* Oleg Nesterov <o...@redhat.com> [2012-09-23 22:19:45]: > A separate patch for better documentation. > > set_swbp()->is_swbp_at_addr() is not needed for correctness, it is > harmless to do the unnecessary __replace_page(old_page, new_page) > when these 2 pages are identical. > > And it can not be counted as optimization. mmap/register races are > very unlikely, while in the likely case is_swbp_at_addr() adds the > extra get_user_pages() even if the caller is uprobe_mmap(current->mm) > and returns false. > > Note also that the semantics/usage of is_swbp_at_addr() in uprobe.c > is confusing. set_swbp() uses it to detect the case when this insn > was already modified by uprobes, that is why it should always compare > the opcode with UPROBE_SWBP_INSN even if the hardware (like powerpc) > has other trap insns. It doesn't matter if this "int3" was in fact > installed by gdb or application itself, we are going to "steal" this > breakpoint anyway and execute the original insn from vm_file even if > it no longer matches the memory. > > OTOH, handle_swbp()->find_active_uprobe() uses is_swbp_at_addr() to > figure out whether we need to send SIGTRAP or not if we can not find > uprobe, so in this case it should return true for all trap variants, > not only for UPROBE_SWBP_INSN. > > This patch removes set_swbp()->is_swbp_at_addr(), the next patches > will remove it from set_orig_insn() which is similar to set_swbp() > in this respect. So the only caller will be handle_swbp() and we > can make its semantics clear. > > Signed-off-by: Oleg Nesterov <o...@redhat.com>
Acked-by: Srikar Dronamraju <sri...@linux.vnet.ibm.com> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
