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oprofile: adding cpu_buffer_entries()

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This is in preparation for changes in the cpu buffer implementation.

Signed-off-by: Robert Richter <robert.richter@amd.com>
This commit is contained in:
Robert Richter
2008-11-27 22:33:37 +01:00
parent 229234ae4a
commit bf589e3296
2 changed files with 29 additions and 29 deletions
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27
drivers/oprofile/cpu_buffer.h
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@ -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