X-Git-Url: https://git.kernel.dk/?a=blobdiff_plain;f=drivers%2Foprofile%2Fcpu_buffer.h;h=6055b5678394bc51fa0ddab7235c15df92682b01;hb=bf589e32960181fa8cbca7bfdd92265e49dc2dfa;hp=d3cc26264db55b60948a71b9f8500a236666a64d;hpb=24924f884cd36603615ea5496244e542b0b513c6;p=linux-2.6-block.git

diff --git a/drivers/oprofile/cpu_buffer.h b/drivers/oprofile/cpu_buffer.h
index d3cc26264db5..6055b5678394 100644
--- a/drivers/oprofile/cpu_buffer.h
+++ b/drivers/oprofile/cpu_buffer.h
@@ -52,6 +52,62 @@ DECLARE_PER_CPU(struct oprofile_cpu_buffer, cpu_buffer);
 
 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