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    SubjectRe: [PATCH 3/5] ring-buffer: read page interface
    On Tue, 02 Dec 2008 15:34:07 -0500
    Steven Rostedt <rostedt@goodmis.org> wrote:

    > From: Steven Rostedt <srostedt@redhat.com>
    >
    > 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.
    >
    > ...
    >
    > +static inline void *
    > +__rb_data_page_index(struct buffer_data_page *page, unsigned index)
    > +{
    > + return page->data + index;
    > +}

    Many kernel developers will fall over stunned and confused when they
    see a variable called `page' which does not have type `struct page *'.
    This is a very strong kernel convention and this code tromps all over
    it :(

    How's about renaming all of these everywhere to `bpage' or whatever?

    >
    > ...
    >
    > + if (!local_read(&cpu_buffer->reader_page->page->commit))
    >

    Rusty (I think it was Rusty) has convincingly argued that local_t is
    irredeemably busted. I forget the details?



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