>
> +#include <linux/workqueue.h>
> +#include <linux/sched.h>
> +#include <linux/module.h>
> +
> +#define CREATE_TRACE_POINTS
> +#include <trace/events/printk.h>
> --- a/kernel/trace/Makefile	2011-11-16 16:37:20.000000000 +0100
> +++ b/kernel/trace/Makefile	2011-11-16 21:38:49.000000000 +0100
> @@ -55,6 +55,7 @@ endif
>  obj-$(CONFIG_EVENT_TRACING) += trace_events_filter.o
>  obj-$(CONFIG_KPROBE_EVENT) += trace_kprobe.o
>  obj-$(CONFIG_TRACEPOINTS) += power-traces.o
> +obj-$(CONFIG_TRACEPOINTS) += printk-trace.o
>  ifeq ($(CONFIG_PM_RUNTIME),y)
>  obj-$(CONFIG_TRACEPOINTS) += rpm-traces.o
>  endif
> 


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