From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 71012 invoked by alias); 16 Jan 2017 13:34:51 -0000 Mailing-List: contact gdb-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-owner@sourceware.org Received: (qmail 70987 invoked by uid 89); 16 Jan 2017 13:34:50 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-5.1 required=5.0 tests=BAYES_00,RP_MATCHES_RCVD,SPF_PASS autolearn=ham version=3.3.2 spammy=non-inherited, noninherited X-Spam-User: qpsmtpd, 2 recipients X-HELO: foss.arm.com Received: from foss.arm.com (HELO foss.arm.com) (217.140.101.70) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Mon, 16 Jan 2017 13:34:49 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 8FF301515; Mon, 16 Jan 2017 05:34:48 -0800 (PST) Received: from e103592.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 95CC23F220; Mon, 16 Jan 2017 05:34:46 -0800 (PST) Date: Mon, 16 Jan 2017 13:34:00 -0000 From: Dave Martin To: Yao Qi Cc: linux-arch@vger.kernel.org, Florian Weimer , libc-alpha@sourceware.org, Ard Biesheuvel , Marc Zyngier , gdb@sourceware.org, Joseph Myers , Szabolcs Nagy , linux-arm-kernel@lists.infradead.org, Alan Hayward , Torvald Riegel , Christoffer Dall Subject: Re: [RFC PATCH 07/10] arm64/sve: Add vector length inheritance control Message-ID: <20170116133443.GP3699@e103592.cambridge.arm.com> References: <1484220369-23970-1-git-send-email-Dave.Martin@arm.com> <1484220369-23970-8-git-send-email-Dave.Martin@arm.com> <20170116122755.GH28060@E107787-LIN> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170116122755.GH28060@E107787-LIN> User-Agent: Mutt/1.5.23 (2014-03-12) X-SW-Source: 2017-01/txt/msg00022.txt.bz2 On Mon, Jan 16, 2017 at 12:27:55PM +0000, Yao Qi wrote: > On 17-01-12 11:26:06, Dave Martin wrote: > > Currently the vector length is inherited across both fork() and > > exec(). > > > > Inheritance across fork() is desirable both for creating a copy of > > a process (traditional fork) or creating a thread (where we want > > all threads to share the same VL by default). > > > > Inheritance across exec() is less desirable, because of the ABI > > impact of large vector lengths on the size of the signal frame -- > > when running a new binary, there is no guarantee that the new > > binary is compatible with these ABI changes. > > > > This flag makes the vector length non-inherited by default. > > Can we make vector length inherited across fork but non-inherited > across exec by default? That is the behaviour: I always inherit across fork/clone, since you are still running the same binary after those. I could word the commit message a bit more clearly here. Cheers ---Dave