On Wed, Jul 13, 2022 at 11:17:27PM +0200, Daniel Bristot de Oliveira wrote:
> Add the da_monitor_instrumentation.rst. It describes the basics
> of RV monitor instrumentation.
>
> Cc: Wim Van Sebroeck <wim@xxxxxxxxxxxxxxxxxx>
> Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
> Cc: Jonathan Corbet <corbet@xxxxxxx>
> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Will Deacon <will@xxxxxxxxxx>
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Marco Elver <elver@xxxxxxxxxx>
> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
> Cc: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
> Cc: Gabriele Paoloni <gpaoloni@xxxxxxxxxx>
> Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>
> Cc: Clark Williams <williams@xxxxxxxxxx>
> Cc: Tao Zhou <tao.zhou@xxxxxxxxx>
> Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
> Cc: linux-doc@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: linux-trace-devel@xxxxxxxxxxxxxxx
> Signed-off-by: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
> ---
> .../trace/rv/da_monitor_instrumentation.rst | 169 ++++++++++++++++++
> Documentation/trace/rv/index.rst | 1 +
> 2 files changed, 170 insertions(+)
> create mode 100644 Documentation/trace/rv/da_monitor_instrumentation.rst
>
> diff --git a/Documentation/trace/rv/da_monitor_instrumentation.rst b/Documentation/trace/rv/da_monitor_instrumentation.rst
> new file mode 100644
> index 000000000000..7b83d6c7dbed
> --- /dev/null
> +++ b/Documentation/trace/rv/da_monitor_instrumentation.rst
> @@ -0,0 +1,169 @@
> +Deterministic Automata Instrumentation
> +========================================
> +
> +The RV monitor file created by dot2k, with the name "$MODEL_NAME.c"
> +includes a section dedicated to instrumentation.
> +
> +In the example of the wip.dot monitor created on [1], it will look like::
> +
> + /*
> + * This is the instrumentation part of the monitor.
> + *
> + * This is the section where manual work is required. Here the kernel events
> + * are translated into model's event.
> + *
> + */
> + static void handle_preempt_disable(void *data, /* XXX: fill header */)
> + {
> + da_handle_event_wip(preempt_disable_wip);
> + }
> +
> + static void handle_preempt_enable(void *data, /* XXX: fill header */)
> + {
> + da_handle_event_wip(preempt_enable_wip);
> + }
> +
> + static void handle_sched_waking(void *data, /* XXX: fill header */)
> + {
> + da_handle_event_wip(sched_waking_wip);
> + }
> +
> + static int start_wip(void)
> + {
> + int retval;
> +
> + retval = da_monitor_init_wip();
> + if (retval)
> + return retval;
> +
> + rv_attach_trace_probe("wip", /* XXX: tracepoint */, handle_preempt_disable);
> + rv_attach_trace_probe("wip", /* XXX: tracepoint */, handle_preempt_enable);
> + rv_attach_trace_probe("wip", /* XXX: tracepoint */, handle_sched_waking);
> +
> + return 0;
> + }
> +
> +The comment at the top of the section explains the general idea: the
> +instrumentation section translates *kernel events* into the *model's
> +event*.
> +
> +Tracing callback functions
> +-----------------------------
> +
> +The first three functions are the starting point of the callback *handler
> +functions* for each of the three events from the wip model. The developer
> +does not necessarily need to use them: they are just starting points.
> +
> +Using the example of::
> +
> + void handle_preempt_disable(void *data, /* XXX: fill header */)
> + {
> + da_handle_event_wip(preempt_disable_wip);
> + }
> +
> +The preempt_disable event from the model connects directly to the
> +preemptirq:preempt_disable. The preemptirq:preempt_disable event
> +has the following signature, from include/trace/events/preemptirq.h::
> +
> + TP_PROTO(unsigned long ip, unsigned long parent_ip)
> +
> +Hence, the handle_preempt_disable() function will look like::
> +
> + void handle_preempt_disable(void *data, unsigned long ip, unsigned long parent_ip)
> +
> +In this case, the kernel event translates one to one with the automata
> +event, and indeed, no other change is required for this function.
> +
> +The next handler function, handle_preempt_enable() has the same argument
> +list from the handle_preempt_disable(). The difference is that the
> +preempt_enable event will be used to synchronize the system to the model.
> +
> +Initially, the *model* is placed in the initial state. However, the *system*
> +might or might not be in the initial state. The monitor cannot start
> +processing events until it knows that the system has reached the initial state.
> +Otherwise, the monitor and the system could be out-of-sync.
> +
> +Looking at the automata definition, it is possible to see that the system
> +and the model are expected to return to the initial state after the
> +preempt_enable execution. Hence, it can be used to synchronize the
> +system and the model at the initialization of the monitoring section.
> +
> +The initialization is informed via a special handle function, the
> +"da_handle_init_event_$(MONITOR)(event)", in this case::
> +
> + da_handle_event_wip(preempt_disable_wip);
In this case, it is da_handle_init_event_wip(preempt_disable_wip). Thanks.
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