Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964977AbbD0Ouy (ORCPT ); Mon, 27 Apr 2015 10:50:54 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34613 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964792AbbD0Oux (ORCPT ); Mon, 27 Apr 2015 10:50:53 -0400 Date: Mon, 27 Apr 2015 16:49:31 +0200 From: Oleg Nesterov To: Bobby Powers Cc: linux-kernel@vger.kernel.org, x86@kernel.org, Borislav Petkov , Ingo Molnar , Andy Lutomirski , Dave Hansen , Fenghua Yu , Linus Torvalds , Pekka Riikonen , Quentin Casasnovas , Rik van Riel , Suresh Siddha Subject: Re: [PATCH] x86/fpu: always restore_xinit_state() when !use_eager_cpu() Message-ID: <20150427144931.GA25690@redhat.com> References: <1430085869-4327-1-git-send-email-bobbypowers@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1430085869-4327-1-git-send-email-bobbypowers@gmail.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2041 Lines: 62 On 04/26, Bobby Powers wrote: > > Oleg's commit f893959b ("x86/fpu: Don't abuse drop_init_fpu() in > flush_thread()") removed drop_init_fpu() usage from flush_thread. > This seems to break things for me - the Go 1.4 test suite fails all > over the place with floating point comparision errors (offending > commit found through bisection). Ah, sorry. And thanks a lot! I simply can't understand what I was thinking about. Of course, we need to reset FPU state unconditionally, exec should start with the new FPU state. ACK, but could you please fix the subject and update the changelog? The subject says "when !use_eager_cpu()", but we need to do this if use_eager_cpu() == T. > Note: used_math() looks at current, and should be switch to > tsk_used_math(tsk), but even with this I see test suite breakage. Agreed, tsk_used_math(tsk) looks more consistent even if used_math() is technically correct. You can change this as well. Thanks! > arch/x86/kernel/process.c | 12 +++++++----- > 1 file changed, 7 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c > index 8213da6..c820baf5 100644 > --- a/arch/x86/kernel/process.c > +++ b/arch/x86/kernel/process.c > @@ -156,11 +156,13 @@ void flush_thread(void) > /* FPU state will be reallocated lazily at the first use. */ > drop_fpu(tsk); > free_thread_xstate(tsk); > - } else if (!used_math()) { > - /* kthread execs. TODO: cleanup this horror. */ > - if (WARN_ON(init_fpu(tsk))) > - force_sig(SIGKILL, tsk); > - user_fpu_begin(); > + } else { > + if (!used_math()) { > + /* kthread execs. TODO: cleanup this horror. */ > + if (WARN_ON(init_fpu(tsk))) > + force_sig(SIGKILL, tsk); > + user_fpu_begin(); > + } > restore_init_xstate(); > } > } > -- > 2.3.6 > -- 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/