Messages in this thread | | | From | "Chen, Kenneth W" <> | Subject | RE: Fix unlock_buffer() to work the same way as bit_unlock() | Date | Tue, 28 Mar 2006 22:50:41 -0800 |
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Nick Piggin wrote on Tuesday, March 28, 2006 12:11 AM > OK, that's fair enough and I guess you do need a barrier there. > However, should the mb__after barrier still remain? The comment > in wake_up_bit suggests yes, and there is similar code in > unlock_page.
Question on unlock_page:
void fastcall unlock_page(struct page *page) { smp_mb__before_clear_bit(); if (!TestClearPageLocked(page)) BUG(); smp_mb__after_clear_bit(); wake_up_page(page, PG_locked); }
Assuming test_and_clear_bit() on all arch does what the API is called for with full memory fence around the atomic op, why do you need smp_mb__before_clear_bit and smp_mb__after_clear_bit? Aren't they redundant?
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