Messages in this thread | | | Date | Tue, 2 Dec 2008 13:36:54 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH 3/5] ring-buffer: read page interface |
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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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