Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756033AbZFJMoS (ORCPT ); Wed, 10 Jun 2009 08:44:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755586AbZFJMoK (ORCPT ); Wed, 10 Jun 2009 08:44:10 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:45337 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755469AbZFJMoJ (ORCPT ); Wed, 10 Jun 2009 08:44:09 -0400 Subject: Re: [tip:tracing/core] x86, bts: reenable ptrace branch trace support From: Peter Zijlstra To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, markus.t.metzger@intel.com, tglx@linutronix.de, oleg@redhat.com, mingo@elte.hu Cc: linux-tip-commits@vger.kernel.org In-Reply-To: References: <20090424094448.A30216@sedona.ch.intel.com> Content-Type: text/plain Content-Transfer-Encoding: 7bit Date: Wed, 10 Jun 2009 14:44:03 +0200 Message-Id: <1244637843.13761.11786.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.26.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1580 Lines: 37 On Thu, 2009-05-07 at 09:25 +0000, tip-bot for Markus Metzger wrote: > Commit-ID: 7e0bfad24d85de7cf2202a7b0ce51de11a077b21 > Gitweb: http://git.kernel.org/tip/7e0bfad24d85de7cf2202a7b0ce51de11a077b21 > Author: Markus Metzger > AuthorDate: Fri, 24 Apr 2009 09:44:48 +0200 > Committer: Ingo Molnar > CommitDate: Fri, 24 Apr 2009 10:18:51 +0200 > > x86, bts: reenable ptrace branch trace support > > The races found by Oleg Nesterov have been fixed. > > Reenable branch trace support. > > Signed-off-by: Markus Metzger > Acked-by: Oleg Nesterov > LKML-Reference: <20090424094448.A30216@sedona.ch.intel.com> > Signed-off-by: Ingo Molnar OK, this whole BTS thing worries me because it seems to expose too much of the Intel Debug Store thingy to the outside world. The thing is, once we do PEBS from inside the kernel, we'll have to share the debug store, and the way this thing sets it up isn't really going to work. So what I'd like to see is having this debug store removed from the interface and abstracted away as cpu resource -- a single page when in use should suffice I think. If you want to expose a buffer to userspace, use the regular mmap() interface and fill those pages from the DS interrupt handler. -- 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/