From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754535Ab3BCPMi (ORCPT ); Sun, 3 Feb 2013 10:12:38 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:34347 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754389Ab3BCO42 (ORCPT ); Sun, 3 Feb 2013 09:56:28 -0500 Message-Id: <20130203144649.101814520@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Sun, 03 Feb 2013 15:47:41 +0100 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: akpm@linux-foundation.org, Stephen Boyd , Patrik Kluba , Russell King Subject: [ 057/128] ARM: 7627/1: Predicate preempt logic on PREEMP_COUNT not PREEMPT alone In-Reply-To: <20130203144644.035172954@decadent.org.uk> X-SA-Exim-Connect-IP: 151.216.67.5 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Stephen Boyd commit 568dca15aa2a0f4ddee255894ec393a159f13147 upstream. Patrik Kluba reports that the preempt count becomes invalid due to the preempt_enable() call being unbalanced with a preempt_disable() call in the vfp assembly routines. This happens because preempt_enable() and preempt_disable() update preempt counts under PREEMPT_COUNT=y but the vfp assembly routines do so under PREEMPT=y. In a configuration where PREEMPT=n and DEBUG_ATOMIC_SLEEP=y, PREEMPT_COUNT=y and so the preempt_enable() call in VFP_bounce() keeps subtracting from the preempt count until it goes negative. Fix this by always using PREEMPT_COUNT to decided when to update preempt counts in the ARM assembly code. Signed-off-by: Stephen Boyd Reported-by: Patrik Kluba Tested-by: Patrik Kluba Signed-off-by: Russell King Signed-off-by: Ben Hutchings --- arch/arm/vfp/entry.S | 6 +++--- arch/arm/vfp/vfphw.S | 4 ++-- 2 files changed, 5 insertions(+), 5 deletions(-) diff --git a/arch/arm/vfp/entry.S b/arch/arm/vfp/entry.S index cc926c9..323ce1a 100644 --- a/arch/arm/vfp/entry.S +++ b/arch/arm/vfp/entry.S @@ -22,7 +22,7 @@ @ IRQs disabled. @ ENTRY(do_vfp) -#ifdef CONFIG_PREEMPT +#ifdef CONFIG_PREEMPT_COUNT ldr r4, [r10, #TI_PREEMPT] @ get preempt count add r11, r4, #1 @ increment it str r11, [r10, #TI_PREEMPT] @@ -35,7 +35,7 @@ ENTRY(do_vfp) ENDPROC(do_vfp) ENTRY(vfp_null_entry) -#ifdef CONFIG_PREEMPT +#ifdef CONFIG_PREEMPT_COUNT get_thread_info r10 ldr r4, [r10, #TI_PREEMPT] @ get preempt count sub r11, r4, #1 @ decrement it @@ -53,7 +53,7 @@ ENDPROC(vfp_null_entry) __INIT ENTRY(vfp_testing_entry) -#ifdef CONFIG_PREEMPT +#ifdef CONFIG_PREEMPT_COUNT get_thread_info r10 ldr r4, [r10, #TI_PREEMPT] @ get preempt count sub r11, r4, #1 @ decrement it diff --git a/arch/arm/vfp/vfphw.S b/arch/arm/vfp/vfphw.S index ea0349f..dd5e56f 100644 --- a/arch/arm/vfp/vfphw.S +++ b/arch/arm/vfp/vfphw.S @@ -168,7 +168,7 @@ vfp_hw_state_valid: @ else it's one 32-bit instruction, so @ always subtract 4 from the following @ instruction address. -#ifdef CONFIG_PREEMPT +#ifdef CONFIG_PREEMPT_COUNT get_thread_info r10 ldr r4, [r10, #TI_PREEMPT] @ get preempt count sub r11, r4, #1 @ decrement it @@ -192,7 +192,7 @@ look_for_VFP_exceptions: @ not recognised by VFP DBGSTR "not VFP" -#ifdef CONFIG_PREEMPT +#ifdef CONFIG_PREEMPT_COUNT get_thread_info r10 ldr r4, [r10, #TI_PREEMPT] @ get preempt count sub r11, r4, #1 @ decrement it