Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754395AbaFJTt4 (ORCPT ); Tue, 10 Jun 2014 15:49:56 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:35123 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754364AbaFJTtx (ORCPT ); Tue, 10 Jun 2014 15:49:53 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Vineet Gupta , Anton Kolesov , Francois Bedard , Linus Torvalds , Kamal Mostafa Subject: [PATCH 3.13 121/160] ARC: !PREEMPT: Ensure Return to kernel mode is IRQ safe Date: Tue, 10 Jun 2014 12:46:01 -0700 Message-Id: <1402429600-20477-122-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1402429600-20477-1-git-send-email-kamal@canonical.com> References: <1402429600-20477-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.13 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.13.11.3 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Vineet Gupta commit 8aa9e85adac609588eeec356e5a85059b3b819ba upstream. There was a very small race window where resume to kernel mode from a Exception Path (or pure kernel mode which is true for most of ARC exceptions anyways), was not disabling interrupts in restore_regs, clobbering the exception regs Anton found the culprit call flow (after many sleepless nights) | 1. we got a Trap from user land | 2. started to service it. | 3. While doing some stuff on user-land memory (I think it is padzero()), | we got a DataTlbMiss | 4. On return from it we are taking "resume_kernel_mode" path | 5. NEED_RESHED is not set, so we go to "return from exception" path in | restore regs. | 6. there seems to be IRQ happening Signed-off-by: Vineet Gupta Cc: Anton Kolesov Cc: Francois Bedard Signed-off-by: Linus Torvalds Signed-off-by: Kamal Mostafa --- arch/arc/kernel/entry.S | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S index 47d09d0..6e8f83a 100644 --- a/arch/arc/kernel/entry.S +++ b/arch/arc/kernel/entry.S @@ -614,11 +614,13 @@ resume_user_mode_begin: resume_kernel_mode: -#ifdef CONFIG_PREEMPT - - ; This is a must for preempt_schedule_irq() + ; Disable Interrupts from this point on + ; CONFIG_PREEMPT: This is a must for preempt_schedule_irq() + ; !CONFIG_PREEMPT: To ensure restore_regs is intr safe IRQ_DISABLE r9 +#ifdef CONFIG_PREEMPT + ; Can't preempt if preemption disabled GET_CURR_THR_INFO_FROM_SP r10 ld r8, [r10, THREAD_INFO_PREEMPT_COUNT] -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/