linux.git/include/linux/rv.h, branch v7.1-rc2

rv: Add support for per-object monitors in DA/HA

2026-03-31T14:47:17+00:00

RV deterministic and hybrid automata currently only support global,
per-cpu and per-task monitors. It isn't possible to write a model that
would follow some different type of object, like a deadline entity or a
lock.

Define the generic per-object monitor implementation which shares part
of the implementation with the per-task monitors.
The user needs to provide an id for the object (e.g. pid for tasks) and
define the data type for the monitor_target (e.g. struct task_struct *
for tasks). Both are supplied to the event handlers, as the id may not
be easily available in the target.

The monitor storage (e.g. the rv monitor, pointer to the target, etc.)
is stored in a hash table indexed by id. Monitor storage objects are
automatically allocated unless specified otherwise (e.g. if the creation
context is unsafe for allocation).

Reviewed-by: Nam Cao 
Link: https://lore.kernel.org/r/20260330111010.153663-9-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco

rv: Add Hybrid Automata monitor type

2026-03-31T14:47:16+00:00

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 
Link: https://lore.kernel.org/r/20260330111010.153663-3-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco

rv: Refactor da_monitor to minimise macros

2026-01-12T06:43:49+00:00

The da_monitor helper functions are generated from macros of the type:

DECLARE_DA_FUNCTION(name, type) \
static void da_func_x_##name(type arg) {} \
static void da_func_y_##name(type arg) {} \

This is good to minimise code duplication but the long macros made of
skipped end of lines is rather hard to parse. Since functions are
static, the advantage of naming them differently for each monitor is
minimal.

Refactor the da_monitor.h file to minimise macros, instead of declaring
functions from macros, we simply declare them with the same name for all
monitors (e.g. da_func_x) and for any remaining reference to the monitor
name (e.g. tracepoints, enums, global variables) we use the CONCATENATE
macro.
In this way the file is much easier to maintain while keeping the same
generality.
Functions depending on the monitor types are now conditionally compiled
according to the value of RV_MON_TYPE, which must be defined in the
monitor source.
The monitor type can be specified as in the original implementation,
although it's best to keep the default implementation (unsigned char) as
not all parts of code support larger data types, and likely there's no
need.

We keep the empty macro definitions to ease review of this change with
diff tools, but cleanup is required.

Also adapt existing monitors to keep the build working.

Reviewed-by: Nam Cao 
Link: https://lore.kernel.org/r/20251126104241.291258-2-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco

rv: Make rv_reacting_on() static

2025-11-11T12:18:56+00:00

There are no external users left.

Signed-off-by: Thomas Weißschuh 
Link: https://lore.kernel.org/r/20251014-rv-lockdep-v1-2-0b9e51919ea8@linutronix.de
Signed-off-by: Gabriele Monaco

rv: Pass va_list to reactors

2025-11-11T12:18:55+00:00

The only thing the reactors can do with the passed in varargs is to
convert it into a va_list. Do that in a central helper instead.
It simplifies the reactors, removes some hairy macro-generated code
and introduces a convenient hook point to modify reactor behavior.

Signed-off-by: Thomas Weißschuh 
Link: https://lore.kernel.org/r/20251014-rv-lockdep-v1-1-0b9e51919ea8@linutronix.de
Signed-off-by: Gabriele Monaco

include/linux/rv.h: remove redundant include file

2025-09-15T06:36:35+00:00

Remove redundant include  to clean up the code.
Move all unique include files inside CONFIG_RV as they are only needed
when CONFIG_RV is enabled. Arrange include files alphabetically.

Fixes: 24cbfe18d55a ("rv: Merge struct rv_monitor_def into struct rv_monitor") [1]
Reported-by: kernel test robot 
Closes: https://lore.kernel.org/r/202507312017.oyD08TL5-lkp@intel.com/
Signed-off-by: Akhilesh Patil 
Reviewed-by: Gabriele Monaco 
Link: https://lore.kernel.org/r/aJneRbHGlNFg7lr9@bhairav-test.ee.iitb.ac.in
Signed-off-by: Gabriele Monaco

rv: Retry when da monitor detects race conditions

2025-07-28T20:47:34+00:00

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 
Cc: Masami Hiramatsu 
Cc: Tomas Glozar 
Cc: Juri Lelli 
Cc: Clark Williams 
Cc: John Kacur 
Cc: Peter Zijlstra 
Link: https://lore.kernel.org/20250728135022.255578-6-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco 
Reviewed-by: Nam Cao 
Signed-off-by: Steven Rostedt (Google)

rv: Remove struct rv_monitor::reacting

2025-07-25T13:04:14+00:00

The field 'reacting' in struct rv_monitor is set but never used. Delete it.

Cc: Masami Hiramatsu 
Cc: Mathieu Desnoyers 
Link: https://lore.kernel.org/a6c16f845d2f1a09c4d0934ab83f3cb14478a71d.1753378331.git.namcao@linutronix.de
Reviewed-by: Gabriele Monaco 
Signed-off-by: Nam Cao 
Signed-off-by: Steven Rostedt (Google)

rv: Remove rv_reactor's reference counter

2025-07-25T13:04:14+00:00

rv_reactor has a reference counter to ensure it is not removed while
monitors are still using it.

However, this is futile, as __exit functions are not expected to fail and
will proceed normally despite rv_unregister_reactor() returning an error.

At the moment, reactors do not support being built as modules, therefore
they are never removed and the reference counters are not necessary.

If we support building RV reactors as modules in the future, kernel
module's centralized facilities such as try_module_get(), module_put() or
MODULE_SOFTDEP should be used instead of this custom implementation.

Remove this reference counter.

Cc: Masami Hiramatsu 
Cc: Mathieu Desnoyers 
Link: https://lore.kernel.org/bb946398436a5e17fb0f5b842ef3313c02291852.1753378331.git.namcao@linutronix.de
Reviewed-by: Gabriele Monaco 
Signed-off-by: Nam Cao 
Signed-off-by: Steven Rostedt (Google)

rv: Merge struct rv_reactor_def into struct rv_reactor

2025-07-25T13:04:14+00:00

Each struct rv_reactor has a unique struct rv_reactor_def associated with
it. struct rv_reactor is statically allocated, while struct rv_reactor_def
is dynamically allocated.

This makes the code more complicated than it should be:

  - Lookup is required to get the associated rv_reactor_def from rv_reactor

  - Dynamic memory allocation is required for rv_reactor_def. This is
    harder to get right compared to static memory. For instance, there is
    an existing mistake: rv_unregister_reactor() does not free the memory
    allocated by rv_register_reactor(). This is fortunately not a real
    memory leak problem as rv_unregister_reactor() is never called.

Simplify and merge rv_reactor_def into rv_reactor.

Cc: Masami Hiramatsu 
Cc: Mathieu Desnoyers 
Link: https://lore.kernel.org/71cb91c86cd40df5b8c492b788787f2a73c3eaa3.1753378331.git.namcao@linutronix.de
Reviewed-by: Gabriele Monaco 
Signed-off-by: Nam Cao 
Signed-off-by: Steven Rostedt (Google)