Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758042Ab1ELVy7 (ORCPT ); Thu, 12 May 2011 17:54:59 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:49449 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757916Ab1ELVy6 (ORCPT ); Thu, 12 May 2011 17:54:58 -0400 Date: Thu, 12 May 2011 23:54:52 +0200 From: Ingo Molnar To: Stephane Eranian Cc: Linus Torvalds , Arnaldo Carvalho de Melo , LKML Subject: Re: [BUG] perf: bogus correlation of kernel symbols Message-ID: <20110512215452.GB20939@elte.hu> References: <20110512213657.GC17596@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.3.1 -2.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1297 Lines: 37 * Stephane Eranian wrote: > >> [...]?So much for having perf in the kernel source tree to keep things?in > >> sync... > > > > What do you mean? > > I meant that when this kptr feature was added, people should have scanned the > entire tree (include tools/perf) to look for potential impact on programs > relying on /proc/kallsyms. Having perf in the tree should have made this > easier to catch. That's all. It was noticed in another case when there was kallsyms twiddling going on so it depends. What wasnt noticed here was how the present but zero value symbols: 0000000000000000 D irq_stack_union 0000000000000000 D __per_cpu_start 0000000000000000 D gdt_page 0000000000000000 d exception_stacks 0000000000000000 d tlb_vector_offset 0000000000000000 d shared_msrs 0000000000000000 d cpu_tsc_khz caused the symbol code of perf consider them non-existing. Perf being in-tree wont magically avoid all bugs, so you should not expect that magical effect from tool integration into the kernel tree. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/