Messages in this thread | | | Date | Wed, 02 Sep 2009 15:37:35 +0800 | From | Lai Jiangshan <> | Subject | Re: [PATCH 1/3] tracing: make splice_read work when data is sufficient |
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Frederic Weisbecker wrote: > On Tue, Sep 01, 2009 at 08:29:53PM +0800, Lai Jiangshan wrote: >> Frederic Weisbecker wrote: >>>> */ >>>> + cpu_buffer->reader_page->read = 0; >>> >>> >>> Wasn't this reset done before? >>> >>> >> This is not reset. It is still used just before this line. > > > > Yeah but after that it's not used anymore because this page
It may be used in next rb_get_reader_page(), see next:
> won't anymore be used as a reader page but will be integrated > as a writable ring buffer page. > > One day it may be reused as a reader page still, but before > any use, rb_reset_reader_page() will be called to reset this offset. > > So I just don't understand why you need to do that. > >
Oh, I know what you mean.
My patch changes the rb_get_reader_page().
rb_get_reader_page(cpu_buffer, 0) is still the same behavior exactly as before.
But rb_get_reader_page(cpu_buffer, 1) returns NULL when reader page is empty and head page is not full, in this condition, we do local_set(&cpu_buffer->reader_page->page->commit, 0), so we need reset cpu_buffer->reader_page->read. Because cpu_buffer->reader_page will be accessed again in next rb_get_reader_page().
Lai
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