Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753777AbaBOWnI (ORCPT ); Sat, 15 Feb 2014 17:43:08 -0500 Received: from mail-ve0-f182.google.com ([209.85.128.182]:34564 "EHLO mail-ve0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753320AbaBOWnF (ORCPT ); Sat, 15 Feb 2014 17:43:05 -0500 MIME-Version: 1.0 In-Reply-To: <20140215222844.GA18201@redhat.com> References: <20140212010941.GM18016@ZenIV.linux.org.uk> <20140212040358.GA25327@redhat.com> <20140212042215.GN18016@ZenIV.linux.org.uk> <20140212054043.GB13997@dastard> <20140212071829.GE13997@dastard> <20140214002427.GN13997@dastard> <20140214160123.GA28125@redhat.com> <20140215222356.GU13997@dastard> <20140215222844.GA18201@redhat.com> Date: Sat, 15 Feb 2014 14:43:03 -0800 X-Google-Sender-Auth: swUowRsGrSNTEo6YcDhjGhC_ZE0 Message-ID: Subject: Re: 3.14-rc2 XFS backtrace because irqs_disabled. From: Linus Torvalds To: Dave Jones , Dave Chinner , Linus Torvalds , Al Viro , Eric Sandeen , Linux Kernel , xfs@oss.sgi.com Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Feb 15, 2014 at 2:28 PM, Dave Jones wrote: > > I've got a shitload of debug options enabled, which may explain it. > Or perhaps that new STACK_PROTECTOR_STRONG stuff ? Well, a lot of it is just the callee-saved registers. The compiler will tend to preferentially allocate registers in the callee-trashed registers, but if the function isn't a leaf function, any registers that are live around a function call will have to be saved somewhere - either explicitly around the function call, or - more likely - in callee-saved registers that then get saved in the prologue/epilogue of the function. And this will happen even in leaf functions when there is enough register pressure that the callee-trashed registers aren't sufficient (which is pretty common). So saving 5-6 registers on the stack (in addition to any actual stack frame) is pretty much the norm for anything but the very simplest cases. But yeah, I'm sure some config options make it worse. STACK_PROTECTOR_STRONG could easily be one of those. Linus -- 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/