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ring-buffer: read page interface

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Impact: new API to ring buffer

This patch adds a new interface into the ring buffer that allows a
page to be read from the ring buffer on a given CPU. For every page
read, one must also be given to allow for a "swap" of the pages.

 rpage = ring_buffer_alloc_read_page(buffer);
 if (!rpage)
	goto err;
 ret = ring_buffer_read_page(buffer, &rpage, cpu, full);
 if (!ret)
	goto empty;
 process_page(rpage);
 ring_buffer_free_read_page(rpage);

The caller of these functions must handle any waits that are
needed to wait for new data. The ring_buffer_read_page will simply
return 0 if there is no data, or if "full" is set and the writer
is still on the current page.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Steven Rostedt 2008-12-02 15:34:07 -05:00 • committed by Ingo Molnar
parent abc9b56d66
commit 8789a9e7df
2 changed files with 171 additions and 0 deletions
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5
include/linux/ring_buffer.h
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@ -124,6 +124,11 @@ void tracing_on(void);
void tracing_off(void);
void tracing_off_permanent(void);
void *ring_buffer_alloc_read_page(struct ring_buffer *buffer);
void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data);
int ring_buffer_read_page(struct ring_buffer *buffer,
void **data_page, int cpu, int full);
enum ring_buffer_flags {
RB_FL_OVERWRITE = 1 << 0,
};