Hi Michael, At the current man page for shmat(2)[1], there is no mentioning whether the returned memory address of shmat(2) will be page size aligned or not. As that is quite important to many applications(e.g., those that use locks heavily and would like to avoid some locks by some atomic guarantees provided by the CPU), it would be great to specify that for Linux. I walked down the current implementation of shmat(2) in the latest kernel src and found that shmat(2) does return a page size aligned memory address: SYSCALL_DEFINE3(shmat, int, shmid, char __user *, shmaddr, int, shmflg) -> do_shmat(...) -> do_mmap_pgoff(...) -> do_mmap(...) -> get_unmapped_area(...) -> get_area(...) -> offset_in_page(addr) there is a `offset_in_page(addr)' assertion at the end and if that is true a -EINVAL would be returned, by which we can be sure that shmat(2) will return a page size aligned memory address on success[2]. I will create a patch later if that is acceptable. Thanks, Yubin [1]: http://man7.org/linux/man-pages/man2/shmat.2.html [2]: there is also a `offset_in_page(2)' in get_unmapped_area(...), but that doesn't lead to -EINVAL...I am not sure whether the logic of that code is right. -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
