From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752922AbbCWMWF (ORCPT ); Mon, 23 Mar 2015 08:22:05 -0400 Received: from terminus.zytor.com ([198.137.202.10]:41227 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752902AbbCWMV7 (ORCPT ); Mon, 23 Mar 2015 08:21:59 -0400 Date: Mon, 23 Mar 2015 05:21:37 -0700 From: tip-bot for Oleg Nesterov Message-ID: Cc: priikone@iki.fi, dave.hansen@intel.com, sbsiddha@gmail.com, luto@amacapital.net, tglx@linutronix.de, quentin.casasnovas@oracle.com, oleg@redhat.com, linux-kernel@vger.kernel.org, fenghua.yu@intel.com, torvalds@linux-foundation.org, bp@suse.de, mingo@kernel.org, hpa@zytor.com, riel@redhat.com Reply-To: tglx@linutronix.de, quentin.casasnovas@oracle.com, sbsiddha@gmail.com, luto@amacapital.net, dave.hansen@intel.com, priikone@iki.fi, hpa@zytor.com, riel@redhat.com, mingo@kernel.org, torvalds@linux-foundation.org, bp@suse.de, fenghua.yu@intel.com, oleg@redhat.com, linux-kernel@vger.kernel.org In-Reply-To: <20150313173030.GA31217@redhat.com> References: <20150313173030.GA31217@redhat.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/fpu] x86/fpu: Don't abuse drop_init_fpu() in flush_thread() Git-Commit-ID: f893959b0898bd876673adbeb6798bdf25c034d7 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: f893959b0898bd876673adbeb6798bdf25c034d7 Gitweb: http://git.kernel.org/tip/f893959b0898bd876673adbeb6798bdf25c034d7 Author: Oleg Nesterov AuthorDate: Fri, 13 Mar 2015 18:30:30 +0100 Committer: Ingo Molnar CommitDate: Mon, 23 Mar 2015 10:13:58 +0100 x86/fpu: Don't abuse drop_init_fpu() in flush_thread() flush_thread() -> drop_init_fpu() is suboptimal and confusing. It does drop_fpu() or restore_init_xstate() depending on !use_eager_fpu(). But flush_thread() too checks eagerfpu right after that, and if it is true then restore_init_xstate() just burns CPU for no reason. We are going to load init_xstate_buf again after we set used_math()/user_has_fpu(), until then the FPU state can't survive after switch_to(). Remove it, and change the "if (!use_eager_fpu())" to call drop_fpu(). While at it, clean up the tsk/current usage. Signed-off-by: Oleg Nesterov Signed-off-by: Borislav Petkov Cc: Andy Lutomirski Cc: Dave Hansen Cc: Fenghua Yu Cc: Linus Torvalds Cc: Pekka Riikonen Cc: Quentin Casasnovas Cc: Rik van Riel Cc: Suresh Siddha Link: http://lkml.kernel.org/r/20150313173030.GA31217@redhat.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/process.c | 15 ++++++--------- 1 file changed, 6 insertions(+), 9 deletions(-) diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 6b05829..1d2ebad 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -132,17 +132,14 @@ void flush_thread(void) flush_ptrace_hw_breakpoint(tsk); memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array)); - drop_init_fpu(tsk); - /* - * Free the FPU state for non xsave platforms. They get reallocated - * lazily at the first use. - */ - if (!use_eager_fpu()) + if (!use_eager_fpu()) { + /* FPU state will be reallocated lazily at the first use. */ + drop_fpu(tsk); free_thread_xstate(tsk); - else if (!used_math()) { + } else if (!used_math()) { /* kthread execs. TODO: cleanup this horror. */ - if (WARN_ON(init_fpu(current))) - force_sig(SIGKILL, current); + if (WARN_ON(init_fpu(tsk))) + force_sig(SIGKILL, tsk); user_fpu_begin(); restore_init_xstate(); }