ring-buffer: Add ring_buffer_record_is_on_cpu()

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.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: https://lore.kernel.org/20250505212236.059853898@goodmis.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

1 files changed, 18 insertions, 0 deletions

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
@@ -4883,6 +4883,24 @@ bool ring_buffer_record_is_set_on(struct trace_buffer *buffer)
 }
 
 /**
+ * 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.
  * @cpu: The CPU buffer to stop