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    SubjectRe: [PATCH 1/3] Add tracing_off_event() to stop tracing when a bug or warning occur
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    On Thu, Mar 18, 2010 at 10:56 AM, Steven Rostedt <rostedt@goodmis.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@canonical.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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