linux-stable.git/kernel/trace/rv, branch master

rv: Fix 32-bit build of nomiss KUnit test

2026-08-04T14:11:27+00:00

Commit 8da2a8838365 ("rv: Add KUnit tests for some DA/HA monitors")
introduced a division of a 64-bit value by 1000 in the nomiss KUnit
test. This does not compile on 32-bit systems, as standard division of
64-bit values leads to an undefined reference to __udivdi3.

Fix the build on 32-bit systems by using div_u64().

Fixes: 8da2a8838365 ("rv: Add KUnit tests for some DA/HA monitors")
Reported-by: kernel test robot 
Closes: https://lore.kernel.org/oe-kbuild-all/202608020311.hYjqOG5k-lkp@intel.com
Reviewed-by: Nam Cao 
Link: https://lore.kernel.org/r/20260803150622.322806-1-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco

rv: Add KUnit tests for some LTL monitors

2026-07-31T14:27:46+00:00

Validate the functionality of LTL monitors by injecting events in a
controlled environment (KUnit) and expecting reactions, just like it is
done in DA monitors.

Reviewed-by: Nam Cao 
Link: https://lore.kernel.org/r/20260723074534.43521-15-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco

rv: Add KUnit mock for current

2026-07-31T14:27:45+00:00

Some monitors do not only rely on tracepoint arguments but also on the
currently executing task.
This makes it more challenging to mock events in KUnit.

Define wrapper functions around current, the functionality is mocked
only during KUnit, an additional function call is avoided using a static
branch unless any (even unrelated) KUnit test is running.

Rely on a global mock_current variable that is set only by the RV KUnit
tests and cleared on teardown. Unrelated KUnit tests that happen to
trigger RV handlers would see it null and use current.

Reviewed-by: Nam Cao 
Reviewed-by: Wen Yang 
Link: https://lore.kernel.org/r/20260723074534.43521-14-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco

rv: Add KUnit tests for some DA/HA monitors

2026-07-31T14:27:45+00:00

Validate the functionality of DA monitors by injecting events in a
controlled environment (KUnit) and expecting reactions.

Events handlers are exported directly from the monitor source files
without using system events and with dummy arguments (e.g. no real
tasks). If the provided sequence of events incurs a violation, the test
expects the stub version of rv_react() to be called.

This testing method can validate the entire monitor implementation since
it sits between the monitor and the system (in place of the
tracepoints). All sorts of system and timing events can be emulated
without affecting the running kernel.

Handlers and monitor functions are exported as part of a struct to
simplify the process of running KUnit tests from kernel modules.

Reviewed-by: Nam Cao 
Link: https://lore.kernel.org/r/20260723074534.43521-13-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco

rv: Export task monitor slot and react symbols

2026-07-31T14:27:45+00:00

Export rv_get_task_monitor_slot, rv_put_task_monitor_slot, and rv_react
to GPL modules so they can be accessed by KUnit and future monitors
built as kernel modules.

Reviewed-by: Nam Cao 
Link: https://lore.kernel.org/r/20260723074534.43521-12-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco

rv: Use generic rv_this for the rv_monitor variable in LTL

2026-07-31T11:53:51+00:00

Align the rv_monitor variable name in LTL to the generic rv_this as it
is already done for DA/HA monitors. This improves consistency and eases
assumptions across model classes.

Reviewed-by: Nam Cao 
Link: https://lore.kernel.org/r/20260723074534.43521-2-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco

rv/rtapp: Add wakeup monitor

2026-07-24T07:01:10+00:00

Add a wakeup monitor to detect a lower-priority task waking up a
higher-priority task.

The rtapp/sleep monitor already detects this. However, that monitor
triggers an error in the context of the wakee task and user only gets
the stacktrace of that task. It is also extremely useful to get the
stacktrace of the waker task, which this monitor offers. In other
words, this monitor complements the rtapp/sleep monitor.

Signed-off-by: Nam Cao 
Reviewed-by: Gabriele Monaco 
Link: https://lore.kernel.org/r/ba5658fa13e49ada466b84a2c211f233037180b5.1781852967.git.namcao@linutronix.de
Signed-off-by: Gabriele Monaco

rv/rtapp/sleep: Stop monitoring kernel threads

2026-07-24T07:01:10+00:00

The rtapp/sleep monitor's primary purpose is detecting common mistakes
with user-space real-time design. Monitoring real-time issues with
kernel threads is a bonus.

However, accomodating kernel threads complicates the monitor due to
the edge cases which is seen by the monitor as lower-priority task
waking higher-priority task:

- kthread_stop() wakes up the task in order to stop it.

- The rcu thread and migration thread can be woken by any task.

- The ktimerd thread is woken near the end of irq_exit_rcu(), where
the preempt counter is "broken" and falsely says this is task
context. This requires the monitor to use the hardirq_context flag
instead of the preempt counter.

Beside complicating the monitor, the final case also requires enabling
CONFIG_TRACE_IRQFLAGS (so that "hardirq_context" can be used). This
adds overhead to the kernel even when the monitor is not active. This
may be an obstacle to enabling this monitor in distros' kernels.

Furthermore, kernel threads usually are started before the monitor is
enabled. Consequently, the threads' states (i.o.w. the monitor's
atomic propositions for the threads) are not fully known to the
monitor. As a result, the kernel threads mostly cannot be monitored.

Overall, the downsides of accomodating kernel threads outweights the
benefits. Thus, exclude kernel threads to simplify the monitor.

Signed-off-by: Nam Cao
Reviewed-by: Gabriele Monaco
Link: https://lore.kernel.org/r/eec2ca5224bcdacc45b8e1eb2f0e68109e1cae7a.1781852967.git.namcao@linutronix.de
Signed-off-by: Gabriele Monaco

rv/rtapp/sleep: Update nanosleep rule

2026-07-24T07:01:10+00:00

CLOCK_REALTIME is the only clock that often is misused in real-time
applications. The other clocks either are safe for real-time uses
(CLOCK_TAI, CLOCK_MONOTONIC, CLOCK_BOOTTIME) or are unlikely to be misused
(CLOCK_AUX, CLOCK_PROCESS_CPUTIME_ID).

Update the monitor to only warn about CLOCK_REALTIME.

While at it, update the out-of-sync documentation.

Signed-off-by: Nam Cao 
Reviewed-by: Gabriele Monaco 
Link: https://lore.kernel.org/r/c7ceb5c6263ee8f43a2676acae669cf486b0d903.1781852967.git.namcao@linutronix.de
Signed-off-by: Gabriele Monaco

rv/rtapp/sleep: Make the error more informative for user

2026-07-24T07:01:10+00:00

The rtapp/sleep monitor detects real-time tasks which go to sleep in an
real-time-unsafe manner. If this happen, the monitor triggers a trace event
in the sched_wakeup tracepoint's handler.

However, the invoking context of that trace event is not the most
informative, because of the stack trace of that event is the wakeup's code
path which is not very helpful:

74.669317: rv:error_sleep: condvar[254]: violation detected
    ltl_validate+0x345 ([kernel.kallsyms])
    handle_sched_wakeup+0x34 ([kernel.kallsyms])
    ttwu_do_activate+0xff ([kernel.kallsyms])
    sched_ttwu_pending+0x104 ([kernel.kallsyms])
    __flush_smp_call_function_queue+0x15b ([kernel.kallsyms])
    __sysvec_call_function_single+0x18 ([kernel.kallsyms])
    sysvec_call_function_single+0x66 ([kernel.kallsyms])
    asm_sysvec_call_function_single+0x1a ([kernel.kallsyms])
    pv_native_safe_halt+0xf ([kernel.kallsyms])
    default_idle+0x9 ([kernel.kallsyms])
    default_idle_call+0x33 ([kernel.kallsyms])
    do_idle+0x234 ([kernel.kallsyms])
    cpu_startup_entry+0x24 ([kernel.kallsyms])
    start_secondary+0xf8 ([kernel.kallsyms])
    common_startup_64+0x13e ([kernel.kallsyms])

What would be much more valuable is the stack trace of the task itself.

Instead of using the sched_wakeup tracepoint, use the sched_exit
tracepoint. This makes the event happen in the task's context, making
the stack trace far more informative for user:

rv:error_sleep: condvar[254]: violation detected
    ltl_validate+0x345 ([kernel.kallsyms])
    handle_sched_exit+0x39 ([kernel.kallsyms])
    __schedule+0x80f ([kernel.kallsyms])
    schedule+0x22 ([kernel.kallsyms])
    futex_do_wait+0x33 ([kernel.kallsyms])
    __futex_wait+0x8c ([kernel.kallsyms])
    futex_wait+0x73 ([kernel.kallsyms])
    do_futex+0xc6 ([kernel.kallsyms])
    __x64_sys_futex+0x121 ([kernel.kallsyms])
    do_syscall_64+0xf3 ([kernel.kallsyms])
    entry_SYSCALL_64_after_hwframe+0x77 ([kernel.kallsyms])
    __futex_abstimed_wait_common64+0xc6 (inlined)
    __futex_abstimed_wait_common+0xc6 (/usr/lib/x86_64-linux-gnu/libc.so.6)

Signed-off-by: Nam Cao 
Reviewed-by: Gabriele Monaco 
Link: https://lore.kernel.org/r/d97b4b5c476e5792b6875ec9bbf8dc214f999516.1781852967.git.namcao@linutronix.de
Signed-off-by: Gabriele Monaco