Re: [PATCH v3 11/17] rv: Prevent unintentional tracepoints during KUnit tests

[Wen Yang]

On 6/25/26 20:14, Gabriele Monaco wrote:
Monitor initialisation also called during KUnit tests may register some
tracepoints, this can lead to issues since we don't expect real monitor
events running during KUnit tests.

Prevent tracepoint registration if an RV KUnit test is running.

Reviewed-by: Nam Cao <nam...@linutronix.de>
Signed-off-by: Gabriele Monaco <gmon...@redhat.com>
---
  include/rv/instrumentation.h |  5 +++++
  include/rv/kunit.h           |  2 ++
  kernel/trace/rv/rv.c         | 11 +++++++++++
  3 files changed, 18 insertions(+)

diff --git a/include/rv/instrumentation.h b/include/rv/instrumentation.h
index d4e7a02ede..761f8f147d 100644
--- a/include/rv/instrumentation.h
+++ b/include/rv/instrumentation.h
@@ -9,12 +9,15 @@
   */
  
  #include <linux/ftrace.h>
+#include <rv/kunit.h>
  
  /*
   * rv_attach_trace_probe - check and attach a handler function to a tracepoint
   */
  #define rv_attach_trace_probe(monitor, tp, rv_handler)                        
                \
        do {                                                                    
        \
+               if (rv_mon_test_is_running())                                   
        \
+                       break;                                                  
        \
                check_trace_callback_type_##tp(rv_handler);                     
        \
                WARN_ONCE(register_trace_##tp(rv_handler, NULL),                
        \
                                "fail attaching " #monitor " " #tp "handler");  
          \
@@ -25,5 +28,7 @@
   */
  #define rv_detach_trace_probe(monitor, tp, rv_handler)                        
                \
        do {                                                                    
        \
+               if (rv_mon_test_is_running())                                   
        \
+                       break;                                                  
        \
                unregister_trace_##tp(rv_handler, NULL);                        
        \
        } while (0)
diff --git a/include/rv/kunit.h b/include/rv/kunit.h
index 5e8c604cf7..0c4c4bc933 100644
--- a/include/rv/kunit.h
+++ b/include/rv/kunit.h
@@ -19,6 +19,7 @@
  
  int rv_set_testing(struct kunit_suite *suite);
  void rv_clear_testing(struct kunit_suite *suite);
+bool rv_mon_test_is_running(void);
  struct task_struct *rv_get_current(void);
  
  struct rv_kunit_ctx {
@@ -59,6 +60,7 @@ void teardown_test(void *arg);
  #else /* !CONFIG_RV_MONITORS_KUNIT_TEST */
  
  #define rv_get_current() current
+#define rv_mon_test_is_running() false
  
  #endif /* CONFIG_RV_MONITORS_KUNIT_TEST */
  #endif /* _RV_KUNIT_H */
diff --git a/kernel/trace/rv/rv.c b/kernel/trace/rv/rv.c
index 61d4f13960..86ef5dee7f 100644
--- a/kernel/trace/rv/rv.c
+++ b/kernel/trace/rv/rv.c
@@ -864,6 +864,14 @@ int __init rv_init_interface(void)
  #include <rv/kunit.h>
  #include <kunit/visibility.h>
  
+static bool rv_mon_test_running;
+
+bool rv_mon_test_is_running(void)
+{
+       return rv_mon_test_running;
+}
+EXPORT_SYMBOL_GPL(rv_mon_test_is_running);
+

The flag rv_mon_test_running is a plain bool with no ordering
guarantees, and the tracepoint handlers that call 
rv_mon_test_is_running() may execute on
arbitrary CPUs. A store to rv_mon_test_running on the test CPU may not
be visible to another CPU's tracepoint handler.
What abbout READ_ONCE/WRITE_ONCE?

--
Best wishes,
Wen




  /*
   * rv_set_testing - ensure mutual exclusion between KUnit tests and real 
monitors
   *
@@ -886,6 +894,8 @@ int rv_set_testing(struct kunit_suite *suite)
                }
        }
  
+	rv_mon_test_running = true;
+
        return 0;
  }
  EXPORT_SYMBOL_IF_KUNIT(rv_set_testing);
@@ -895,6 +905,7 @@ EXPORT_SYMBOL_IF_KUNIT(rv_set_testing);
   */
  void rv_clear_testing(struct kunit_suite *suite)
  {
+       rv_mon_test_running = false;
        mutex_unlock(&rv_interface_lock);
  }
  EXPORT_SYMBOL_IF_KUNIT(rv_clear_testing);