From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753346AbbAMQeC (ORCPT ); Tue, 13 Jan 2015 11:34:02 -0500 Received: from mx1.redhat.com ([209.132.183.28]:33720 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753066AbbAMQeA (ORCPT ); Tue, 13 Jan 2015 11:34:00 -0500 Message-ID: <54B548EA.7020005@redhat.com> Date: Tue, 13 Jan 2015 11:33:46 -0500 From: Rik van Riel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: Oleg Nesterov CC: linux-kernel@vger.kernel.org, mingo@redhat.com, hpa@zytor.com, matt.fleming@intel.com, bp@suse.de, pbonzini@redhat.com, tglx@linutronix.de, luto@amacapital.net Subject: Re: [RFC PATCH 05/11] x86,fpu: ensure FPU state is reloaded from memory if task is traced References: <1421012793-30106-1-git-send-email-riel@redhat.com> <1421012793-30106-6-git-send-email-riel@redhat.com> <20150113161938.GA24447@redhat.com> In-Reply-To: <20150113161938.GA24447@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 01/13/2015 11:19 AM, Oleg Nesterov wrote: > On 01/11, riel@redhat.com wrote: >> >> @@ -412,8 +412,14 @@ static inline void switch_fpu_prepare(struct >> task_struct *old, struct task_struc bool preload = >> tsk_used_math(new) && (use_eager_fpu() || new->thread.fpu_counter >> > 5); if (__thread_has_fpu(old)) { - if (!__save_init_fpu(old)) >> + /* + * Make sure the FPU state is restored from memory next >> time, + * if the task has an FPU exception pending, or the >> task's in + * memory FPU state could be changed by a debugger. >> + */ + if (!__save_init_fpu(old) || >> task_is_stopped_or_traced(old)) cpu = ~0; > > Well, if debugger wants to change FPU state, it should call > init_fpu() which resets .last_cpu ? Does the ptrace (and utrace, and ... ) code actually do that? > Plus "is_stopped" is not needed, ptracer no longer can do STOPPED > -> TRACED transition. I will remove _is_stopped. - -- All rights reversed -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQEcBAEBAgAGBQJUtUjqAAoJEM553pKExN6DtXIIAKzZj0zbQq4cQ08oKr6zMZqn qz0MyTD91+1phywX+CFOoQ45tQUzAzpAw2k+2yGUFWhMsdEQEaANirK3stZj2Lte Jh/VTlX1Y2ZpjoHFH69S6+5jy6nAqHaUTsMQ3jiXvi4YkzjYn9JGYY/N1E7BgRV/ T2HozdKD9+h27NetPaVPymZOwgIP5Qykbl77mH3SqwFaah/8DI3K3rMem5Ze88op hlk3FFAgB4n8WsHDKtDXOARnF1dYCnxyR9f+3mRIuLgCdYDvktXOizTUumsbojE6 hMN9lwM/r469kVh3L20asAbXNdCAAG6U/tZcoQOizGrj/L9M4V5ACAzn7w+y+kE= =8971 -----END PGP SIGNATURE-----