void unlock_page (struct page * page);
Unlocks the page and wakes up sleepers in ___wait_on_page_locked. Also wakes sleepers in wait_on_page_writeback because the wakeup mechananism between PageLocked pages and PageWriteback pages is shared. But that's OK - sleepers in wait_on_page_writeback just go back to sleep.
The first mb is necessary to safely close the critical section opened by the TestSetPageLocked, the second mb is necessary to enforce ordering between the clear_bit and the read of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked).
Unlocks the page and wakes up sleepers in ___wait_on_page_locked. Also wakes sleepers in wait_on_page_writeback because the wakeup mechananism between PageLocked pages and PageWriteback pages is shared. But that's OK - sleepers in wait_on_page_writeback just go back to sleep.
The first mb is necessary to safely close the critical section opened by the TestSetPageLocked, the second mb is necessary to enforce ordering between the clear_bit and the read of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked).