From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexey Brodkin Subject: [RESEND PATCH v2] devres: Really align data field to unsigned long long Date: Mon, 9 Jul 2018 07:44:44 +0300 Message-ID: <20180709044444.6397-1-abrodkin@synopsys.com> Return-path: Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org Cc: linux-snps-arc@lists.infradead.org, linux-arch@vger.kernel.org, Greg KH , Alexey Brodkin , Greg Kroah-Hartman , Thomas Gleixner , stable@vger.kernel.org List-Id: linux-arch.vger.kernel.org Depending on ABI "long long" type of a particular 32-bit CPU might be aligned by either word (32-bits) or double word (64-bits). Make sure "data" is really 64-bit aligned for any 32-bit CPU. At least for 32-bit ARC cores ABI requires "long long" types to be aligned by normal 32-bit word. This makes "data" field aligned to 12 bytes. Which is still OK as long as we use 32-bit data only. But once we want to use native atomic64_t type (i.e. when we use special instructions LLOCKD/SCONDD for accessing 64-bit data) we easily hit misaligned access exception. That's because even on CPUs capable of non-aligned data access LL/SC instructions require strict alignment. Signed-off-by: Alexey Brodkin Cc: Greg Kroah-Hartman Cc: Thomas Gleixner Cc: stable@vger.kernel.org --- Changes v1 -> v2: * Reworded commit message * Inserted comment right in source [Thomas] drivers/base/devres.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/base/devres.c b/drivers/base/devres.c index f98a097e73f2..466fa59c866a 100644 --- a/drivers/base/devres.c +++ b/drivers/base/devres.c @@ -24,8 +24,12 @@ struct devres_node { struct devres { struct devres_node node; - /* -- 3 pointers */ - unsigned long long data[]; /* guarantee ull alignment */ + /* + * Depending on ABI "long long" type of a particular 32-bit CPU + * might be aligned by either word (32-bits) or double word (64-bits). + * Make sure "data" is really 64-bit aligned for any 32-bit CPU. + */ + unsigned long long data[] __aligned(sizeof(unsigned long long)); }; struct devres_group { -- 2.17.1 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtprelay4.synopsys.com ([198.182.47.9]:37974 "EHLO smtprelay.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750818AbeGIEo6 (ORCPT ); Mon, 9 Jul 2018 00:44:58 -0400 From: Alexey Brodkin Subject: [RESEND PATCH v2] devres: Really align data field to unsigned long long Date: Mon, 9 Jul 2018 07:44:44 +0300 Message-ID: <20180709044444.6397-1-abrodkin@synopsys.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: linux-kernel@vger.kernel.org Cc: linux-snps-arc@lists.infradead.org, linux-arch@vger.kernel.org, Greg KH , Alexey Brodkin , Greg Kroah-Hartman , Thomas Gleixner , stable@vger.kernel.org Message-ID: <20180709044444.Ua1zbdDnYuhVDq558xKeJ4vWzWuuAJ3jMuB9ib1VI1c@z> Depending on ABI "long long" type of a particular 32-bit CPU might be aligned by either word (32-bits) or double word (64-bits). Make sure "data" is really 64-bit aligned for any 32-bit CPU. At least for 32-bit ARC cores ABI requires "long long" types to be aligned by normal 32-bit word. This makes "data" field aligned to 12 bytes. Which is still OK as long as we use 32-bit data only. But once we want to use native atomic64_t type (i.e. when we use special instructions LLOCKD/SCONDD for accessing 64-bit data) we easily hit misaligned access exception. That's because even on CPUs capable of non-aligned data access LL/SC instructions require strict alignment. Signed-off-by: Alexey Brodkin Cc: Greg Kroah-Hartman Cc: Thomas Gleixner Cc: stable@vger.kernel.org --- Changes v1 -> v2: * Reworded commit message * Inserted comment right in source [Thomas] drivers/base/devres.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/base/devres.c b/drivers/base/devres.c index f98a097e73f2..466fa59c866a 100644 --- a/drivers/base/devres.c +++ b/drivers/base/devres.c @@ -24,8 +24,12 @@ struct devres_node { struct devres { struct devres_node node; - /* -- 3 pointers */ - unsigned long long data[]; /* guarantee ull alignment */ + /* + * Depending on ABI "long long" type of a particular 32-bit CPU + * might be aligned by either word (32-bits) or double word (64-bits). + * Make sure "data" is really 64-bit aligned for any 32-bit CPU. + */ + unsigned long long data[] __aligned(sizeof(unsigned long long)); }; struct devres_group { -- 2.17.1