void cpu_buffer_reset(struct oprofile_cpu_buffer *cpu_buf);
+static inline
+struct op_sample *cpu_buffer_write_entry(struct oprofile_cpu_buffer *cpu_buf)
+{
+ return &cpu_buf->buffer[cpu_buf->head_pos];
+}
+
+static inline
+void cpu_buffer_write_commit(struct oprofile_cpu_buffer *b)
+{
+ unsigned long new_head = b->head_pos + 1;
+
+ /*
+ * Ensure anything written to the slot before we increment is
+ * visible
+ */
+ wmb();
+
+ if (new_head < b->buffer_size)
+ b->head_pos = new_head;
+ else
+ b->head_pos = 0;
+}
+
+static inline
+struct op_sample *cpu_buffer_read_entry(struct oprofile_cpu_buffer *cpu_buf)
+{
+ return &cpu_buf->buffer[cpu_buf->tail_pos];
+}
+
+/* "acquire" as many cpu buffer slots as we can */
+static inline
+unsigned long cpu_buffer_entries(struct oprofile_cpu_buffer *b)
+{
+ unsigned long head = b->head_pos;
+ unsigned long tail = b->tail_pos;
+
+ /*
+ * Subtle. This resets the persistent last_task
+ * and in_kernel values used for switching notes.
+ * BUT, there is a small window between reading
+ * head_pos, and this call, that means samples
+ * can appear at the new head position, but not
+ * be prefixed with the notes for switching
+ * kernel mode or a task switch. This small hole
+ * can lead to mis-attribution or samples where
+ * we don't know if it's in the kernel or not,
+ * at the start of an event buffer.
+ */
+ cpu_buffer_reset(b);
+
+ if (head >= tail)
+ return head - tail;
+
+ return head + (b->buffer_size - tail);
+}
+
/* transient events for the CPU buffer -> event buffer */
#define CPU_IS_KERNEL 1
#define CPU_TRACE_BEGIN 2