Hi, some thoughts on shared futexes;
Could we get rid of the mmap_sem on the shared futexes in the following manner: - do a page table walk to find the pte; - get a page using pfn_to_page (skipping VM_PFNMAP) - get the futex key from page->mapping->host and page->index and offset from addr % PAGE_SIZE. or given a key: - lookup the page from key.shared.inode->i_mapping by key.shared.pgoff possibly loading the page using mapping->a_ops->readpage(). then: - perform the futex operation on a kmap of the page This should all work except for VM_PFNMAP. Since the address is passed from userspace we cannot trust it to not point into a VM_PFNMAP area. However, with the RCU VMA lookup patches I'm working on we could do that check without holding locks and without exclusive cachelines; the question is, is that good enough? Or is there an alternative way of determining a pfnmap given a pfn/struct page? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
