[PATCH v2] tracing: fix return value in __ftrace_event_enable_disable for TRACE_REG_UNREGISTER

[Gabriele Paoloni <gpaoloni@redhat.com>]

When __ftrace_event_enable_disable invokes the class callback to
unregister the event, the return value is not reported up to the
caller, hence leading to event unregister failures being silently
ignored.

This patch assigns the ret variable to the invocation of the
event unregister callback, so that its return value is stored
and reported to the caller, and it raises a warning in case
of error.

Signed-off-by: Gabriele Paoloni <gpaoloni@redhat.com>
---
Changes from v1:
     Added WARN_ON_ONCE(ret) according to the feedbacks from
     v1 RFC [1]

[1] https://lore.kernel.org/linux-trace-kernel/20250314125725.6425-1-gpaoloni@redhat.com/T/#u
---
 kernel/trace/trace_events.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 513de9ceb80e..8e7603acca21 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -790,7 +790,9 @@ static int __ftrace_event_enable_disable(struct trace_event_file *file,
 				clear_bit(EVENT_FILE_FL_RECORDED_TGID_BIT, &file->flags);
 			}
 
-			call->class->reg(call, TRACE_REG_UNREGISTER, file);
+			ret = call->class->reg(call, TRACE_REG_UNREGISTER, file);
+
+			WARN_ON_ONCE(ret);
 		}
 		/* If in SOFT_MODE, just set the SOFT_DISABLE_BIT, else clear it */
 		if (file->flags & EVENT_FILE_FL_SOFT_MODE)
-- 
2.48.1