linux-kernel - [PATCH 08/12] ring-buffer: Add ring_buffer_record_is_on

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Message-ID: <20250502205349.134949967@goodmis.org>
Date: Fri, 02 May 2025 16:51:55 -0400
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>
Subject: [PATCH 08/12] ring-buffer: Add ring_buffer_record_is_on_cpu()

From: Steven Rostedt <rostedt@...dmis.org>

Add the function ring_buffer_record_is_on_cpu() that returns true if the
ring buffer for a give CPU is writable and false otherwise.

Also add tracer_tracing_is_on_cpu() to return if the ring buffer for a
given CPU is writeable for a given trace_array.

Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 include/linux/ring_buffer.h |  1 +
 kernel/trace/ring_buffer.c  | 18 ++++++++++++++++++
 kernel/trace/trace.h        | 15 +++++++++++++++
 3 files changed, 34 insertions(+)

diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
index 56e27263acf8..cd7f0ae26615 100644
--- a/include/linux/ring_buffer.h
+++ b/include/linux/ring_buffer.h
@@ -192,6 +192,7 @@ void ring_buffer_record_off(struct trace_buffer *buffer);
 void ring_buffer_record_on(struct trace_buffer *buffer);
 bool ring_buffer_record_is_on(struct trace_buffer *buffer);
 bool ring_buffer_record_is_set_on(struct trace_buffer *buffer);
+bool ring_buffer_record_is_on_cpu(struct trace_buffer *buffer, int cpu);
 void ring_buffer_record_disable_cpu(struct trace_buffer *buffer, int cpu);
 void ring_buffer_record_enable_cpu(struct trace_buffer *buffer, int cpu);
 
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index c0f877d39a24..1ca482955dae 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -4882,6 +4882,24 @@ bool ring_buffer_record_is_set_on(struct trace_buffer *buffer)
 	return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF);
 }
 
+/**
+ * ring_buffer_record_is_on_cpu - return true if the ring buffer can write
+ * @buffer: The ring buffer to see if write is enabled
+ * @cpu: The CPU to test if the ring buffer can write too
+ *
+ * Returns true if the ring buffer is in a state that it accepts writes
+ *   for a particular CPU.
+ */
+bool ring_buffer_record_is_on_cpu(struct trace_buffer *buffer, int cpu)
+{
+	struct ring_buffer_per_cpu *cpu_buffer;
+
+	cpu_buffer = buffer->buffers[cpu];
+
+	return ring_buffer_record_is_set_on(buffer) &&
+		!atomic_read(&cpu_buffer->record_disabled);
+}
+
 /**
  * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
  * @buffer: The ring buffer to stop writes to.
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 79be1995db44..294d92179a02 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -671,6 +671,21 @@ struct dentry *trace_create_file(const char *name,
 				 void *data,
 				 const struct file_operations *fops);
 
+
+/**
+ * tracer_tracing_is_on_cpu - show real state of ring buffer enabled on for a cpu
+ * @tr : the trace array to know if ring buffer is enabled
+ * @cpu: The cpu buffer to check if enabled
+ *
+ * Shows real state of the per CPU buffer if it is enabled or not.
+ */
+static inline bool tracer_tracing_is_on_cpu(struct trace_array *tr, int cpu)
+{
+	if (tr->array_buffer.buffer)
+		return ring_buffer_record_is_on_cpu(tr->array_buffer.buffer, cpu);
+	return false;
+}
+
 int tracing_init_dentry(void);
 
 struct ring_buffer_event;
-- 
2.47.2