From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754839AbbILILe (ORCPT ); Sat, 12 Sep 2015 04:11:34 -0400 Received: from mail-wi0-f172.google.com ([209.85.212.172]:34414 "EHLO mail-wi0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754776AbbILILY (ORCPT ); Sat, 12 Sep 2015 04:11:24 -0400 Date: Sat, 12 Sep 2015 10:11:20 +0200 From: Ingo Molnar To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, vincent.weaver@maine.edu, acme@kernel.org, eranian@google.com, jolsa@redhat.com, alexander.shishkin@linux.intel.com Subject: Re: [RFC][PATCH 2/3] perf: Fix u16 overflows Message-ID: <20150912081120.GB9737@gmail.com> References: <20150910161621.363774906@infradead.org> <20150910162007.946742153@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150910162007.946742153@infradead.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Peter Zijlstra wrote: > Vince reported that its possible to overflow the various size fields > and get weird stuff if you stick too many events in a group. > > Put a lid on this by requiring the fixed record size not exceed 16k. > This is still a fair amount of events (silly amount really) and leaves > plenty room for callchains and stack dwarves while also avoiding > overflowing the u16 variables. Does this leave a natural ABI extension route here, in case in the future it becomes a problem? We should take aside a value to mean 'larger record' or such? Could we list exactly which fields this concerns, in which structures? Thanks, Ingo