Re: [PATCH 3/3] ring-buffer: add design document

[Steven Rostedt]

On Thu, 11 Jun 2009, Hidetoshi Seto wrote:
> Steven Rostedt wrote:
> > +
> > +  +------+
> > +  |reader|          RING BUFFER
> > +  |page  |-------------------+
> > +  +------+ <---------------+ v
> > +    |  ^          +---+   +---+   +---+
> > +    |  |          |   |-->|   |-->|   |
> > +    |  |          |   |<--|   |<--|   |<-+
> > +    |  |          +---+   +---+   +---+  |
> > +    |  |             |             ^ |   |
> > +    |  |             +-------------+ |   |
> > +    |  +-----------------------------+   |
> > +    +------------------------------------+
> 
> It seems the middle of three pages have 2 prev arrows... ?

Yes that is a mistake. Thanks, I'll fix it.
> > +
> > +It does a cmpxchg with the pointer to the previous head page to make it
> > +point to the reader page. Note that the new pointer does not have the HEADER
> > +flag set.  This action atomically moves the head page forward.
> > +
> > +  +------+
> > +  |reader|          RING BUFFER
> > +  |page  |-------H-----------+
> > +  +------+ <---------------+ v
> > +    |  ^          +---+   +---+   +---+
> > +    |  |          |   |-->|   |-->|   |
> > +    |  |          |   |<--|   |<--|   |<-+
> > +    |  |          +---+   +---+   +---+  |
> > +    |  |             |             ^ |   |
> > +    |  |             +-------------+ |   |
> > +    |  +-----------------------------+   |
> > +    +------------------------------------+
> > +
> 
> Ditto.

Ditto too ;-)

Thanks,

-- Steve

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