linux-kernel - [RFC PATCH] tracing: fix return value in __ftrace_event_enable_disable for TRACE_REG

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Message-ID: <20250314125725.6425-1-gpaoloni@redhat.com>
Date: Fri, 14 Mar 2025 13:57:25 +0100
From: Gabriele Paoloni <gpaoloni@...hat.com>
To: rostedt@...dmis.org,
	mhiramat@...nel.org,
	mathieu.desnoyers@...icios.com,
	linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org
Cc: Gabriele Paoloni <gpaoloni@...hat.com>
Subject: [RFC PATCH] tracing: fix return value in __ftrace_event_enable_disable for TRACE_REG_UNREGISTER

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.

Signed-off-by: Gabriele Paoloni <gpaoloni@...hat.com>
---
Sending this as RFC since I am not sure if checking the ret
value is really needed.
I have been mainly driven by the implementation of
disable_trace_kprobe, disable_trace_fprobe,
tracepoint_probe_unregister, disable_trace_eprobe that can
return an error.

 kernel/trace/trace_events.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 513de9ceb80e..8d92b271ce0d 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -790,7 +790,7 @@ 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);
 		}
 		/* If in SOFT_MODE, just set the SOFT_DISABLE_BIT, else clear it */
 		if (file->flags & EVENT_FILE_FL_SOFT_MODE)
-- 
2.48.1