linux-kernel - [PATCH 10/14] tracing: Stop the tracing while changing the ring buffer subbuf size

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Message-ID: <20231210040451.136611306@goodmis.org>
Date:   Sat, 09 Dec 2023 22:54:14 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tzvetomir Stoyanov <tz.stoyanov@...il.com>,
        Vincent Donnefort <vdonnefort@...gle.com>,
        Kent Overstreet <kent.overstreet@...il.com>
Subject: [PATCH 10/14] tracing: Stop the tracing while changing the ring buffer subbuf size

From: "Steven Rostedt (Google)" <rostedt@...dmis.org>

Because the main buffer and the snapshot buffer need to be the same for
some tracers, otherwise it will fail and disable all tracing, the tracers
need to be stopped while updating the sub buffer sizes so that the tracers
see the main and snapshot buffers with the same sub buffer size.

Fixes: TBD ("ring-buffer: Add interface for configuring trace sub buffer size")
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 kernel/trace/trace.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 7faaaf29b504..9e5f2392d521 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -9397,13 +9397,16 @@ buffer_order_write(struct file *filp, const char __user *ubuf,
 	if (val < 0 || val > 7)
 		return -EINVAL;
 
+	/* Do not allow tracing while changing the order of the ring buffer */
+	tracing_stop_tr(tr);
+
 	old_order = ring_buffer_subbuf_order_get(tr->array_buffer.buffer);
 	if (old_order == val)
-		return 0;
+		goto out;
 
 	ret = ring_buffer_subbuf_order_set(tr->array_buffer.buffer, val);
 	if (ret)
-		return 0;
+		goto out;
 
 #ifdef CONFIG_TRACER_MAX_TRACE
 
@@ -9430,11 +9433,15 @@ buffer_order_write(struct file *filp, const char __user *ubuf,
 			 */
 			tracing_disabled = 1;
 		}
-		return ret;
+		goto out;
 	}
  out_max:
 #endif
 	(*ppos)++;
+ out:
+	if (ret)
+		cnt = ret;
+	tracing_start_tr(tr);
 	return cnt;
 }
 
-- 
2.42.0