From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755381AbbESHWB (ORCPT ); Tue, 19 May 2015 03:22:01 -0400 Received: from terminus.zytor.com ([198.137.202.10]:60460 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752933AbbESHV6 (ORCPT ); Tue, 19 May 2015 03:21:58 -0400 Date: Tue, 19 May 2015 00:21:23 -0700 From: tip-bot for David Hildenbrand Message-ID: Cc: mingo@kernel.org, hpa@zytor.com, torvalds@linux-foundation.org, tglx@linutronix.de, linux-kernel@vger.kernel.org, dahi@linux.vnet.ibm.com, peterz@infradead.org Reply-To: hpa@zytor.com, mingo@kernel.org, dahi@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, peterz@infradead.org, tglx@linutronix.de, torvalds@linux-foundation.org In-Reply-To: <1431359540-32227-12-git-send-email-dahi@linux.vnet.ibm.com> References: <1431359540-32227-12-git-send-email-dahi@linux.vnet.ibm.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched/preempt, arm/futex: Disable preemption in UP futex_atomic_op_inuser() explicitly Git-Commit-ID: 388b0e0adbc98a1b12a077dc92851a3ce016db42 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 388b0e0adbc98a1b12a077dc92851a3ce016db42 Gitweb: http://git.kernel.org/tip/388b0e0adbc98a1b12a077dc92851a3ce016db42 Author: David Hildenbrand AuthorDate: Mon, 11 May 2015 17:52:16 +0200 Committer: Ingo Molnar CommitDate: Tue, 19 May 2015 08:39:17 +0200 sched/preempt, arm/futex: Disable preemption in UP futex_atomic_op_inuser() explicitly The !CONFIG_SMP implementation of futex_atomic_op_inuser() seems to rely on disabled preemption to guarantee mutual exclusion. >>From commit e589ed23dd27 ("[ARM] 5218/1: arm: improved futex support"): "For UP it's enough to disable preemption to ensure mutual exclusion..." >>From the code itself: "!SMP, we can work around lack of atomic ops by disabling preemption" Let's make this explicit, to prepare for pagefault_disable() not touching preemption anymore. Reviewed-and-tested-by: Thomas Gleixner Signed-off-by: David Hildenbrand Signed-off-by: Peter Zijlstra (Intel) Cc: David.Laight@ACULAB.COM Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: airlied@linux.ie Cc: akpm@linux-foundation.org Cc: benh@kernel.crashing.org Cc: bigeasy@linutronix.de Cc: borntraeger@de.ibm.com Cc: daniel.vetter@intel.com Cc: heiko.carstens@de.ibm.com Cc: herbert@gondor.apana.org.au Cc: hocko@suse.cz Cc: hughd@google.com Cc: mst@redhat.com Cc: paulus@samba.org Cc: ralf@linux-mips.org Cc: schwidefsky@de.ibm.com Cc: yang.shi@windriver.com Link: http://lkml.kernel.org/r/1431359540-32227-12-git-send-email-dahi@linux.vnet.ibm.com Signed-off-by: Ingo Molnar --- arch/arm/include/asm/futex.h | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/arch/arm/include/asm/futex.h b/arch/arm/include/asm/futex.h index 255bfd1..5eed828 100644 --- a/arch/arm/include/asm/futex.h +++ b/arch/arm/include/asm/futex.h @@ -127,7 +127,10 @@ futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr) if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32))) return -EFAULT; - pagefault_disable(); /* implies preempt_disable() */ +#ifndef CONFIG_SMP + preempt_disable(); +#endif + pagefault_disable(); switch (op) { case FUTEX_OP_SET: @@ -149,7 +152,10 @@ futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr) ret = -ENOSYS; } - pagefault_enable(); /* subsumes preempt_enable() */ + pagefault_enable(); +#ifndef CONFIG_SMP + preempt_enable(); +#endif if (!ret) { switch (cmp) {