From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753143AbcFVWyw (ORCPT ); Wed, 22 Jun 2016 18:54:52 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:47175 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752814AbcFVWrE (ORCPT ); Wed, 22 Jun 2016 18:47:04 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Andy Lutomirski , Andy Lutomirski , Borislav Petkov , Brian Gerst , Denys Vlasenko , "H. Peter Anvin" , Linus Torvalds , Oleg Nesterov , Peter Zijlstra , Thomas Gleixner , Ingo Molnar Subject: [PATCH 4.6 60/81] x86/entry/traps: Dont force in_interrupt() to return true in IST handlers Date: Wed, 22 Jun 2016 15:46:23 -0700 Message-Id: <20160622223746.300805627@linuxfoundation.org> X-Mailer: git-send-email 2.9.0 In-Reply-To: <20160622223743.240652686@linuxfoundation.org> References: <20160622223743.240652686@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Andy Lutomirski commit aaee8c3c5cce2d9107310dd9f3026b4f901d441c upstream. Forcing in_interrupt() to return true if we're not in a bona fide interrupt confuses the softirq code. This fixes warnings like: NOHZ: local_softirq_pending 282 ... which can happen when running things like selftests/x86. This will change perf's static percpu buffer usage in IST context. I think this is okay, and it's changing the behavior to match historical (pre-4.0) behavior. Signed-off-by: Andy Lutomirski Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Thomas Gleixner Fixes: 959274753857 ("x86, traps: Track entry into and exit from IST context") Link: http://lkml.kernel.org/r/cdc215f94d118d691d73df35275022331156fb45.1464130360.git.luto@kernel.org Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/traps.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -95,6 +95,12 @@ static inline void cond_local_irq_disabl local_irq_disable(); } +/* + * In IST context, we explicitly disable preemption. This serves two + * purposes: it makes it much less likely that we would accidentally + * schedule in IST context and it will force a warning if we somehow + * manage to schedule by accident. + */ void ist_enter(struct pt_regs *regs) { if (user_mode(regs)) { @@ -109,13 +115,7 @@ void ist_enter(struct pt_regs *regs) rcu_nmi_enter(); } - /* - * We are atomic because we're on the IST stack; or we're on - * x86_32, in which case we still shouldn't schedule; or we're - * on x86_64 and entered from user mode, in which case we're - * still atomic unless ist_begin_non_atomic is called. - */ - preempt_count_add(HARDIRQ_OFFSET); + preempt_disable(); /* This code is a bit fragile. Test it. */ RCU_LOCKDEP_WARN(!rcu_is_watching(), "ist_enter didn't work"); @@ -123,7 +123,7 @@ void ist_enter(struct pt_regs *regs) void ist_exit(struct pt_regs *regs) { - preempt_count_sub(HARDIRQ_OFFSET); + preempt_enable_no_resched(); if (!user_mode(regs)) rcu_nmi_exit(); @@ -154,7 +154,7 @@ void ist_begin_non_atomic(struct pt_regs BUG_ON((unsigned long)(current_top_of_stack() - current_stack_pointer()) >= THREAD_SIZE); - preempt_count_sub(HARDIRQ_OFFSET); + preempt_enable_no_resched(); } /** @@ -164,7 +164,7 @@ void ist_begin_non_atomic(struct pt_regs */ void ist_end_non_atomic(void) { - preempt_count_add(HARDIRQ_OFFSET); + preempt_disable(); } static nokprobe_inline int