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authorRobert Richter <robert.richter@amd.com>2008-11-27 22:33:37 +0100
committerRobert Richter <robert.richter@amd.com>2008-12-10 14:20:15 +0100
commitbf589e32960181fa8cbca7bfdd92265e49dc2dfa (patch)
treea5690c62071771e2e325cb748d83fb1cc5565daa /drivers/oprofile/cpu_buffer.h
parent229234ae4a5ed9376b2e0524da04b0e5edadbf76 (diff)
downloadlinux-sh-bf589e32960181fa8cbca7bfdd92265e49dc2dfa.tar.gz
oprofile: adding cpu_buffer_entries()
This is in preparation for changes in the cpu buffer implementation. Signed-off-by: Robert Richter <robert.richter@amd.com>
Diffstat (limited to 'drivers/oprofile/cpu_buffer.h')
-rw-r--r--drivers/oprofile/cpu_buffer.h27
1 files changed, 27 insertions, 0 deletions
diff --git a/drivers/oprofile/cpu_buffer.h b/drivers/oprofile/cpu_buffer.h
index e6089768ae66..6055b5678394 100644
--- a/drivers/oprofile/cpu_buffer.h
+++ b/drivers/oprofile/cpu_buffer.h
@@ -81,6 +81,33 @@ 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