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>

diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
index 56e27263acf892d68f64fe1653776e756398b1e8..cd7f0ae266150cf2a4669d8c7c166f014b598f61 100644 (file)
--- 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 c0f877d39a241d0217670fb4a4fb897176f0dc7b..1ca482955dae3ac87189cd9da2804e2da83dafcf 100644 (file)
--- 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 74f1fe5788d46bb6620fd0a31766c47ab9ae6103..69c1ecfb229009bb7815a3014c755e1f9918c221 100644 (file)
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -673,6 +673,21 @@ 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;