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Daniel Bristot de Oliveirarostedt
Daniel Bristot de Oliveira
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rv/monitor: Add the wwnr monitor
Per task wakeup while not running (wwnr) monitor. This model is broken, the reason is that a task can be running in the processor without being set as RUNNABLE. Think about a task about to sleep: 1: set_current_state(TASK_UNINTERRUPTIBLE); 2: schedule(); And then imagine an IRQ happening in between the lines one and two, waking the task up. BOOM, the wakeup will happen while the task is running. Q: Why do we need this model, so? A: To test the reactors. Link: https://lkml.kernel.org/r/473c0fc39967250fdebcff8b620311c11dccad30.1659052063.git.bristot@kernel.org Cc: Wim Van Sebroeck <wim@linux-watchdog.org> Cc: Guenter Roeck <linux@roeck-us.net> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Ingo Molnar <mingo@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Will Deacon <will@kernel.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Marco Elver <elver@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: Shuah Khan <skhan@linuxfoundation.org> Cc: Gabriele Paoloni <gpaoloni@redhat.com> Cc: Juri Lelli <juri.lelli@redhat.com> Cc: Clark Williams <williams@redhat.com> Cc: Tao Zhou <tao.zhou@linux.dev> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: linux-doc@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: linux-trace-devel@vger.kernel.org Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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‎Documentation/trace/rv/index.rst‎

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da_monitor_synthesis.rst
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da_monitor_instrumentation.rst
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monitor_wip.rst
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monitor_wwnr.rst

‎Documentation/trace/rv/monitor_wwnr.rst‎

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Monitor wwnr
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============
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- Name: wwrn - wakeup while not running
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- Type: per-task deterministic automaton
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- Author: Daniel Bristot de Oliveira <bristot@kernel.org>
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Description
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-----------
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This is a per-task sample monitor, with the following
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definition::
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|
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|
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v
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wakeup +-------------+
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+--------- | |
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| | not_running |
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+--------> | | <+
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+-------------+ |
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| |
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| switch_in | switch_out
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v |
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+-------------+ |
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| running | -+
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+-------------+
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This model is borken, the reason is that a task can be running
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in the processor without being set as RUNNABLE. Think about a
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task about to sleep::
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1: set_current_state(TASK_UNINTERRUPTIBLE);
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2: schedule();
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And then imagine an IRQ happening in between the lines one and two,
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waking the task up. BOOM, the wakeup will happen while the task is
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running.
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- Why do we need this model, so?
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- To test the reactors.
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Specification
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-------------
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Grapviz Dot file in tools/verification/models/wwnr.dot

‎include/trace/events/rv.h‎

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@@ -122,6 +122,18 @@ DECLARE_EVENT_CLASS(error_da_monitor_id,
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__entry->event,
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__entry->state)
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);
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#ifdef CONFIG_RV_MON_WWNR
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/* id is the pid of the task */
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DEFINE_EVENT(event_da_monitor_id, event_wwnr,
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TP_PROTO(int id, char *state, char *event, char *next_state, bool final_state),
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TP_ARGS(id, state, event, next_state, final_state));
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DEFINE_EVENT(error_da_monitor_id, error_wwnr,
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TP_PROTO(int id, char *state, char *event),
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TP_ARGS(id, state, event));
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#endif /* CONFIG_RV_MON_WWNR */
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#endif /* CONFIG_DA_MON_EVENTS_ID */
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#endif /* _TRACE_RV_H */
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‎kernel/trace/rv/Kconfig‎

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For further information, see:
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Documentation/trace/rv/monitor_wip.rst
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config RV_MON_WWNR
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depends on RV
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select DA_MON_EVENTS_ID
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bool "wwnr monitor"
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help
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Enable wwnr (wakeup while not running) sample monitor, this is a
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sample monitor that illustrates the usage of per-task monitor.
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The model is borken on purpose: it serves to test reactors.
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For further information, see:
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Documentation/trace/rv/monitor_wwnr.rst
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config RV_REACTORS
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bool "Runtime verification reactors"
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default y

‎kernel/trace/rv/Makefile‎

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obj-$(CONFIG_RV) += rv.o
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obj-$(CONFIG_RV_REACTORS) += rv_reactors.o
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obj-$(CONFIG_RV_MON_WIP) += monitors/wip/wip.o
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obj-$(CONFIG_RV_MON_WWNR) += monitors/wwnr/wwnr.o

‎kernel/trace/rv/monitors/wwnr/wwnr.c‎

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// SPDX-License-Identifier: GPL-2.0
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#include <linux/ftrace.h>
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#include <linux/tracepoint.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/rv.h>
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#include <rv/instrumentation.h>
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#include <rv/da_monitor.h>
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#define MODULE_NAME "wwnr"
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#include <trace/events/rv.h>
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#include <trace/events/sched.h>
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#include "wwnr.h"
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struct rv_monitor rv_wwnr;
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DECLARE_DA_MON_PER_TASK(wwnr, unsigned char);
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static void handle_switch(void *data, bool preempt, struct task_struct *p,
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struct task_struct *n, unsigned int prev_state)
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{
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/* start monitoring only after the first suspension */
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if (prev_state == TASK_INTERRUPTIBLE)
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da_handle_start_event_wwnr(p, switch_out_wwnr);
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else
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da_handle_event_wwnr(p, switch_out_wwnr);
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da_handle_event_wwnr(n, switch_in_wwnr);
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}
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static void handle_wakeup(void *data, struct task_struct *p)
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{
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da_handle_event_wwnr(p, wakeup_wwnr);
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}
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static int enable_wwnr(void)
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{
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int retval;
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retval = da_monitor_init_wwnr();
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if (retval)
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return retval;
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rv_attach_trace_probe("wwnr", sched_switch, handle_switch);
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rv_attach_trace_probe("wwnr", sched_wakeup, handle_wakeup);
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return 0;
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}
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static void disable_wwnr(void)
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{
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rv_wwnr.enabled = 0;
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rv_detach_trace_probe("wwnr", sched_switch, handle_switch);
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rv_detach_trace_probe("wwnr", sched_wakeup, handle_wakeup);
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da_monitor_destroy_wwnr();
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}
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struct rv_monitor rv_wwnr = {
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.name = "wwnr",
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.description = "wakeup while not running per-task testing model.",
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.enable = enable_wwnr,
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.disable = disable_wwnr,
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.reset = da_monitor_reset_all_wwnr,
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.enabled = 0,
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};
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static int register_wwnr(void)
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{
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rv_register_monitor(&rv_wwnr);
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return 0;
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}
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static void unregister_wwnr(void)
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{
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rv_unregister_monitor(&rv_wwnr);
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}
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module_init(register_wwnr);
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module_exit(unregister_wwnr);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Daniel Bristot de Oliveira <bristot@kernel.org>");
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MODULE_DESCRIPTION("wwnr: wakeup while not running monitor");

‎kernel/trace/rv/monitors/wwnr/wwnr.h‎

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/*
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* Automatically generated C representation of wwnr automaton
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* For further information about this format, see kernel documentation:
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* Documentation/trace/rv/deterministic_automata.rst
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*/
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enum states_wwnr {
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not_running_wwnr = 0,
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running_wwnr,
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state_max_wwnr
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};
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#define INVALID_STATE state_max_wwnr
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enum events_wwnr {
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switch_in_wwnr = 0,
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switch_out_wwnr,
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wakeup_wwnr,
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event_max_wwnr
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};
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struct automaton_wwnr {
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char *state_names[state_max_wwnr];
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char *event_names[event_max_wwnr];
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unsigned char function[state_max_wwnr][event_max_wwnr];
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unsigned char initial_state;
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bool final_states[state_max_wwnr];
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};
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struct automaton_wwnr automaton_wwnr = {
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.state_names = {
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"not_running",
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"running"
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},
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.event_names = {
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"switch_in",
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"switch_out",
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"wakeup"
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},
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.function = {
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{ running_wwnr, INVALID_STATE, not_running_wwnr },
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{ INVALID_STATE, not_running_wwnr, INVALID_STATE },
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},
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.initial_state = not_running_wwnr,
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.final_states = { 1, 0 },
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};

‎tools/verification/models/wwnr.dot‎

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digraph state_automaton {
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{node [shape = plaintext, style=invis, label=""] "__init_not_running"};
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{node [shape = ellipse] "not_running"};
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{node [shape = plaintext] "not_running"};
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{node [shape = plaintext] "running"};
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"__init_not_running" -> "not_running";
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"not_running" [label = "not_running", color = green3];
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"not_running" -> "not_running" [ label = "wakeup" ];
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"not_running" -> "running" [ label = "switch_in" ];
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"running" [label = "running"];
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"running" -> "not_running" [ label = "switch_out" ];
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{ rank = min ;
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"__init_not_running";
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"not_running";
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}
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}

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