From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751988Ab3CAQKO (ORCPT ); Fri, 1 Mar 2013 11:10:14 -0500 Received: from mail-qc0-f174.google.com ([209.85.216.174]:55577 "EHLO mail-qc0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751346Ab3CAQJe (ORCPT ); Fri, 1 Mar 2013 11:09:34 -0500 From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , Li Zhong , Kevin Hilman , Mats Liljegren , Peter Zijlstra , Ingo Molnar , Steven Rostedt , Namhyung Kim , Andrew Morton , Thomas Gleixner Subject: [PATCH 3/5] context_tracking: Restore preempted context state after preempt_schedule_irq() Date: Fri, 1 Mar 2013 17:08:57 +0100 Message-Id: <1362154139-1139-4-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.7.5.4 In-Reply-To: <1362154139-1139-1-git-send-email-fweisbec@gmail.com> References: <1362154139-1139-1-git-send-email-fweisbec@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>From the context tracking POV, preempt_schedule_irq() behaves pretty much like an exception: It can be called anytime and schedule another task. But currently it doesn't restore the context tracking state of the preempted code on preempt_schedule_irq() return. As a result, if preempt_schedule_irq() is called in the tiny frame between user_enter() and the actual return to userspace, we resume userspace with the wrong context tracking state. Fix this by using exception_enter/exit() which are a perfect fit for this kind of issue. Signed-off-by: Frederic Weisbecker Cc: Li Zhong Cc: Kevin Hilman Cc: Mats Liljegren Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Steven Rostedt Cc: Namhyung Kim Cc: Andrew Morton Cc: Thomas Gleixner --- kernel/sched/core.c | 6 +++++- 1 files changed, 5 insertions(+), 1 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index b7b03cd..db36e11 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3074,11 +3074,13 @@ EXPORT_SYMBOL(preempt_schedule); asmlinkage void __sched preempt_schedule_irq(void) { struct thread_info *ti = current_thread_info(); + enum ctx_state prev_state; /* Catch callers which need to be fixed */ BUG_ON(ti->preempt_count || !irqs_disabled()); - user_exit(); + prev_state = exception_enter(); + do { add_preempt_count(PREEMPT_ACTIVE); local_irq_enable(); @@ -3092,6 +3094,8 @@ asmlinkage void __sched preempt_schedule_irq(void) */ barrier(); } while (need_resched()); + + exception_exit(prev_state); } #endif /* CONFIG_PREEMPT */ -- 1.7.5.4