linux-kernel - [PATCH] trace: Return ENOTCONN instead of EBADF

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Date:   Mon, 12 Oct 2020 10:26:42 +0200
From:   Peter Enderborg <peter.enderborg@...y.com>
To:     <linux-kernel@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>
CC:     Peter Enderborg <peter.enderborg@...y.com>
Subject: [PATCH] trace: Return ENOTCONN instead of EBADF

When there is no clients listening on event the trace return
EBADF. The file is not a bad file descriptor and to get the
userspace able to do a proper error handling it need a different
error code that separate a bad file descriptor from a empty listening.

Signed-off-by: Peter Enderborg <peter.enderborg@...y.com>
---
 kernel/trace/trace.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index d3e5de717df2..6e592bf736df 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6651,8 +6651,8 @@ tracing_mark_write(struct file *filp, const char __user *ubuf,
 	event = __trace_buffer_lock_reserve(buffer, TRACE_PRINT, size,
 					    irq_flags, preempt_count());
 	if (unlikely(!event))
-		/* Ring buffer disabled, return as if not open for write */
-		return -EBADF;
+		/* Ring buffer disabled, return as if not connected */
+		return -ENOTCONN;
 
 	entry = ring_buffer_event_data(event);
 	entry->ip = _THIS_IP_;
@@ -6731,8 +6731,8 @@ tracing_mark_raw_write(struct file *filp, const char __user *ubuf,
 	event = __trace_buffer_lock_reserve(buffer, TRACE_RAW_DATA, size,
 					    irq_flags, preempt_count());
 	if (!event)
-		/* Ring buffer disabled, return as if not open for write */
-		return -EBADF;
+		/* Ring buffer disabled, return not connected */
+		return -ENOTCONN;
 
 	entry = ring_buffer_event_data(event);
 
-- 
2.17.1