linux-kernel - Re: [PATCH 1/3 v3] Add tracing_off_event() to stop tracing when a bug or warning occur

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Message-ID: <1269287120.2957.55.camel@gandalf.stny.rr.com>
Date:	Mon, 22 Mar 2010 15:45:20 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Chase Douglas <chase.douglas@...onical.com>
Cc:	linux-kernel@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Randy Dunlap <randy.dunlap@...cle.com>
Subject: Re: [PATCH 1/3 v3] Add tracing_off_event() to stop tracing when a
 bug or warning occur

On Mon, 2010-03-22 at 14:48 -0400, Chase Douglas wrote:
> The tracing_off_event() function calls tracing_off() to stop tracing
> when an event occurs. By default, only BUG-type events stop tracing,
> while WARNING type events do not. This is controlled through the
> tracing_off={none,warn,bug} commandline parameter.
> 
> Call this function from bug and warning event handlers to enable a user
> to debug their kernel by starting a trace, hitting an event, and then
> retrieving trace info knowing that the trace was stopped right after the
> event was hit.
> 
> Signed-off-by: Chase Douglas <chase.douglas@...onical.com>

Please run the code through checkpatch.pl

> ---
>  include/linux/kernel.h     |    7 +++++++
>  kernel/trace/ring_buffer.c |   35 +++++++++++++++++++++++++++++++++++
>  2 files changed, 42 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index 7f07074..a19d545 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -478,16 +478,23 @@ static inline char *pack_hex_byte(char *buf, u8 byte)
>   *
>   * Most likely, you want to use tracing_on/tracing_off.
>   */
> +typedef enum {
> +	TRACE_EVENT_BUG = 0,
> +	TRACE_EVENT_WARN,
> +} trace_event_t;

No need for a typedef here.

> +
>  #ifdef CONFIG_RING_BUFFER
>  void tracing_on(void);
>  void tracing_off(void);
>  /* trace_off_permanent stops recording with no way to bring it back */
>  void tracing_off_permanent(void);
> +void tracing_off_event(trace_event_t event);
>  int tracing_is_on(void);
>  #else
>  static inline void tracing_on(void) { }
>  static inline void tracing_off(void) { }
>  static inline void tracing_off_permanent(void) { }
> +static inline void tracing_off_event(trace_event_t event) { }
>  static inline int tracing_is_on(void) { return 0; }
>  #endif
>  #ifdef CONFIG_TRACING
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index 0287f9f..6a5f535 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -193,6 +193,41 @@ void tracing_off_permanent(void)
>  	set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags);
>  }
>  
> +static trace_event_t tracing_off_event_ctrl = TRACE_EVENT_BUG;
> +
> +/**
> + * tracing_off_event - turn off tracing depending on event type
> + * @event: type of event that occurred
> + *
> + * This function checks the event type to determine whether tracing should be
> + * disabled. Useful for disabling tracing on bugs or warnings.
> + */
> +void tracing_off_event(trace_event_t event)
> +{
> +	if (event <= tracing_off_event_ctrl)
> +		tracing_off();
> +}
> +EXPORT_SYMBOL_GPL(tracing_off_event);
> +
> +static int __init tracing_off_event_setup(char *str)
> +{
> +	if (!strcmp("none", str))
> +		tracing_off_event_ctrl = -1;
> +	else if (!strcmp("bug", str))
> +		tracing_off_event_ctrl = TRACE_EVENT_BUG;
> +	else if (!strcmp("warn", str))
> +		tracing_off_event_ctrl = TRACE_EVENT_WARN;
> +	else
> +	{

Must be "else {"

-- Steve

> +		printk(KERN_NOTICE "Invalid value passed for tracing_off parameter\n");
> +		return 1;
> +	}
> +
> +	return 0;
> +}
> +
> +__setup("tracing_off=", tracing_off_event_setup);
> +
>  /**
>   * tracing_is_on - show state of ring buffers enabled
>   */


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