From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754681AbcEXWyL (ORCPT ); Tue, 24 May 2016 18:54:11 -0400 Received: from mail.kernel.org ([198.145.29.136]:37003 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752427AbcEXWyJ (ORCPT ); Tue, 24 May 2016 18:54:09 -0400 From: Andy Lutomirski To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, Borislav Petkov , Andi Kleen , Oleg Nesterov , Andy Lutomirski , stable@vger.kernel.org Subject: [PATCH v2] x86/traps: Don't force in_interrupt() to return true in IST handlers Date: Tue, 24 May 2016 15:54:04 -0700 Message-Id: X-Mailer: git-send-email 2.5.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 that 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. Cc: stable@vger.kernel.org Fixes: 959274753857 ("x86, traps: Track entry into and exit from IST context") Signed-off-by: Andy Lutomirski Message-Id: --- This is intended for x86/urgent. Changes from v1: - Get rid of the 3* crap (Linus) - Improve changelog (PeterZ) arch/x86/kernel/traps.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 06cbe25861f1..87bd6b6bf5bd 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -95,6 +95,12 @@ static inline void cond_local_irq_disable(struct pt_regs *regs) 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 *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 *regs) */ void ist_end_non_atomic(void) { - preempt_count_add(HARDIRQ_OFFSET); + preempt_disable(); } static nokprobe_inline int -- 2.5.5