From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-bn3nam01on0120.outbound.protection.outlook.com ([104.47.33.120]:58346 "EHLO NAM01-BN3-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1031886AbeCAPXd (ORCPT ); Thu, 1 Mar 2018 10:23:33 -0500 From: Sasha Levin To: "stable@vger.kernel.org" , "stable-commits@vger.kernel.org" CC: Steven Rostedt , Arnd Bergmann , Ingo Molnar , Sasha Levin Subject: [added to the 4.1 stable tree] ARM: Hide finish_arch_post_lock_switch() from modules Date: Thu, 1 Mar 2018 15:22:33 +0000 Message-ID: <20180301152116.1486-12-alexander.levin@microsoft.com> References: <20180301152116.1486-1-alexander.levin@microsoft.com> In-Reply-To: <20180301152116.1486-1-alexander.levin@microsoft.com> Content-Language: en-US Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org List-ID: From: Steven Rostedt This patch has been added to the 4.1 stable tree. If you have any objections, please let us know. =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D [ Upstream commit ef0491ea17f8019821c7e9c8e801184ecf17f85a ] The introduction of switch_mm_irqs_off() brought back an old bug regarding the use of preempt_enable_no_resched: As part of: 62b94a08da1b ("sched/preempt: Take away preempt_enable_no_resched() from = modules") the definition of preempt_enable_no_resched() is only available in built-in code, not in loadable modules, so we can't generally use it from header files. However, the ARM version of finish_arch_post_lock_switch() calls preempt_enable_no_resched() and is defined as a static inline function in asm/mmu_context.h. This in turn means we cannot include asm/mmu_context.h from modules. With today's tip tree, asm/mmu_context.h gets included from linux/mmu_context.h, which is normally the exact pattern one would expect, but unfortunately, linux/mmu_context.h can be included from the vhost driver that is a loadable module, now causing this compile time error with modular configs: In file included from ../include/linux/mmu_context.h:4:0, from ../drivers/vhost/vhost.c:18: ../arch/arm/include/asm/mmu_context.h: In function 'finish_arch_post_lock= _switch': ../arch/arm/include/asm/mmu_context.h:88:3: error: implicit declaration o= f function 'preempt_enable_no_resched' [-Werror=3Dimplicit-function-declara= tion] preempt_enable_no_resched(); Andy already tried to fix the bug by including linux/preempt.h from asm/mmu_context.h, but that didn't help. Arnd suggested reordering the header files, which wasn't popular, so let's use this workaround instead: The finish_arch_post_lock_switch() definition is now also hidden inside of #ifdef MODULE, so we don't see anything referencing preempt_enable_no_resched() from a header file. I've built a few hundred randconfig kernels with this, and did not see any new problems. Tested-by: Guenter Roeck Signed-off-by: Steven Rostedt Signed-off-by: Arnd Bergmann Acked-by: Russell King Cc: Alexander Shishkin Cc: Andy Lutomirski Cc: Andy Lutomirski Cc: Ard Biesheuvel Cc: Arnaldo Carvalho de Melo Cc: Borislav Petkov Cc: Frederic Weisbecker Cc: Jiri Olsa Cc: Linus Torvalds Cc: Mel Gorman Cc: Peter Zijlstra Cc: Russell King - ARM Linux Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver Cc: linux-arm-kernel@lists.infradead.org Fixes: f98db6013c55 ("sched/core: Add switch_mm_irqs_off() and use it in th= e scheduler") Link: http://lkml.kernel.org/r/1463146234-161304-1-git-send-email-arnd@arnd= b.de Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin --- arch/arm/include/asm/mmu_context.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/arm/include/asm/mmu_context.h b/arch/arm/include/asm/mmu_= context.h index 9b32f76bb0dd..10f662498eb7 100644 --- a/arch/arm/include/asm/mmu_context.h +++ b/arch/arm/include/asm/mmu_context.h @@ -61,6 +61,7 @@ static inline void check_and_switch_context(struct mm_str= uct *mm, cpu_switch_mm(mm->pgd, mm); } =20 +#ifndef MODULE #define finish_arch_post_lock_switch \ finish_arch_post_lock_switch static inline void finish_arch_post_lock_switch(void) @@ -82,6 +83,7 @@ static inline void finish_arch_post_lock_switch(void) preempt_enable_no_resched(); } } +#endif /* !MODULE */ =20 #endif /* CONFIG_MMU */ =20 --=20 2.14.1