Deterministic automata define which events are allowed in every state,
but cannot define more sophisticated constraint taking into account the
system's environment (e.g. time or other states not producing events).
Add the Hybrid Automata monitor type as an extension of Deterministic
automata where each state transition is validating a constraint on a
finite number of environment variables.
Hybrid automata can be used to implement timed automata, where the
environment variables are clocks.
Also implement the necessary functionality to handle clock constraints
(ns or jiffy granularity) on state and events.
Reviewed-by: Nam Cao <namcao@linutronix.de>
Link: https://lore.kernel.org/r/20260330111010.153663-3-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
DA monitor can be accessed from multiple cores simultaneously, this is
likely, for instance when dealing with per-task monitors reacting on
events that do not always occur on the CPU where the task is running.
This can cause race conditions where two events change the next state
and we see inconsistent values. E.g.:
[62] event_srs: 27: sleepable x sched_wakeup -> running (final)
[63] event_srs: 27: sleepable x sched_set_state_sleepable -> sleepable
[63] error_srs: 27: event sched_switch_suspend not expected in the state running
In this case the monitor fails because the event on CPU 62 wins against
the one on CPU 63, although the correct state should have been
sleepable, since the task get suspended.
Detect if the current state was modified by using try_cmpxchg while
storing the next value. If it was, try again reading the current state.
After a maximum number of failed retries, react by calling a special
tracepoint, print on the console and reset the monitor.
Remove the functions da_monitor_curr_state() and da_monitor_set_state()
as they only hide the underlying implementation in this case.
Monitors where this type of condition can occur must be able to account
for racing events in any possible order, as we cannot know the winner.
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Tomas Glozar <tglozar@redhat.com>
Cc: Juri Lelli <jlelli@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/20250728135022.255578-6-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Reviewed-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
The current behaviour of rvgen when running with the -a option is to
append the necessary lines at the end of the configuration for Kconfig,
Makefile and tracepoints.
This is not always the desired behaviour in case of nested monitors:
while tracepoints are not affected by nesting and the Makefile's only
requirement is that the parent monitor is built before its children, in
the Kconfig it is better to have children defined right after their
parent, otherwise the result has wrong indentation:
[*] foo_parent monitor
[*] foo_child1 monitor
[*] foo_child2 monitor
[*] bar_parent monitor
[*] bar_child1 monitor
[*] bar_child2 monitor
[*] foo_child3 monitor
[*] foo_child4 monitor
Adapt rvgen to look for a different marker for nested monitors in the
Kconfig file and append the line right after the last sibling, instead
of the last monitor.
Also add the marker when creating a new parent monitor.
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Tomas Glozar <tglozar@redhat.com>
Cc: Juri Lelli <jlelli@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Link: https://lore.kernel.org/20250723161240.194860-5-gmonaco@redhat.com
Reviewed-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Monitors describing complex systems, such as the scheduler, can easily
grow to the point where they are just hard to understand because of the
many possible state transitions.
Often it is possible to break such descriptions into smaller monitors,
sharing some or all events. Enabling those smaller monitors concurrently
is, in fact, testing the system as if we had one single larger monitor.
Splitting models into multiple specification is not only easier to
understand, but gives some more clues when we see errors.
Add the possibility to create container monitors, whose only purpose is
to host other nested monitors. Enabling a container monitor enables all
nested ones, but it's still possible to enable nested monitors
independently.
Add the sched monitor as first container, for now empty.
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Link: https://lore.kernel.org/20250305140406.350227-3-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
dot2k suggests a list of changes to the kernel tree while adding a
monitor: edit tracepoints header, Makefile, Kconfig and moving the
monitor folder. Those changes can be easily run automatically.
Add a flag to dot2k to alter the kernel source.
The kernel source directory can be either assumed from the PWD, or from
the running kernel, if installed.
This feature works best if the kernel tree is a git repository, so that
its easier to make sure there are no unintended changes.
The main RV files (e.g. Makefile) have now a comment placeholder that
can be useful for manual editing (e.g. to know where to add new
monitors) and it is used by the script to append the required lines.
We also slightly adapt the file handling functions in dot2k: __open_file
is now called __read_file and also closes the file before returning the
content; __create_file is now a more general __write_file, we no longer
return on FileExistsError (not thrown while opening), a new
__create_file simply calls __write_file specifying the monitor folder in
the path.
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Kacur <jkacur@redhat.com>
Link: https://lore.kernel.org/20241227144752.362911-8-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
While creating a new monitor in RV, besides generating code from dot2k,
there are a few manual steps which can be tedious and error prone, like
adding the tracepoints, makefile lines and kconfig.
This patch restructures the existing monitors to keep some files in the
monitor's folder itself, which can be automatically generated by future
versions of dot2k.
Monitors have now their own Kconfig and tracepoint snippets. For
simplicity, the main tracepoint definition, is moved to the RV
directory, it defines only the tracepoint classes and includes the
monitor-specific tracepoints, which reside in the monitor directory.
Tracepoints and Kconfig no longer need to be copied and adapted from
existing ones but only need to be included in the main files.
The Makefile remains untouched since there's little advantage in having
a separated Makefile for each monitor with a single line and including
it in the main RV Makefile.
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Kacur <jkacur@redhat.com>
Link: https://lore.kernel.org/20241227144752.362911-6-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
