From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754119Ab0IDBSY (ORCPT ); Fri, 3 Sep 2010 21:18:24 -0400 Received: from mail-qw0-f46.google.com ([209.85.216.46]:59457 "EHLO mail-qw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753410Ab0IDBR5 (ORCPT ); Fri, 3 Sep 2010 21:17:57 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:to:cc:subject:date:message-id:x-mailer:in-reply-to:references; b=QLcMDifwjA2ZilhSCCaXhBOmkD7BQh0Y2J+FDVqXAGAvYSyIA9zJD6n77mAH51uq4c KQJTc8aL2Mo+QC3EMO1zgQGI9iMTo7Cu/TGrYyuInXD94IdSLD9J2B1EpoiX7bCSjYN7 oASBOAykFpzaEZgoU8taVg+pPTXerDnZK4lYg= From: Brian Gerst To: hpa@zytor.com Cc: x86@kernel.org, linux-kernel@vger.kernel.org, penberg@kernel.org Subject: [PATCH 05/12] x86-64: Disable preemption when using TS_USEDFPU Date: Fri, 3 Sep 2010 21:17:12 -0400 Message-Id: <1283563039-3466-6-git-send-email-brgerst@gmail.com> X-Mailer: git-send-email 1.7.2.2 In-Reply-To: <1283563039-3466-1-git-send-email-brgerst@gmail.com> References: <1283563039-3466-1-git-send-email-brgerst@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Consolidates code and fixes the below race for 64-bit. commit 9fa2f37bfeb798728241cc4a19578ce6e4258f25 Author: torvalds Date: Tue Sep 2 07:37:25 2003 +0000 Be a lot more careful about TS_USEDFPU and preemption We had some races where we testecd (or set) TS_USEDFPU together with sequences that depended on the setting (like clearing or setting the TS flag in %cr0) and we could be preempted in between, which screws up the FPU state, since preemption will itself change USEDFPU and the TS flag. This makes it a lot more explicit: the "internal" low-level FPU functions ("__xxxx_fpu()") all require preemption to be disabled, and the exported "real" functions will make sure that is the case. One case - in __switch_to() - was switched to the non-preempt-safe internal version, since the scheduler itself has already disabled preemption. BKrev: 3f5448b5WRiQuyzAlbajs3qoQjSobw Signed-off-by: Brian Gerst --- arch/x86/include/asm/i387.h | 15 --------------- arch/x86/kernel/process_64.c | 2 +- 2 files changed, 1 insertions(+), 16 deletions(-) diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h index 88065e3..8b40a83 100644 --- a/arch/x86/include/asm/i387.h +++ b/arch/x86/include/asm/i387.h @@ -387,19 +387,6 @@ static inline void irq_ts_restore(int TS_state) stts(); } -#ifdef CONFIG_X86_64 - -static inline void save_init_fpu(struct task_struct *tsk) -{ - __save_init_fpu(tsk); - stts(); -} - -#define unlazy_fpu __unlazy_fpu -#define clear_fpu __clear_fpu - -#else /* CONFIG_X86_32 */ - /* * These disable preemption on their own and are safe */ @@ -425,8 +412,6 @@ static inline void clear_fpu(struct task_struct *tsk) preempt_enable(); } -#endif /* CONFIG_X86_64 */ - /* * i387 state interaction */ diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 3d9ea53..b3d7a3a 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -424,7 +424,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) load_TLS(next, cpu); /* Must be after DS reload */ - unlazy_fpu(prev_p); + __unlazy_fpu(prev_p); /* Make sure cpu is ready for new context */ if (preload_fpu) -- 1.7.2.2