From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_2 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 603B9C10DCE for ; Tue, 10 Mar 2020 19:38:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 39C9C22B48 for ; Tue, 10 Mar 2020 19:38:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727531AbgCJTiW (ORCPT ); Tue, 10 Mar 2020 15:38:22 -0400 Received: from mail.kernel.org ([198.145.29.99]:35214 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726729AbgCJTiW (ORCPT ); Tue, 10 Mar 2020 15:38:22 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id EA3C3208E4; Tue, 10 Mar 2020 19:38:21 +0000 (UTC) Date: Tue, 10 Mar 2020 15:38:20 -0400 From: Steven Rostedt To: Artem Savkov Cc: linux-kernel@vger.kernel.org, live-patching@vger.kernel.org Subject: Re: [PATCH v2] ftrace: return first found result in lookup_rec() Message-ID: <20200310153820.436a8583@gandalf.local.home> In-Reply-To: <20200306174317.21699-1-asavkov@redhat.com> References: <20200306121246.5dac2573@gandalf.local.home> <20200306174317.21699-1-asavkov@redhat.com> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: live-patching-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org On Fri, 6 Mar 2020 18:43:17 +0100 Artem Savkov wrote: > It appears that ip ranges can overlap so. In that case lookup_rec() > returns whatever results it got last even if it found nothing in last > searched page. > > This breaks an obscure livepatch late module patching usecase: > - load livepatch > - load the patched module > - unload livepatch > - try to load livepatch again > > To fix this return from lookup_rec() as soon as it found the record > containing searched-for ip. This used to be this way prior lookup_rec() > introduction. > > v2: break instead of two returns Thanks Artem, I applied your patch. But just an FYI, it's best to place the "v2" statement below the three dashes "---" so that it doesn't get pulled into the git commit when this patch is applied via a script. -- Steve > > Fixes: 7e16f581a817 ("ftrace: Separate out functionality from ftrace_location_range()") > Signed-off-by: Artem Savkov > --- > kernel/trace/ftrace.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > index 3f7ee102868a..fd81c7de77a7 100644 > --- a/kernel/trace/ftrace.c > +++ b/kernel/trace/ftrace.c > @@ -1547,6 +1547,8 @@ static struct dyn_ftrace *lookup_rec(unsigned long start, unsigned long end) > rec = bsearch(&key, pg->records, pg->index, > sizeof(struct dyn_ftrace), > ftrace_cmp_recs); > + if (rec) > + break; > } > return rec; > }