Re: [Qemu-devel] [PATCH v7 08/13] trace-state: always compile support for controlling and querying trace event states

[Stefan Hajnoczi <stefanha@gmail.com>]

On Thu, Aug 25, 2011 at 09:18:24PM +0200, Lluís wrote:
> The current interface is generic for this small set of operations, and thus
> other backends can easily modify the "trace/control.c" file to add their own
> implementation.
> 
> Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
> ---
>  docs/tracing.txt |   39 +++++++++++++++++++++------------------
>  hmp-commands.hx  |    7 +++++--
>  monitor.c        |    9 +++++----
>  3 files changed, 31 insertions(+), 24 deletions(-)
> 
> diff --git a/docs/tracing.txt b/docs/tracing.txt
> index 1ad106a..017ff59 100644
> --- a/docs/tracing.txt
> +++ b/docs/tracing.txt
> @@ -108,6 +108,27 @@ portability macros, ensure they are preceded and followed by double quotes:
>     of trace events.  Marking trace events disabled by default saves the user
>     from having to manually disable noisy trace events.
>  
> +== Generic interface and monitor commands ==
> +
> +You can programmatically query and control the dynamic state of trace events
> +through a backend-agnostic interface:
> +
> +* trace_print_events
> +
> +* trace_event_set_state
> +
> +Note that some of the backends do not provide and implementation for this

s/and/an/

> +interface, in which case QEMU will just print a warning.
> +
> +This functionality is also provided through monitor commands:
> +
> +* info trace-events
> +  View available trace events and their state.  State 1 means enabled, state 0
> +  means disabled.
> +
> +* trace-event NAME on|off
> +  Enable/disable a given trace event.
> +
>  == Trace backends ==
>  
>  The "tracetool" script automates tedious trace event code generation and also
> @@ -157,27 +178,9 @@ unless you have specific needs for more advanced backends.
>    flushed and emptied.  This means the 'info trace' will display few or no
>    entries if the buffer has just been flushed.
>  
> -* info trace-events
> -  View available trace events and their state.  State 1 means enabled, state 0
> -  means disabled.
> -
> -* trace-event NAME on|off
> -  Enable/disable a given trace event.
> -
>  * trace-file on|off|flush|set <path>
>    Enable/disable/flush the trace file or set the trace file name.
>  
> -==== Enabling/disabling trace events programmatically ====
> -
> -The st_change_trace_event_state() function can be used to enable or disable trace
> -events at runtime inside QEMU:
> -
> -    #include "trace.h"
> -    
> -    st_change_trace_event_state("virtio_irq", true); /* enable */
> -    [...]
> -    st_change_trace_event_state("virtio_irq", false); /* disable */
> -

Please update and move this example to where trace_event_set_state() is
documented.  Having an example makes it clear what this function does.

Stefan