From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f54.google.com (mail-wg0-f54.google.com [74.125.82.54]) by kanga.kvack.org (Postfix) with ESMTP id D975B6B007B for ; Wed, 6 May 2015 13:51:12 -0400 (EDT) Received: by wgyo15 with SMTP id o15so19855546wgy.2 for ; Wed, 06 May 2015 10:51:12 -0700 (PDT) Received: from e06smtp17.uk.ibm.com (e06smtp17.uk.ibm.com. [195.75.94.113]) by mx.google.com with ESMTPS id w6si1588038wib.76.2015.05.06.10.50.52 for (version=TLSv1 cipher=AES128-SHA bits=128/128); Wed, 06 May 2015 10:50:53 -0700 (PDT) Received: from /spool/local by e06smtp17.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 6 May 2015 18:50:52 +0100 Received: from b06cxnps4074.portsmouth.uk.ibm.com (d06relay11.portsmouth.uk.ibm.com [9.149.109.196]) by d06dlp01.portsmouth.uk.ibm.com (Postfix) with ESMTP id A566217D805D for ; Wed, 6 May 2015 18:51:35 +0100 (BST) Received: from d06av05.portsmouth.uk.ibm.com (d06av05.portsmouth.uk.ibm.com [9.149.37.229]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id t46Hoobk64225426 for ; Wed, 6 May 2015 17:50:50 GMT Received: from d06av05.portsmouth.uk.ibm.com (localhost [127.0.0.1]) by d06av05.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id t46Honvx027896 for ; Wed, 6 May 2015 11:50:50 -0600 From: David Hildenbrand Subject: [PATCH RFC 11/15] arm/futex: UP futex_atomic_op_inuser() relies on disabled preemption Date: Wed, 6 May 2015 19:50:35 +0200 Message-Id: <1430934639-2131-12-git-send-email-dahi@linux.vnet.ibm.com> In-Reply-To: <1430934639-2131-1-git-send-email-dahi@linux.vnet.ibm.com> References: <1430934639-2131-1-git-send-email-dahi@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-kernel@vger.kernel.org Cc: dahi@linux.vnet.ibm.com, mingo@redhat.com, peterz@infradead.org, yang.shi@windriver.com, bigeasy@linutronix.de, benh@kernel.crashing.org, paulus@samba.org, akpm@linux-foundation.org, heiko.carstens@de.ibm.com, schwidefsky@de.ibm.com, borntraeger@de.ibm.com, mst@redhat.com, tglx@linutronix.de, David.Laight@ACULAB.COM, hughd@google.com, hocko@suse.cz, ralf@linux-mips.org, herbert@gondor.apana.org.au, linux@arm.linux.org.uk, airlied@linux.ie, daniel.vetter@intel.com, linux-mm@kvack.org, linux-arch@vger.kernel.org The !CONFIG_SMP implementation of futex_atomic_op_inuser() seems to rely on disabled preemption to guarantee mutual exclusion. >>From commit e589ed23dd27: "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. Signed-off-by: David Hildenbrand --- 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) { -- 2.1.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org