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

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Message-ID: <40ec3ea41003180927y52bae53hfb8aca0d00ac8de8@mail.gmail.com>
Date:	Thu, 18 Mar 2010 12:27:28 -0400
From:	Chase Douglas <chase.douglas@...onical.com>
To:	rostedt@...dmis.org
Cc:	linux-kernel@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 1/3] Add tracing_off_event() to stop tracing when a bug or 
	warning occur

On Thu, Mar 18, 2010 at 10:56 AM, Steven Rostedt <rostedt@...dmis.org> wrote:
> [ Expanded the Cc list ]
>
> On Thu, 2010-03-18 at 09:48 -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>
>> ---
>>  include/linux/kernel.h     |    5 +++++
>>  kernel/trace/ring_buffer.c |   34 ++++++++++++++++++++++++++++++++++
>>  2 files changed, 39 insertions(+), 0 deletions(-)
>>
>> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
>> index 7f07074..107091f 100644
>> --- a/include/linux/kernel.h
>> +++ b/include/linux/kernel.h
>> @@ -478,16 +478,21 @@ static inline char *pack_hex_byte(char *buf, u8 byte)
>>   *
>>   * Most likely, you want to use tracing_on/tracing_off.
>>   */
>> +#define TRACE_EVENT_BUG 0
>> +#define TRACE_EVENT_WARN 1
>
> This should probably be an enum.
>
>> +
>>  #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(long 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(long 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..b148862 100644
>> --- a/kernel/trace/ring_buffer.c
>> +++ b/kernel/trace/ring_buffer.c
>> @@ -193,6 +193,40 @@ void tracing_off_permanent(void)
>>       set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags);
>>  }
>>
>> +static long tracing_event_mask = TRACE_EVENT_BUG;
>
> That's a bad name. It does not seem to be a mask but seems to be a
> control setting. Maybe call it tracing_event_off_ctrl ?

I'll fix these two things up and resend.

Thanks,
Chase
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